New results counter prior negative findings regarding the preventive-health potential of multivitamin and antioxidant vitamin supplements 08/03/2009
As folks who follow health-nutrition news know, vitamin D and omega-3s boast exceptionally positive research records.
But last fall, the authors of several large studies reported disappointing results: Supplemental vitamin E and C showed no reduction in cancer or heart disease rates, vitamin E and selenium supplements did not lower men's risk of prostate cancer, B vitamins did not reduce the risk of cardiovascular problems, and vitamin C seemed to protect cancer cells.
However, her article should have been headlined, “Some Vitamin Supplements May Lack Short-Term Disease-Prevention Power; Results Clouded by Generally Healthier Lifestyles of Vitamin Users.”
And those negative findings contrast sharply with those of countless studies which link diets high in vitamin- and mineral-rich plant foods to generally lower rates of heart disease and reduced risks of certain cancers.
Some critics of the cluster of negative research results noted that supplemental nutrients often come in forms not found in nature (e.g., synthetic vitamin E), and that the isolated vitamins and minerals in supplements probably exert different effects when consumed as components of whole foods.
Other critics pointed to the well-established fact that people who use multivitamins are generally healthier and more likely to engage in healthy habits, and therefore are less likely to show reduced disease rates from their supplement use.
In addition, surveys show that physicians and nurses who take supplements most often do so for “overall health/wellness benefits, not to prevent cancer and heart disease,” while 41 percent of physicians and 62 percent of nurses who recommend supplements generally do so for the same reason (HCPIS 2008).
|FDA-approved nutrient health claims
For the details of each claim, see the FDA's pages concerning Health Claims and Qualified Health Claims.
This is because they know that Americans do not get adequate amounts of several essential nutrients—especially vitamin D—and do not get optimal amounts of many more, such as omega-3s and magnesium.
And there are many nutrients for which the FDA has approved full or qualified health claims, on the basis of persuasive evidence… see our “FDA-approved nutrient health claims” sidebar.
Despite these caveats, three of four recently published studies suggest that standard vitamin supplements (and fish oil) may help maintain optimal health.
Recent vitamin-health studies: a summary
Here are quick summaries of several recent studies that examined links between vitamins and health:
Study #1 - Multivitamins may lower heart disease death risk
The results of a new study from the University of Washington contradicts conclusions from a controversial meta-analysis published in the Journal of the American Medical Association, which reported that supplements of vitamins A and E, and beta-carotene may increase mortality risk by up to 16 percent.
The Seattle-based researchers recruited 77,719 Washington State residents aged between 50 and 76 (Pocobelli G et al. 2009).
They used the results of self-administered questionnaires to compare the participants' health outcomes with their use of multivitamin or vitamin C and E supplements over a five-year period.
The new study found four things... with three of them being positive:
- Multivitamins may reduce the risk of dying from heart disease by 16 percent.
- Vitamin E may reduce the risk of dying from cardiovascular disease by 28 percent.
- Vitamins C and E were associated with small but statistically significant reductions in risk of death.
- Multivitamins did not reduce the risk of death or death from cancer.
Still, this news supports the use of multivitamins and vitamin E, which was linked to increased risk of “all-cause mortality” in a controversial meta-analysis (evidence review) published in 2004.
According to new research from the U.S. National Institute of Environmental Health Sciences, the cells of multivitamin users appear to enjoy a younger biological age than cells from non-users (Xu Q et al. 2009).
The scientists looked at the length of DNA sequences at the end of chromosomes—called “telomeres—that shorten as cells replicate and age.
Compared to non-multivitamin users, the researchers noted that that telomeres were on average 5.1 per cent longer for daily multivitamin users.
The aging and lifespan of normal, healthy cells are linked to the so-called telomerase shortening mechanism, which limits cells to a fixed number of divisions.
Like the ends of shoelaces, without which the lace would unravel, telomeres ensure the cell's chromosomes do not fuse with each other or rearrange during cell replication, which can lead to cancer.
With each replication the telomeres shorten, and when the telomeres are gone, the cells are programmed to commit a form of “suicide” called apoptosis.
Telomeres are highly susceptible to oxidative stress from free radicals generated by normal metabolism, inflammation, and ingestion of polluted air and water… which is one reason why antioxidants can help maintain health.
Telomere length is considered a marker of ageing, and multivitamins may help preserve telomere length by reducing oxidative stress and chronic inflammation.
The team led by Honglei Chen, M.D., Ph.D., compared the multivitamin and nutrient intakes of 586 women aged between 35 and 74 to the length of the telomeres on the ends of their chromosomes (strands of DNA).
A diet questionnaire was used to determine multivitamin use and nutrient intakes.
In addition to the finding that telomeres were on average 5.1 per cent longer for daily multivitamin users, the researchers found a positive relationship between telomere length and intakes of vitamins C and E from foods.
And as they noted, “Whereas the evidence is not sufficient to conclude that these 2 dietary antioxidants mediated the observed relation, the results are consistent with experimental findings that vitamins C and E protect telomeres in vitro [i.e., in test tube cell studies]”
Study #3 - Multivitamins fail to protect women from cancers and heart disease
Multivitamin supplements have “little or no influence” on a woman's risk of cardiovascular disease, cancer, or death, according to an analysis of data collected as part of the famed Women's Health Initiative study (Neuhouser ML et al. 2009).
The WHI study involved 161,808 postmenopausal women aged between 50 and 79.
The new analysis of WHI data found that multivitamins had no effect on the risks related to cardiovascular disease, cancer, or death over a period of eight years.
The authors concluded that while nutrition should remain a principle focus for the prevention of chronic diseases, “multivitamin supplements showed no benefit in this population…” (Neuhouser ML et al. 2009).
However, the multivitamin supplements did not appear to cause any harm, and the authors noted that the results relate only to postmenopausal women.
Furthermore, they acknowledged that eight years may have been too few for the many cancers that take longer to develop, such as colorectal cancer.
A clearer picture of the prevention value of multivitamin supplements awaits the results of large, well-control trials such as the Physician's Health Study, which is looking at the use of a commonly used multivitamin compared to placebo in thousands of male physicians (The results are expected in 2012).
Study #4 - Supplement users may have better lung-cancer survival rates
A comparison of the diets and health outcomes among 68,518 participants of the Norwegian Women and Cancer study suggest that lung cancer patients who were regular dietary supplement users prior to diagnosis had better survival chances than non-users (Skeie G et al. 2009).
The most common supplement used was cod liver oil—which is generally rich in omega-3s, vitamin D, and vitamin A—followed by multivitamin and mineral supplements. Our unrefined Salmon Oil resembles cod liver oil in key respects (omega-3s plus significant vitamin A levels) and is much higher in vitamin D.
Use of cod liver oil supplements was associated with a 44 percent lower risk of death for lung cancer patients, while daily use of other dietary supplements was associated with a 30 percent reduction in the risk of death among lung cancer patients.
The benefits may even extend beyond lung cancer, since the use of cod liver oil and multivitamin and mineral supplements was associated with improved survival rates for people with any kind of solid tumor, including breast and colorectal cancer.
As the University of Tromso, Norway team wrote, “This study has shown that in lung cancer patients taking dietary supplements before diagnosis was associated with better survival. Whether this is due to beneficial effects of supplements, or differences between supplement users and non-users cannot be determined” (Skeie G et al. 2009).
And they made a key point: “More research is needed to understand the interplay between nutrients, whether in food or supplements and cancer survival” (Skeie G et al. 2009).
The researchers stressed this point: “Given that randomized controlled trials have demonstrated no effects or increased incidence of lung cancer in supplementation studies in well-nourished populations, our results may be somewhat surprising. However, these studies used pharmacological doses of specific nutrients, and cannot easily be compared with ours.”
By this they meant that they studied the effects of a “whole food” supplement (cod liver oil) and potentially synergistic blends of nutrients found in multivitamin and mineral supplements
And, the researchers made three critical points:
- “If the most relevant [critical] period for supplementation is after diagnosis, it is likely that our results underestimate the effect of supplementation, as some of the patients most likely have [already] initiated supplementation.
- “On the other hand, if a certain level of the nutrients or long-term supplementation is required for an effect, dietary supplement use before diagnosis might be more relevant for the association with survival.
- “And if dietary supplement use only is an indicator of a set of health behaviors or beliefs, pre-diagnosis use [of cod liver oil and multivitamin-mineral supplements] might be more important, as these characteristics probably are stronger in those who already take supplements before diagnosis, than in those who initiate use afterwards.”
- Healthcare Professionals Impact Study (HCPIS). “Life...supplemented”. September 16, 2008. Accessed online at http://www.lifesupplemented.org/ articles/news/physicians_prescribe_prevention.htm
- Neuhouser ML, Wassertheil-Smoller S, Thomson C, Aragaki A, Anderson GL, Manson JE, Patterson RE, Rohan TE, van Horn L, Shikany JM, Thomas A, LaCroix A, Prentice RL. Multivitamin use and risk of cancer and cardiovascular disease in the Women's Health Initiative cohorts. Arch Intern Med. 2009 Feb 9;169(3):294-304.
- Parker-Pope T. News Keeps Getting Worse for Vitamins. The New York Times. November 20, 2008. Accessed online at http://well.blogs.nytimes.com/2008/11/20/ news-keeps-getting-worse-for-vitamins/
- Pocobelli G, Peters U, Kristal AR, White E. Use of supplements of multivitamins, vitamin C, and vitamin E in relation to mortality. Am J Epidemiol. 2009 Aug 15;170(4):472-83. Epub 2009 Jul 13.
- Skeie G, Braaten T, Hjartåker A, Brustad M, Lund E. Cod liver oil, other dietary supplements and survival among cancer patients with solid tumours. Int J Cancer. 2009 Sep 1;125(5):1155-60.
- Xu Q, Parks CG, DeRoo LA, Cawthon RM, Sandler DP, Chen H. Multivitamin use and telomere length in women. Am J Clin Nutr. 2009 Jun;89(6):1857-63. Epub 2009 Mar 11.