Contrary to opinion published by JAMA (Mortality In Randomised Trials of Antioxidant Supplements For Primary and Secondary Prevention, 28th February 2007), vitamins and minerals pose no health risks and are essential to the daily wellbeing of many people, who fail to consume enough of the vital nutrients on a daily basis from diet alone.
In the following short article, from the Health Supplements Information Service, independent nutritionist Pamela Mason comments on the JAMA report of the 28th February.
When I saw this latest meta-analysis, I was immediately concerned about the confusion it would cause about vitamins and minerals. Vitamins and minerals are important to health and it is unfortunate that the public could get the impression from this meta-analysis that they are harmful.
For a start, this was not a well-conducted meta-analysis. What do I mean by that? Well, a fundamental aspect of a proper meta-analysis is that the studies pooled together for analysis should be comparable. However, there is no way that the subjects in the studies chosen for this latest meta-analysis were comparable. Apart from the diversity in their health, it included people of all ages, with both smokers and non-smokers. There were also huge sources of variability in the antioxidants themselves, their combinations and the doses in the studies selected. Even the duration of the intervention varied enormously, from a 1-day trial to a 12-year study.
But it is important to note that when all the studies were put together, the authors found no effect on mortality. It was only when they used their own criteria for judging a good or a bad trial and threw out those that they considered bad, that any effect on mortality was seen. This kind of data manipulation is regrettable – with so many imponderables, any results are worthless and only serve to confuse the public.
Though the meta-analysis raises issues for debate, it does not advance knowledge of the role of antioxidants in maintaining health. There are plenty of good quality antioxidant trials that have shown substantial benefits and reduced mortality rates with antioxidant supplements. In short, it ignored the totality of the evidence, not only from randomised controlled clinical trials, but also from epidemiological evidence, such as observational studies.
In a nutshell, this meta-analysis did not compare like with like and the disparity among the studies was enormous. The hallmark of a good meta-analysis is one which includes similar types of studies with similar design, similar types of subjects or patients and similar interventions. The trials included in this meta-analysis used different combinations of antioxidants, different doses and were conducted over different periods of time. Though large numbers of people are included in this meta-analysis and a huge amount of data, its conclusions are not transferable to the overall population, many of whom could benefit from vitamin supplements. This is because vitamin and mineral intakes in some groups of the UK population are very poor.
DAILY NUTRIENT MUST-HAVES .
The most recent National Diet and Nutrition Survey (2003) in British adults showed that significant numbers of adults fail to achieve the daily Reference Nutrient Intake (RNI) for several vitamins and minerals. For example, 20% of men and 28% of women failed to achieve the RNI for riboflavin, while 50% of men and 74% of women failed to achieve the RNI for magnesium. Ninety-one per cent of women did not achieve the RNI for iron.
The mineral and trace element intakes of women in the 19-24 age group were a particular cause for concern, with high percentages of these women failing to achieve these RNIs:
· 96% for iron
· 76% for magnesium
· 57% for zinc
· 62% for copper.
Significant numbers of young women did not even achieve the Lower Reference Nutrient Intake (LRNI), with 42% and 22% failing to achieve the LRNIs for iron and magnesium respectively.
As a nutritionist I would advocate the importance of a healthy diet in achieving adequate amounts of vitamins and minerals. However, it is clear that the diets of many people in Britain are far from ideal and are lacking in vitamins and minerals. A multivitamin and mineral supplement helps to close this nutritional gap and offers a beneficial addition to the daily diet.
LAST WORD.
This meta-analysis has done nothing to clarify antioxidant science. It has muddied the waters still further and created more confusion for the public.
CLINICAL EVIDENCE
Here is an at-a-glance guide to some of the clinical evidence supporting the use of antioxidant vitamins.
Heart disease and strokes
· The Cambridge Heart Antioxidant Study published in the Lancet concluded that vitamin E doses of 400 to 800 IU per day, in people with atherosclerosis, reduced the risk of heart attack by 77 per cent.¹
· Another report – titled Multivitamin Use and Mortality in a Large Prospective Study” – showed that out of over 1 million participants, those adults who used vitamin E, or other antioxidant vitamins, in combination with a daily multivitamin had a 15 per cent lower risk of dying from heart disease or stroke than those who did not take vitamins2.
· Blood levels of the antioxidant nutrients vitamins A, C, and E and beta-carotene are reported to be lower in people with a history of heart attack, compared with healthy individuals3.
· The results from the Physicians Health Study 2 (PHS2) indicated apparent benefits of beta-carotene supplementation on subsequent vascular events among 333 men with prior angina or revascularisation.
· With regards to the safety of beta-carotene for long-term use, the PHS2 results indicated that beta-carotene supplementation (50mg on alternate days) had no significant detrimental effects on cardio-vascular disease during more than 12 years of treatment and follow-up4. NOTE: Smokers are NOT advised to use beta-carotene supplements.5
· The results of a report titled “Multivitamin Use and Mortality in a Large Prospective Study” showed those adults who used vitamin E, or other antioxidant vitamins, in combination with their multivitamin had a 15 percent lower risk of dying from heart disease or stroke than those who did not take vitamins. In the report, which was published in the American Journal of Epidemiology, five researchers from the Atlanta centre reported on their research into causes of death among more than one million adults.
· Inositol hexaphosphate acid (IP-6), also known as phytic acid, is a powerful antioxidant that’s naturally present in whole grains and high-fibre foods. A University of Maryland study found that IP-6 reduces platelet activity (blood clotting, which can lead to heart disease or stroke by inhibiting blood flow) by 45 percent. A study published in The New England Journal of Medicine found that 8.8 grams of IP-6 a day reduced urinary calcium levels in men at high risk of kidney stones, preventing further stone growth in 80 percent of test subjects during two years of treatment. A 1995 Japanese study found that IP-6 reduced fatty deposits in the liver, a major risk factor for liver disease.
Antioxidant supplementation
· At the Second International Symposium on Antioxidants, in Berlin, Germany in 1994, conclusive evidence, in the form of 134 research studies presented at the event, showed that antioxidants are essential in the role of maintaining human health.
Parkinsons disease
· Research has shown that patients with Parkinsons disease have decreased levels of antioxidant enzyme activity.6
Cancer
· A study of 30,000 residents of linxian County, Henan Province in north-central China, where cancer death rates are among the highest in the world, showed that antioxidants could reduce the risk of dying from cancer. The residents aged 40 to 69, who received antioxidants over a five-year period saw their overall cancer death rate drop by 13%.
Immune functions
· A study of 30 older women (average age of 72 years) in Spain assessed the effect of antioxidants (1,000 mg vitamin C and 200 mg vitamin E/day for 16 weeks) on immune function. The results showed that antioxidant supplementation resulted in a significant improvement in parameters of immune function and a significant decrease in lipid peroxide levels in healthy older women. The same was also true in older women with coronary heart disease or major depression disorders.7
References
Cambridge University scientists conducted the research and published their findings in the March 23, 1996 issue of the Lancet.
2 Published in the Jul 15 2000 issue if the American Journal of Epidemiology, five researchers from the Atlanta centre reported on their research into causes of death among more than one million adults.
3 Singh RB, Niaz MA, Sharma JP, et al. Plasma levels of antioxidant vitamins and oxidative stress in patients with acute myocardial infarction. Acta Cardiol 1994;49:441-52
4 Christen WG; Gaziano JM; Hennekens CH. Design of Physicians’ Health Study II–a randomized trial of beta-carotene, vitamins E and C, and multivitamins, in prevention of cancer, cardiovascular disease, and eye disease, and review of results of completed trials. Ann Epidemiol 2000 Feb;10(2):125-34
5 There is some evidence to suggest that beta-carotene supplementation may exacerbate the detrimental effects of smoking (Chem Res Toxicol 1999 Jun; 12(6): 535-43)
6. Fahn, S. and Cohen, G. (1992) The oxidant stress hypothesis in Parkinson’s disease: evidence supporting it. Ann. Neurol., 32(6):804-812).
7. De la Fuente, M., Ferrandez, M.D., Burgos, M.S., Soler, A., Prieto, A. and Miquel, J. Immune Function in Aged Women is Improved by Ingestion of Vitamins C and E. Can. J. Physiol. Pharmacol. 76:373-380, 1998)