Paleo and Ketogenic Diets on the Brain

Followers of the Paleo diet believe our genes are not evolved to properly digest the foods that have become prevalent since the agricultural revolution, such as grains, sugars, legumes, dairy products, processed oils, salt, alcohol, and coffee. Instead we should eat the way our Paleolithic ancestors did, and fill our plates with fresh fruits and vegetables, nuts, roots, and meat.

No research has yet looked at whether the Paleo diet can prevent cognitive decline or dementia. One study reported the Paleo diet did not improve memory in overweight, post-menopausal women when compared to the national dietary recommendations in Nordic countries (recommendations which include more carbohydrates and less fat/protein than the Paleo diet). On the other hand, preliminary studies indicate that the Paleo diet might improve measures of metabolic health, including triglyceride levels, cholesterol levels, and blood pressure—potential risk factors for Alzheimer’s disease and vascular dementia. But the Paleo diet has not been studied in many people and its long-term effects are unclear. Although it promotes eating healthy foods, some food groups are cut out, and individuals at risk for osteoporosis should avoid the diet since it may lead to calcium and vitamin D deficiency.

Another diet growing in popularity is the ketogenic diet. Initially developed in the 1920s as a potential therapy for children with difficult-to-treat epilepsy, the ketogenic diet is high in fats, very low in carbs, with moderate protein. Usually, carbohydrates are our brain’s primary energy source but ketone molecules generated from fats are also a potential source of fuel. The brains of patients with Alzheimer's disease start to lose the ability to use carbohydrates but may still be able to use ketones.

When Alzheimer's disease mouse models are given a ketogenic diet, they may perform better on some cognitive tasks, even though their brains don’t have lower levels of amyloid beta or tau, the misfolded proteins common in Alzheimer's disease patients. Although no study has tested the effect of the ketogenic diet in Alzheimer's patients, one small study suggested that overweight elderly individuals with age-related memory decline performed better on memory tasks after six weeks on a low carbohydrate diet.

The ketogenic diet is not without its own concerns, however. If you eat few carbohydrates, you may miss out on important nutrients found in carbohydrate-rich foods such as fruits and vegetables. This is especially concerning in elderly individuals, particularly Alzheimer's patients, who may be at greater risk for anorexia and frailty. In addition, low-carb diets may also increase your risk of high cholesterol, kidney problems, and osteoporosis. A different question is whether foods that are readily converted to ketones can prevent dementia. Our report on medium-chain triglycerides provides more information.

Though the Paleo and ketogenic diets are growing in popularity, there is not much data available to suggest they improve brain health. If you are planning your diet for long-term cognitive vitality, stronger evidence for benefit is available for the Mediterranean, MIND, and DASH diets. See our previous blog post for more information on these options.

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