The big picture on blood pressure and vitamin C

To study the potential connections between vitamin C supplements and blood pressure levels, researchers used meta-analysis to combine and analyze data from 29 previous randomized, controlled trials on this topic. Hypertension is defined by categories of severity with a blood pressure:

• Between 120/80 and 139/89 as prehypertension,
• between 140/90 and 159/99 as hypertension stage 1,
• between 160/100 and 179/100 as hypertension stage 2, and
• above 180/110 as a hypertensive crisis, which requires immediate, emergency medical care.

Using the meta-analysis approach, the study authors found the following:

• The median dose of vitamin C used in the studies was 500 mg per day, and the range studied was 60 to 4,000 mg daily.
• The median length of the studies was eight weeks, and the duration of the studies ranged from 2 to 26 weeks.
• In all participants, vitamin C supplementation reduced systolic blood pressure--the top number in a reading--by an average of 3.84, and reduced diastolic blood pressure--the bottom number--by an average of 1.48.
• In participants with hypertension--a blood pressure reading of 140/90 and above--vitamin C supplementation reduced systolic blood pressure by 4.85, and reduced diastolic blood pressure by 1.67.

Vitamin C for a healthier BP

The meta-analysis approach allows for larger numbers of people to be studied together, and typically, more study subjects makes for a stronger study. As well, this research only included controlled trials of vitamin C supplementation, not observational studies. Controlled, blinded trials are considered the "gold standard" of research, so results are more likely to have uncovered a true connection between vitamin C and blood pressure reduction than observational studies.

Our tips on vitamin C and other ideas for supporting a healthy blood pressure will put you on the path to your best cardiovascular health:

• Take it right. The median amount of vitamin C was 500 mg per day, which is considered safe for most people. Talk to your doctor about whether this is right for you, and if you may benefit from amounts above 500 mg per day.
• Know your numbers. Hypertension has no obvious outward symptoms. The only way to know your blood pressure is to get it checked. Talk to your doctor about how often you need to get checked.
• Eat well. Base your diet around lots of fresh vegetables and fruit--at least five servings per day--and include two or three servings of low-fat dairy daily. Eat no more than a few servings of red meat per week.
• Skip salt. Limit processed foods high in sodium (salt), and up your potassium intake, by including green leafy vegetables, beans and lentils, low-sodium tomato juice and sauce, oranges and orange juice, prunes and plums, bananas, apricots, and raisins.
• Move more. Regular exercise can help keep blood pressure lower, and help control weight, important because being overweight is a high blood pressure risk factor.

(Am J Clin Nutr 2012;95:1079-88)