Some studies show flavonoids may improve brain health, by blocking neurotoxicity in the brain, which is associated with Alzheimer’s disease.
After following the diets of 50,000 people for more than 20 years, Tian-shin Yeh, research fellow in epidemiology at Harvard TH Chan School of Public Health, found that those who eat more flavonoid-rich foods, including oranges, peppers, celery, and grapefruit, have lower levels of cognitive decline and dementia.
While there’s currently no cure for dementia and cognitive impairment in later life, Yeh says that eating more flavonoid-rich foods can help to lower the risk. However, participants who saw the most benefits were those who’d consistently been eating a flavonoid-rich diet for 20 years.
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Eating a colourful diet, Yeh says, can also help people avoid possible adverse effects of eating too much of one food.
“Food is very complex. For example, research has found that orange juice is associated with a lower risk of cognitive decline, but too much intake is associated with type 2 diabetes,” she says. Although, this is because of its sugar content, not flavonoids.
But eating a rainbow diet may also be complex, says Victoria Taylor, a senior dietitian at the British Heart Foundation.
“It could be really tricky to get every colour every day – you could tie yourself in knots,” she says.
We also need to eat from other food groups to get all the macronutrients we need, such as protein, she says.
However, Minich argues that the rainbow diet isn’t limited to fruit and vegetables, but includes other natural foods, such as herbs, spices, legumes, nuts, seeds, wholegrains, and even tea. She also considers white food as part of the rainbow diet, including tofu, which contains numerous different isoflavones, which have been associated with a lower risk of heart disease and some cancers, as well as cognitive decline.
Eating a variety of colours could mean we eat more fruit and vegetables overall. One study found that prompting people to eat a colourful meal increased their consumption of healthy food.
“If you’re eating the same fruit, you’ll become satisfied, but if you have a plate of different fruit and vegetables that vary in colour, you’re likely to want eat for longer,” says Rochelle Embling, PhD student at Swansea University, who wasn’t involved in the study.
“This effect is specific to the food being eaten, so after a meal, dessert remains desirable because it has different sensory characteristics,” Embling says.