Fruits and vegetables are an important part of our diet. They provide nutrients and fibre, and many contain additional compounds (known as bioactives) that can improve health. But not all foods are created equal – with big differences in the amount of bioactives we get from cabbages, carrots, pulses and peppers.
The well-known “five-a-day” campaign forms the basis of current dietary recommendations for fruit and vegetable consumption. The campaign focuses mainly on reminding people to consume at least five portions of fruits or vegetables each day.
This is a sensible approach, because it’s always better to eat some fruits and vegetables instead of none. But could we do better? Could choosing fruits and vegetables more carefully help us to get important bioactives from our foods?
My latest research suggests this is the case. We found that following current dietary recommendations might not be good enough when it comes to getting these important, health-boosting bioactive compounds from fruits and veggies. This could have particularly important implications for heart health.
In the study my colleagues and I conducted, we specifically investigated flavanols. This group of bioactive compounds are found in many plant-based foods, including tea, apples and berries.
Flavanols have been shown to reduce the risk of heart disease. About 500mg of flavanols per day are enough for most people to see health benefits from flavanols.
We wanted to find how many people eat at least 500mg of flavanols per day – and whether these are the people who eat their five-a-day and follow dietary recommendations.
To do this, we did not rely on food diaries or dietary questionnaires – methods that are known to be unreliable. People often forget what they’ve eaten, and the flavanol content in food is very variable.
Instead, we measured flavanol intake directly, using a biomarker in urine that reflects what the body actually absorbed. We did this in around 30,000 participants across two large studies in the UK and the US.
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Our findings revealed there was good and bad news. The good news was that it’s perfectly possible to get 500mg of flavanols per day from a normal diet. The bad news was that fewer than one in five participants actually did this – even among those who ate their five a day.
This is not surprising. Many fruits and vegetables do not contain a lot of flavanols. Cauliflower, carrots or cucumber, for instance, don’t contain any, while mangoes, medlars and kiwis only very small amounts. When choosing a random selection of five fruits or vegetables, it’s very unlikely that they’ll add up to 500mg a day.
Another surprising result was that there was a big difference between participants in the US and UK.
US participants were more likely to get their daily flavanol intake if they followed US dietary recommendations (which are similar to the UK’s fruit and veg recommendations) – although only one in five did so. Around 20% of US participants consumed 500mg of flavanols daily.
Gunter Kuhnle, Author provided (no reuse)
But in the UK, the opposite was true. Only about 10% of those who consumed their recommended five portions a day also consumed 500mg of flavanols. Yet this number was closer to 20% in those who did not follow these recommendations.
We also found that those who reported eating the smallest amount of fruits and vegetables daily had the higher flavanol intake.
There may be a couple of key reasons for these findings.
There are some key differences between the two studies: the UK participants came from the Epic Norfolk study, which was designed to be representative of the general public. The baseline diet data we used was collected in the 1990s. In contrast, the US participants of the Cosmos study were recruited in the 2010s and generally had a better diet than the population average.
But if we look at just the UK cohort alone, the explanation for the disparities in flavanol intake can be found in a cup of tea. Literally.
Tea is a great source of flavanols, and a few cups of tea daily can already provide 200-300mg. In a country where tea is a staple, this can make an important contribution. It’s not surprising that the UK has one of the highest flavanol intakes in Europe.
In countries where coffee is the staple drink – such as the US – tea consumption is often associated with an overall healthier diet. But this is not the case in the UK, where tea is not a marker of a particular healthy – or unhealthy – lifestyle. Indeed, people with high tea consumption don’t eat more fruits and vegetables than others.
Although tea is not part of any dietary recommendations, it may be the main driver for flavanol intake in the UK. This means that a good cup of tea may do more for flavanol intake than a randomly chosen portion of fruit or veg.
What does this mean?
People who follow current dietary recommendations are unlikely to consume a sufficient amount of flavanols. It’s likely the same applies to other bioactives, such as carotenoids, (which can support vision).
There’s also huge variability in the bioactive content of different fruits and vegetables. A random selection of five fruits and veg each day is unlikely to provide meaningful amounts.
This isn’t surprising, as bioactives are generally not part of dietary recommendations. But our increasing understanding of the important role of bioactives in disease prevention and public health raises the question of whether this should change.
Five-a-day guidance continues to be an important dietary recommendation, especially as most of us do not eat enough fruits and vegetables. But as we learn more about the benefits of different plant compounds, we should consider prioritising consumption of certain fruits and vegetable daily to increase intake of these compounds. Whether you manage two portions or five, choosing wisely makes a difference.
