In an article published online on December 17, 2008 in Nutrition Journal, Gladys Block of the University of California, Berkeley and her associates report that young women who have higher plasma levels of vitamin C have lower systolic and diastolic blood pressure as well as a reduced increase in blood pressure over a one year period compared with those whose levels of the vitamin are low.
The current analysis included 242 African-American and Caucasian participants in the National Heart, Lung and Blood Institute Growth and Health Study, a ten year longitudinal study designed to evaluate the development of obesity in adolescent girls aged 8 to 11 upon enrollment. Blood pressure was measured at the ninth and tenth annual follow-up visit, and blood samples obtained at the tenth visit were analyzed for plasma ascorbic acid (vitamin C) levels.
Following adjustment for body mass index and other factors, the research team found that women whose plasma vitamin C levels were among the top 25 percent had systolic blood pressure that averaged 4.66 mmHg lower and diastolic blood pressure that averaged 6.04 mmHg lower than women whose vitamin C was in the lowest 25 percent. When blood pressure readings from the tenth year of the study were compared with those of the ninth year, women with plasma vitamin C in the lowest 25 percent were found to have experienced an average diastolic increase of 5.97 mmHg, while those whose vitamin C levels were highest had only a 0.23 mmHg increase. A similar effect was observed for systolic blood pressure.
In their discussion of the findings, the authors remark that the antioxidant effect of vitamin C helps protect against oxidative mechanisms involved in the development of hypertension. Additionally, in a clinical trial conducted by Dr Block and colleagues, vitamin C was shown to reduce C-reactive protein, a marker of inflammation, which is associated with endothelial dysfunction and high blood pressure. "Thus, vitamin C may have a beneficial effect on blood pressure by mitigating the adverse effects of inflammation and oxidative stress," they write.
The authors note that their results were comparable in magnitude to those of the Dietary Approaches to Stop Hypertension (DASH) trial, which found a 5.5 mmHg average reduction in systolic blood pressure and a 3.0 mmHg average diastolic reduction in participants who consumed the DASH diet. They suggest that increasing plasma vitamin C to levels comparable with those of participants in the top one-fourth of the current study might achieve a similar effect.
"The findings suggest the possibility that vitamin C may influence blood pressure in healthy young adults," the authors conclude. "Since lower blood pressure in young adulthood may lead to lower blood pressure and decreased incidence of age-associated vascular events in older adults, further investigation of treatment effects of vitamin C on blood pressure regulation in young adults is warranted."Related Health Concern: High blood pressure
Men and women with prehypertension (120-139/80-89 mm Hg) should have a goal of lowering their blood pressure to 115/75 mm Hg, unless they have chronic kidney disease or diabetes, in which case the goal should be less than 130/80 mm Hg (Chobanian AV et al 2003). Prehypertension can be treated with lifestyle modifications, unless the individual has chronic kidney disease or diabetes, in which case antihypertensive drugs are often recommended (Chobanian AV et al 2003).
People with high blood pressure or those who are prehypertensive can lower their blood pressure by losing weight and increasing physical activity (especially by doing aerobic activity for at least 30 minutes every day). The following major dietary modifications can also be helpful:
- Initiate the DASH (Dietary Approaches to Stop Hypertension) eating plan, which increases dietary potassium, fiber, and calcium intake through a diet rich in fruits, vegetables, low-fat dairy products, whole grains, and foods with reduced saturated fat and reduced total fat content (Chobanian AV et al 2003). The DASH plan is also rich in magnesium, a crucial mineral that may help promote optimal blood pressure levels (Geleijnse JM et al 2004).
- Limit alcohol consumption to no more than two drinks a day for men and no more than one drink a day for women (Chobanian AV et al 2003).
- Reduce salt intake to no more than 2.4 grams (g) of sodium or 6 g of sodium chloride each day.
Vitamin C, also known as ascorbic acid, is an antioxidant that protects other biochemicals from oxidation by being oxidized itself. A small, well-controlled study of 39 participants showed that treatment with vitamin C significantly lowered blood pressure after 30 days, while placebo had no effect (Duffy SJ et al 1999).
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