Doctor, is there scientific evidence for the daily use of a multivitamin?
Yes. In December 2013, an extensive review on this subject was published in the American medical journal: Annals of Internal Medicine (Vitamin and Mineral Supplements in the Primary Prevention of Cardiovascular Disease and Cancer: An Updated Systematic Evidence Review for the U.S. Preventive Services Task Force.1) These authors disregarded studies in which only one vitamin or one mineral was being studied and searched throughout medical literature exclusively for those studies which used a multivitamin (more than 3 vitamins and/or minerals), which had good scientific quality (double-blind, randomized trial), and which had a large number of participants (to give statistical significance).
Two papers were found that fulfilled these high levels of exigency.
The first, was a study that tracked 12,741 healthy Frenchmen for an average of 7.5 years, called “The SU.VI.MAX Study: a randomized, placebo-controlled trial of the health effects of antioxidant vitamins and minerals“2. In this study, the participants were divided into two groups. The first group received a multivitamin with 3 antioxidant vitamins and 2 minerals (Vitamin C 120 mg, Vitamin E 30 IU, Betacarotene 6 mg, Selenium 100 µg and Zinc 20 mg), and the second group received a placebo.
The main positive findings of this study were:
- A 37% reduction of general mortality in men;
- A 31% reduction of the incidence of cancer in men;
- A 23% reduction in overall mortality in men and women.
Can You Imagine That Taking A Daily Multivitamin Pill Leads To A 30% To 40% Reduction In Overall Mortaliy And Cancer In Men?
If these results were so impressive, why was this work criticised? Because it generated a seemingly inexplicable finding: a great effect on men and an apparent lack of effect on women. However, the authors of the study did initial blood tests of the applied nutrients and concluded that this apparent discrepancy between the results of men and women could be explained by the fact that the serum levels of betacarotene and Vitamin C in women were higher than in men at the beginning of the study. These substances are markers of the constant use of fruits and vegetables. Thus, it can be inferred that women have better eating habits than men and therefore the result of the supplementation of these nutrients in women was not as expressive as in men.
The second major study was a men-only study that tracked 14,641 American physicians over the age of 50, of which 1,312 had already had cancer before starting the study, for an average of 11.2 years, Multivitamins in the prevention of cancer in men: the Physicians’ Health Study II randomized controlled trial.3 One group was given a commercial multivitamin with a low dosage (Recommended Daily Allowance, RDA) and the other group was given a placebo.
The main positive findings of this study were:
- A 27% reduction in the incidence of cancer in those who had already had cancer;
- A 12% reduction of the incidence of cancer excluding prostate cancer;
- A 12% reduction of cancer mortality.
The lower results of this study in comparison with the previous one are explained due to the smaller administered dose of vitamins. However, if we recap the two studies, we conclude that there is significant evidence that the use of multivitamins can reduce the incidence of cancer and mortality in men.
BUT WHAT ABOUT WOMEN?
In December 2013, a large study was published by the “After Breast Cancer Pooling Project” (ABCPP); a meta-analysis of four studies, made only with women who were treated for breast cancer and were taking a multivitamin. For the analysis 12,019 women were grouped and followed for a period of 1 to 5 years after the diagnosis of breast cancer.
The main positive results of this study were:
- The use of antioxidants associated with multivitamins reduced overall mortality by 21%;
- The use of a multivitamin reduced overall mortality by 16%.
With this work, we can conclude that multivitamins have a proven preventative effect in both women and men, reducing the incidence of cancer, or recurrence of those who have had cancer, and thus reducing overall mortality.
DIFFICULTIES IN MULTIVITAMINAL RESEARCH
The difficulties of scientifically proving the preventative efficacy of the daily use of a multivitamin in the general population are due to the complexity and multifactoriality involved.
The first question is the proper composition of a multivitamin. It is now known that the appropriate dose of some vitamins is much higher than the dose established as necessary to prevent nutritional deficits, known as RDA (Recommended Daily Dose). For example, you need 45mg a day of Vitamin C to avoid having scurvy (the disease resulting from lack of Vitamin C), but for its antioxidant benefits and effects, much larger doses are needed.
Another issue is the bioavailability of the ingredients, which favours the body in absorbing and using the nutrients. Minerals in oxide form, as found in most commercial multivitamins, are of low bioavailability, and are hardly useful for body cells. Minerals chelated with amino acids are more absorbed than mineral oxides. Chelation, which derives from the Greek word chel, or "claw," means to grasp or clamp. Then, minerals are combined with amino acids, which are more easily absorbed, thus providing their own absorption to the mineral.
Among the various chelated minerals on the market, minerals from the brand Albion®, which invented this process more than 50 years ago, are the ones with the highest bioavailability.5,6
Genetic interference may also influence how much one benefits from vitamins depending one’s ability to use them. Vitamins need to be metabolized by specific enzymes so that they become active and play their role within the cells, being, in fact, precursors of active substances. For example, folic acid is absorbed from food and multivitamins, but this substance needs to be metabolized into its active form, which is called methylfolate, by an enzyme called methylene tetrahydrofolate reductase (MTHFR); but there is a genetic change in which the gene that signals the production of that enzyme becomes altered. This genetic alteration is increasingly common (ranging from 10 to 40%, depending on the population studied) and thus people with this mutation will not be able to synthesize the active form of folic acid and will have metabolic alterations due to this. A multivitamin in which vitamins are in their most active form will certainly be more effective as it will overcome this genetic limitation.7,8
WHY WOULD IT BE NECESSARY TO TAKE A MULTIVITAMIN?
If a person consumes 5 to 7 servings of fruits and vegetables every day, which is the required amount of food to get all the necessary daily nutrients, then he will not need to supplement his food with a multivitamin. Food is undoubtedly the best source of minerals and vitamins, but due to modern life and our eating habits only few people are able to consume the recommended daily allowance of fruits and vegetables.
The Suvimax study has proven that those who benefit most from the constant use of a multivitamin are those who have poor eating habits, and the intention of using a multivitamin is to ensure that there is no subclinical lack of minerals and vitamins which are essential for the proper nutrition of the body.
The interesting thing to observe is that the lack of micronutrients and vitamins is related to the incidence of cancer and to the relapse of those who previously had cancer. What protects us from cancer, or its non-relapse after treatment, is the immune system. The immune system is sensitive to nutritional deficiencies and requires adequate doses of these nutrients to optimize its action.3,4
In addition to this, the earth’s soil continues to be impoverished, which leads to a reduction in the micronutrient content of fruits and vegetables. The use of fertilizers that return only the macronutrients (nitrogen, phosphorus and potassium) to the earth causes a reduction of micronutrients such as zinc and magnesium in plants. From this depleted soil, 'weaker' plants grow, which need more agricultural pesticides and chemical fertilizers to survive. The consumption of food of organic origin (without the use of pesticides) has become a necessity, since eating a large quantity of vegetables and fruits rich in pesticides may bring more harm than benefit.
After reviewing the literature there is sufficient evidence indicating the daily use of a multivitamin to supplement diet, as it has been shown to result in reduction of cancer incidence and overall mortality. New studies may show greater benefits if they use a multivitamin with high bioavailability, in adequate doses and follow a methodology appropriate for its evaluation.
"WITH MODERN LIFE AND TODAY’S FOOD HABITS FEW PEOPLE ARE ABLE TO CONSUME THE RECOMMENDED DAILY DOSE OF FRUITS AND VEGETABLES."
1. 1 Fortmann SP, Burda BU, Senger CA, Lin JS, Whitlock EP. Vitamin and Mineral Supplements in the Primary Prevention of Cardiovascular Disease and Cancer: An Updated Systematic Evidence Review for the U.S. Preventive Services Task Force. Annals of Internal Medicine. Dez 17, 2013.
2. Hercberg S, Galan P, Preziosi P, Bertrais S, Mennen L, Malvy D, Roussel AM, Favier A, Briançon S. The SU.VI.MAX Study: a randomized, placebo-controlled trial of the health effects of antioxidant vitamins and minerals. Arch Intern Med. 2004 Nov 22;164(21):2335-42. Erratum in: Arch Intern Med. 2005 Feb 14;165(3):286. PubMed PMID: 15557412.
3. Gaziano JM, Sesso HD, Christen WG, Bubes V, Smith JP, MacFadyen J, Schvartz M, Manson JE, Glynn RJ, Buring JE. Multivitamins in the prevention of cancer in men: the Physicians’ Health Study II randomized controlled trial. JAMA. 2012 Nov 14;308(18):1871-80.
4. 4 Poole EM, Shu X, Caan BJ, Flatt SW, Holmes MD, Lu W, Kwan ML, Nechuta SJ, Pierce JP, Chen WY. Post diagnosis supplement use and breast cancer prognosis in the After Breast Cancer. Pooling Project Breast Cancer Res. Treat., 139(2), 529-37 (2013).
5. OS MINERAIS: tendências e complexidade de USO. Revista Funcional e Nutracêuticos. Disponível em: http://www.insumos.com.br/funcionais_e_nutraceuticos/materias/90.pdf accession: 21/07/2014.
6. Chelated Minerals for Human Nutrition. Disponível em: http://www.albionminerals.com/human-nutrition/ accession: 21/07/2014.
7. Dell’edera, D., Tinelli, A., Milazzo, G.N., Malvasi, A., Domenico, C., Pacella, E., Pierluigi, C., Giuseppe, T., Marcello, G., Francesco, L., Epifania, A.A. Effect of multivitamins on plasma homocysteine in patients with the 5,10 methylene-tetrahydrofolate reductase C677T homozygous state. Mol Med Rep. 2013 Aug;8(2):609-12.
8. Czeizel, A.E., et al. Prevention of Neural-Tube Defects with Periconceptional Folic Acid, Methylfolate, or Multivitamins? Ann Nutr Metab 2011; 58:263–271.