The role of diet in mental health
Mental health and cognition are affected by countless factors but in some cases, diet choices can help achieve a difference or lower the risk. A vegan diet that’s naturally high in antioxidants, fibre and low in saturated fats seems to be able to lower the risk of cognitive decline and neurodegenerative diseases.
In a study of dietary habits and cognitive function, Eskelinen et al. (2011) found that people whose mid-life diets were characterised as healthy (high in plant-based foods, low in saturated fats, etc.) had a decreased risk of dementia and Alzheimer’s disease later in life compared with people with unhealthy diets. The difference was staggering - persons who ate the healthiest had an 86-90 per cent decreased risk of dementia and a 90-92 per cent decreased risk of Alzheimer’s disease compared with people whose diet was the least healthy.
Another long-term study with a similar design following participants for 20-30 years revealed that people with higher cholesterol levels in mid-life have a significantly higher risk of Alzheimer’s disease (1.5 times higher for people with high cholesterol) and dementia (1.5 times higher risk for people with increased cholesterol levels) later in life (Solomon et al., 2009).
Apart from genetic and age-related factors, the risk of Alzheimer’s disease is also increased by elevated blood lipids, blood pressure and diabetes. At the International Conference on Nutrition and the Brain in Washington (USA) in 2013, experts in the field were asked to draw and comment on evidence-based guidelines for the prevention of Alzheimer’s disease (Barnard et al., 2014). They agreed on the following:
1. Minimise your intake of saturated fats and trans fats. Saturated fat is found primarily in dairy products, meats, and certain oils (coconut and palm oils). Trans fats are found in many snack pastries and fried foods and are listed on labels as “partially hydrogenated oils.”
2. Vegetables, legumes (beans, peas, and lentils), fruits and wholegrains should replace meats and dairy products as primary staples of the diet.
3. Vitamin E should come from foods, rather than supplements. Healthful food sources of vitamin E include seeds, nuts, green leafy vegetables, and wholegrains. The recommended dietary allowance (RDA) for vitamin E is 15 mg per day.
4. A reliable source of vitamin B12, such as fortified foods or a supplement providing at least the recommended daily allowance (2.4 mg per day for adults), should be part of your daily diet. Have your blood levels of vitamin B12 checked regularly as many factors, including age, may impair absorption.
5. If using multiple vitamins, choose those without iron and copper and consume iron supplements only when directed by your physician.
6. Although aluminium’s role in Alzheimer’s disease remains a matter of investigation, those who desire to minimise their exposure can avoid the use of cookware, antacids, baking powder, or other products that contain aluminium.
7. Include aerobic exercise in your routine, equivalent to 40 minutes of brisk walking 3 times per week.
Although it’s the diet as a whole that matters, berries in particular have been shown by independent long-term studies to have a protective effect due to their high flavonoid content. Flavonoids are a group of natural compounds found only in plants, they have antioxidant properties and might be neuroprotective. In one of the long-term studies, nearly 130,000 participants were followed for over 20 years. At the end of the study, scientists analysed the data and found that those who consumed the most berries had significantly lower risk of developing Parkinson’s disease (Gao et al., 2012). Another study followed over 16,000 people, also for over 20 years, analysed their diets and measured cognitive function (Devore et al., 2012). The results showed that high intake of flavonoids, especially from berries, slowed rates of cognitive decline.
More and more studies are now linking mental and physical health, as illustrated above, many dietary risk factors that can contribute to cardiovascular disease, diabetes and other chronic diseases can also increase the speed of cognitive decline. Although we don’t know the precise mechanisms of how exactly the nerve system is affected by diet, we now know that a diet based on plant foods can be protective and reduce the risk of neurodegenerative diseases.