April 27, 2000 -- A new study from the U.K. confirms previous research showing vitamin C supplements can lower blood pressure. But other research shows that vitamin C supplements also might harden the arteries, increasing the risk for heart attack or stroke. So what should you do?
"I believe vitamin C from a balanced diet is much better for people than popping capsules," says study co-author, Martin D. Fotherby, MD.
Blood pressure is the force of the blood pushing against the walls of arteries each time the heart beats. When the heart contracts and pumps blood the pressure it exerts on blood vessel walls is called systolic pressure. The pressure on the vessel walls between beats is called diastolic pressure. Blood pressure is always given as these two numbers, systolic and diastolic pressures. Usually they are written one above the other, for example 120/80 mmHg, with the top number the systolic pressure, and the bottom the diastolic pressure.
In the new study conducted at The Glenfield Hospital in Leicester, 40 adults all between the ages of 60 and 80 with slightly elevated blood pressure were given 250 mg of vitamin C capsules twice a day for three months. At the end of the study researchers noted a small but significant fall in systolic blood pressure but not in diastolic blood pressure. The study appeared in the May 2000 issue of the Journal of Hypertension.
Fotherby, who is a senior lecturer at the University of Leicester, in England, says the dose of vitamin C used in this study, 500 mg per day, is substantially larger than the level recommended for healthy adults. For some time, that amount was 60 mg, but the Institute of Medicine in the U.S. recommended it be raised to 75 mg per day for women and 90 mg per day for men. According to the American Dietary Association (ADA) one 8-ounce serving of orange juice contains about 97 mg of vitamin C.
Fotherby concluded that the results confirmed previous research showing a relationship between higher vitamin C intake and lower risk of cardiovascular disease and stroke. Most recently, two studies at the Boston University School of Medicine showed that the average systolic pressure of the subjects had fallen after one month of taking 500 mg of vitamin C.
On the other hand, recent research conducted at the University of Southern California and presented at an American Heart Association meeting showed that men who took 500 mg of vitamin C developed thickening of their artery walls, increasing their risk of heart attacks or strokes.
So how can vitamin C both reduce blood pressure and harden the arteries? Fotherby says no one really knows, but he has a theory. "Although we gave capsules to the subjects in our study, food sources of vitamin C are far superior," says Fotherby. "Since foods contain many other nutrients, including other antioxidants, they work together to promote overall health."
Sound nutrition has long been the advice of the American Heart Association, the American Cancer Society and other health organizations, particularly those that promote a minimum of five servings of fruits and vegetables per day.
The ADA says research on the relationship between diet and disease has indicated the importance of a variety of nutrients. The best nutritional strategy for promoting optimal health and reducing the risk of chronic disease is to obtain adequate nutrients from a wide variety of foods, according to the ADA. Vitamin and mineral supplementation is appropriate when scientific evidence shows safety and effectiveness, but good nutrition depends on a good diet, the ADA says.
- Different studies have shown that vitamin C supplements lower blood pressure but can also cause hardening of the arteries.
- In these studies, people took 500 mg of vitamin C supplements per day, which is much greater than the recommended daily amount.
- Researchers do not know how vitamin C causes these effects, but they advise people to continue to get vitamin C from their diet, which is much healthier than taking a supplement.