Fresh research published in the journal Food and Function has cast doubt on whether simply consuming five portions of fruit and vegetables daily provides sufficient heart-protective nutrients.
The study, which examined dietary habits of 30,000 participants across Britain and the United States, discovered fewer than one in five individuals obtain adequate levels of flavanols – antioxidants believed to support cardiovascular health and blood vessel function.
Even among those diligently following the familiar five-a-day guidance, these beneficial compounds were frequently found to be lacking.
The findings suggest the particular fruits and vegetables one selects may prove more significant than merely hitting a numerical target.
However, some experts have urged caution, questioning whether increased flavanol consumption would genuinely prevent cardiac problems.
The researchers identified several foods particularly rich in these compounds, with plums emerging as the standout option – a single punnet delivering approximately 450mg of flavanols.
Cranberries followed closely at 300mg per punnet, whilst blackberries provided around 250mg.
For those seeking alternatives beyond fruit, a 250ml cup of green tea offers roughly 200mg, and a small handful of broad beans contains 140mg.
Cherries, apples with their skin intact, strawberries, and blueberries also featured on the recommended list, although with lower concentrations.
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The US Academy of Nutrition and Dietetics suggests approximately 500mg daily appears beneficial for cardiovascular health, though the NHS has not established an official recommended intake.
Notably, the research team has conducted flavanol studies in collaboration with chocolate manufacturer Mars Inc.
Dr Javier Ottaviani, who led the investigation, suggested straightforward dietary adjustments could "make a real difference" to the absorption of these beneficial compounds.
"Most people assume that eating plenty of fruit and vegetables covers this, but what this research shows is that the specific choices you make matter far more than the total amount," he said.
Prof Gunter Kuhnle, from the University of Reading, maintained five-a-day remained sound advice, although greater consideration should be given to which items comprise those portions.
"Different fruits and vegetables offer very different nutritional benefits beyond vitamins and minerals," he explained. "As our understanding of these compounds grows, there is a real opportunity to make dietary guidance more specific and more effective."
Prof Naveed Sattar, a heart specialist at the University of Glasgow, offered a more measured assessment of the findings.
He acknowledged certain small trials had demonstrated favourable effects of flavonoids on blood pressure, yet stressed there remained no genuine evidence of actual reductions in heart disease outcomes.
Further trials would be necessary before such compounds could be recommended as a means "to reduce cardiovascular events", including heart attacks and strokes, he cautioned.
The British Heart Foundation noted flavanol content varies considerably depending on growing conditions, climate, ripeness and storage methods.
Dell Stanford, of the BHF, explained: "Our gut bacteria help break down flavanols into forms the body can use, but everyone's gut bacteria are different, so the benefits people get from flavanols may vary too."
Both the BHF and British Nutrition Foundation continue to recommend a balanced diet containing diverse fruits and vegetables.
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