Timing key to multivitamin benefits

People who have been taking multivitamins for a long period of time could see a reduced risk of colorectal cancer, report researchers in the US. However they noted that the vitamins had no effect after a short period of use.

The study, published in the recent issue of the American Journal of Epidemiology​, shows that people who took multivitamins regularly from 10 years before the start of the study had an approximately 30 per cent lower risk of developing the cancer. Those who had only recently begun to use multivitamins saw no significant benefits however.

Previous studies suggest that multivitamin use may reduce colorectal cancer risk but only after a long latency period, reported the researchers from the Atlanta-based American Cancer Society. The authors, investigating the role of timing in vitamin use, examined the relationship between regular multivitamins (four or more times per week) and colorectal cancer incidence among 145,260 men and women in the Cancer Prevention Study II Nutrition Cohort.

Current multivitamin use was reported on a questionnaire at enrollment in 1992-1993, while multivitamin use had already been obtained for a different study approximately 10 years earlier.

The authors observed 797 incident cases of colorectal cancer during follow-up from 1992 to 1997. After adjustment for multiple risk factors, they found that regular multivitamin use at enrollment was not associated with risk of the cancer, whereas regular multivitamin use 10 years before enrollment was associated with a 30 per cent reduced risk.

The researchers were cautious about the study results, calling it 'limited evidence' of the association between multivitamins and the cancer. They are also lacking evidence to determine the component in multivitamins linked to the protective effect.

However while research showing the positive association between multivitamin use and cancer prevention remains conflicting, a second US report out last week suggested that use of the supplements could help save billions of dollars in healthcare.

Funded by Wyeth Consumer Healthcare and conducted by the US-based Lewin Group, the report found that if older adults took daily multivitamins, the country could save more than $1.6 billion in Medicare over the next five years.

"We were able to identify significant cost savings based on improved immune functioning and a reduction in the relative risk of coronary artery disease through providing a daily multivitamin to the 65 and over population,"​ said Dr Allen Dobson, senior vice president and director of Healthcare Finance at The Lewin Group at a conference on multivitamins in Washington last week. "In my experience, finding any cost savings for preventive measures is unusual and finding cost savings of this magnitude is very rare."​

The study was based on a rigorous review of literature on the health effects of multivitamin use among adults over 65 years old. The researchers analysed Medicare claims files and widely accepted Congressional Budget Office (CBO) cost accounting methods to determine the costs and potential savings from the protection afforded by multivitamin supplementation

Over the five-year period from 2004-2008, the study results show potential savings from a reduction in hospitalisations for heart attacks, as well as from a reduction in hospitalisations, Medicare nursing home stays and home healthcare associated with infection.

The preventive benefits of multivitamins on colorectal cancer, prostate cancer, diabetes and osteoporosis were not included in the cost estimation, however, because the researchers concluded that evidence currently available in these areas did not support a direct translation from health effect to reduced heath care use within a health insurance framework, they said.

Experts at the 'Multivitamins and Public Health: Exploring the Evidence' meeting also concluded that multivitamins are safe, affordable, cost-effective and accessible and that there is promising evidence supporting multivitamin use for theprevention of some chronic diseases such as cardiovascular disease.