Millions of Americans would no sooner forgo taking their daily multivitamins than they would stop brushing their teeth.
Yet scientific proof is scant about whether multivitamins and other dietary supplements provide people with any health benefit or cause no harm, said Dr. Emily White, an investigator in the Hutch's Public Health Sciences Division.
"There is remarkably little evidence that multivitamins do anything beneficial for Americans," White said.
"We generally have a good diet in this country. And even for specific supplements like vitamins E and C, which have undergone a number of scientific studies, there is conflicting evidence about their benefits."
White and collaborators in PHS hope that a study they've initiated - to determine whether vitamin, mineral or herbal supplements reduce the risk of cancer - will provide Americans with some helpful answers.
The Vitamins and Lifestyle (VITAL) study, a five-year, $4.2 million project funded by the National Cancer Institute, will track vitamin and supplement use and cancer incidence among 75,000 residents of western Washington.
First comprehensive study
VITAL is the first such comprehensive study in the country to address the health effects of what has become a billion-dollar industry, said Dr. Ruth Patterson, PHS researcher and co-principal investigator of the project.
"More than half of Americans use vitamins, minerals or other plant-derived dietary supplements, and it's on the increase," she said.
"People are spending billions of dollars on these products, so now is really the time to begin looking at their effects. Our investigators have to maintain a neutral attitude and consider whether supplements are beneficial, harmful or have no effects on health."
How do products with unproven efficacy wind up on drugstore shelves?
The federal Dietary Supplement Health and Education Act in 1994 put dietary supplements in a different category from other drugs, triggering a flood of new products, said White, also a professor of epidemiology at the University of Washington.
"This act gave manufacturers the ability to distribute a wider variety of supplements and limited the power of the FDA to regulate them," she said. "The legislation puts the burden on the FDA to prove that these supplements are dangerous, not on the manufacturer to prove they are safe and effective. For most other drugs, manufacturers must prove safety and efficacy."
Hundreds of promises
The net effect for consumers is store shelves filled with hundreds of pills promising everything from improved memory to cold prevention.
With so many products on the market, VITAL study participants are asked dozens of detailed questions about their vitamin and supplement use during the past 10 years.
The 75,000 participants, age 50 to 75, come from a mailing list of residents in 13 counties of western Washington, White said.
"To make recruitment systematic, we recruit from a mailing list and are not looking for additional volunteers," she said.
So far, 32,000 participants have been enrolled, with accrual expected to be complete by September 2002. The study is in its third year of funding.
The initial mailing includes a 24-page questionnaire that queries individuals on vitamin and supplement use, diet, exercise, personal and family medical history and use of non-steroidal, anti-inflammatory drugs such as aspirin or ibuprofen.
By focusing on dietary-supplement use and not just food-intake habits, White anticipates addressing questions about health effects of nutrients more effectively than has been possible in previous studies.
"Diet by itself is difficult to measure," she said. "Supplements are easier because people take relatively large doses. We anticipate this may help us answer questions about cancer risk more efficiently than by just looking at diet alone."
Participants are also mailed a sterile brush for obtaining cheek cell samples to be sent back to the Hutch, where they will be frozen and stored for possible future DNA studies, Patterson said.
"We anticipate this will be a big resource for future studies by a number of Hutch investigators who are looking for interactions between genes and nutrients that may influence risk of developing specific cancers," she said.
The VITAL researchers will track cancer incidence among participants using the Hutch's Cancer Surveillance System, a population-based cancer registry that is part of NCI's Surveillance, Epidemiology and End Results program. Total mortality also will be followed.
Results from the study will be analyzed in a variety of ways, White said.
"We'll be analyzing the data, nutrient by nutrient," she said. "For example, we'll compare vitamin-E users to non-E users as well as look for dose trends among the vitamin-E users. Multivitamins will also be considered as a separate exposure."
Female median: four products
Preliminary analysis reveals that 86 percent of female respondents take at least one supplement, with a median use of four different products. Seventy-two percent of male respondents take at least one supplement, with a median use of three products.
Other VITAL co-investigators are Dr. John Potter, head of the Cancer Prevention Research Program, and Drs. Mark Thornquist, Alan Kristal, Irena King and Jessie Satia of PHS. Ann Shattuck, also of PHS, serves as project director.
White and Patterson intend to apply for more funding to continue the VITAL study beyond the first five years, which will be spent largely on assembling the participant group. Additional aspects of the study design will include a follow-up questionnaire to be sent participants after four or five years.
Would harmful aspects of vitamin and mineral supplements have become apparent throughout the years in which Americans have taken them? Patterson said that such hard data comes slowly.
"Look how long it took for us to prove that smoking causes cancer," she said. "The effects of supplements are lot a more subtle than those of cigarettes, so this will take time."