75 blueberries a day could help keep the brain healthy
- Eating a handful of wild blueberries each day could strengthen cognitive and cardiovascular health, according to a new study.
- The study finds that blueberries’ anthocyanins are responsible for improving vascular and cerebral blood flow, which are some of the likely mechanisms behind healthy cognitive function.
- Anthocyanins are polyphenols, a family of plant-based compounds increasingly associated with health benefits.
A cup of wild blueberries is more than a tasty snack, according to a new study from King’s College London Faculty of Life Sciences and Medicine in the United Kingdom. It can also provide a brain boost, lower blood pressure, and contribute to better cardiovascular health.
The randomized, double-blind, placebo-controlled trial found that blueberry eaters exhibited improved executive function, strengthened short-term memory, and had faster reaction times.
Study participants who had a daily drink made out of 26 grams (g) of freeze-dried wild blueberry powder for 12 weeks saw a 3.59 millimeters of mercury (mmHG) reduction in systolic blood pressure, and improved blood vessel function compared to individuals consuming a placebo powder.
Participants who consumed blueberries were better at immediately recalling word lists, and exhibited improved switching accuracy. The researchers observed no improvement in delayed recall, however.
The study appears in the American Journal of Clinical Nutrition.
178 grams of blueberries a day
The study involved 61 healthy male and female participants from London, aged between 65–80 years. Over 12 weeks, half of them drank a beverage each day containing 26 g of freeze-dried wild blueberry powder, while the other half consumed a taste-, appearance-, macro-nutrient-, fiber-, and vitamin C-matched placebo.
It is common for food studies to use powdered substances for precision measurements.
The 26 g of blueberry powder participants drank each day was the equivalent of 178 g of whole blueberries. This translates to somewhere between 75–80 blueberries, since they vary in size.
Senior investigator Dr. Ana Rodriguez-Mateos noted to Medical News Today that the blueberries need not be wild, since “there are other studies that have been conducted with other types of blueberries showing benefits in cognitive and vascular health.”
Anthocyanins: Healthy natural pigments
The researchers believe the blueberries’ beneficial effects are due to their blue pigments called anthocyanins. Each daily dose of wild blueberry powder in the study contained 302 milligrams (mg) of anthocyanins. The placebo beverage contained none.
“Anthocyanins are a class of polyphenols,” explained Michelle Routhenstein, a heart health dietitian not involved in this study.
“[T]here are about 8,000 different types of polyphenols that provide health benefits,” she added. “Some other types of foods that have beneficial polyphenols include green tea, broccoli, pears, and spices like turmeric and cinnamon.”
Anthocyanins are also present in strawberries, raspberries, red grapes, and purple vegetables.
“There is some evidence on health benefits of other anthocyanin-rich foods, and there is no reason to think that they will not work as well as blueberries, as long as the amount of anthocyanins provided with such foods is enough, and that the anthocyanins are bioaccessible and bioavailable.”
– Dr. Ana Rodriguez-Mateos
How the study came to be
Dr. Rodriguez-Mateos and co-author Dr. Claire Williams had been separately investigating the cognitive and cardiovascular benefits of blueberries, and seeing similar results.
As a result, said Dr. Rodriguez-Mateos, they “decided to investigate the effects on vascular and cognitive function simultaneously in one clinical study.”
They set out to measure cerebral blood flow since other research has suggested it may be a mechanism behind polyphenols’ beneficial effects along with increased vascular blood flow.
In addition, recent insights into the gut microbiota and gut-brain axis prompted them to explore this relationship as well.
What polyphenols may be doing
The mechanism behind the beneficial effects of polyphenols is not yet fully understood.
One theory is that polyphenol “metabolites may act as signaling molecules, acting through several cell-signaling pathways, modulating nitric oxide bioavailability and different enzymes,” said Dr. Rodriguez-Mateos.
The researchers found increases in anthocyanin metabolites in participants’ urine after the 12-week study period.
Dr. Rodriguez-Mateos is certain that “the mechanism of action in the blood vessels is endothelium-dependent and therefore mediated through the nitric oxide pathway.”
While the study found evidence that blueberries improved cerebral and vascular blood flow, they saw no difference in arterial stiffness and blood lipids between people consuming the fruit and the placebo group.
Still, “[w]hen blood flow is improved, both heart and brain health benefit,” said Routhenstein.
As far as the role of gut microbiota goes, Dr. Rodriguez-Mateos said, “a hypothesis we proposed in our study is that polyphenols may act via enhancing the abundance of butyrate-producing beneficial bacteria, and therefore the production of butyrate.”
She added this needs to be confirmed in further studies.
Other foods good for heart, brain health
According to the American Heart Association, a better cardiovascular and cognitive health is promoted by a diet rich in vegetables, fruits, whole grains, healthy proteins, minimally processed foods, and moderate oil and salt intake.
Recent research has indicated that a Mediterranean diet may be the optimal diet for heart health.
Routhenstein mentioned the benefits of “green veggies, specifically spinach, Swiss chard, and kale rich in nitrates, which can help dilate the arteries.”
“This helps to improve blood flow and improve vascular, heart, and cognitive function,” she noted.
There are numerous other foods linked to cognitive health, said Routhenstein. “Omega-3 fats like wild salmon and sardines are linked to better cognition because of their rich DHA content and potent anti-inflammatory properties,” she pointed out.
In addition, “[s]ome studies suggest unsaturated fats, like omega-3 fats, may also help lower levels of beta-amyloid, a component in the development and progression of Alzheimer’s disease.”
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