The Risks of the Keto Diet

A recent review has questioned the short- and long-term benefits of a ketogenic, or “keto,” diet. The review, published in 2021 in the journal Frontiers in Nutrition, examined the effects and risks of keto diets on diet quality and several common chronic diseases. The authors conclude the long-term risks may outweigh the short-term benefits.

A keto diet is one that is very low in carbohydrates, modest in protein, and high in fat, with a dietary fat to combined dietary protein and carbohydrate ratio of 4:1 or 3:1. When carbs are in short supply in the body, a process called ketosis occurs by which protein and fat are broken down into energy rather than carbs. Practitioners monitor adherence to the diet most often with a urine test.

For ketosis to occur, a patient’s carbohydrate intake must be very low. As a result, diet quality can be affected. A patient on a keto diet needs to curtail or eliminate fruits, vegetable, whole grains, and legumes, while increasing the intake of animal proteins. The results are deficiencies in vitamins, minerals, fiber, and phytochemicals. The reduction in fiber affects intestinal function, nutrient absorption, immune function, and gut permeability. These deficiencies may not be completely negated by taking dietary vitamins and supplements.

For the 30% of patients with epilepsy that cannot eliminate seizures with medication, a keto diet has been shown to reduce seizure frequency in up to half of such patients. It is believed that the lack of glucose available to fuel neurons in a keto diet benefits the epilepsy sufferer. However, staying on a keto diet long-term is challenging because of limited food choices and the potential long-term health risks.

The authors of the review examined many studies and metadata analyses comparing keto diets to other diets for weight management and obesity. While there was considerable variability between individuals and between studies, some studies showed keto diets led to initial rapid weight loss, but it was not sustainable. Overall, keto diets were not seen as more effective for obesity and weight management than other diets with lower risk profiles.

The review also looked at the effects of a keto diet on several other chronic conditions. Key findings included:

• For adults with type 1 diabetes, a comprehensive study strongly recommended against sustained use of a keto diet.
• The benefits of the diet for people with type 2 diabetes appear to wane over time.
• A keto diet may increase the risk of developing non-alcoholic fatty liver disease.
• Researchers have theorized that by nearly eliminating available glucose with a keto diet, it could be used by cancer patients to stress the cancer cells. However, large, well-designed clinical trials are needed to determine the safety and effectiveness of keto diets as a cancer treatment.
• The intake of foods high in unsaturated fats and red and processed meats typical in a keto diet have been linked to an increased risk of diabetes, cancer, and Alzheimer’s disease. In addition, the limited intake of fruits and vegetables is a diet profile associated with increased risks of developing Alzheimer’s disease and cancer, and overall mortality.
• Low carbohydrate diets, like the keto diet, are associated with increased LDL-C (“bad cholesterol”) across numerous studies.
• The increased intake of animal proteins in a keto diet may lead to patients developing chronic kidney disease, and those with chronic kidney disease have an increased risk of developing kidney stones.
• Low-carbohydrate diets, like the keto diet, followed by women up to a year prior to conception, and immediately before and after conception are associated with an increased risk of birth defects of the brain, spine, and spinal cord, and gestational diabetes, respectively.