How Does Vitamin C Affect Blood Pressure?

How Does Vitamin C Affect Blood Pressure?

(Last Updated On: May 31, 2020)

Vitamin C

If you have borderline high blood pressure and your doctor doesn’t think you need medications yet, you might wonder what you can do from a natural standpoint to lower your blood pressure. While there are foods and certain supplements that may modestly reduce blood pressure, an overall healthy lifestyle is the best approach. Strategies that help lower blood pressure include weight loss, exercise, and consuming a nutrient-dense, whole food diet that contains potassium-rich fruits and vegetables. Some people also question whether vitamin C can lower blood pressure.

Can Vitamin C Lower Blood Pressure?

Vitamin C is an antioxidant vitamin, one that helps reduce oxidative stress. It plays a key role in immune and connective tissue health. Vitamin C also aids in wound healing and helps you absorb iron from the foods you eat. The best source is fruits and vegetables, as animal foods contain little or no vitamin C. Therefore, if you aren’t eating your fruits and veggies, you may fall short in this vitamin that Linus Pauling popularized.

According to Johns Hopkins, taking rather large doses of supplemental vitamin C helps lower blood pressure. They concluded this after reviewing 29 randomized, controlled studies of people who took vitamin C over various periods of time. The RDA for vitamin C is 75 milligrams daily for women and 90 milligrams for men.

The conclusion was that taking in 500 milligrams of vitamin C, over 5 times the RDA, can lower blood pressure as much as 5 mm. Hg. in those who have hypertension. The effects were more subdued in those who didn’t have hypertension. In these subjects, there was only, on average, 3.84 mm. Hg. Still, that would be enough for some people to potentially avoid taking blood pressure medications.

What few people realize is that vitamin C has a mild diuretic effect on the kidneys. By removing sodium from the body, vitamin C can lower blood pressure. Another way vitamin C may lower blood pressure is by improving endothelial function, the way blood vessels behave. It may do this is by boosting nitric oxide, a gas that expands the walls of arteries, thereby lowering pressure. When your arteries expand, the resistance to blood flow drops and so does your blood pressure.

How Safe Is It to Take High Doses of Vitamin C?

Despite evidence that taking 5 times more than the RDA for vitamin C can lower blood pressure, is it practical or safe to do so? Vitamin C supplements are safe for most people, although taking 5 times the recommended daily dose could be problematic for some. For example, consuming high doses of vitamin C increases the risk of developing calcium oxalate kidney stones in people already at high risk. If you’ve had kidney stones in the past, it’s best to avoid consuming a high dose. According to WebMD.com, taking over 1,000 milligrams of vitamin C in supplement form daily elevates the risk of kidney stone recurrence. The tolerable upper limit for vitamin C is 2,000 milligrams daily.

Another problem with taking high doses of vitamin C are the digestive side effects. Taking vitamin C supplements can cause digestive upset, nausea, stomach cramps, and diarrhea. The tolerance to taking vitamin C supplements varies between individuals. You might experience no problems taking 500 milligrams of vitamin C daily while someone else might have diarrhea.

Diabetics should be wary of consuming vitamin C as a supplement too since vitamin C supplements can trigger a rise in blood glucose in some diabetics. Plus, studies show that taking over 300 milligrams of vitamin C each day may increase the risk of dying of heart disease in diabetics.

Vitamin C also boosts iron absorption from the gut. A percentage of the population has a condition called hemochromatosis where their body absorbs and stores too much iron. Some have a milder version of the disease and don’t even know it. If these individuals take high-dose vitamin C, they’ll absorb more iron and can build up dangerous levels of iron in their liver, kidneys, and other tissues. So, it’s best to talk to a doctor before taking a vitamin C or iron supplement.

Can Vitamin C Reduce the Risk of Cardiovascular Disease?

Studies have looked at whether vitamin C lowers the risk of cardiovascular disease. If it can reduce your odds of heart disease AND lower blood pressure, that might be more reason to take it. Some studies suggest moderate benefits from taking vitamin C for heart health, however, most of these studies were observational. Randomized controlled trials show little benefit.

The Bottom Line

Evidence suggests that taking at least 500 milligrams of vitamin C daily may lead to a modest fall in blood pressure. However, there are drawbacks to taking vitamin C in supplement form, especially at high doses. Another approach would be to eat more vitamin C -rich foods including fruit. Some of the best sources are citrus fruit, kiwi, papaya, strawberries, and cantaloupe.

Some vegetables are also high in vitamin C, particularly bell peppers, broccoli, and sweet potatoes. However, cooking these vegetables destroys some of the vitamin C. Some so-called superfoods are also rich in vitamin C. These include rose hips, acerola cherries, and camu. For example, a half-cup of acerola cherries contains 822 milligrams of vitamin C. So, a cup of acerola cherries contains more than the quantity of vitamin C shown to lower blood pressure. Plus, you’re getting vitamin C in the context of food.

If you include a variety of fruits and vegetables in your diet, you should be able to get enough vitamin C in your diet for a healthy heart and blood vessels. Plus, fruits and veggies are an excellent source of potassium for heart health and phytonutrients with an anti-inflammatory effect. Science now shows that inflammation is a driver of cardiovascular disease too. So, enjoy more plant-based foods!

 

References:

  • Johns Hopkins Medicine. “Big Doses of Vitamin C May Lower Blood Pressure”
  • com. “Vitamin C”
  • National Institutes of Health. “Vitamin C”
  • Am J Clin Nutr. 2012 May; 95(5): 1079–1088.Published online 2012 Apr 4. doi: 10.3945/ajcn.111.027995.
  • Can J Physiol Pharmacol. 2002 Dec;80(12):1199-202.
  • com. “Vitamin C (Ascorbic Acid)”
  • Int J Mol Sci. 2016 Aug; 17(8): 1328.Published online 2016 Aug 12. doi: 10.3390/ijms17081328.
  • 2014 Jul;235(1):9-20. doi: 10.1016/j.atherosclerosis.2014.04.004. Epub 2014 Apr 18.
  • MedLine Plus. “Vitamin C”
  • com. “20 Foods That Are High in Vitamin C”

 

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