Not Enough Flavanols: Five Servings Of Fruits, Vegetables May Not Lower Heart Disease Risk

Most Americans have been told their whole lives that loading up on fruits and vegetables is the key to a healthy heart. Follow the dietary guidelines, fill the plate with produce, and the body will take care of itself. But a large new study is raising doubts about that assumption, finding that playing by the rules may not be enough to reach a flavanol level that has been linked to cardiovascular benefits in a major trial.

Researchers set out to answer a surprisingly straightforward question. If someone actually follows the government’s dietary guidelines, eating the recommended amounts of fruits and vegetables and maintaining an overall healthy diet, do they end up consuming enough of a specific group of plant compounds called flavanols to protect their heart?

Flavanols are natural compounds found in foods like apples, berries, beans, tea, and cocoa products, and a major clinical trial called COSMOS had already shown that 500 milligrams per day was linked to significantly reduced cardiovascular disease mortality in older adults, making it the natural benchmark to test against.

Even among the most health-conscious eaters in the study, those who met or exceeded recommendations for fruit and vegetable intake and scored highest on overall diet quality, fewer than one in four consumed enough flavanols to reach that threshold. That does not mean fruits and vegetables are unimportant for heart health; it means they may not reliably supply this one group of compounds at the level studied in COSMOS.

Urine Samples Gave a More Accurate Picture of Flavanol Levels

Published in Food & Function, the study analyzed data from two large studies conducted on different continents. In the United States, COSMOS included more than 6,500 older adults, with women aged 65 and up and men aged 60 and up. In the United Kingdom, EPIC-Norfolk included more than 24,000 adults recruited between 1993 and 1997, ranging in age from 40 to 79.

Rather than relying solely on participants’ self-reported food diaries, a method known to be unreliable because people tend to misremember or misreport what they eat, the researchers used biological markers measured in urine samples. These markers are chemical byproducts the body produces after consuming flavanols, making them a more objective way to estimate absorption. Using these urine-based measurements, the team could estimate whether participants were likely to be at or above the 500-milligram-per-day flavanol level.

Diet quality was evaluated using established scoring systems. For COSMOS, researchers used a score reflecting adherence to the Dietary Guidelines for Americans, along with tracking fruit and vegetable servings. For EPIC-Norfolk, researchers used a comparable scoring system based on UK dietary recommendations and also measured blood levels of vitamin C as an additional indicator of produce intake.

Fewer Than 1 in 4 Healthy Eaters Hit the Daily Flavanol Target

Across both studies, the results were consistent. In COSMOS, only about 19% of all participants met the 500-milligram flavanol threshold. Among those who ate the most fruits and vegetables, the top quarter of the group, just 21% reached that level. Even participants who scored highest on overall diet quality only hit the target 22% of the time. In EPIC-Norfolk, the pattern was similar: only around 16% of participants in the top quarter of fruit and vegetable intake met the threshold.

One finding from the UK data stood out: participants who most closely followed dietary guidelines were actually among the least likely to reach the flavanol target. Higher tea intake was associated with better odds of reaching the threshold, but even among the heaviest tea drinkers in EPIC-Norfolk, only about 19% made it to 500 milligrams per day.

Researchers also ran computer simulations to model what would happen if someone ate five servings of commonly consumed fruits and vegetables per day, the kind of standard advice found in most dietary guidelines. When those servings were drawn from foods Americans most commonly eat, like bananas, apples, tomatoes, grapes, oranges, and carrots, reaching 500 milligrams of flavanols per day was unlikely. Even when the simulations were set up to favor produce with the highest flavanol content, the probability of hitting the threshold remained below 50%.

Part of the reason, the researchers explain, is that flavanol content in fruits and vegetables is highly variable. Even within the same variety of apple, the amount of these compounds can swing more than tenfold depending on the plant’s breed, growing conditions, and harvest timing. Dietary guidelines were never designed with flavanol levels in mind; they were built around nutrients like vitamins and minerals, so there is no reason to expect that following them would reliably deliver a specific flavanol dose.

A Gap That Current Heart Health Guidelines Can’t Fill

Getting specific benefits from specific compounds may require specific recommendations, and right now, no official government dietary guidelines in the United States or the United Kingdom include a recommended daily intake for flavanols. Eating well, it turns out, and eating to hit a specific heart-health target may be two very different goals.

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Disclaimer: This article is based on a peer-reviewed study and is intended for informational purposes only. It should not be construed as medical advice. Consult a qualified healthcare provider before making any changes to your diet or health regimen.

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