Researchers from the University of Barcelona in Spain followed nearly 850 French citizens over the age of 65 for more than a decade. Participants were split fairly evenly between women and men, and all were dementia-free at the start of the study. They monitored a panel of biomarkers—like healthy omega-3 fatty acids EPA and DHA, found in foods consumed on the diet—every few years and performed five neuropsychological evaluations on each participant during the course of the study.

Those who closely followed the plant-based diet, rich in healthy fats—as evidenced by results of blood tests, not participant-completed food diaries or questionnaires—were less likely to experience cognitive decline as they aged.

Previous studies have examined the relationship between the diet and cognitive decline and produced mixed results, perhaps because participants didn’t accurately recall and/or report what they ate, researchers hypothesized. That’s why they opted to monitor diet adherence with biomarkers—an objective, versus subjective, approach.

The research is “a step forward towards the use of more accurate dietary assessment methodologies,” Mercè Pallàs, professor of pharmacology at the university’s Neurosciences Institute, said in a news release about the findings, published last year in Molecular Nutrition & Food Research.

The study indeed “echoes previous studies that have shown that following a Mediterranean style diet is associated with healthy brain aging,” Caroline Susie, a registered dietitian, tells Fortune. “While there is no proven way to prevent dementia and cognitive decline, following this diet is associated with lower risk of cognitive decline.”

What is the Mediterranean diet?

This plant-based way of eating—with roots in ancient Roman and Greek tradition and the cuisine of the Middle Ages—was studied and solidified in the 1950s. It focuses on consuming a variety of healthy foods, including:

• Vegetables
• Fruit
• Beans
• Lentils
• Nuts
• Seeds
• Potatoes
• Whole grains
• Extra virgin olive oil, a healthy fat
• Herbs and spices (in lieu of salt)

The following foods are allowed in low to moderate amounts:

• Dairy
• Eggs
• Fish, which contain healthy omega-3 fatty acids
• Poultry
• Wine with meals (if you don’t drink, don’t start)

The following foods are to be avoided:

• Red, fatty, and/or processed meats
• Sweets
• Salt
• Highly processed foods
• Refined carbohydrates
• Saturated fats
• Butter
• Sugary drinks

While dubbed a “diet,” it focuses on general guidelines as opposed to a strict method of eating and should be accompanied by daily physical exercise. Sharing meals with family and friends is also encouraged.

Those who choose to go Mediterranean should “opt for fruits, vegetables, nuts, seeds, olive oil, beans, whole grains, and olive oil,” Susie says. They should also aim for two servings of fish per week, and to keep active.

What are the benefits of a Mediterranean diet?

In addition to apparently lowering the risk of cognitive decline with age, the diet offers a wide variety of health benefits, including:

• Lowering the risk of heart disease, metabolic syndrome, and some cancers
• Supporting healthy body weight, blood sugar, blood pressure, and cholesterol
• Balancing gut microbiota
• Increasing life expectancy

That’s because of its numerous healthy aspects, including:

• Limited saturated and trans fats
• Limited sodium
• Limited sugar
• Increased healthy unsaturated fats
• Increased fiber and antioxidants

Micronutrients are ‘strikingly lower’ in Alzheimer’s brains

Levels of five micronutrients often found in Mediterranean diet foods are “strikingly lower” in the brains of those who have Alzheimer’s disease, compared with those who don’t, according to a study published this fall that analyzed the brains of 31 donors, the average age of which was 75 years. 

Most, but not all, had died with Alzheimer’s disease. Compared with unaffected brains, the researchers found that brains of those with the disease had around half the level of the following micronutrients—vitamins and minerals critical to the body’s function, but needed in only small amounts:

• Lycopene: An antioxidant that could help protect cells from damage, lycopene gives some fruits and vegetables—like tomatoes, watermelon, red oranges, pink grapefruits, apricots, and guavas—their red hue.
• Retinol: A form of vitamin A that helps the immune system work properly, retinol helps you see in dim lighting and keeps skin healthy. It’s found in foods like cheese, eggs, oily fish, milk, yogurt, and liver. Indirect sources include yellow, red, and green leafy vegetables like spinach, carrots, sweet potatoes, and red peppers, in addition to yellow fruits like mangoes, papaya, and apricots.
• Lutein: Often referred to as the “eye vitamin,” lutein is thought to protect eye tissue from sun damage. You can find it in foods like egg yolks, spinach, kale, corn, orange peppers, kiwis, grapes, zucchinis, and squash.
• Zeaxanthin: An antioxidant, zeaxanthin is known to protect eye tissues from the sun. It’s found in eggs, oranges, grapes, corn, goji berries, mangoes, and orange peppers.
• Vitamin E: Also an antioxidant, vitamin E keeps free radicals in check, improves immune function, and can prevent clots from forming in the arteries of the heart. It can be found in plant-based oils, nuts, seeds, fruits, and vegetables like sunflower oil, soybean oil, almonds, peanuts, spinach, pumpkin, red bell peppers, asparagus, mangoes, and avocados. 

Multiple studies have also found that those who follow MIND (Mediterranean/Dietary Approaches to Stop Hypertension Diet Intervention for Neurodegenerative Delay)—which emphasizes the consumption of antioxidant-rich fruits, vegetables, legumes, nuts, and fish with very little meat, dairy, and sweets—had a lower risk of developing Alzheimer’s disease, better cognitive function prior to death, and fewer signs of Alzheimer’s disease in those who did develop the condition.

“This study, for the first time, demonstrates deficits in important dietary antioxidants in Alzheimer’s brains,” Virginia Tech Carilion School of Medicine professor C. Kathleen Dorey said at the time, in a news release about the study.

“We believe eating carotenoid-rich diets will help keep brains in top condition at all ages,” she added.