Challenging Dr. Mercola’s Recent Low-Carb Stances

Dr. Joseph Mercola has long been a polarizing figure in the wellness space, gaining notoriety for advocating natural remedies and alternative health solutions that appealed to countless followers, including those in the Carnivore and low-carb communities. 

 

Over the years, however, some of his positions have shifted significantly, sparking debates and prompting questions about the credibility of his recent health recommendations. While it’s true that health insights naturally evolve as new research emerges, it’s important to take a closer, more nuanced look to recognize biases or potential fallacies in any updated stance. 

 

We’ll examine Mercola’s past teachings and challenge several of his more recent claims, shedding light on why his latest views may not hold up under scrutiny—even for dedicated followers in the alternative wellness space.

 

 

Who Is Dr. Joseph Mercola?

Dr. Joseph Mercola is an osteopathic physician and best-selling author who rose to prominence in the early days of Internet health resources. Founding Mercola.com in 1997, he quickly established a robust digital platform focused on natural health and wellness, gaining a large following drawn to his unconventional insights on nutrition, fitness, and preventive care.

 

Before venturing into online health advocacy, Mercola served as Chairman of the Family Medicine Department at St. Alexius Medical Center in Illinois. His clinical background and hands-on experience with patients provided a foundation for his later work, allowing him to explore alternative remedies and integrative approaches to healthcare. 

 

Over the years, he has published multiple books, several of which reached best-seller status, further cementing his position as a leading voice in alternative medicine.

 

Key aspects of Mercola’s career include:

• Early Digital Adoption: Recognized for leveraging the internet to connect with a global audience at a time when few physicians were taking their practices online.
• Natural Health Focus: Prioritizes nutrition, lifestyle adjustments, and preventive strategies that go beyond conventional Western medicine. Known for advocating and following low-carb and ketogenic (keto) diets for almost two decades. 
• Public Recognition: Featured in various media outlets and often cited by those seeking integrative health information, particularly regarding diet and supplementation.

 

Mercola’s early warnings about widely used products and practices—such as cautioning against Vioxx in 1999, GMOs in 2000, mercury-based fillings in 2001, and water fluoridation in 2002—demonstrate his history of being ahead of conventional healthcare advisories. 

 

Over time, many of these concerns were often validated by subsequent research and became key talking points in alternative health circles. While these notable contributions solidified Mercola’s reputation for pioneering certain natural health perspectives, it’s crucial to remember that both past and current accuracy does not necessarily guarantee the validity of all his recent positions.

 

Mercola’s Recent Arguments Against Low-Carb and Keto Diets

Over the past couple of years, Mercola has significantly shifted his perspective on low-carb and keto diets—despite spending nearly two decades recommending them as part of a comprehensive health strategy. 

 

In recent articles, he questions the long-term sustainability and cites many risks associated with trying these diets, pointing to various alleged issues. These arguments stand in stark contrast to his long-standing endorsements of low-carb eating in which he frankly built a considerable following around. 

 

We will take a closer look into Mercola’s recent claims and examine why they may not hold up under scrutiny.

 

Mercola’s Recent Articles on Low-Carb and Keto Diets:

• January 5, 2025: How to Produce the Healthiest Foods Imaginable
• January 2, 2025: Fat Oxidation—The Hidden Accelerator of Aging and Disease
• November 26, 2024: What Did Your Great-Great-Great Grandparents Eat?
• September 30, 2024: The Ketogenic Diet Can Put Your Cardiovascular Health at Risk
• April 2, 2024: Consequences of Low-Carb Diets

 

The following are claims made by Mercola from his last five recent articles on the topic of low-carb and keto diets: 

 

Claim #1: “Zero carbs equals guaranteed nutrient deficiencies.”

 

 

Mercola contends that removing carbs from your diet automatically results in severe vitamin and mineral deficiencies. This claim doesn’t take into account a deeper, nuanced view on nutrition—there are actually plenty of nutrient-dense foods in a low-carb or even zero-carb lifestyle. 

 

Animal foods—including muscle meats, organ meats, seafood, and eggs—have superior protein bioavailability compared to most plant-based options because they provide complete amino acid profiles without limiting amino acids. In contrast, many plant proteins lack sufficient amounts of one or more essential amino acids (e.g., lysine, methionine), which can make them less effective for building and repairing tissues.

 

Furthermore, anti-nutrients in certain plant foods—such as phytates and oxalates—can bind to minerals (such as iron, zinc, or calcium) and reduce their absorption. Anti-nutrients can also reduce the digestibility and bioavailability of plant-based proteins. Meanwhile, animal-based foods supply heme iron, which is more readily absorbed than non-heme iron from plants.

 

 

Animal-based proteins also provide vitamin B12, retinol (preformed vitamin A), vitamin K2, carnosine, and taurine—nutrients largely absent or poorly converted from plant sources. Therefore, labeling “zero carbs” as a guaranteed nutritional crisis oversimplifies the fact that food quality, bioavailability, and variety matter. 

 

Our meat-based functional medicine practice rarely sees malnutrition because of diet alone. Usually, it is because of undereating, infections (e.g., mold, Lyme), methylation issues (e.g., MTHFR mutations), or gut imbalances causing issues with nutrient assimilation. Once we care for these imbalances that aren’t caused by diet, malnutrition is rarely an issue with low-carb, meat-based diets. (In case you’re wondering how we know, we run blood tests, stool tests, and Spectracell or Genova Ion nutrient status tests that measure nutrient status in the cells.)

 

You can also view my blood work results from six-plus years of being Carnivore here.

 

Claim #2: “Fat-fueled metabolism drives chronic constipation and gut dysbiosis.”

 

 

Mercola posits that when your body relies mainly on fat for fuel, gut motility suffers, beneficial bacteria diminish, and toxins build up in the colon—resulting in constipation and gut dysbiosis. However, gastrointestinal health is significantly influenced by more than whether you’re eating carbs or not. In fact, one prevailing myth is that dietary fiber, commonly found in plant foods, is essential for proper gut function.

 

Emerging research and clinical observations—including those from our meat-based functional medicine practice—indicate that fiber is not the sole pathway for maintaining a healthy microbiome. The beneficial short-chain fatty acids (SCFAs) often associated with fiber can also be produced from protein-derived substrates in the absence of substantial dietary carbs. Many individuals experience less inflammation and improved digestion when removing plant fibers that irritate their gut or trigger immune responses.

 

Additionally, numerous people following a Carnivore or low-carb approach, report stable or even enhanced digestive well-being without relying on plant fibers. Once the body adapts to a higher-fat, protein-rich diet, it can still generate SCFAs to support gut integrity, energy metabolism, and overall health.

 

 

Sharing passages from the Carnivore Cure—fiber is also a carb, and the human body can’t break down it. However, gut bacteria can extract nutrients from fiber as fuel and convert them into SCFAs. Some conventional practitioners argue that fiber is required for intestinal nutrients, such as butyrate. Buter has butyrate, or you can produce a type of ketone called beta-hydroxybutyrate. 

 

Fiber is broken down into SCFAs, such as butyrate (butyric acid), propionate (propionic acid), and acetate (acetic acid). Butyrate is essential because it is the preferred fuel source by the large intestine’s endothelial cells. Butter, cream, and cheese contain butyrate in its absorbable form. 

 

In fact, the origins of the word butyric acid are from the Latin word, butyrum—the same origins of the word butter.

 

 

The number one dietary source of butyrate is butter. According to a 2016 microbiome study, “Butter contains three to four percent of butyric acid, in the form of tributyrin (butyryl triglyceride), making it the richest dietary source of butyrate…” 

 

Butyrate is also made in small quantities in mammalian cells through the breakdown of fats and the metabolism of glucose. Yes, butyrate can be found in animal fats and dairy. The best source for acetate (another short-chain fatty acid) is vinegar. If you are concerned about the lack of acetic acid in a meat-based diet, add a couple of drops of vinegar to water.

 

Some Carnivores don’t consume any dairy. It may be possible that the minimal amounts of butyrate obtained from animal fats are sufficient. Bacteria also make butyrate from the leftovers of cells and mucus. In fact, the end of the colon (the sigmoid colon) relies more on this type of butyrate than the butyrate from foods.

 

In 2012, a study in the Journal of Gastroenterology showed that reducing fiber helped participants with chronic constipation. The study lasted six months, and after two weeks of having zero fiber, these participants were allowed to increase fiber, as needed. These participants felt such relief after two weeks of zero fiber that they continued zero fiber for the full six-month period. Of the high-fiber, small-fiber, and zero-fiber groups, the zero-fiber participants had the most frequency of bowel movements.

 

This means it’s misleading to claim that fiber is mandatory for everyone or that a fat-focused eating plan inherently translates to chronic constipation or dysbiosis. Properly formulated Carnivore or low-carb diets can adequately support the gut microbiome and normal bowel function—even without carb-based fiber sources.

 

You can learn more about fiber myths here.

 

Claim #3: “Excessive fat oxidation increases the risk of cardiac arrhythmias.”

 

 

Mercola suggests that relying heavily on fat for fuel can drive electrolyte imbalances—especially for minerals such as magnesium and potassium—and raise the likelihood of abnormal heart rhythms.

 

However, electrolyte fluctuations can happen with any major diet change, particularly when you reduce carbs and experience a shift in how your body retains water and sodium. Crucially, these imbalances are not an automatic consequence of burning fat for fuel; they’re usually tied to insufficient electrolyte intake and inadequate hydration.

 

In fact, we, in addition to the overall Carnivore and low-carb communities, regularly stress the importance of monitoring and supplementing electrolytes as you transition to this way of eating. Approaching a low-carb or keto diet methodically—ensuring you replenish sodium, potassium, and magnesium—helps maintain normal cardiac function. 

 

Supplementing electrolytes is generally only needed during the transition to a low-carb diet. If you’re finding that you’re unable to balance your electrolytes naturally after six months or so, then it’s time to look for a deeper root cause. 

 

One example is ADH. When you eat a low-carb diet, your body stores less glycogen (the storage form of glucose in muscles and liver). For every gram of glycogen, your body holds onto about 3-4 grams of water. With fewer carbs, glycogen stores deplete, leading to less water retention. This reduced water storage can make you more sensitive to electrolyte imbalances because the electrolytes, such as sodium and potassium, are excreted with water. On a high-carb diet, the excess water in your body can mask electrolyte imbalances, but on a low-carb diet, the loss of water can reveal or amplify symptoms such as fatigue, dizziness, or muscle cramps.

 

When osmolality rises (e.g., from dehydration or electrolyte imbalances), antidiuretic hormone (ADH), also known as vasopressin, is released to help the kidneys retain water, maintaining proper hydration and blood concentration. However, ADH can become imbalanced in some conditions including Chronic Inflammatory Response Syndrome (CIRS), leading to improper water regulation. This imbalance can result in excessive water loss through urine (even when dehydrated) or abnormal water retention, causing diluted electrolytes. 

 

On a low-carb diet, where water loss is already significant due to glycogen depletion, an underlying ADH imbalance can exacerbate dehydration and electrolyte disturbances, making symptoms such as dizziness, fatigue, and muscle cramps more pronounced. Addressing root causes of ADH dysfunction, like CIRS, is critical for restoring proper fluid balance. (It’s not always the case of carbs vs. no carbs).

 

You can see a deeper dive into this topic here.

 

So, while electrolyte management is indeed critical during fat adaptation, there’s no evidence that fat oxidation alone inherently causes heart rhythm problems.

 

Claim #4: “Cutting down on dietary fats is the only way to prevent ‘fatty organ’ disorders.”

 

 

According to Mercola, the solution to avoiding fatty buildup in organs such as the liver and pancreas is to reduce dietary fat intake. This oversimplification suggests that excessive fat oxidation inherently drives conditions such as non-alcoholic fatty liver disease (NAFLD). 

 

In reality, fatty organ disorders are usually linked to excessive caloric intake, high fructose consumption, and insulin resistance—all of which contribute more directly to the accumulation of unwanted fat in tissues than the mere presence of dietary fats.

 

In fact, low-carb and keto diets often help improve liver markers and function in individuals with NAFLD, primarily by fostering better insulin sensitivity, reducing visceral fat, and enhancing overall metabolic health. 

 

By labeling fat reduction as the only strategy, this argument overlooks the multifactorial nature of organ fat accumulation, including genetics, lifestyle factors (such as physical activity and sleep), and the role of excessive carbs and sugars in the diet. 

 

Claim #5: “Keto diets permanently disrupt hormones and impair fertility.”

 

 

Mercola suggests that spending long stretches in ketosis leads to irreversible hormone issues, negatively impacting fertility in women and lowering testosterone in men. In reality, there is no clinical evidence or data supporting this notion.

 

Sex hormones, such as estrogen, progesterone, and testosterone, are derived from cholesterol, which is obtained from dietary fats and synthesized in the body. Proteins provide the amino acids necessary to create hormone transport molecules and enzymes essential for hormone production and function. Without sufficient fat and protein in the diet, the body cannot produce adequate levels of these hormones, which are vital for reproductive health. 

 

However, beyond just eating these nutrients, the body must feel a sense of abundance and safety to prioritize reproductive functions. If the body perceives stress, scarcity, or malnutrition, it will conserve resources for survival, effectively shutting down processes such as ovulation and pregnancy to protect itself. Factors such as obesity, stress levels, sleep, environmental toxins, and ensuring adequate protein and healthy fats all significantly influence hormonal health. 

 

The issue often isn’t a low-carb diet itself—especially when it’s rich in nutrient-dense fats and proteins—but rather the chronic stress and exposure to toxins in modern living. These stressors disrupt hormone balance, overburden the body’s detoxification pathways, and impair gut function, reducing nutrient absorption even when the diet is sufficient. 

 

A well-formulated low-carb diet, assuming it includes ample calories and supports gut health, can provide the nourishment required for hormone production while lowering inflammation and stabilizing blood sugar. This approach allows the body to feel safe, adequately nourished, and ready for reproductive processes, provided other stressors such as toxins, chronic inflammation, and emotional stress are addressed.

 

In fact, research supports this notion. For individuals with insulin resistance—often a culprit behind reproductive challenges—switching to a low-carb diet enhances hormone balance and improves fertility markers by stabilizing blood sugar and reducing inflammation.

 

Thus, a well-formulated keto diet—particularly one that meets energy needs, provides essential nutrients, and accounts for lifestyle factors— does not cause irreversible hormonal dysfunction. If anything, it can be a tool for improving metabolic health, which in turn can support more balanced hormone levels.

 

You can also learn more about the nuance around low-carb diets and thyroid markers here.

 

Claim #6: “Ketosis leads to chronic mental fog and memory decline.”

Mercola makes the argument that fueling your body with primarily fat for extended periods deprives the brain of its “preferred fuel,” causing long-term mental cloudiness and eventual memory decline. However, this notion overlooks the well-documented brain benefits reported by many people following low-carb or keto diets as well as clinical studies. Research even indicates that ketones can have a neuroprotective effect, supporting mental clarity rather than undermining it.

 

It’s true that some individuals experience temporary side effects such as “keto flu” when they first reduce carb intake. This short adaptation window can include fatigue or mental fog. 

 

However, once the body fully transitions to using ketones, most people find that their cognitive function stabilizes or improves, rather than deteriorates. Consequently, labeling ketosis as a path to permanent mental fog fails to account for these positive adaptations and the growing body of clinical evidence supporting ketones’ role in brain health.

 

Mental decline, particularly diseases such as Alzheimer’s, is increasingly being recognized as a condition rooted in chronic inflammation and insulin resistance. Insulin resistance in the brain impairs glucose uptake, starving brain cells of their primary energy source and contributing to cognitive decline. This lack of fuel, coupled with inflammation, damages neurons and disrupts communication pathways critical for memory and cognitive function. 

 

A keto diet, however, offers an alternative fuel source in the form of ketones, which are produced from dietary fats or stored fat during periods of low-carb intake. Unlike glucose, ketones can easily cross the blood-brain barrier and provide a clean, efficient energy source to nourish and sustain brain cells, even in the presence of insulin resistance. 

 

Additionally, a keto diet has been shown to reduce inflammation, stabilize blood sugar, and support mitochondrial function, further protecting the brain from damage. By offering this alternative fuel and addressing underlying inflammation, keto diets often play a vital role in preserving cognitive function and even slowing the progression of neurodegenerative diseases including Alzheimer’s.

 

Claim #7: “Low-carb diets accelerate neurological decline in older adults.”

 

 

Mercola contends that limiting carbs hastens age-related memory issues and cognitive decline, suggesting that the brain requires a continual supply of glucose for optimal function.

 

However, ketone utilization is a well-documented phenomenon indicating that the brain can adapt to, and even thrive on, ketones in place of a heavy glucose intake—particularly in cases of insulin resistance or type 2 diabetes. Many people following a keto or low-carb diet report stable or improved mental clarity once they’ve adjusted to using fats as their primary fuel source.

 

Additionally, the existing research paints a different picture than Mercola’s claim would suggest. Several studies point toward the neuroprotective benefits of ketosis, especially in treating epilepsy or mild cognitive impairment. One study found that ketone utilization reduces oxidative stress and enhances mitochondrial efficiency in neurons, offering protective effects against neurodegenerative diseases.

 

Neurological decline in older adults is often linked to insulin resistance, chronic inflammation, and oxidative stress, all of which low-carb diets help address. As mentioned above, keto diets provide ketones as an alternative fuel source for the brain, bypassing the impaired glucose metabolism often seen in aging brains or conditions such as Alzheimer’s. 

 

Studies have shown that ketones can enhance mitochondrial function, reduce neuroinflammation, and improve cognitive performance, even in individuals already experiencing cognitive decline. There is no evidence to suggest that a well-formulated low-carb diet accelerates neurological decline, and on the contrary, it can provide critical metabolic and anti-inflammatory support to preserve cognitive health as we age.

 

Claim #8: “Keto diets cause hair thinning and weakness.”

 

 

Mercola suggests that relying heavily on fat for fuel can trigger widespread hair loss, implying the keto diet lacks the nutrients needed for strong, healthy hair. In reality, several common factors—such as rapid dietary shifts, substantial calorie reductions, or increased stress—can temporarily affect hair growth, regardless of whether a person is following a high-carb or low-carb eating plan.

 

One key point is balanced nutrient intake. Hair health depends on adequate protein, along with essential vitamins and minerals like B vitamins, vitamin D, zinc, and iron—all of which can be obtained on a well-rounded keto regimen. 

 

Hair growth relies heavily on nutrients found in meats, particularly amino acids and minerals such as zinc, iron, and sulfur, which are essential for building keratin, the protein that makes up hair. Hair growth follows a three- to five-year cycle, including phases of growth (anagen), transition (catagen), resting (telogen), and shedding (exogen). Any disruption to this cycle, such as nutrient deficiencies, stress, or toxicity, can lead to noticeable hair loss. 

 

In our practice, the most common causes of hair loss we observe include undereating, which deprives the body of essential nutrients for hair production, high-stress lifestyles that disrupt hormone balance and blood flow to hair follicles, and toxic environments such as mold exposure, which creates inflammation and impairs nutrient absorption. Addressing these root causes by ensuring adequate protein intake, managing stress, and reducing environmental toxin exposure is often key to restoring healthy hair growth.

 

Additionally, ketones or fat oxidation by themselves aren’t direct culprits for hair problems. When first starting a low-carb diet, temporary hair thinning can occur because of a significant diet change, rapid weight loss, or nutrient imbalances, factors that can arise in any eating pattern if not properly managed. Remember, hair growth follows a three-plus-year cycle. If everyone were losing hair on a low-carb diet, no one would follow one. 

 

You can learn more about the root causes of hair loss and how to support them here.

 

Claim #9: “High-protein, low-carb eating inevitably degrades bone density.”

 

 

Mercola claims that prioritizing protein and fats while limiting carbs causes chronic calcium loss from bones, leading to or worsening osteoporosis. Contrary to this notion, protein intake can actually support bone health by improving calcium absorption and preserving muscle mass—both of which help maintain bone density. In fact, many studies link adequate dietary protein with better musculoskeletal outcomes, not a decline in bone integrity.

 

It’s also essential to consider individual variability in factors such as vitamin D status, magnesium intake, and physical activity, all of which greatly influence bone health. There’s no substantial evidence pinpointing low-carb diets as a direct trigger for overall bone mineral loss. 

 

The Bone Clinic in Australia, a leading research facility specializing in bone health, has identified genetics and lifting heavy weights as the top two factors for maintaining strong, healthy bones. While genetics provide the foundation by determining bone density potential and overall structure, the role of mechanical loading—lifting heavy things—cannot be overstated. 

 

(Significantly heavy) weight-bearing and resistance exercises stimulate osteogenesis, the process of creating new bone tissue, by signaling the bones to adapt and grow stronger to handle the applied forces. This is particularly important as we age, when bone loss accelerates, increasing the risk of osteoporosis. Lifting very heavy weights strengthens bones and improves muscle mass, balance, and joint support, reducing the likelihood of fractures. You can learn more here.

 

Claim #10: “Long-term low-carb diets directly trigger chronic kidney disease.”

 

 

Although Dr. Mercola insists that long-term low-carb, high-protein diets inevitably cause chronic kidney disease, extensive research shows otherwise: kidneys can adapt to higher protein loads by naturally adjusting their filtration rate. 

 

According to the American Kidney Fund, diabetes (47% of new cases) and hypertension (29% of new cases) together account for 76% of kidney failure, while one study identified more than 15 risk factors for chronic kidney disease (CKD) without including high-protein intake. Current research consistently finds no link between high protein consumption and developing or worsening kidney disease in healthy individuals, indicating that dietary protein isn’t a significant factor in CKD.

 

Even studies that suggest protein restriction for kidney disease emphasize that there may be a modest benefit for slowing kidney function decline—however, the results are underwhelming and don’t have the statistical importance for blanket recommendations. 

 

In our meat-based functional practice, where we regularly run kidney function tests, we never see kidney damage as a result of low-carb diets. Instead, we often find that imbalanced kidney markers are more commonly linked to inadequate water intake. Low-carb diets, which eliminate the mix of fat, sugar, and salt found in processed foods, can reduce the body’s natural thirst signals, leading to dehydration. 

 

Dehydration can temporarily elevate markers such as blood urea nitrogen (BUN) and creatinine, which can be mistaken for kidney dysfunction. However, these markers typically normalize when hydration improves. We normally see eGFR improve on a Carnivore diet. Proper hydration, paired with sufficient electrolytes, is key to ensuring kidney health while following any low-carb diet.

 

You can learn more about why high-protein diets aren’t problematic for kidney function here.

 

Claim #11: “Low-carb diets are incompatible with an active lifestyle.”

 

 

According to Mercola, individuals who regularly exercise or train at high intensity can’t sustain proper performance or recovery without substantial carb intake.

 

However, many athletes have successfully embraced fat adaptation, running on low-carb or even keto diets without sacrificing endurance, strength, or stamina. In fact, numerous endurance competitors report improved fat oxidation and metabolic flexibility, which can be advantageous for prolonged events where consistent energy availability is key.

 

One study found that the keto diet had no significant impact on strength performance, while another study reported that the keto diet reduced body and fat mass without compromising strength or lifting performance. A 2016 study demonstrated that keto-adapted ultra-endurance runners exhibited extraordinarily high fat oxidation rates during exercise, comparable glycogen depletion patterns, and no decline in endurance performance compared to their high-carb counterparts.

 

While traditional perspectives emphasize carb intake for enhancing exercise performance, some evidence suggests the performance benefits may not directly stem from physiological effects, but rather from psychological influences, such as a “nocebo” effect. 

 

The nocebo effect refers to a phenomenon where individuals experience perceived detriments or lessened performance due to expectations despite the absence of a physiological basis. For example, studies indicate that carb supplementation may not consistently enhance short-duration, high-intensity exercise performance, as seen in trials showing no significant difference in muscle metabolism or performance between carb and placebo treatments. 

 

Additionally, meta-analyses reveal variability in carb benefits across studies, often influenced by expectations rather than physiological necessity.

 

Claim #12: “Increased fat oxidation is linked to cellular senescence and aging.”

He contends that relying heavily on fat for fuel, as is common in low-carb or keto diets, accelerates cellular senescence—the point at which cells stop dividing and enter a sort of “dormant” phase. 

 

Fat oxidation, however, is simply the body’s natural process of converting fat into energy, and there’s limited evidence that this process alone directly causes cells to age prematurely. Cellular senescence depends on a number of factors—such as oxidative stress, mitochondrial function, DNA integrity, and inflammation—not just whether you’re getting your energy from carbs or fats.

 

In other words, while increased fat oxidation can contribute to oxidative stress under certain conditions, it typically won’t singlehandedly trigger cellular senescence if you’re supporting your body with enough micronutrients, maintaining mitochondrial health, and keeping inflammation in check. 

 

If you’re otherwise healthy and attentive to overall lifestyle factors, a low-carb or keto approach doesn’t inherently spell faster aging.

 

Claim #13: “Reactive oxygen species (ROS) play a significant role in promoting senescence.”

Mercola points out how ROS—natural byproducts of metabolism—can damage cells and hasten senescence when present in excessive amounts. This is partly true: at high concentrations, ROS can indeed drive oxidative stress, contribute to DNA damage, and potentially speed up the aging process. 

 

However, it’s important to remember that the body has built-in antioxidant systems that help keep ROS levels in check. Additionally, not all ROS activity is harmful; moderate levels are actually essential for normal cellular signaling and adaptation.

 

In the context of low-carb or keto diets, the goal is to shift the body’s primary fuel source from glucose to fats. While this can increase the production of ROS under certain conditions—especially if nutrient intake is inadequate or metabolic health is compromised—most individuals following well-formulated low-carb or keto plans can support healthy ROS balance through proper nutrition, antioxidant intake, and overall lifestyle measures. 

 

So, the fact that ROS can cause damage when unregulated doesn’t itself make low-carb or keto diets inherently problematic provided these diets are approached thoughtfully and holistically.

 

Claim #14: “Shifting from glucose to fat metabolism accelerates cellular dysfunction and aging.”

 

 

Mercola suggests that moving away from glucose-based metabolism toward fat-based energy (a cornerstone of low-carb or keto diets) hastens cellular damage and aging. 

 

The claim that shifting from glucose to fat metabolism accelerates cellular dysfunction and aging is not supported by scientific evidence and is, in fact, contradicted by numerous studies. Numerous studies link ketosis and fat oxidation to benefits such as improved mitochondrial function, reduced inflammation, more stable blood sugar control, and autophagy promotion—a process where damaged or dysfunctional cellular components are cleared out to make way for healthier ones. In fact, animal research even points to potential longevity advantages from keto diets, possibly due to enhanced mitochondrial resilience and a decrease in chronic inflammation.

 

While fat metabolism can produce ROS, it also drives mitochondrial biogenesis and other protective adaptations. Unlike glucose metabolism, which generates more ROS and contributes to inflammation when consumed in excess, ketones provide a cleaner, more efficient fuel source that reduces oxidative damage. 

 

Research also highlights the role of ketones in activating pathways such as AMPK and sirtuins, which are associated with longevity and improved cellular repair. By contrast, chronically relying on glucose—especially in the context of insulin resistance or obesity—carries its own serious risks for cellular dysfunction and accelerated aging. 

 

Overall, there is no substantial evidence that fat metabolism inherently speeds up aging, and a well-formulated low-carb or keto approach can deliver a range of health benefits.

 

Claim #15: “Certain drugs mimic increased fat oxidation and exacerbate aging.”

This assertion likely centers around medications such as fibrates, which may activate pathways linked to fat metabolism. While these drugs can have side effects—ranging from minor digestive issues to more serious complications in some cases—it’s inaccurate to generalize that “increased fat oxidation” alone is what drives any aging effects. 

 

Medications work via complex mechanisms, and linking them solely to faster aging oversimplifies the issue. In reality, many factors—such as dosage, individual health status, and lifestyle—contribute to how a drug interacts with the body’s fat metabolism and overall cellular processes. Consequently, it’s important to look at the broader medical context rather than assuming that any agent boosting fat oxidation automatically accelerates aging.

 

Moreover, equating the effects of pharmacological interventions directly to those of dietary fat oxidation is a stretch. Low-carb and keto diets rely on whole foods and natural metabolic shifts, rather than artificially induced pathways. As a result, comparing side effects seen with specific drugs to the body’s natural adaptation to a fat-fueled metabolism is misleading and a flawed argument because it compares two fundamentally different processes—pharmacological interventions and natural metabolic states—without accounting for context or mechanisms. 

 

By conflating the two (also known as false equivalence), the claim creates a strawman argument, attributing the potential negative effects of pharmacological interventions to the natural process of fat metabolism, which has entirely different regulatory controls and outcomes. This is not an apples-to-apples comparison and fails to provide a fair or accurate assessment of the benefits of increased fat oxidation and the health benefits of dietary ketosis.

 

Claim #16: “Strategies to reduce fat oxidation and promote glucose metabolism delay aging.”

Mercola’s suggestion that prioritizing glucose metabolism over fat oxidation leads to healthier aging is highly debatable. The claim is overly simplistic and does not align with the growing body of evidence demonstrating the benefits of fat oxidation for cellular health and longevity. 

 

This argument assumes that glucose metabolism is inherently superior, ignoring the fact that excessive reliance on glucose as a primary fuel source often leads to metabolic dysfunctions, such as insulin resistance, chronic inflammation, and oxidative stress—all of which are major drivers of aging. Fat oxidation, particularly through ketosis, provides a cleaner, more efficient fuel for the mitochondria, reducing the production of ROS and supporting metabolic flexibility, a key indicator of health and longevity. 

 

Additionally, fat oxidation activates pathways such as AMPK and sirtuins, which are directly linked to anti-aging benefits such as improved cellular repair and reduced inflammation. While promoting glucose metabolism may be beneficial in certain scenarios, such as for individuals with low energy availability, blanket statements that dismiss fat oxidation ignore its vital role in reducing aging-related cellular stress and optimizing energy production. 

 

Aging is not delayed by prioritizing one fuel source over the other but rather by achieving metabolic flexibility that allows the body to efficiently use both glucose and fat as needed. Consistently promoting glucose metabolism is linked to worsening conditions such as type 2 diabetes or cardiovascular disease. 

 

Consequently, this shouldn’t deter anyone from trying a low-carb or keto diet, especially when such approaches can enhance metabolic flexibility and offer protective effects against age-related health issues.

 

Claim #17: “Prolonged fat oxidation triggers ‘metabolic overload’ in the adrenals.”

 

 

Mercola argues that staying in a fat-fueled state for too long strains the adrenal glands, possibly causing fatigue, hormone imbalances, and poor stress resilience. In reality, he oversimplifies and misrepresents how the endocrine system and energy metabolism work. The endocrine system, particularly the adrenal glands, requires an abundance of fat for hormone production, as cholesterol—a fat-derived molecule—is the building block for all steroid hormones, including cortisol, aldosterone, and sex hormones. 

 

While prolonged stress (chronic cortisol production) can tax the adrenals, this is not simply tied to fat oxidation but rather to overall systemic stressors, which can include poor sleep, environmental toxins, psychological stress, and nutrient deficiencies—factors common in our modern world. There isn’t strong scientific support for the notion that simply burning fat (as in a well-planned low-carb or keto diet) automatically overloads the adrenals. 

 

Real talk: Why are hypothyroid and adrenal diseases increasing when most people are not on a low-carb diet? 

 

Fat oxidation, particularly through a well-formulated low-carb diet, can actually reduce metabolic stress by stabilizing blood sugar, lowering inflammation, and supporting mitochondrial efficiency, which reduces the overall workload on the adrenals. The claim conflates natural fat metabolism with a pathological state, ignoring the broader picture that adrenal “overload” is more likely to result from chronic stressors rather than from fat oxidation itself. 

 

A balanced endocrine system thrives on sufficient fat intake, proper stress management, a clean environment, sufficient sleep, and overall lifestyle support—not from prioritizing one metabolic pathway over another.

 

Claim #18: “High fat oxidation reduces the body’s capacity to detoxify.”

 

 

Mercola makes the argument that relying on fat as your main energy source compromises the liver’s ability to process and eliminate toxins, causing harmful substances to build up. However, this is not supported by scientific evidence and reflects a misunderstanding of how detoxification works in the body. 

 

The liver primarily carries out detoxification in two phases: Phase I, which involves converting toxins into intermediate metabolites, and Phase II, which processes these metabolites for excretion. Both phases rely on a wide array of nutrients, including amino acids, B vitamins, antioxidants such as glutathione, and fat-soluble vitamins (A, D, E, K), many of which are abundant in a nutrient-dense, high-fat, and protein-rich diet. 

Fat oxidation, particularly through a keto diet, is not harmful to these pathways. In fact, ketosis has been shown to reduce systemic inflammation and oxidative stress—key factors that can impair the liver’s detoxification processes.

The body’s ability to detoxify is far more likely to be hindered by chronic inflammation, excessive sugar, processed food consumption, seed oils, environmental toxin exposure, dehydration, or nutrient deficiencies rather than by fat oxidation. 

Additionally, low-carb, high-fat diets often improve liver function by stabilizing blood sugar levels and reducing insulin resistance, which helps protect against conditions such as NAFLD—a significant barrier to proper detoxification. 

 

In fact, improvements in insulin sensitivity and reductions in inflammation—benefits often associated with low-carb or keto approaches—can bolster overall metabolic health, indirectly supporting liver function. Studies also show how keto diets can improve serum liver function markers and decrease liver fat content.

 

Ketones, produced during fat oxidation, also serve as a clean and efficient energy source for the liver, supporting its metabolic functions. When paired with adequate hydration, proper mineral balance, and sufficient nutrient intake, high-fat oxidation enhances rather than reduces the body’s capacity to detoxify. 

 

What matters more for effective detox is maintaining proper hydration, adequate micronutrient intake, removing toxins that disrupt the process, and opening drainage pathways, rather than solely focusing on whether fat or carbs fuel your body. (However, it’s important to note that excess carbs also hinder the liver’s detox process.)

 

This claim mistakenly conflates fat metabolism with metabolic dysfunction, ignoring the beneficial role that fat oxidation can play in promoting overall health and detoxification efficiency.

 

Now that we’ve challenged many of Mercoloa’s recent claims on low-carb and keto diets, let’s examine his past teachings and history on these topics. 

 

Mercola’s History With Low-Carb and Keto Eating

Mercola partially gained recognition for advocating low-carb lifestyles as far back as the early 2000s. In 2003, he published The No-Grain Diet, which laid out a blueprint for reducing carbs—especially those derived from grains—to improve health markers such as insulin sensitivity and weight management. 

 

Over the ensuing years, Mercola released multiple books praising the benefits of low-carb and keto diets. Translated into numerous languages, these works positioned him as a leading voice in the space, inspiring followers worldwide to embrace a low-carb approach. Notably, Mercola himself followed—and publicly championed—low-carb eating during that period.

 

 

In a stark departure, Mercola has recently shifted his stance, voicing drastic concerns about low-carb and keto diets. Intriguingly, he now appears to align with the late Ray Peat’s teachings, which emphasize higher carb intake—often from sources such as fruit juices and table sugar—while cautioning against polyunsaturated fats (PUFAs). 

 

Ray Peat was a somewhat elusive figure—he kept a low profile for years, and many people never saw him publicly until shortly before he passed away. Anecdotally, numerous individuals who tried Peat’s high-carb, pro-sugar approach reported weight gain, sugar/carb addiction challenges, and other health concerns, and ultimately reverted to low-carb eating. 

 

Adding to the intrigue, Ray Peat died without much public announcement or clarity about the cause of his death, sparking rumors and speculation within the health community. Consequently, Mercola’s pivot from staunch low-carb proponent to adopting (and promoting) the Ray Peat paradigm has stirred further controversy around the reliability and consistency of his evolving dietary advice.

 

You can learn more about our thoughts on the Ray Peat diet here and the nuance behind animal-based PUFAs here.

 

Real Talk: What’s Behind Mercola’s Drastic Changes on Low-Carb Diets?

Mercola’s abrupt turnabout—shifting from a two-decade advocacy of low-carb eating to consuming 500 grams of carbs daily—raises critical questions about why the switch happened now. If low-carb diets were truly detrimental, one would expect him to have encountered problems much earlier in his own experience or with the countless patients and followers he’s influenced. 

 

Instead, he maintained a relatively low-carb regimen (somewhere between under 50 to 100 grams of carbs a day) for years, only recently leaping to a much higher carb intake of mostly rice and ripe fruits. This sudden pivot suggests there might be more to the story—possibly an unaddressed root cause that emerged post-COVID, heightened by the scrutiny and stress he faced during that period.

 

A plausible theory is that Mercola could be dealing with an underlying condition that makes him feel better temporarily when he ups his carbs. In our clinical practice and from working with diverse wellness practitioners, we often see a trigger—be it viral, inflammatory, or autoimmune in nature—that prompts people to abandon the low-carb diets they once tolerated well. Carbs become a stimulant that the body now uses as a bandaid.

 

 

Adding carbs can mask symptoms or provide short-term relief, but it doesn’t necessarily address what’s truly driving the discomfort, fatigue, or other imbalances. Of course, this is speculative; without seeing Mercola’s personal bloodwork or a full medical evaluation, it’s impossible to know for sure. Similarly, Paul Saladino went down a similar route as Mercola—we believe that Saladino has more root-cause issues at play as addressed here.  

 

What’s clear, however, is that Mercola’s new stance dismisses the success that countless individuals have had reversing metabolic dysfunction with low-carb methods, as well as the mental health side of carb addiction (an aspect he appears to overlook). 

 

And real talk, how many people can eat 500 grams of carbs, stick to only rice and fruits for carbs,  and not suffer from insulin resistance? Mercola is talking to a country where 74% of Americans are classified as either obese or overweight. Know your audience.

 

Potentially relying on his personal anecdote (n=1), he risks making sweeping health recommendations that may not apply to the broader population. Ultimately, only time will reveal whether his drastic dietary change confers lasting benefits—or if it’s simply a short-term fix masking deeper unaddressed health issues. (And getting a bunch of Ray Peat advocates to regurgitate Peat’s research is not evidence-backed data. We’d like to see clinical studies demonstrating optimal health with the near elimination of linoleic acid (PUFAs) and the daily inclusion of 300+ grams of glucose/fructose consumption. It also begs the questions, why don’t most Ray Peat advocates look metabolically healthy? And what really happened to Peat?)

 

P.S. Rice, even when organic, can be problematic for health due to several factors. It is often contaminated with arsenic, a toxic heavy metal found in soil and water, which rice absorbs more readily than other crops. Long-term arsenic exposure is linked to cancer, cardiovascular disease, and developmental issues. 

 

Additionally, rice is prone to mold contamination during storage, which leads to the exposure of mycotoxins, harmful compounds that stress the liver and immune system. Even the proteins in rice, such as prolamins, can mimic the inflammatory effects of gluten for some people, particularly those with gut sensitivities, impairing gut barrier function and contributing to conditions including leaky gut. 

 

Rice is also high in anti-nutrients, such as phytates, which can block the absorption of essential minerals such as zinc, magnesium, and iron, further impairing health. While occasional rice consumption may not pose an immediate risk for everyone, regular or excessive consumption—especially in modern, toxic environments—can compound these effects, contributing to systemic inflammation and overall poor health.

 

Closing Thoughts on Mercola’s Low-Carb Diet Recommendations

Judy Cho’s Perspective: 

Mercola’s recent shift from decades of advocating low-carb, keto lifestyles to vehemently warning against them has rightfully sparked debate in the wellness community. While health insights naturally evolve as research advances, it’s essential to evaluate the reasoning and evidence behind such drastic changes, especially when they contradict years of success experienced by countless individuals who trusted his earlier recommendations. 

 

Blanket statements dismissing low-carb diets fail to account for the nuanced science supporting metabolic flexibility, fat oxidation, and their proven roles in improving chronic conditions such as insulin resistance, inflammation, and neurological decline. 

 

In a country where 74% of the population is overweight or obese and nearly half have prediabetes or diabetes, advocating for a high-carb diet of 500 grams daily—as Mercola now suggests—raises serious concerns about its practicality and risks, particularly for the metabolically unwell and chronically ill. (Frankly, if I’d write this article my way, I’d call it unethical and irresponsible.)

 

It’s worth reflecting on the responsibility held by influential voices in the wellness space. For 20 years, people have followed Mercola’s low-carb recommendations and seen remarkable improvements in their health—many finally escaping chronic pain, reversing metabolic diseases, and avoiding prescription medications. A sudden pivot like this, coupled with fear-mongering against low-carb (including keto and Carnivore) diets, could jeopardize the progress of those who trusted his earlier advice. 

 

Why can’t Mercola share that his new approach works for him personally without tearing down a lifestyle that has transformed the lives of so many others? There’s a saying: “You can grow by building your own empire or by tearing down others’ empires.” This shift feels unnecessarily divisive, particularly in a health space where we should celebrate individual approaches rather than vilify them. We don’t see Carnivore advocates attacking paleo dieters because, at the core, we accept that different diets work for different people.

 

If carbs work for some, that’s great, but for many others, reducing carbs allows them to manage pain, avoid medications, and have a better quality of life. For many, abstaining from all carbs helps them abstain from the darkness of food addictions. (Raising my hand here.) 

 

Why tear down what’s working for so many? 

 

It’s disheartening to see fear-mongering replace nuanced discussion, especially when the chronically ill—the autoimmune sufferers, the insulin-resistant, the metabolically unfit—often lack the flexibility to swing between diets without consequence. In our private practice, we respect individuality in healing and meet people where they are. For many, low-carb and meat-based diets are not simply a preference—they’re a lifeline to living pain-free and thriving. Let’s leave space for people to choose what works for them, free of unnecessary fear and judgment. 

 

I’ll leave you with statistics of the chronically ill community and, frankly, a low-carb, meat-based diet can reverse many of these illnesses. Do you think telling all the Americans affected below that they need to remove all seed oils (or linoleic acid) and eat an abundance of carbs, but mostly rice and fruits, will fix their health issues? Including the children? Make this make sense.

 

 

• Obesity and Overweight: In 2021, 15.1 million children aged 5–14 years and 21.4 million adolescents aged 15–24 years in the U.S. were classified as overweight or obese. Among adults aged 25+ years, 172 million were affected. Health Data
• Childhood Obesity: Obesity among children aged 2–19 years has been increasing over the past two decades and impacting 14.7 million youths. (Ages 2–5 years: 12.7%. Ages 6–11 years: 20.7%. Ages 12–19 years: 22.2%)  CDC Stacks
• Type 2 Diabetes: In adults, type 2 diabetes accounts for 90–95% of all diagnosed cases of diabetes. Nearly 5,300 youth are diagnosed each year. (Not too long ago, type 2 diabetes was called adult-onset diabetes. Now, children are getting this disease that can be managed with diet and lifestyle.) CDC 
• Prediabetes: 97.6 million U.S. adults aged 18+ years had prediabetes in 2021, about 38.0% of the adult population. CDC
• Autoimmune Diseases: Nearly 10% of Americans suffer from an autoimmune disease.
• Chronic Illness in Children: More than 40% of school-aged children and adolescents have at least one chronic health condition. CDC
• Chronic Illness in Adults: 60% of Americans have at least one chronic disease. 40% have at least two or more chronic illnesses. CDC
• Prescription Medication Use: In 2023, the United States spent approximately $449.7 billion on prescription drugs, marking an 11.4% increase from the previous year. Centers for Medicare & Medicaid Services. This expenditure translates to a per capita spending of about $1,564, the highest among developed countries. Statista. More than 66% of U.S. adults use prescription drugs, with utilization particularly high among older individuals and those with chronic conditions. HPI Georgetown
• Prescriptions for Obesity: In 2019 dollars, the estimated annual medical cost of obesity among U.S. children was $1.3 billion. Medical costs for children with obesity were $116 higher per person per year than for children with healthy weight. CDC

 

Know your audience. Empathy goes a long way. 

 

 

Work With Our Trusted Carnivore Diet Functional Medicine Practitioners

The Nutrition with Judy practice is honored to be a trusted carnivore diet practitioner support serving patients from around the globe. We’re passionate about helping our patients achieve root-cause healing in order to lead the best quality of life possible that’s nearly symptom-free. Our team is dedicated to providing the nuanced research you need to make informed health decisions. We welcome you to explore our free resources and are always available to support you through personalized protocols. Our Symptom Burden Assessment (SBA) is the perfect starting point for discovering your root cause and is required to work with our team— you can learn more in-depth about this powerful tool here.