Multivitamin use and risk of cancer and cardiovascular disease in women
There has been much media interest in a recent study of post-menopausal women which concluded that using multivitamins has little or no effect on total mortality, or the risk of cancer or cardiovascular disease. Dr Carrie Ruxton, Health Supplement's Information Service looks at the pros and cons.
Before writing off multivitamin supplements as a waste of time, it’s worth considering the main purpose of supplementation – to address poor intakes of vitamins and minerals. Government surveys show that a significant proportion of British people have intakes of key nutrients which fail to meet dietary recommendations. Of particular concern are low intakes of minerals such as iron, magnesium, zinc and copper in young adult women,2 low intakes of iron and vitamin A in young children3 and inadequate iron and calcium intakes in teenage girls.4
Despite public health campaigns, few women of reproductive age consume the recommended amount of folate.2 Moreover, low vitamin D status is of increasing concern throughout the British population, but particularly in the elderly, the housebound, children, people from minority ethnic groups, and those living in northern parts of the UK.
The recently published multivitamin study combined data on nearly 162,000 women from a few different sources. There was a large cohort trial which looked at multivitamin use, hormone therapy, dietary modification and calcium and vitamin D supplements in 68,132 women taking part in three clinical trials. This was added to data from an observational study which involved 93,676 women. In all of these studies, use of multivitamins was simply observed, i.e. no advice was given to the participants to take multivitamins as part of an intervention. The women were then followed-up for around 8 years to track any changes in health..
So, what were the findings? Firstly, it was discovered that 42% of women used multivitamins on a regular basis. During the follow-up period, there were 9619 diagnosed cases of cancer (breast, colorectal, endometrial, renal, bladder, stomach, lung or ovarian cancer), 8751 cardiovascular events and 9865 deaths. There was no evidence that multivitamin use influenced the risk of cancer, and no associations were found between multivitamin use and the risk of cancer. Women who took multivitamins were slightly less likely to experience a cardiovascular event, although the relationship failed to reach statistical significance. In summary, in this cohort of post-menopausal women, there were no significant associations between multivitamin use and risk of several common cancers and CVD.
Despite the media’s take on the study, these findings are not surprising. Although vitamins and minerals have physiological functions, such maintaining enzyme function and cellular metabolism or sometimes acting as antioxidants, it is not clear how they could specifically prevent chronic conditions, such as CVD or cancer. These develop over many years and have multiple risk factors, including genetics, smoking and obesity. Thus, it would take much more than a multivitamin supplement to influence chronic disease risk. In addition, vitamins and minerals differ considerably in their actions from drugs, e.g. statins or anti-hypertensives, or functional ingredients, such as, stanols or sterols, which do influence CVD risk factors.
Multivitamins are primarily intended to address the issue of poor vitamin and mineral intakes, which is a common problem in the UK. Though frank deficiency diseases, such as scurvy or beri-beri, are less common nowadays than was the case prior to World War II, recent UK dietary surveys in adults,2 young children,3 young people4 and people aged > 65 years5 show that intakes of several key vitamins and minerals are lower than recommended levels. Moreover, rickets, the result of a poor vitamin D status, does still occur in certain groups of ‘at risk’ urban children.
Eating a healthy balanced diet with plenty of fresh fruit and vegetables, low-fat dairy produce, wholegrains, potatoes and pulses, with fish and lean meat (if desired) could supply all the nutrients required for health. However, intakes of these foods, particularly fruit, vegetables and oily fish (and hence the vitamins and minerals they supply), fall short of Food Standards Agency recommendations. Healthcare professionals should encourage the consumption of a healthy diet wherever the opportunity arises. However, dietary changes take time to achieve, and a multivitamin supplement is a reasonable option for helping to bridge the dietary gap.
References
1. Neuhouser ML, Wassertheil-Smoller S, Thomson C, Aragaki A, Anderson GL, Manson JE et al. Multivitamin use and risk of cancer and cardiovascular disease in the Women’s Health Initiative Cohorts. Arch Int Med 2009; 169 (3):294-304.
2. L, Irving K, Gregory J, Bates CJ, Prentice A, Parks J, et al. The National Diet and Nutrition Survey: adults aged 19 to 64 years. Volume 3. Vitamin and mineral intake and urinary analysis. : Stationery Office. 2003.
3. Gregory J, Collins D, Davies P, Hughes J, Clarke P. National Diet and Nutrition Survey: children aged 1 ½ to 4 ½ years. Volume 1. Report of the Diet and Nutrition Survey.
4. Gregory J, Lowe S, Bates C, Prentice A, Jackson L, Smithers G, et al. National Diet and Nutrition Survey: young people aged 4 to 18 years. Volume 1 Report of the Diet and Nutrition Survey. : The Stationery Office. 2000.
5. Finch S, Doyle W, Lowe C, Bates C, Prentice A, Smithers G, et al. The National Diet and Nutrition Survey: people aged 65 years and over. Vol 1: Report of the Diet and Nutrition Survey. : The Stationery Office. 1998.
Dr Carrie Ruxton,
Health Supplement’s Information Service
