Main Menu To Health Library Antioxidants and Heart Disease
VITAMIN C and CARDIOVASCULAR DISEASE
Abstract: Vitamin C in amounts of about 400 mg per day reduces the risk of heart and probably cardiovascular diseases by a risk factor of 0.75, or about 25%. As it probably acts as an antioxidant it will reduce risk only over time at a rate of about 0.97 per year of use and require 10 years of use to obtain this 25% reduction in risk. Note an accompanying review of research that shows that Vitamin C also reduces risk of cancer. Because few people obtain an optimum amount of Vitamin C from foods, research suggests that most health-interested persons should take a Vitamin C supplement of about 500 mg/day.
The benefit of Vitamin C on health has been a subject of much controversy and interest since the popularization of its benefits by well known Linus Pauling in the 1970's. Vitamin C is probably the most popular vitamin used as a supplement, and usually is included in amounts of about 200-250 mg per day in multi-vitamins and at 500 mg per day and more in direct supplements. The RDA value of 60 mg/day is presumably an amount needed to prevent diseases of insufficiency such as scurvy. This amount has little relevance today to the amounts of vitamin C useful for reducing risks of heart disease and cancer.
Results of key research found that identifies the effect of Vitamin C supplements on risk of coronary heart disease are summarized in Table C following.. The individual risk ratios vary from 0.59 to 1.00, but this is the expected variation for results for studies of their identified individual margins of error. Studies showing nil effect of the vitamin used very small amounts in their comparisons. All are statistically consistent with an average risk ratio of 0.75 for 10 years use of about 400 mg per day of the vitamin and an average likely benefit from all studies is confirmed with adequate statistical significance. Vitamin C has been identified as an antioxidant by biochemical research. Its effect on coronary risk probably will be duration dependent as is true for Vitamin E, although no data were found available that show this directly. An average duration value for the average difference of about 400 IU of vitamin C in the Table C is a risk ratio-time of exposure value about 0.97 per year. Life Ahead now acknowledges duration related reduction in risk only for a period of 20 years. Thus although Vitamin C is not as useful as Vitamin E in reducing risk, it still should provide some useful antioxidant protection.
The margins of error of the individual studies found are too high to identify clearly an effect of amount or dose. The amount of vitamin C from foods in usual US diets usually ranges from 150 to 300 mg. Dietary amounts can be increased substantially by eating more fruits and vegetables. Because of a lack of data confirming the benefit of higher values Life Ahead limits the amount of Vitamin C that can contribute to risk to 750 mg per day from both food and supplements, and assumes benefit will be related to its amount within this range. As for all Life Ahead risk measurements, these are derived as differences from base values of the US population that for Vitamin C is assumed at 200 mg/day. See the discussion of overall use of antioxidants.
The results on Vitamin C provide an example of the fallacy of the 'Statistically Significant" dogma now popular among health researchers when results from multiple studies become available. The average margin of error in studies C1-C7 is the usual risk ratio spread of 0.6 or 60% obtained in health research, and the average or probable best risk ratio value is 0.75. Thus if a correct risk ratio is 0.75, a typical study will have an error range of from 0.45 to 1.05. Because risk ratios of multiple studies thus will by statistical definition range from below 0.45 to above 1.05, about a third of such studies will be classed as "Not significant" and results can be reported incorrectly via present dogma that "Vitamin C has no effect'. This is very misleading. For research having such error margins and risk ratios only an averaged result of all useful multiple studies available can have useful meaning. Continuing research forever will continue to obtain a similar mix of "significant" and "not-significant" studies from a value of null. .
By combining study results as usually is done in a meta Analysis we can reach a conclusion. From results of the nine comparisons below that all are statistically consistent with this 0.75 value, we can compute that the probable risk value is 0.75 with a 5-95% margin of perhaps 0.6-0.9. This a modest effect that is very difficult to measure because of the usual margins of error of population type studies. But it supports a potential health action that probably should increase Well-Days of life to some extent.
Vitamin C is not valued directly in Life Ahead. As for other antioxidants its potential effect is combined with those of Vitamins A, E, and Selenium. A maximum effect of all these antioxidants is recognized. This means that if a person is taking other supplements as for example Vitamin E in amounts of more than 200 IU per day and some Vitamin A, there may be no measurable added benefit for taking Vitamin C. Thus health-interested populations that use healthful diets and and also use vitamin supplements may fail to develop benefits from a next added supplement. This behavior which may confuse results of some population studies is recognized in Life Ahead.
Vitamin C also reduces risk of cancer. Benefits for cancer seem verified to amounts of about 750 mg/day. Because foods in most diets usually include only 200 to 350 mg/day, health-interested persons should consider adding Vitamin C in amounts of 500 mg/day to their diets.
Table C