A new study raises the disturbing possibility that taking vitamin C pills could speed up hardening of the arteries. Researchers called their discovery a surprise and cautioned that more experiments are needed to know for sure whether megadoses of the vitamin actually are harmful.

Many people load up on vitamin C and other nutrients on the assumption that these supplements are good for their health, even though there is little scientific evidence this is true. In theory, vitamin C and some other nutrients might protect the circulatory system and other organs by suppressing the damaging effects of oxygen. "When you extract one component of food and give it at very high levels, you just don't know what you are doing to the system, and it may be adverse."

The researchers studied 573 outwardly healthy middle-aged men and women who work for an electric utility in Los Angeles. About 30 percent of them regularly took various vitamins. The study found no clear-cut sign that getting lots of vitamin C from food or a daily multivitamin does any harm. But those taking vitamin C pills had accelerated thickening of the walls of the big arteries in their necks. In fact, the more they took, the faster the buildup.

People taking 500 milligrams of vitamin C daily for at least a year had a 2 2/4 times greater rate of thickening than did those who avoided supplements. Among smokers, the rate was five times greater. If you are a healthy person and taking them in hopes of preventing cardiovascular disease, the heart association does not recommend it.

The research shows the uncertainties of picking out a single vitamin among the plethora of nutrients in a healthy diet. It's a challenge to sort out what it is in what people eat that makes them live longer. In general, experts recommend that people get their vitamins and other nutrients from fruits, vegetables, whole grains and nuts. Clogged arteries - what doctors call atherosclerosis - are the major underlying cause of heart attacks and strokes. In the latest study, doctors looked for early signs of this process by twice performing ultrasound scans on the volunteers' carotid arteries, once at the study's start and again 18 months later.

Meeting of the American Heart Association San Diego March 2, 2000

Dr. Mercola's Comments:

I intentionally avoid most traditional media, so I don't read newspapers, watch any television (aside from ER) or listen to the radio (aside from instrumental). So I am not sure if this study was widely disseminated, but I suspect it was. It may shatter many people's vision of vitamin C. There are several important principles to keep in mind. The first is that this study is not even published, it was merely reported at a meeting. So it is very preliminary and not peer reviewed. There may be some flaw in the methodology of the study. However, there is the possibility that the study is perfectly valid and that high dose vitamin C may cause worsening of plaque build up. If this is true, it would turn traditional supplement nutrition on its head as that is one of the foundational basic tenets that vitamin C is virtually harmless. It is clear further study is required by additional investigators that confirm this finding. In the meantime, it is wise to get most of your vitamin C, as nearly all vitamins, from clean organic food. Vegetables are generally the highest sources of most of these nutrients, especially if eaten raw. It is hard to go wrong when you get the entire nutrient base rather than selectively extracting what our limited science perceives to be the active ingredient. Many vitamin companies are very similar to drug companies with the same greed models involved. More and more my goal is to get patients off of vitamins and supplements and to support their program with whole foods. I think it is still wise to take a balanced vitamin C with bioflavanoids just prior to exercise to limit the oxidative damage that exercise causes. My personal supplements consist of MSM-three twice a day (a source of organic sulfur); evening primrose oil-two in the morning; one fish oil capsule in the morning and two phosphatidyl choline capsules in the morning (an extract of lecithin). I also take phosphatidyl serine at night to enhance my memory recall.