We’re often told to eat more fruits and vegetables—and for good reason. Many of the nutrients found in fruits and vegetables are responsible for important health benefits, in particular preventing a wide range of diseases, including heart disease and diabetes.
A growing body of evidence even suggests that flavonoids, a group of compounds found in almost every fruit and vegetable—including tea, citrus fruit, berries, red wine, apples, and legumes—can actually reduce your risk of developing certain cancers, heart disease, and stroke. Now, recent evidence suggests that diets high in flavonoids can lower your risk of dementia.
Flavonoids are thought to lower cancer risk by making malignant cancer cells less able to divide and grow. They also act as antioxidants, which can prevent or slow damage to cells caused by unstable molecules. They even reduce inflammation in the body, which is a common feature of many chronic diseases. Most of these mechanisms explain the health benefits reported in animal or cell-based studies. The data from these studies can reveal how flavonoids work on the human body as well.
However, previous studies using animal or cell models don’t necessarily translate to people. In humans, even when diets are high in flavonoids, these aren’t always readily absorbed into the gut. Flavonoids are also difficult to study as they belong to a very diverse group of chemical compounds. Not much is known about how they are metabolized after being consumed, or their potential to enter and act in certain tissues of the body, such as the brain.
We know that Alzheimer’s disease is associated with a number of factors, including genetics, family history, aging, environmental factors, health conditions (particularly obesity and diabetes), race, and sex. This is why predicting and preventing the disease is often difficult.
But several studies suggest that consuming flavonoid-rich diets can help manage some of the symptoms of Alzheimer’s disease and benefit cognitive ability. Which perhaps is not surprising, as dementia is linked to chronic diseases such as diabetes, cardiovascular disease, and stroke. Flavonoids have been shown to help manage and prevent these diseases.
Until now, studies have struggled to pinpoint which flavonoids make the difference. This latest study has been able to show which flavonoids are linked with lower risk of dementia.
Alzheimer’s and diet
The recent study published in The American Journal of Clinical Nutrition is one of the most detailed to date.
Researchers followed 2,801 subjects between the ages of 28 and 62 over a period of 19.7 years. Participants had their consumption of flavonoids measured throughout. These numbers were also statistically adjusted if participants changed the amount of flavonoids they ate on average during the study.
The researchers found that higher long-term dietary intake of flavonoids is associated with lower risks of dementia in American adults.
Given the complexity of flavonoids, the authors looked at the effect of different types of flavonoids in the diet. They found those eating a higher amount of three classes of flavonoids (specifically flavonols, anthocyanins, and flavonoid polymers) had lower risk of dementia. Flavonols and anthocyanins had a similar association with Alzheimer’s specifically.
The foods they looked at included orange juice, tea, oranges, apples, blueberries, pears, and strawberries. Tea, apples, and pears were common sources of flavonols and flavonoid polymers. Anthocyanins are found in berries and red wine.
However, these types of studies can be affected by many variables in the sample study. These include a wide range of population factors, known as “confounders,” that have to be accounted for, as they can impact the reported results. Confounders can include anything from social status, gender, race, to weight or occupation.
The study accounted for several confounders including age, sex, education level, energy intake, smoking, cholesterol levels, hypertension, genetics, and diabetes. They were able to show that regardless of these confounders, eating a diet rich in flavonoids over your lifetime helped reduce Alzheimer’s risk.
Though this study doesn’t explain why flavonoids have this beneficial effect on Alzheimer’s disease, it’s clear that high, long-term dietary intake of a wide range of flavonoids is associated with lower risks of dementia in adults. However, it doesn’t claim flavonoids cure dementia, nor will consuming flavonoids on their own prevent it.
Eating foods high in flavonoids will be even more beneficial alongside other lifestyle changes, such as quitting smoking, managing a healthy weight, and exercising.
is an academic associate at the Cardiff Metropolitan University in Whales, and is a professor of biomedical sciences and biostatistics at the Cardiff Metropolitan University. This article was first published on The Conversation.