A Critical Analysis of The National Academy of Sciences' Attack on Dietary SupplementsAugust 2000
By William Faloon
Consumers of vitamin supplements have been hit with a lot of negative press lately, and The Life Extension Foundation has been on the forefront in evaluating whether these anti-supplement reports have scientific merit.
Two months ago, we examined a presentation made at an American Heart Association meeting where a doctor stated that compared to non-supplement users, vitamin C takers had higher rates of carotid artery wall thickening. In response to this claim, The Foundation conducted an identical test on 30 members who had been taking very high doses of vitamin C (and many other nutrients) for many years. Results showed that these vitamin C supplement takers as a group had remarkably healthy carotid arteries compared to the average population. The group we tested were significantly older than the people evaluated by the American Heart Association. Our group should have had more evidence of carotid atherosclerosis and thickening. Instead, Foundation members as a group were found to have no indication of increased carotid wall thickening in response to their very high vitamin C intake. We also showed how this American Heart Association presentation, which looked at people taking relatively low potencies of vitamin C (500 mg a day and less), had no relationship to Life Extension Foundation members who are taking very high doses (2000 mg a day and higher) of vitamin C along with other nutrients that have been shown to reduce the risk of atherosclerosis.
On April 10, 2000, the National Academy of Sciences issued a press release that stated:
"Insufficient evidence exists to support claims that taking megadoses of dietary antioxidants, such as selenium and vitamins C and E, or carotenoids, including beta-carotene, can prevent chronic diseases."
This report received widespread media attention, and many news articles questioned the value of dietary supplements altogether. The National Academy of Sciences’ press release was based on the conclusions of a 512-page book that ostensibly looked at all the published scientific literature about the intake of certain nutrients and subsequent risk of developing disease.
Contradiction and Omission
The name of this 512-page book is Dietary Reference Intakes For Vitamin C, Vitamin E, Selenium and the Carotenoids. This book contains a startling contradiction. The negative conclusions drawn by the authors are opposite to the positive findings about the supplements that are described in the very same book. This contradiction is not surprising, considering that the book is authored by two “committees” comprised of 40 members.
The book omits published studies about antioxidants. It also fails to take into account that supplement takers usually consume a wide variety of nutrients to protect their health, not just vitamin C or E alone. The authors of the book did capably describe many of the positive studies indicating a disease risk reduction in response to a particular supplement. But it turns pessimistic when even one study fails to confirm the many positive ones. An example of the pessimistic tone can be seen in the following quotation that appeared on page 187:
"A large and growing body of experimental evidence suggests that high intakes of vitamin E may lower the risk of some chronic diseases, especially heart disease. However, the limited and discordant clinical trial evidence available precludes recommendations at this time of higher vitamin E intakes to reduce disease risk."
This statement is followed by numerous pages itemizing the studies showing that vitamin E prevents chronic diseases. For instance, the author’s analysis of observational human studies shows “risk reductions of 30% to 60%” in coronary heart disease risk in those consuming the highest amounts of vitamin E. Despite these reductions in heart attack risk, the authors stated, “As of this date, there are insufficient data on which to base a recommendation for vitamin E as a heart disease preventive to the general population.” The authors did, however, raise the “safe” upper dose limit of vitamin E to 1500 IU a day.
It should be emphasized that the book essentially supports dietary supplementation for the purpose of disease reduction. In fact, this book makes a strong case that these supplements (vitamin C, vitamin E, selenium and the carotenoids) produce significant health benefits. The negative twist, however, comes when the authors conclude that there is “insufficient evidence” to recommend that the general population supplement with these nutrients.
What are "Dietary Reference Intakes"?
The primary purpose of this book is to establish new government recommended daily allowances for vitamin C, vitamin E, selenium and the carotenoids. The new term for RDA is “Dietary Reference Intakes,” which is defined as “reference values that are quantitative estimates of nutrient intakes to be used for planning and accessing diets for apparently healthy people.”
One problem with this definition of “Dietary Reference Intakes” is that it fails to take into account that as people age, they are no longer “apparently healthy.” While some aging people optimistically claim to be as healthy as ever, aging wreaks havoc in every cell of the body. The authors recognized their limits in setting new “Dietary Reference Intakes” by admitting that they were not able to estimate the amount of these nutrients “required by children, adolescents, lactating women and the elderly.”
Unfortunately, when the press reported on this book, it failed to mention the limitations that the authors themselves placed on their conclusions. In setting these new “Dietary Reference Intakes,” the authors emphasized their limitations by stating that “scientific judgement was required for evaluating the evidence and in setting the reference values.”
“Scientific judgement” is a fancy way of saying that these new recommendations are based on the arbitrary conclusions of two committees. This subjective approach should not be confused with bona fide science, as an evaluation by another group could yield completely different conclusions.
The vitamin E recommendations are a good example of what “scientific judgement” really means. Those concerned about protecting their health take vitamin E because of studies showing “risk reductions of 30% to 60%” in heart attack risk. Yet, in the “scientific judgement” of the committees, there is still “insufficient data” to recommend that people actually take vitamin E supplements.
What They Said About Vitamin C
While increasing the maximum safe daily intake of vitamin C to 2000 mg a day, the authors of the 512-page book set the recommended daily intake of vitamin C as follows:
Males 90 mg
Females 75 mg
Smokers 35 mg additional
(to compensate for the increased “oxidative stress” smoking induces)
These doses of vitamin C, the authors noted, “should maintain near maximal neutrophil ascorbate concentrations with little urinary excretion.”
Supplement users, however, are taking vitamin C for reasons other than to maintain their “neutrophil ascorbate concentrations.” (Neutrophils are specialized immune cells that require vitamin C to kill pathogens and still maintain their cellular integrity.)
As was the case with vitamin E, the 512-page book contains numerous pages of summaries of published papers indicating significant health benefits in response to vitamin C supplementation. One study describes that when smokers were supplementing with 2000 mg a day of vitamin C, “the adhesion of their monocytes to endothelium decreased to that seen in non-smokers.” (Monocyte adhesion is an initial factor leading to the development of atherosclerosis). Instead of recommending that smokers take 2000 mg of vitamin C as the people did in the study, the authors suggest that smokers obtain only 110 to 125 mg per day of vitamin C.
This kind of illogical recommendation is pervasive through the vitamin C chapter. For instance, page 103 of the book states:
"Numerous investigators have reported a beneficial effect of high-dose vitamin C administration, either orally or intraarterially, on vasodilation. This beneficial effect of vitamin C is most likely related to its antioxidant effect. Vitamin C improves endothelial function and vasodilation, possibly by scavenging superoxide radicals, conserving intracellular glutathione, or potentiating intracellular nitric oxide synthesis."
Strangely, the authors interpret these kinds of positive findings as an indication to not take high doses of vitamin C. The 512-page book makes it clear that high doses provide the beneficial effect of vitamin C on the arterial system. The contradictory conclusion, however, is that people only need between 75 and 125 mg of vitamin C a day. These types of contradictions may be explained by the fact that many different people were involved in writing the 512-page book.
When it comes to vitamin C and cancer, the authors again provide substantial data from the published literature to show both potential risk reduction benefit, definitive risk reduction benefit or no risk reduction benefit. Since some studies show no risk reduction benefit, the authors advise against vitamin C supplementation for the purpose of cancer prevention.
A partial list of supplements typically consumed by the serious vitamin consumer
Each one of the above nutrients has been shown to provide specific health benefits, and many work together in a synergistic fashion to protect against the onset of degenerative disease.
The same hold true with immune function. Some studies show positive benefit, others show no benefit. Therefore, according to the authors, vitamin C supplementation is not recommended.
On page 125 of the 512-page book, the authors offer the following conclusion regarding vitamin C and cancer:
"Although many of the above studies suggest a protective effect of vitamin C against specific cancers by site, the data are not consistent, or specific enough to estimate a vitamin C requirement based on cancer."
When evaluating the potential benefit of vitamin C to prevent cataract, the authors describe the following studies:
- 490 mg a day of vitamin C resulted in a 75% reduction in cataract compared to doses less than 125 mg a day.
- 300 mg a day of vitamin C associated with a 70% reduction in cataract.
- Higher intake of vitamin C is associated with a 20% reduction in cataract.
- No association found in cataract risk in people taking 260 mg a day of vitamin C compared to those taking 115 mg a day. (This is considered a negative study.)
- Cataract risk was 45% lower in nurses taking vitamin C supplements for ten years, but no effect was observed for those taking vitamin C for less than ten years.
(This, too, is considered a negative study by the authors.)
Based on the above studies, the authors of the 512-page book concluded:
"Although many of the above studies suggest a protective effect of vitamin C against cataracts, the data are not consistent or specific enough to estimate the vitamin C requirement based on cataract.."
When evaluating the effects of vitamin C on asthma and chronic obstructive pulmonary disease, again the authors cite studies showing a significant protective effect, but their conclusion is:
"Although many of the above studies suggest a protective effect of vitamin C against asthma and obstructive pulmonary disease, the data are not consistent or specific enough to estimate the vitamin C requirement based on asthma or pulmonary disease."
In the summary, the authors make an argument that optimal cardiovascular and cancer protection may occur with total daily vitamin C intake of 90 mg, but state it may be difficult to conduct large-scale clinical studies in the U.S. and Canada to prove this because it would be hard to isolate a group that consumes less than 90 mg a day of vitamin C. The authors go on to provide examples of vitamin C protecting against a wide range of other diseases, but discount all these studies as “insufficient” to warrant wide scale supplementation.
While the 512-page book cited many published studies documenting the beneficial effects of vitamin C, there were serious omissions. The most significant study that was omitted was published in the American Journal of Clinical Nutrition in August 1996. This study examined 11,178 elderly people over a 9-year period. The results of the study showed that those who took high potency supplements of vitamin C and E had an overall 42% mortality risk reduction. Said differently, there were 42% fewer people dead over a nine year period who took high potency vitamin C and E supplements compared to those taking low potency or no supplements.
In addition, we discovered numerous positive studies about vitamin C that met the criteria for inclusion in the 512-page book (as defined by the authors) which were ignored.(1-166) Had these positive studies been included, they would have erased the doubt the authors expressed about the disease prevention potential of vitamin C.
What Are Vitamin C's Side Effects?
The authors speculated about the potential toxic effects of vitamin C, but concluded that the extent of toxicity appears to be diarrhea in some people at high doses. Had the media read the 512-page book, instead of relying on the biased press release that implied a health risk to vitamin C supplements, the media would have reported that high doses of vitamin C are remarkable safe.