Healthnotes Newswire —People who consume the most vitamin C from their diets may only have half the death rate of people who consume the least vitamin C, according to the findings of a four-year study that will appear in Saturday’s Lancet.1
The most dramatic finding was a 93% decrease in the risk of death from heart disease in women who consumed the most vitamin C compared with those who consumed the least. Men in the highest category for vitamin C intake had a 68% lower risk of dying from heart disease and a 53% lower risk of dying from cancer than men who consumed the least vitamin C. Except for a weak association between increased vitamin C intake in women and reduced cancer deaths, all of these findings were statistically significant.
Fruits and vegetables provide the best dietary sources of vitamin C. As a result, the correlation between vitamin C intake and consumption of fruits and vegetables was very high. The researchers believe the association between high vitamin C intake and low death rates reflects the protective effects of eating fruits and vegetables, although they acknowledge that vitamin C itself may have played a significant role. For every increase of 50 grams of fruit and vegetables per day—less than two ounces—there was a corresponding 20% reduction in the risk of dying during the four-year study. The researchers concluded, “Small increases in fruit and vegetable intake of about one serving daily has encouraging prospects for possible prevention of disease.”
People who consumed more dietary vitamin C had lower blood pressures and were less likely to be smokers, to have diabetes, or to be overweight. However, the associations between eating foods high in vitamin C and reduced death rates remained statistically significant even when the researchers looked beyond these associations. For example, overweight smokers with high vitamin C intake fared better than overweight smokers with low vitamin C intake.
Several previous studies measured vitamin C intake by asking people about their diets. However, such dietary questionnaires are known to be somewhat inaccurate. In an attempt to avoid this problem, these researchers measured blood levels of vitamin C, which reflect recent intake of the vitamin. Categories of vitamin C intake were represented by “quintiles” of blood levels of the vitamin; those in the lowest fifth of blood vitamin C levels were compared with those in all higher levels, and also with those in the highest fifth of blood vitamin C levels.
The subjects of the new report were more than 19,000 men and women from Norfolk, England, with no history of heart disease, cancer, or stroke. The vitamin C blood levels were measured only once. The researchers acknowledged that the lack of further measurement of vitamin C levels might have weakened the findings of their report, because blood levels of the vitamin can vary significantly in one person over time.
How About Supplements?
People who took any supplements had almost the same risk of dying during the four-year period as did people who took no supplements. However, researchers did not focus on the isolated effects of taking vitamin C supplements.
When use of all supplements is placed into one category, scientists know that interpreting the data becomes difficult. Some people take supplements because they are sick. Other people who take supplements are health-conscious and are likely to engage in other health-promoting behaviors. These and other factors make supplement takers different from people who do not take supplements. The authors of the report acknowledge that their study does not tell us whether adding vitamin C supplements to a vitamin C-rich diet would drive death rates even lower.
How Much is Enough?
Men in the group with the highest intake of vitamin C consumed an average of about seven ounces of fruit and almost four ounces of vegetables per day. Women in the highest intake group consumed approximately an ounce more fruit and the same amount of vegetables as the men.
The relationship between higher vitamin C intake and reduced death rates was approximately linear—the higher the C intake, the lower the death rate. People consuming even less vitamin C from their diets than those in the lowest quintile studied might suffer even higher death rates, an idea supported mostly by animal research and reasonable guesswork on the part of scientists. At the other end of the continuum, people who consume a diet even richer in vitamin C than those with the highest intake studied in the new report might have an even lower death rate, but the current study does not provide the information necessary to resolve this question.References