Scientists explain how eating a rainbow of foods reduces your risk of chronic disease

Scientists explain how eating a rainbow of foods reduces your risk of chronic disease

What's the simple secret to living longer and reducing your risks of heart disease, diabetes and cancer? If you mix up your daily fruits, vegetables and teas, a comprehensive study suggests.

Study:High diversity of flavonoid dietary intake is associated with a lower risk of all-cause mortality and major chronic diseases. Photo credit: Marilyn Barbone/Shutterstock.com

A recently published study in the magazineNatural foodhighlights the importance of consuming a variety of dietary flavonoids to reduce the risk of chronic disease and all-cause mortality.

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Flavonoids are polyphenolic compounds present in the human diet. These compounds are found in various foods and drinks, including vegetables, fruits, nuts, legumes, wines and tea.

Several flavonoids are present in various foods and beverages among classes of flavonoids, including flavonols, anthocyanins, flavan-3-OLs, flavanones, and flavones. Due to variations in their chemical structure, bioavailability and metabolism, these subclasses have a range of biological effects.

The most prominent and well-documented properties of various flavonoids are antioxidant, anti-inflammatory, anticancer and cardio-protective properties, which are crucial for reducing the risk of chronic diseases and related mortality.

Some flavonoids have more specific functions, such as promoting endothelial function, delaying age-related tissue deterioration, and exerting anti-proliferation effects related to cancer prevention.

Given that different flavonoids have different biological effects, the current study was designed to evaluate the effects of consumption of a variety of dietary flavonoids on the risk of major chronic diseases and all-cause mortality.

The study population included 124,805 participants from the UK Biobank, a large population-based cohort study involving over 500,000 participants.

Participants were adults aged 40 or older, with an average age of approximately 60 years. Over a follow-up period of 8.7-10.6 years, researchers recorded incidences of mortality and chronic diseases, including cardiovascular disease (CVD), type 2 diabetes, cancer, respiratory diseases and neurodegenerative diseases.

Impact of total flavonoids on chronic diseases and all-cause mortality

After adjusting for sociodemographic, lifestyle, nutritional and medical risk factors, the study found that both the amount and diversity of flavonoids in a person's diet were independently associated with a lower risk of several chronic diseases and reduced all-cause mortality.

Specifically, participants with the highest diversity of flavonoid intake showed a 14% lower risk of all-cause mortality, a 10% lower risk of cardiovascular disease, a 20% lower risk of type 2 diabetes, an 8% lower risk of cancer, and an 8% lower risk of respiratory disease.

No association was observed between flavonoid diversity and the risk of neurodegenerative diseases, except at the highest overall levels of flavonoid intake, where a 20% lower risk was observed.

Given the diversity constant, the study found that participants who consumed approximately 500 mg of flavonoids per day had a lower risk of all-cause mortality, cardiovascular disease, diabetes and respiratory disease than those who consumed approximately 230 mg of flavonoids per day. The lowest risk of diabetes, cancer and neurodegenerative diseases was observed in participants who consumed the highest amount of flavonoids (approximately 1400 mg per day).

Interestingly, the study found that higher total flavonoid intake was associated with lower diversity, often reflecting a diet dominated by a single source. Such cases of single-source recording were dominated by tea. Those with high diversity included a wider range of foods such as berries, apples, grapes, red wine and oranges.

AComposition of flavonoid intake.bKey dietary contributors to flavonoid intake, showing only key contributors to intake; Empty spaces up to 100% represent other smaller contributors that are not shown.CTwo-tailed Pearson correlation between quantity and diversity of flavonoid intake.DVariety of flavonoid consumption among participants with the most diverse intakes (Q5) and the least (Q1). InDThe bar graphs will correspond for the amount of flavonoid intake (1,000 mg d - 1) and show the average frequency (% intake) of each flavonoid per day. The dotted areas represent each diet, with each circle being an individual flavonoid and each color being a different flavonoid (corresponding to the colors and distribution in the bar graphs). Data from participants with ≥2 Oxford Webq questionnaires (n = 124,805).

Impact of flavonoid subclasses on chronic diseases and all-cause mortality

Wider diversity of flavonoid intake within the flavan-3-ol and flavanone subclasses is associated with a lower risk of all-cause mortality, even after adjusting for potential confounding factors.

Participants with the widest diversity of flavonoid intake within the flavan-3-ol subclass showed 13% and 8% lower risks of diabetes and cancer, respectively. Similarly, the flavanone subclass was associated with 7% and 6% lower risks of cancer and respiratory diseases. A lower risk of diabetes and neurodegenerative diseases of 13% and 18% was observed among participants with the widest intake diversity within the flavone subclass.

However, for some disease endpoints such as neurodegenerative diseases, not all flavonoid subclasses or all diversity levels showed significant associations. This shows that benefits may vary by both subclasses and health outcomes.

Influence of flavonoid-rich foods on chronic diseases and all-cause mortality

Study analysis, adjusting for confounding factors, found a progressively lower risk of all-cause mortality with greater diversity of flavonoid-rich dietary intake. Participants who consumed more than four servings of flavonoid-rich foods or drinks showed a 16% lower risk of all-cause mortality than those who consumed an adequate serving.

The study found an 8% lower risk of respiratory disease in participants with the highest variety of flavonoid-rich food intake, particularly in relation to chronic disease.

No strong associations have been found between the diversity of flavonoid-rich dietary intake and the incidence of certain diseases such as cancer or neurodegenerative diseases.

Specifically, diversity disregard, higher intake of flavonoid-rich foods beyond a certain threshold, was primarily associated with a lower risk of type 2 diabetes across all outcomes.

Among the major contributors to flavonoid intake, tea (black and green) was the major source totaling 67%. This was followed by apples, red wine, berries, dark chocolate, oranges and orange juice, each of which provides different types of flavonoids.

Investigate significance

The study shows that consuming a higher amount and a wider variety of flavonoids, flavonoid-rich foods, or specific subclasses of flavonoids is better for long-term health benefits than consuming a higher amount or a higher variety of flavonoids alone.

According to the study's findings, the risk of all-cause mortality and the incidence of several chronic diseases can be reduced by consuming the widest variety of flavonoids and flavonoid-rich foods and drinks such as tea, berries, apples, oranges and grapes.

The health benefits of flavonoids can be attributed to their multiple biological activities, including inhibition of platelet aggregation, improvement of nitric oxide bioavailability, reduction of endothelial cell oxidative stress, modulation of vascular ion channel activity, mitigation of atherosclerotic lesion formation, improvement of insulin sensitivity, reduction of inflammatory responses, inhibition of cancer cell growth, induction of cancer cell death, and prevention of angiogenesis and invasion of cancer cells.

The 2022 Flavonoid Guideline recommends consuming 400 to 600 mg of flavan-3-ols daily for potential cardiometabolic health benefits. The study results suggest that future guidelines could be changed to recommend intake from different sources.

Due to the observational study design, researchers were unable to determine the causality of the observed associations. The Oxford WebQ questionnaires used in the study do not collect data on specific types of flavonoid-rich foods, which may limit diversity assessment for certain subclasses such as anthocyanins.

Despite the limitations, the study suggests that simply incorporating several different servings of flavonoid-rich foods or drinks into the daily diet can significantly impact population health.

The study's results suggest that targeting greater variety and amount of flavonoid intake, particularly from different plant-based foods and beverages, may provide more health benefits than just focusing on a single source or high intake.

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