|
For almost a decade, researchers have understood that oxidized LDL plays a critical role in the formation of atherosclerotic plaques. Animal experiments show that antioxidant supplements inhibit atherosclerosis, while epidemiologic studies link high intake of antioxidants, especially vitamin E, with reduced risk of heart disease.
Because it is water soluble, vitamin C is one of the most effective antioxidants in blood plasma. In lab tests it inhibits oxidation of LDL cholesterol and is the first plasma antioxidant used up during oxidative processes. It also either spares vitamin E from oxidation or helps regenerate it.
In 1991, Jukka Salonen, Riitta Salonen and colleagues at the Research Institute of Public Health at the University of Kuopio in Finland published an article in the British Medical Journal that linked low blood levels of vitamin C to increased progression of atherosclerosis. These same researchers, joined by Kristiina Nyyssonen, recently completed an eight-year study of the relationship between vitamin C deficiency and heart attack risk.
In 1984 the researchers gathered 1,605 men aged 42 to 60 who had no heart disease and measured their plasma ascorbate (vitamin C) levels at baseline. They repeated the measurement four to nine years later. Vitamin C concentrations below 11.4 µM/L (micromole/liter) (2 mg/L) defined deficiency.
Researchers also measured the men's blood pressure, blood cholesterol levels and triglyceride levels. In the course of investigating subjects' personal and family history of heart disease, tobacco and alcohol use, diet and supplement intake, researchers discovered that only 5.5 percent of subjects took extra vitamin C.
Of the 1,605 men, 91 were vitamin C-deficient. These men tended to be older and of lower socioeconomic class. They also smoked more, exercised less, and drank more alcohol and coffee.
Baseline vitamin C deficiency increased the risk of heart attack during subsequent years. Of the men deficient in vitamin C, 13.2 percent had heart attacks, compared to 3.8 percent of the men with higher levels--a four-fold increased risk. After adjustment for other risk factors, low blood levels of vitamin C still doubled the relative risk (2.5) of heart attack. Vitamin C-deficient men also tended toward higher blood pressures.
Men at intermediate vitamin C levels had no statistically significant increased risk. The authors concluded that failing to meet minimum requirements posed a danger but that high intakes of vitamin C probably would not further reduce heart attack risk.
--British Medical Journal, 314: 634-38, March 1997
|
