Even people who meet the recommendations for fruits and vegetables rarely consume enough flavanols to match the levels associated with reduced cardiovascular risk, raising new questions about whether flavanol-specific dietary guidance is needed.
Study: Adherence to dietary guidelines does not yield levels of flavanol intake associated with beneficial cardiovascular outcomes. Image credit: Tatjana Baibakova/Shutterstock.com
A recent study in Food and Function investigated whether current dietary recommendations for fruit, vegetables and overall diet quality correspond to levels of flavanol intake associated with cardiovascular health benefits.
Current dietary advice lacks specific flavanol targets
Flavanols are a subclass of flavonoids, a group of plant-derived polyphenolic compounds defined by a 3-hydroxyflavan structure. These molecules are widespread in a wide range of foods, including fruits, vegetables, tea, cocoa and legumes. Flavanols possess distinct biological activities, including antioxidant functions and the ability to modulate vascular and inflammatory processes associated with cardiometabolic health.
Large-scale studies such as COSMOS showed that a daily intake of 500 mg of flavanols was associated with reductions in cardiovascular mortality and cardiovascular events in older adults, fueling interest in establishing dietary recommendations for flavanols. Despite these findings, US, UK and World Health Organization (WHO) dietary guidelines focus on general fruit, vegetable and legume intake without specific flavanol targets. Although experts recommend 400–600 mg of flavanols daily for cardiometabolic health, it remains unclear whether current guidelines achieve these amounts.
Validated dietary biomarkers, such as 5-(3′,4′-dihydroxyphenyl)-γ-valerolactone metabolites (gVLMB) and structurally related (-)-epicatechin metabolites (SREMB), now allow objective quantification of flavanol intake. However, there are limited data on whether following established dietary patterns and using biomarker-based measures leads to sufficient flavanol intake to confer the observed health benefits. Addressing these gaps is critical to informing evidence-based recommendations.
Two large groups looked at flavanol intake levels
The current study examined whether the recommended fruit and vegetable intake and healthy dietary patterns lead to a flavanol intake of at least 500 mg/day, an amount associated with cardiovascular benefits in the COSMOS trial and recommended by experts.
Data were collected from two studies: the COSMOS trial (USA), which evaluated cocoa flavanols and multivitamins for cardiovascular disease and cancer prevention in 21,442 adults aged 60 years and older, and the EPIC-Norfolk cohort (UK), which recruited 30,447 adults aged 40–79 years. Dietary intake was assessed by questionnaire in COSMOS and 7-day diary in EPIC-Norfolk.
In COSMOS, 6,509 participants provided spot urine samples for analysis of flavanol biomarkers. In EPIC-Norfolk, 24,154 participants provided similar samples. The current study quantified gVLMB and SREMB from urine samples. In addition to the flavanol biomarker, plasma vitamin C was also assessed.
Flavanol intake from fruits and vegetables was simulated using Phenol-Explorer and 2017 NHANES data. The simulations tested various daily portion numbers and food selection strategies using 10,000 Monte Carlo simulations per scenario. Flavanol content was obtained from reported series of related compounds.
Healthy diets rarely provide adequate flavanol intake
COSMOS participants were generally older, more likely to be male and had a higher BMI, while EPIC Norfolk had less ethnic diversity. Food intake comparisons were limited by differences in measurements, except for tea, which was consumed much more frequently in EPIC Norfolk and is a major source of flavanols.
Flavanol biomarker levels were broadly similar in the two cohorts, although EPIC Norfolk participants had higher levels of the (−)-epicatechin biomarker. Overall, only 19% of COSMOS participants and 18% of EPIC Norfolk participants achieved the biomarker-estimated flavanol intake equivalent to 500 mg/day. Men were more likely to reach this threshold in both studies, while age and BMI showed different associations between cohorts.
Adherence to healthy dietary patterns did not significantly increase the likelihood of meeting the flavanol target. In COSMOS, even participants with the highest fruit and vegetable intake or diet quality scores rarely met the threshold, with only about 21% doing so. Those with the highest diet quality had moderately higher odds of achieving the goal than those with the lowest scores, but overall associations between diet quality, fruit intake, tea consumption, and flavanol biomarkers were weak.
Similar findings emerged in EPIC Norfolk. Only 16% of participants with the highest intake of fruit and vegetables met the flavanol target, and those who followed UK dietary guidelines more closely were no more likely to meet it. Higher tea consumption was associated with greater flavanol intake, but even among the heaviest tea drinkers, fewer than one in five participants reached the target level.
Computer simulations supported these observations, showing that frequently consumed fruits and vegetables were unlikely to provide 500 mg/day of flavanols, even when consumed in recommended amounts. While choosing foods particularly high in flavanols improved the odds of reaching the goal, the odds remained below 50%.
The researchers suggest that the wide variation in flavanol content among foods, even among varieties of the same fruit or vegetable, may explain why adherence to general dietary recommendations does not reliably yield flavanol intake associated with cardiovascular benefits.
Importantly, the biomarker thresholds used in the analysis were deliberately chosen to err on the side of overestimating flavanol intake, suggesting that the true proportion of subjects reaching the 500 mg/day target may be even lower.
Existing dietary guidelines omit cardioprotective flavanol levels
Current dietary guidelines alone are insufficient to ensure flavanol intake at levels shown to reduce CVD risk, as demonstrated in the COSMOS trial. The authors note that existing dietary guidelines were designed to meet nutrient requirements rather than to optimize the intake of specific bioactive compounds, such as flavanols.
Establishing specific dietary reference values for flavanols may be needed to help the public achieve these health benefits. Although the US has not prioritized Dietary Reference Intake (DRI)-like values for flavanols and other bioactive substances, other agencies may be able to move this process forward more quickly. Recent initiatives to establish recommended intakes for bioactive substances, along with guidelines for flavanol intake from groups such as the Academy of Nutrition and Dietetics, are promising steps in this direction.
