We sort the phenols from the flannel to bring you the facts about the alleged health benefits of blueberries.
The grandad of the superfood trend, this cute little North American fruit packs a powerful nutritional punch.
Blueberries are a good source of vitamin K. They also contain vitamin C, fibre, manganese and other antioxidants (notably anthocyanins).
Valued for its high levels of antioxidants, some nutritionists believe that if you make only one change to your diet, it should be to add blueberries.
Die-hards claim blueberries can help protect against heart disease and some cancers, as well as improve your memory.
We've teamed up with the British Dietetic Association (BDA) to examine the evidence to see if blueberries live up to their hype.
The evidence on blueberries
Heart health and blueberries
A study in 2012 of 93,000 women found that participants who ate three or more portions of blueberries and strawberries a week had a 32% lower risk of a heart attack compared with those who ate berries once a month or less. However, the study could not prove that these fruits definitely caused the lower risk.
Can blueberries combat high blood pressure and atherosclerosis?
While the evidence is inconclusive, it is thought that blueberries may relax the walls of the blood vessels, which may help reduce this risk of atherosclerosis – hardening of the arteries. Atherosclerosis can increase the risk of a heart attack and stroke.
A small study in 2015 involving 48 post-menopausal women, found that women who were given blueberry powder supplements over the course of eight weeks experienced a small, but clinically significant, drop in blood pressure.
A study from the same year involving 44 adults with metabolic syndrome (a combination of diabetes, high blood pressure and obesity), who were given blueberry smoothies, had less promising results as there was no effect on blood pressure.
A similar finding was presented in a 2013 study involving 21 men. Though these men were described as healthy so the results may not be applicable for people with underlying chronic diseases.
Though it is important to note that all of these studies were relatively small which gives less “weight” to their results. They also involved different populations so the results may not be applicable to the general population.
Can blueberries prevent cancer?
There is so far very little evidence that blueberries can help protect against cancer. In laboratory studies on cells and animals, blueberry extracts (such as anthocyanins) have been shown to decrease free radical damage that can cause cancer. However, it is not clear how well humans absorb these compounds from eating blueberries and whether or not they have a protective effect.
Does eating blueberries lead to a better memory?
A number of small studies have found a link between blueberry consumption and improved spatial learning and memory. However, most of these studies relied on small sample groups or animals. There is currently no evidence of a link between eating blueberries and improved memory.
The dietitian's verdict on blueberries
Alison Hornby, a dietitian and BDA spokesperson, says: "While research on the health claims of blueberries is inconclusive, they are a fantastic choice as one of your five portions of fruit and vegetables a day.
"They are low in calories and high in nutrients, including phenolic compounds with an antioxidant capacity significantly higher than vitamins C or E.
"Try adding them to your breakfast cereal, including them in a packed lunch or mixing with low-fat yoghurt for a delicious dessert."
More on superfoods
Check out the evidence behind the health claims made about these other so-called superfoods: