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Just a cup a day of these tiny treats helps fend off heart disease and cancer.
If you still think of blueberries as an occasional summer treat, think again. Research confirms that eating just a cup a day helps fend off heart disease and cancer.
In a remarkable study from Florida State University, researchers found that a daily serving of blueberries could be key to fighting cardiovascular disease.
They conducted a double-blind, placebo-controlled clinical trial with 48 post-menopausal women with pre-hypertension or stage one hypertension. Every day half the women were given either a placebo or 22 grams of freeze-dried blueberry powder. The powder was equivalent to one cup of fresh blueberries.
During the trial researchers evaluated the women's blood pressure, as well as their levels of nitric oxide.
They also measured arterial stiffness using brachial ankle pulse wave velocity (PWV), considered the gold standard in evaluating arterial damage. Arterial stiffness is a symptom of atherosclerosis and is predictive of cardiovascular risk. It indicates that the heart has to work harder to circulate blood to the peripheral blood vessels.
The study results were published in the Journal of the Academy of Nutrition and Dietetics.[i] After just 8 weeks the women who took the blueberry powder had significantly lowered their systolic (5.1%) and diastolic (6.3%) blood pressure. Those on the placebo had no change.
In addition, women taking the blueberry powder reduced their arterial stiffness on average by 6.5%. No change was seen in the placebo group.
The researchers attributed the beneficial effects to an amazing 68.5% increase in blood levels of nitric oxide in the women who took the blueberry powder. Nitric oxide is known to widen blood vessels to increase blood flow and lower blood pressure. Those on the placebo had no changes in nitric oxide levels.
The authors noted that their results were "of clinical significance because they demonstrate that blood pressure can be favorably altered by the addition of a single dietary component (eg, blueberries)."
They went on to suggest that "daily blueberry consumption may be effective in preventing the progression of pre-hypertension to hypertension in postmenopausal women."
Many berries contain polyphenols that have been proven to improve blood pressure, endothelial function, and arterial stiffness. But blueberries are one of the richest sources of polyphenols, including flavonoids, phenolic acids, and stilbenes, which are powerful antioxidants.
Prior research showed that wild blueberries improve endothelial function.
And another study found that eating three or more servings of blueberries per week slashes the risk of heart attack by as much as 32%.
Blueberries Boost Cancer Defenses
The Florida State University results were backed up by another recent study released around the same time in the journal Nutrition Research.
In that study researchers from North Carolina found that daily blueberries helped people with pre-hypertension significantly reduce their diastolic blood pressure compared to placebo.[ii]
But the North Carolina study also found that blueberries increase natural killer (NK) cells. NK cells are white blood cells that play a critical role in the immune system's defense against foreign invaders like viruses and tumors. They scan the body for abnormal cells and destroy them before they can develop into actual cancers.
The researchers divided 25 sedentary men and post-menopausal women in two groups. Every day one group received a placebo while the other was given 38 grams of blueberry powder. The powder was equivalent to 250 grams of fresh fruit.
After six weeks the blueberry group saw significant increases in NK cells. The results were consistent with earlier research by the same team finding that blueberries improve NK cell counts, oxidative stress, and inflammation in trained athletes.
Other research has found that anthocyanins in blueberries may help prevent the free-radical damage associated with cancer.
In addition to polyphenols, blueberries are an excellent source of vitamins K and C, manganese, and fiber. During the summer months enjoy them fresh. Out of season you can easily find them frozen or dried. Add them to salads, yogurt, oatmeal, or smoothies. Or just eat them by the handful.
Check out these 10 health benefits of blueberries.
[i] Johnson, Sarah A. et al. "Daily Blueberry Consumption Improves Blood Pressure and Arterial Stiffness in Postmenopausal Women with Pre- and Stage 1-Hypertension: A Randomized, Double-Blind, Placebo-Controlled Clinical Trial." Journal of the Academy of Nutrition and Dietetics, 2015; Volume 115, Issue 3, pp. 369 – 377.
[ii] McAnulty LS et al. "Six weeks daily ingestion of whole blueberry powder increases natural killer cell counts and reduces arterial stiffness in sedentary males and females." Nutr Res. 2014 Jul;34(7):577-84. doi: 10.1016/j.nutres.2014.07.002.