The women, who had either pre-hypertension or hypertension, received freeze-dried blueberry powder – an amount equivalent to about one cup of fresh blueberries – or a placebo powder daily for eight weeks.
At the end of the study, systolic blood pressure (the top number) dropped by 5 percent and diastolic blood pressure (the bottom number) dropped by more than 6 percent in the blueberry group, while no significant changes occurred in the placebo group.
Measurements of nitric oxide (NO) were also significantly increased in the blueberry group, with no such change in the control group. Nitric oxide helps your blood vessels maintain their elasticity and also dilates your blood vessels, thereby reducing your blood pressure. According to the study authors:
“Daily blueberry consumption may reduce blood pressure and arterial stiffness, which may be due, in part, to increased nitric oxide production.”
Blueberries Are Excellent for Your Heart Health – in the Right 'Dose'
Berries like blueberries are among the healthiest fruits you can eat, assuming you don’t overdo it. They’re relatively low in sugar while being high in fiber and heart-healthy antioxidants. Past research has shown that women who ate more than three servings per week of blueberries (and strawberries) had a 32 percent lower risk of having a heart attack.4
The benefit was due to flavonoids in the berries known as anthocyanins, which are antioxidants that give these fruits their characteristic red and purple hues. Anthocyanins are known to benefit the endothelial lining of your circulatory system, possibly preventing plaque buildup in arteries as well as promoting healthy blood pressure.
Other research has shown these antioxidants to protect against heart disease by reducing oxidative stress and inflammation, while enhancing capillary strength and inhibiting platelet formation.5 Researchers have further noted:6
“Epidemiological studies suggest that increased consumption of anthocyanins lowers the risk of cardiovascular disease (CVD), the most common cause of mortality among men and women.
Anthocyanins frequently interact with other phytochemicals, exhibiting synergistic biological effects but making contributions from individual components difficult to decipher.
Over the past 2 decades, many peer-reviewed publications have demonstrated that in addition to their noted in vitro antioxidant activity, anthocyanins may regulate different signaling pathways involved in the development of CVD.”
Eating whole fruit can be beneficial to your health, but it’s important to remember to eat fruit in moderation, especially if you have high blood pressure, because of its sugar content.
While a cup of fresh blueberries a day would be acceptable (at just over 7 grams of fructose, see below for the details), if you’re consuming other sources of sugar you could easily reach excessive levels and end up making your high blood pressure worse.
The main offenders in this category are not whole, natural organic fruits, but added sugars/fructose that Americans are consuming in an alarming amount on a daily basis, however. Soda, fruit juice, and high-fructose corn syrup in processed foods is likely to contribute far more to your daily fructose load than a handful of berries. If you are going to drink juice, opt for brands like Uncle Matt's; their juices are certified organic, and they don't add any flavor packets or peel oil.
Excess Sugar May Be Your Blood Pressure’s Worst Enemy
In a review in the journal Open Heart, the authors argued that the high consumption of added sugars in the US diet may be more strongly and directly associated with high blood pressure than the consumption of sodium. They wrote:7
“Evidence from epidemiological studies and experimental trials in animals and humans suggests that added sugars, particularly fructose, may increase blood pressure and blood pressure variability, increase heart rate and myocardial oxygen demand, and contribute to inflammation, insulin resistance and broader metabolic dysfunction.
Thus, while there is no argument that recommendations to reduce consumption of processed foods are highly appropriate and advisable, the arguments in this review are that the benefits of such recommendations might have less to do with sodium—minimally related to blood pressure and perhaps even inversely related to cardiovascular risk—and more to do with highly-refined carbohydrates.”
Take, for instance, one 2010 study that showed consuming a high-fructose diet lead to an increase in blood pressure of about 7mmHg/5mmHg, which is greater than what is typically seen with sodium (4mmHg/2mmHg).8
Research also shows that drinking a single 24-ounce fructose-sweetened beverage leads to greater increases in blood pressure over 24 hours than drinking a sucrose-sweetened beverage,9 which again points to the detrimental effects of fructose on your health.
What Is Sugar’s Role in High Blood Pressure?
Fructose elevates uric acid, which drives up your blood pressure by inhibiting the nitric oxide in your blood vessels. (Uric acid is a byproduct of fructose metabolism.)
In addition, high blood pressure is often related to your body producing too much insulin and leptin in response to a high-carbohydrate and processed food diet. As your insulin and leptin levels rise, it causes your blood pressure to increase. Eventually, you may become insulin and/or leptin resistant.
As explained by Dr. Rosedale, insulin helps store magnesium, but if your insulin receptors are blunted and your cells grow resistant to insulin, you can't store magnesium so it passes out of your body through urination. Magnesium stored in your cells relaxes muscles.
If your magnesium level is too low, your blood vessels will be unable to fully relax, and this constriction raises your blood pressure. By eliminating excess sugar/fructose from your diet, you can address all three issues (insulin, leptin, and uric acid) at once.
As a standard recommendation, I recommend keeping your total fructose consumption below 25 grams per day, and that includes fructose from fruit. If you have high blood pressure (or insulin resistance, diabetes, heart disease, or other chronic diseases) you'd be wise to limit your fructose to 15 grams or less per day until your condition has normalized.
As mentioned, one cup of blueberries has 7.4 grams of fructose, so if you limit your intake from other sources, you can eat a cup of blueberries a day and still be well within the healthy limits.
Blood Pressure Medications Might Shorten Your Life
High blood pressure can be deadly, but you need to think carefully before using drugs to treat it, especially if your levels are only mildly elevated. In the vast majority of cases, drugs are not needed to reverse hypertension, and in some cases the drugs may end up shortening your lifespan instead of extending it. In one study, diabetic participants received one or more blood pressure medications (a combination of calcium antagonist, beta-blocker, ACE inhibitor, and diuretic) in whatever combination required to achieve a systolic blood pressure less than 130 mm Hg (the standard hypertension guidelines for diabetics).
Researchers discovered that tighter control of blood pressure in these patients was not associated with better outcomes. The uncontrolled group fared worst, which wasn’t surprising, but the group whose systolic blood pressure was held between 130 and 140 actually showed a slightly lower risk of death than the group whose systolic was maintained at the recommended level—under 130 mm Hg.10 Past research has also shown that aggressive blood pressure control may lead to too low of a blood pressure and increased risk of cardiovascular events.11 There is a major difference between achieving a healthy blood pressure number by eating well, exercising and managing stress, versus “forcing” your body to produce that number with a drug.