Adverse Effects of the Ketogenic Diet

Adverse Effects of the Ketogenic Diet

adverse Effects of the Ketogenic Diet

They say an apple a day keeps the doctor away, but what happens when you’re on the ketogenic diet and you’re avoiding high-carbohydrate fruits like the plague? An adverse effect is an unwanted or harmful effect that is the result of an intervention.

Interventions can include medication, surgery, and diet. The ketogenic diet has grown significantly in popularity in recent years. While the ketogenic diet has numerous benefits to health, the ketogenic diet does not come without potential adverse effects.

Like all dietary regimes, what is the correct course of action for one does not necessarily mean that it is the right course of action for another. The following are the most common, and serious adverse effects known about the ketogenic diet.

Micronutrient Deficiencies

The classic ketogenic diet is a high-fat, moderate protein, carbohydrate restricted diet that forces the body into a state of ketosis. Fat comprises 80-90% of the calories of the diet, while the remaining calories are first allocated to the necessary protein requirements of the individual and secondly to carbohydrate.

In one study, a 3-day planned ketogenic diet with a 4:1( fat: non-fat ratio) was analyzed for micronutrient content. Nutrient-dense foods were purposely selected for this study to optimize results.

The Dietary Reference Intakes (DRI) published by the Institute of Medicine, National Academies of the US were utilized as standard goals for micronutrient intake.

However, of the 24 micronutrients evaluated, 19 were below the DRI. Of the 19 nutrients below the DRI, 11 nutrients were provided at less than 50% of the DRI: Thiamin, Folate, Pantothenic Acid, Calcium, Copper, Iron, Magnesium, Manganese, Molybdenum, Selenium and Zinc.

In addition, the omega-3 and omega-6 fatty acids were provided at 11% and 70 % of the DRI respectively [1].  Most astonishingly, a selection of less nutritionally dense foods would have resulted in even lower intakes of these nutrients.

The ketogenic diet provides sub-optimal levels of many micronutrients and of essential fatty acids required as determined by the DRI standards.

Thus, the ketogenic diet may lead to micronutrient deficiency, and supplementation with vitamins and minerals is recommended. Inclusion of dietary sources of omega-3 and omega-6 fatty acids is also recommended or supplementation if this cannot be achieved in the diet. Or, a modified ketogenic diet that includes greater carbohydrate intake may be warranted.

Adverse Effects on Lipids

Lipids may increase in ketogenic diets and should be monitored. A study of serve et al. [1] He found a significant increase in total cholesterol in fasting at 3 and 6 months in the diet, with an average cholesterol increase of 208 mg/dL (range, 120-304) at 291 mg/dL (220-395).

Triglycerides also increased at 3 months from the mean of 190 mg/dL (41 – 542) to 203 mg/dL (68 – 417), and then stabilized [2]. The extension of this study continued to show a significant increase in total cholesterol and cholesterol/HDL ratio at the time of diet disruption after up to 35 months of diet [3].

If extreme lipid changes occur, it may justify the interruption of dietary therapy [4]. However, it should be noted that elevated lipids are not present in all patients or in all studies, and triglycerides and LDL may not change [5].

Lipids also increase in MAD [6], although the final lipid levels in some studies were maintained within the average cardiovascular risk ranges [7]. A study of the MAD actually found a decrease in triglycerides with the treatment of the ketogenic diet in 12 months [8 ].

It is worth noting that lipids can increase during the initial phase of the diet, and then return to baseline: A study of 37 adults with MAD for at least 3 months found that while total cholesterol and LDL had increased by 3 months, there was no difference with respect to the beginning after 1 year (p = 0.2 YP = 0.5, respectively) [9].

In addition, in the case of hypercholesterolemia, it can still be manageable without interrupting dietary therapy. A patient whose LDL doubled after 3 months continued the MAD, and with carnitine supplementation (and replacement of saturated fats with polyunsaturated fats) their cholesterol and LDL returned to the normal ranges. [10].

Carnitine supplementation also successfully reduced elevated triglycerides in three other patients [11].  Thus, carnitine supplementation may improve the ketogenic diet’s adverse effects on lipids.

Hormonal Effects of the Ketogenic Diet

Menstrual irregularities and cessation of menstruation are common in the state of starvation. Since the ketogenic diet is designed to mimic starvation, it is not surprising that it may also cause menstrual irregularity. Barborka et al reported in 1930 than 21% of women had stopped menstruation during the treatment of ketogenic diet.

However, in the seven that interrupted the diet, normal menstruation was resumed [12].  In the 1999 Sirben et al study, nine women (100%) developed menstrual irregularities (irregular cycles or cessation of menstruation), which were resolved with the interruption of the diet [13].

Menstrual irregularities were also frequent in the study of Mady et al. In 2003 on the ketogenic diet (45% of the women) [14].

However, menstrual irregularities appear to be much less common in a modified ketogenic diet, and no menstrual irregularities were found in any of the 19 women in the study [15]. None were reported in nine women in a second study [10], and only 1 of 17 women in a third study [16].  

Adverse Effects of the Ketogenic Diet on Children

Although these adverse effects of the ketogenic diet mentioned above are the most common in adults, it is known that there are other less common adverse effects of the ketogenic diet in children, which justifies additional considerations for Long-term adherence to a ketogenic diet for children and adults alike.

In a 2011 study comparing the short-term (8 months) versus the long-term (> 24 months), Kang HC et al., they found that there were no significant differences in the tendency to relapse, correlated EEG findings, and development outcome data among two groups studied for untreatable infantile spasms [17].

The study found that of the short-term group of 8 months, 37.5% experienced nausea/vomiting, diarrhea/constipation, and 50% experienced hypertriglyceridemia, 31%  hypercholesterolemia, 31%  hepatitis, 10% osteopenia.

However, in the 2-year long-term group, 41% experienced nausea/vomiting, diarrhea/constipation, 33%  hypertriglyceridemia, 29% hypercholesterolemia, 25% hepatitis, and 20% osteopenia. Therefore, serious complications such as osteopenia, hepatitis, ureteral calculi, and growth failure occurred significantly only in the long-term test group compared to the short-term group (p > 0.05).

Indeed, the usefulness of the ketogenic diet for 8 months may well be justified, however, prolonged treatment with KD may give similar results, but with more serious complications. More research is needed on the long-term effects of the ketogenic diet on children.

Adverse Gastrointestinal Effects 

Gastrointestinal side effects are common, as half of the patients report some nausea, constipation, abdominal distention, or vomiting at some point in ketogenic dietary therapy.

However, these symptoms are usually resolved after the first few days or weeks of treatment with the ketogenic diet [181920]. As indicated in these studies, it was rare that patients could not continue with the treatment of ketogenic diet due to nausea, constipation or vomiting. However, the patients involved in these studies did not continue with the treatment of the ketogenic diet for more than a period of 9 months.


While research on the ketogenic diet has shown numerous positive effects, potential adverse effects also deserve attention and consideration from those who have opted for the popular diet both for purposes of weight loss and metabolic improvements, as for the treatment of neurological disorders.

While all diets should be performed under the supervision of a doctor, the ketogenic diet may require more observation than other diets to ensure that these more serious adverse effects are well managed.



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