“Diet is a key determinant of healthy aging,” says Dr. Frank Hu, professor and chair of the department of nutrition at Harvard T.H. Chan School of Public Health. “It can influence risk of major chronic diseases such as cardiovascular disease and cancer, which are leading causes of death.”

Several studies have looked at the impact of diet on health and aging, including 2023 research published in JAMA Internal Medicine that explored the long-term impact of different diets on the risks of disease and death.

When it comes to reducing the risk of age-related cognitive decline, chronic disease, or early death, these diets are tops.

Mediterranean diet

Adopting a diet similar to those living in countries that border the Mediterranean Sea has been linked to a host of health benefits, from improved sleep to preventing major cardiovascular events.

The Mediterranean diet emphasizes whole grains, legumes, fruits, vegetables, fish, nuts, and extra virgin olive oil. In addition to being low in sugar and salt, these foods are also low in saturated fat, which is important for cognitive health.

“In the case of the aging brain, saturated fat is thought to be particularly harmful,” says Jennifer Ventrelle, dietitian and assistant professor at Rush University Medical Center.

In contrast, Ventrelle notes that extra virgin olive oil, nuts, and nut butters—all staples of the Mediterranean diet—are high in unsaturated fats and high in vitamin E, polyunsaturated fatty acids, and other polyphenols that have been directly linked to prevention of Alzheimer’s disease in research studies.

DASH diet

The Diet Approaches to Stop Hypertension (DASH) diet was developed in the 1990s to help treat high blood pressure.

Like the Mediterranean diet, the DASH diet emphasizes fruits, vegetables, whole grains, legumes and beans, and nuts and seeds but allows for higher consumption of animal protein, including red meat and eggs. The DASH diet is also lower in fat and sodium than the Mediterranean diet.

Initial research found that the diet helped lower systolic blood pressure, and additional studies have found the DASH diet was also linked to slower epigenetic age acceleration, which indicates that participants who followed the diet were aging slower than their chronological age.

MIND diet

The Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diet is a hybrid of the Mediterranean and DASH diets and shares the recommendations for a diet made up of whole grains and lean meats. 

The biggest difference: The MIND diet prioritizes leafy greens and berries, which are among “the most powerful foods recognized for the effects on brain health,” according to Ventrelle.

A recent study in obese, middle-aged women found that the MIND diet could reverse the impact of obesity on cognition and improve cognitive performance.

“The exciting part about the MIND diet is that even when it was followed only in moderation, the risk for Alzheimer’s disease was shown to be reduced by 35%,” Venterelle adds. “This sends the message that people don’t have to be on strict ‘diets’ to reap the benefits of healthy eating for the brain.”

Alternative Healthy Eating Index

The Harvard-created Alternative Healthy Eating Index (AHEI) ranks foods and nutrients based on their associations with chronic disease and awards a score from zero to 100 based on how often you consume healthy foods. The higher the AHEI score, the healthier the diet. Examples of high-scoring foods include vegetables, fruits, whole grains, tofu, nuts, legumes, and fish.

High scores on AHEI were linked to lower risk of chronic disease, a 40% reduced risk of dying of cardiovascular disease, and a 25% lower risk of all-cause mortality than those with lower scores. It was also one of the diets included in Hu’s JAMA Internal Medicine research found to have a strong association with healthy aging.

“Interestingly, higher scores on…the AHEI were associated with lower risk of death from neurodegenerative disease,” Hu says.

Hydration is key

Researchers at the National Heart, Lung, and Blood Institute (NHLBI) found that higher rates of serum sodium, a sign of dehydration, were linked to greater biological age.

Dehydration forces hormones into overdrive, affecting organs and tissues and triggering accelerated aging, according to Natalia Dmitrieva, Ph.D., NHLBI senior research scientist.

“People already at middle age [with high] serum sodium…were more likely to be biologically older and, later in life, a larger proportion of them developed chronic diseases and died at a younger age,” Dmitrieva says.

Drinking water is an obvious way to stay hydrated, but regular unsweetened plain tea and seltzer also count toward hydration goals.

Choosing the best plan

The nuances of these diets may be different, but they share common approaches to healthy eating, including prioritizing plant-based foods and minimizing ultra-processed foods that are high in sugar and sodium and refined starch. 

When it comes to the best diet for healthy aging, Hu recommends a “flexitarian” approach.

“One does not need to stick to only one dietary approach for their whole life; [you] can switch between these various healthy diets,” he says. “It is helpful for individuals to adapt these healthy eating patterns to their own food and cultural preferences so that they can enjoy the food and stick to the diet over the long run.”