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VITAMIN C and CARDIOVASCULAR DISEASE

Abstract:  Vitamin C in amounts of about 500 mg more per day above low amounts of 50 mg in diets probably will reduce the risk of heart and probably cardiovascular diseases by a risk factor of 0.77, or about 23%.  As an antioxidant this benefit may reduce risk only over time at a rate of about 0.98 per year of use and require 15 years of use to obtain a 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 consider taking a Vitamin C supplement of about 400-500 mg/day.  Life Ahead now includes Vitamin C as one of four antioxidants that in combination and over a time of 20 years should produce this benefit.

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 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.  26 of the 30 comparison values listed from observation studies confirmed a benefit for Vitamin C.  The individual risk ratios average 0.77 and vary from 0.32 to 1.00, but this is the expected variation for results for studies of their identified individual margins of error.  Six studies of Vitamin C and Stroke indicated an average risk ratio of about 0.60 or a 40% reduction in risk.  Studies that did not show a useful effect of the vitamin used very small amounts of Vitamin C. Nearly all studies are statistically consistent with an average risk ratio of 0.75 for 15 years use of about 500 mg per day of the vitamin and an average likely benefit from all studies is confirmed with more than adequate statistical significance.  Results on Vitamin C were measured from amounts in diets that in some cases included additional amounts in supplements.

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 500 IU of vitamin C in the Table C is a risk ratio-time of exposure value about 0.985 per year over 20 years. Values for duration in Table C assume that duration of use at start of studies probably was about 10 years.   Life Ahead now acknowledges a duration related reduction in risk only for a period of 20 years.  Vitamin C together with Vitamin A usually are the primary antioxidants in fruits and is a key factor involved in their positive role in health.  Assuming a usual amount of 150-300 mg in a diet, a useful health target for Vitamin C will be about 600 mg per day. While this can be achieved by targeted diets, a supplement usually will be needed. 

The amount of vitamin C from foods in usual US diets usually ranges from 50 to 150 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.  An average risk of 0.77 is computed from all data on heart and cardiovascular disease.  Study C7 provides an estimate of 0.76 from pooled analysis of results of nine studies that included results of either diet or diet plus supplements. This study included some but not all of the studies in the following table and developed results similar to those suggested above.   Study 20 provides an average risk of 0.84 from a pooling of 15 studies but this did not list amounts involved.   An average  benefit found for 4 studies of amounts of Vitamin C in blood showed an average risk of 0.53, or a 47% reduction in risk.  See the discussion of overall use of antioxidants. A formula is discussed following Table C that relates likely risks of amounts of Vitamin C and duration of the vitamin use.  Results from the formula are in the following table should provide a conservative estimate of risk.

                    Risk of Cardiovascular Disease vs

               Amount and Duration of use of Vitamin C

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.  This problem as caused massive confusion among researchers who usually view results only of a few recent studies about the effects of antioxidants and other factors.

No effect of Vitamin C was found is a studies RC1 of women professionals that were patients of CVD or related diseases or in CO1 for those having diabetes. .  This confirms the usual finding that antioxidants do not improve the risk of those suffering the disease or who have advanced atherosclerosis.

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 also use vitamin supplements may fail to develop benefits from a next added supplement.  This behavior that probably confuses results of some population studies is recognized in Life Ahead.

Vitamin C also probably 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.

See other papers of antioxidants and CV disease for Vitamin E;  Vitamin A;   Selenium , papers of antioxidants and cancer for Vitamin E;  Vitamin A;  Vitamin C; and Selenium, and Antioxidants, Death from All Causes. and Antioxidants, a Global Analysis.

                                                              Table C

       Risk of Heart or Cardiovascular Disease vs. Amounts of Vitamin C in Diets plus Supplements

A formula for estimating risk of cardiovascular diseases from use of Vitamin C"

amt is amount of Vitamin C in mg

yrs is duration of use of Vitamin C

Risk ratio =  exp( -0.00094 * yrs * amt^^{0.5 )}

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