Eat smart: the best foods to boost your brain health
We know we need our fruit and veg. Research shows they help ward off cognitive decline, but some are better than others.
If you find you are more prone to forgetfulness with advancing years, a brain-boosting diet packed with brightly coloured fruits and vegetables could help to curb mild cognitive decline. In a study published recently in the journal Neurology scientists from Harvard University reported that people with the highest intake of flavonoids — powerful antioxidant plant compounds — were 19 per cent less likely to report confusion and forgetfulness as they got older, but also that some fruits and vegetables are better for the brain than others.
Flavonoids are found in a wide range of plant produce, including apples, berries, onions and dark chocolate, as well as in plant-based drinks such as tea and red wine. They are known to reduce inflammation in the body, which underlies many health problems. It is also thought that they may play a role in slowing cognitive decline as we age.
For the study Dr Tian-Shin Yeh, a researcher in the department of epidemiology and nutrition at the Harvard TH Chan School of Public Health and a senior author of the paper, used data from two large studies involving 46,693 women and 51,529 men to calculate intake of a range of flavonoids including flavones, found predominantly in yellow or orange fruits and vegetables, and anthocyanins, found in berries.
They tested participants’ level of subjective cognitive decline by assessing whether they had trouble remembering things from one second to the next or remembering recent events; could recall a short list of items; follow a group conversation and a set of spoken instructions; had difficulty finding their way around local streets; and if they had noticed any changes in their ability to remember and recall events. After controlling for factors such as age, alcohol intake, weight and activity, as well as other nutrients in the diet, it became clear that fruits and vegetables played a key role in offsetting memory loss.
Best cognitive function was seen in those with consistently high intakes of flavonoid-rich foods over the study’s two-decade follow-up, but it was also observed that the younger you are when you start eating them, the better. However, Yeh says that you can still reap benefits whenever you increase your intake. “We found improved cognitive function whether you consumed flavonoids 20 years ago or more recently, for example six years prior to the cognitive function assessments we carried out,” she says. “This may suggest that it’s never too late to start incorporating these fruits and vegetables into your healthy diet.”
When Yeh and her team looked at specific flavonoids, they found that flavones had the strongest protective qualities and were associated with a 38 per cent reduction in the risk of cognitive decline, while anthocyanins were associated with a 24 per cent reduction. Strawberries, spinach and onions were among the specific flavonoid-containing foods that topped the list of scores in the memory questionnaire. But the list is comprehensive and the more brain-protective foods you can pack into your diet, the better. “People in our study who did the best over time ate an average of at least half a serving per day of flavonoid-rich foods,” Yeh says, “although five or more fruits and vegetables on a daily basis with a wide variety may be good for our overall health, including brain health.”
Their advice is to consume fruits and vegetables as close to their natural state as possible. Any form of processing has been shown to diminish flavonoid content, with boiling causing leaching of the phytonutrients into water that is discarded.
It’s a step even the researchers themselves have taken. Walter Willett, a professor of epidemiology and nutrition at Harvard TH Chan School of Public Health and one of the co-authors of the new study, says that he has long eaten a daily bowl of berries but has “now added a glass of orange juice for breakfast each morning”. Yeh says that she eats about two servings of the brain-boosting fruits and three servings of the vegetables, including spinach, celery, peppers and onions, daily but has made a concerted effort to increase her flavonoid intake on the back of her findings. “I have increased my consumption of citrus, citrus juice, berries and peppers after seeing the results of our study,” she says. “Incorporating these healthy food choices and doing it in the long run would be great for brain health.” Here are their picks of the bunch.
STRAWBERRIES
You could do far worse for your brain than eat some strawberries several times a week. With about 180mg of total flavonoids per 100g serving, the fruit ranked as one of the best brain-boosting foods in the Harvard study. Yeh says that fisetin, one of the flavonoids in strawberries, has a powerful neuroprotective action. It’s not the first time the fruit has been hailed for its cognitive protection. Last year a study of 2,800 people aged 50 and older by nutrition scientists at Tufts University’s Human Nutrition Research Center on ageing showed that a low intake of anthocyanins from blueberries and strawberries was associated with a fourfold increased risk of developing Alzheimer’s disease and related dementias over 20 years.
BLUEBERRIES
Blueberries, which have about 164mg of anthocyanins per 100g serving and are also rich in proanthocyanidins, another flavonoid source, ranked highly in the Harvard study. Researchers at the University of Exeter found that healthy people aged 65 to 77 who drank 30ml of concentrated blueberry juice – providing the equivalent of 230g of blueberries – every day for 12 weeks showed improvements in cognitive function compared with those who took a placebo drink. According to the study leader, Professor Joanna Bowtell, the head of sport and health sciences at the University of Exeter, MRI scans taken before and after the test period revealed “brain blood flow, brain activation and some aspects of working memory were improved” in the blueberry group.
CHERRIES
There is evidence that consumption of cherries provides a brain boost in older adults, with one trial published in the journal Food & Function showing that a daily intake of Montmorency tart cherry juice improved memory scores in adults aged 65 to 80. Researchers at the University of Delaware asked participants to consume 480ml of cherry juice or the same amount of a placebo drink, half in the morning and half in the evening, every day for three months. Results showed that the cherry group displayed a 5 per cent increase in satisfaction with their ability to remember things and a 23 per cent reduction in errors made in a visual memory task.
CAPSICUM
Green, yellow and red capsicum are a rich source of flavonoids, antioxidants and carotenoids, all of which can help to boost brain health and, according to scientists from Mahidol University in Thailand, are useful in the fight against Alzheimer’s. Yeh says that, partly because people tend to add them to cooking, peppers were “one of the top food contributors of flavones in our study”.
ORANGES
Oranges contain about 43mg of flavonoids per 100g and are particularly rich in flavanones. Even orange juice counts. Juicing doesn’t greatly affect phytonutrient content and a glass can contain higher amounts than the flesh alone if peel and pith are added too. In a previous study on men, conducted in 2019, some of the Harvard team showed that those who regularly drank orange juice were 47 per cent less likely to develop poor thinking skills than the men who drank less than one serving a month. A total of 6.9 per cent of older men who drank orange juice every day developed poor cognitive function, compared with 8.4 per cent of men who drank it less than once a month. Yeh says there is a caveat – it contains relatively high amounts of sugar, so one glass a day is enough. “Although orange juice was associated with lower risk of subjective cognitive decline in our study, high intakes have been associated with higher risks of type 2 diabetes,” she says. “A variety of fruits and vegetables, including some orange juice, is the best approach.”
APPLES AND PEARS
Apples contain about 113mg of flavonoids and pears 40mg per 100g serving. While the Harvard team found that eating just one pear or half an apple a day made some difference to cognition if eating in addition to other flavonoid-rich foods, they reported that the more eaten, the better the improvements. A low intake of flavonols in apples and pears – that meant eating only one and a half apples or pears a month – was associated with twice the risk of developing Alzheimer’s by the Tufts researchers, whereas eating at least eight apples and pears a month provided the level of flavonols needed for brain protection.
SPINACH
According to the Harvard research, just two heaped tablespoons of cooked spinach were enough to help to prevent mental decline, but adding the raw vegetable to salads provides an extra boost of flavonoids. Like other leafy greens, spinach is rich in other brain-healthy nutrients such as vitamin K, lutein, folate and beta carotene. Studies of 960 older adults at Rush University in Chicago found that one serving (100g) of cooked spinach a day can help to slow age-related cognitive decline and that people who ate one to two servings daily had the cognitive ability of a person 11 years younger than those who consumed none.
ONIONS AND GARLIC
Renowned as a prebiotic that can keep your gut healthy, onions are also a brain food, partly because of the high content of a flavonoid called quercetin. Researchers have shown that a regular intake of quercetin-rich onions improves cognitive function and helps to prevent dementia in elderly people. Garlic should also be added to your cooking. It has been suggested that a compound it contains called allyl sulfide may help to counteract age-related changes in gut bacteria associated with memory problems, while a review published last year found that garlic extract, an odourless product available in supplement form, can help to slow age-related cognitive decline and memory loss.
BRUSSELS SPROUTS AND CAULIFLOWER
A high consumption of cruciferous vegetables such as cauliflower and brussels sprouts, both rich in flavonoids, was associated with lower levels of cognitive decline in a group of older women in one study. Cauliflower also contains an essential nutrient called choline, which plays multiple roles in the body, including creating neurotransmitters that allow brain processes such as learning, reading and memory to take place. Yeh’s advice is to not eat brussels sprouts every day. “Although they were up there with lower odds of subjective cognitive decline, we have seen adverse associations with other outcomes when it comes to brussels sprouts, so we suggest being cautious about very high intakes of them,” she says. “As wide a range of flavonoid-rich vegetables as possible is your best bet.”
The Times
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