Many studies have evaluated the effect of vitamin C (ascorbic acid) on cardiovascular health, with disappointing results. That is why the report of Dr Gladys Block and her colleagues at the University of California, Berkeley was met with surprise, and well, scepticism.
The Berkeley researchers report in the Nutritional Journal that the concentration of vitamin C in the plasma is inversely linked to blood pressure. This means that the higher the vitamin C levels in the plasma, the lower is the blood pressure. This association was observed among 242 young women aged 18 to 21 years old who were participants in the 10-year National Heart, Lung, and Blood Institute Growth and Health Study on adolescent obesity.
The author notes:
“It appears that the BP is less likely to rise if people have a good level of plasma vitamin C…This study suggests that vitamin C may be an important factor in BP regulation even among healthy young adults and that further study is warranted.”
The possible mechanism for this blood pressure lowering properties might be that vitamin C significantly decreases the levels of 2 substances: F2-isprostane, which is a marker of oxidative stress, and C-reactive protein (CRP), which is a marker of inflammation. Both inflammation and oxidative stress play a role in cardiovascular disorders, including hypertension.
Many experts do not believe that vitamin C can have some cardiovascular benefits. For one thing, the data was criticized as poor, being based only on women who are overweight or obese. In cases like this, comparative studies just simply give more credibility.
Hypertension expert Dr Franz Messerli of St Luke’s Roosevelt Hospital, New York comments at heartwire:
“To my way of thinking, plasma vitamin-C level in this population could be simply a good biomarker for intake of fruit and vegetables. Thus, the more fruits and vegetables these young women ate (ie, the healthier their diet), the lower their salt intake and not surprisingly, the lower their blood pressure… Vitamin C is a powerful antioxidant in vitro, and in some animal studies it has been shown to act as a vasodilator, possibly by enhancing the bioavailability of nitric oxide. But a recent study has failed to show an effect of the acute oral ingestion of vitamin C on oxidative stress, arterial stiffness, or blood pressure in healthy subjects.”
Despite the criticisms and scepticism, Dr. Block is planning to further investigate the vitamin C – blood pressure link in a large-scale randomized study.
Regardless whether vitamin C can lower blood pressure or not, the fact remains that eating fresh fruit and vegetables is beneficial to our health. And eating vitamin C-rich fruit such as oranges and other citrus fruits cannot hurt anybody.