NIH calls for more science for multivitamins/minerals
before strong recommendations about multivitamin/mineral
supplements can be made, conclusions welcomed by industry
associations.
However, other comments made at the State-of-the-Science conference on multivitamin/mineral (MVM) supplements and chronic disease prevention concerning revision of the DHSEA and FDA authority were less well received.
The conference closed yesterday after three days of presentation and discussion and concluded: "the present evidence is insufficient to recommend either for or against the use of MVMs by the American public to prevent chronic disease."
Multivitamin/mineral supplement are regularly taken by over one-third of American adults, equivalent to about 73m people, and make up a substantial part of the $23bn spent by consumers every year on dietary supplements.
The 13-member panel, chaired by J Michael McGinnis from the Institute of Medicine, The National Academies, reviewed literature of both single and multivitamin/mineral randomized clinical trials (RCT).
For the single vitamin/mineral supplement trials, the panel reported that most reported some measure of beneficial effects for certain disease prevention, but the overall conclusion of the experts was: "Few trials of individual or paired vitamins and minerals for the prevention of chronic disease produced beneficial effects."
In terms of secondary outcomes, the experts did note that selenium may reduce colorectal, prostate and lung cancers, vitamin E could reduce heart disease in women and prostate cancer risk in male smokers, and vitamin A and zinc may decrease stomach cancer.
Multivitamins and minerals supplements, defined as any supplement containing three or more vitamins and minerals, produced mixed results in terms of benefits for chronic diseases.
"The uncertainty resulting from the trials suggests that multivitamin trials are unlikely to lead to generalizable knowledge. They cannot distinguish the effects of individual components; they are likely to be contaminated by MVM use in the placebo group; they have a weaker biological basis than single vitamin or mineral studies; and they will become outdated because of changing composition of commonly used MVMs," they said.
The panel voiced concerns that specific nutrients in the US diets were actually exceeding the recommended upper limits (UL), due to MVM supplement use and the increasing fortification of foods in the US.
"We are concerned that a growing proportion of the population may be consuming levels considerably above the UL and thus increasing the risk for adverse effects," said the panel.
This concern was rejected by industry association, the National Nutritional Foods Association (NNFA). Daniel Fabricant, VP of scientific affairs at NNFA told NutraIngredients-USA.com: " NNFA maintains that multivitamins do not pose a health risk - as the panel theorizes - and asserts that serious adverse health reactions would have long since been apparent.
As an example, according to the most recent data from the American Association of Poison Control Centers, adverse reactions to all vitamins represented only four percent of the category that includes prescription and over the counter (OTC) drugs (an adverse reaction is an unintended result, such as an allergic reaction, of taking a product according to directions) in the same time period," said Fabricant.
This was echoed by Steven Mister, president and CEO of the Council for Responsible Nutrition (CRN), who said: "For millions of Americans who struggle with diet and nutrition, a daily multivitamin provides a safe, affordable, and reliable means of filling nutrition gaps and promoting overall good health… Consumers should be encouraged to eat a well-balanced diet, get plenty of exercise, and take a multivitamin every day."
The panel also said that the FDA currently has "insufficient resources and legislative authority" to properly regulate MVMs while saying that the biological activities were "similar, if not identical" to medications.
This point was questioned by Mister, who said: "Consideration should be given as to whether the drug model for clinical research is the appropriate way to assess the preventative benefits of nutrients."
Fabricant went one step further and said: "NNFA believes the panel's claim that the FDA doesn't have enough regulatory authority is irresponsible. While it certainly may be true that the agency that regulates dietary supplements, is both underfunded and understaffed, it is not powerless to enforce the law."
The general conclusion of the conference was that significant knowledge gaps exist that must be filled, and made seven recommendations to fill the holes, including using study populations that reflect the diversity of the general US population, and the design and execution of rigorous, yet cost-effective and innovative, RCTs.
The panel also called for the building of new MVM databases detailing the exact composition of supplements, and assuring their constant availability to the research community.
A third recommendation was for the development of a strategy to support a better understanding of possible interactions between MVMs and prescribed or over-the-counter medications.
These recommendations were wholly supported by both NNFA and CRN, but Fabricant warned: "While waiting for conclusive clinical data, observational data and cohort studies should not be ignored. For instance, in the time spent determining conclusively that folic acid prevents birth defects, many women and their children would have benefited from taking this safe B vitamin daily."
The final statement from the State-of-the-Science panel will be available in several weeks, but a draft statement is already available at http://consensus.nih.gov
