Blueberries Could Lower Your Blood Pressure: RCT Data

By Dr. Mercola

One out of every three US adults has high blood pressure (hypertension),¹ while another 59 million Americans have pre-hypertension² (which means you may soon develop full-blown hypertension).

If you are diagnosed with high blood pressure, dietary strategies will be crucial to controlling your levels. And if you have pre-hypertension, you can typically stop its progression and regain healthy levels just by changing the way you eat.

New research published in the Journal of the Academy of Nutrition & Dietetics showed just how powerful a strategy this can be, using a food that many people love to eat – blueberries.³

Daily Blueberries May Help Lower Your Blood Pressure

The study involved postmenopausal women, who have an especially high rate of hypertension and often develop arterial stiffness, increasing their risk of heart disease considerably.

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.

My Top-Recommended Strategies to Prevent Hypertension

Avoiding processed foods (due to their being high in sugar/fructose, grains, trans fat and other damaged fats and processed salt) is my number one recommendation if you have high blood pressure. Instead, make whole, ideally organic, foods the focus of your diet. As you reduce processed foods, and other sources of non-vegetable carbs, from your diet, you'll want to replace them with healthy fat. Sources of healthy fats to add to your diet include:

It's not only your diet that matters for healthy blood pressure… a comprehensive fitness program is another strategy that can improve your blood pressure and heart health on multiple levels (such as improving your insulin sensitivity). To reap the greatest rewards, I strongly suggest including high-intensity interval exercises in your routine. You'll also want to include weight training. When you work individual muscle groups you increase blood flow to those muscles, and good blood flow will increase your insulin sensitivity. If you want to kill several birds with one stone, exercise barefoot outdoors on sunny days.

Not only will you get much-needed sunshine to promote production of heart-healthy vitamin D, but bright daylight sun exposure will also help maintain a healthy circadian clock, which will help you sleep better. Poor sleep is yet another oft-ignored factor that can cause resistant hypertension. Going barefoot, meanwhile, will help you ground to the earth.

Experiments show that walking barefoot outside—also referred to as Earthing or grounding—improves blood viscosity and blood flow, which help regulate blood pressure. Keep in mind that, in most cases, high blood pressure is a condition that can be managed and oftentimes reversed with natural lifestyle changes. I encourage you to read through my full list of strategies to prevent and treat hypertension, however, below you'll find some additional highlights.

1. Skip breakfast: Research shows that intermittent fasting helps fight obesity and type 2 diabetes, both of which are risk factors for high blood pressure. Your body is most sensitive to insulin and leptin after a period of fasting. While there are many types of fasting regimens, one of the easiest to comply with is an eating schedule where you limit your eating to a specific, narrow window of time each day. I typically recommend starting out by skipping breakfast, and making lunch your first meal of the day until you resolve insulin resistance, then you can eat breakfast if your fasting insulin levels remain normal.
2. Optimize your vitamin D levels: Arterial stiffness (atherosclerosis) is a driving factor for high blood pressure. As your blood travels from your heart, cells in the wall of your aorta, called baroreceptors, sense the pressure load, and signal your nervous system to either raise or lower the pressure. However, the stiffer your arteries are, the more insensitive your baroreceptors become, and the less efficient they become at sending the appropriate signals. Vitamin D deficiency is, in turn, linked to stiff arteries, which is why optimizing your levels is so important.
3. Address your stress: The link between stress and hypertension is well documented. Suppressed negative emotions such as fear, anger, and sadness can severely limit your ability to cope with the unavoidable every day stresses of life. It's not the stressful events themselves that are harmful, but your lack of ability to cope. I recommend the Emotional Freedom Technique (EFT) to transform your suppressed, negative emotions and relieve stress.
4. Normalize your omega 6:3 ratio: Most Americans get too much omega-6 in their diet and far too little omega-3. Consuming omega-3 fats will help re-sensitize your insulin receptors if you suffer from insulin resistance. Omega-6 fats are found in corn, soy, canola, safflower, and sunflower oil. If you're consuming a lot of these oils, you'll want to avoid or limit them. For omega-3s, your best bet is to find a safe source of fish, or if this proves too difficult or expensive, supplement with a high-quality krill oil, which has been found to be 48 times more potent than fish oil.
5. Optimize your gut flora: Compared to a placebo, people with high blood pressure who consumed probiotics lowered systolic blood pressure (the top number) by 3.56 mm Hg and diastolic blood pressure (the bottom number) by 2.38 mm Hg.¹² The best way to optimize your gut flora is by avoiding sugar and processed foods and including naturally fermented foods in your diet, which may contain about 100 times the amount of bacteria in a bottle of high-potency probiotics. Using fermented foods with a starter culture like Kinetic culture will also add therapeutic levels of important nutrients like vitamin K2.
6. Maintain an optimal sodium-potassium ratio: As mentioned, an imbalanced ratio may lead to hypertension. To ensure yours is optimal, ditch all processed foods, which are very high in processed salt and low in potassium and other essential nutrients. Instead, eat a diet of whole, unprocessed foods, ideally organically and locally-grown to ensure optimal nutrient content. This type of diet will naturally provide much larger amounts of potassium in relation to sodium.
7. Eliminate caffeine: The connection between coffee consumption and high blood pressure is not well understood, but there is ample evidence to indicate that if you have hypertension, coffee and other caffeinated drinks and foods may ex­acerbate your condition.
8. Vitamins C and E: Studies indicate that vitamins C and E may be helpful in lowering blood pressure. If you're eating a whole-food diet, you should be getting sufficient amounts of these nutrients through your diet alone. If you decide you need a supplement, make sure to take a natural (not synthetic) form of vitamin E. You can tell what you're buying by care­fully reading the label. Natural vitamin E is always listed as the "d-" form (d-alpha-tocopherol, d-beta-tocopherol, etc.) Synthetic vitamin E is listed as "dl-" forms.
9. Olive leaf extract: In one 2008 study, supplementing with 1,000 mg of olive leaf extract daily over eight weeks caused a significant dip in both blood pressure and LDL ("bad") cholesterol in people with borderline hypertension. If you want to incorporate olive leaves as a natural adjunct to a nutrition­ally sound diet, look for fresh leaf liquid extracts for maximum synergistic potency. You can also prepare your own olive leaf tea by placing a large teaspoon of dried olive leaves in a tea ball or herb sack. Place it in about two quarts of boiling water and let it steep for three to 10 minutes. The tea should be a medium amber color when done.
10. Quick tricks: Increasing nitric oxide in your blood can open con­stricted blood vessels and lower your blood pressure. Methods for in­creasing the compound include taking a warm bath, breathing in and out through one nostril (close off the other nostril and your mouth), and eating bitter melon, rich in amino acids and vitamin C.