Despite the regular onslaught of mixed messages from those in scientific research land, I still take a multivitamin most days. (Thanks, Mom, for starting me off young with those delicious Flinstone Kids niblets of nutrition.)
Placebo effect? I don't know. I do know that I feel better when I remember to take my multivitamin, iron and vitamin D supplements, and the occasional fish oil horse pill. But will it help me in the long run with any aspect of my health?
Sheldon (from The Big Bang Theory): If you're eating all the vegetables you're buying, you don't need those supplements. What you're really getting when you take those supplements is expensive pee.
Penny: Maybe that's what I'm going for.
Sheldon: Oh, well then you're definitely going to want to buy some manganese.
An article published online on the Journal of the National Cancer Institute is in line with Sheldon's opinion: supplementation with vitamin C, vitamin E or beta carotene offers no overall benefits in the primary prevention of total cancer incidence or cancer mortality.
Brought to you by the letters C, E and the precursor to vitamin A
The idea to test vitamins C, E and beta carotene came from observational studies suggesting the antioxidants in fruits and veggies could convey some protective effects against cancer. Yet randomized clinical trials haven't found much in the way to support that hypothesis.
The authors evaluated a double-blind, placebo-control 2x2x2 factorial trial of 8,171 women in the Women's Antioxidant Cardiovascular Study who were randomly assigned to receive vitamin C (daily), vitamin E (every other day) and beta carotene (every other day). The objective was to determine whether use of any of the three supplements had a preventive effect on total cancer incidence or cancer mortality. (7,627 of the women were cancer-free before their random assignment.)
Relative risks for each supplement were around 1 when testing for cancer incidence. RR for E and beta carotene were down in the mid-0.80s when testing for mortality, but 1.28 for vitamin C. Duration and combined use had no effect on either incidence or mortality.
A total of 624 of the women developed cancer, and 176 died from it during the period of the study.
The authors did note that the study was designed to have 80 percent power to detect a 30 percent reduction in the overall risk of cancer, and had very limited statistical power to investigate any effect of dietary antioxidants on the risk of specific cancers. The implications, the authors state: there is no basis for a recommendation that individuals increase dietary levels of antioxidants as a means of reducing cancer risk.
Snarkiness ahead (although not as snarky as this amazing article)
The relative risks weren't all that impressive (although you could make a weak argument for E and beta carotene on cancer mortality), but I wouldn't bet the ranch on these findings. Sure, the n was large, which usually helps your confidence. But these women, on average aged 60 years, were at high risk for cardiovascular disease, potentially complicating whatever benefit or adverse effect the vitamins had on their health. They were also only followed for nine years on average - cancer can take decades to develop, so who knows what would have happened had the study continued for another 10 years or so. And these women had decent diets, so they were probably getting a good amount of vitamins and minerals from their food. Not to mention that we need different amounts of nutrients depending on our stage in life.
I like the idea of the trial, and I am not questioning whether it was well-designed or conducted because I wasn't part of it. But are we even asking the right questions? Or using the right population? You can't really generalize these results to the broad population.
Consider the impact that food has on certain pharmaceutical drugs. You have to take certain drugs with a meal, as lack of food will alter the pharmacokinetics and dynamics. Why can't this be true of vitamins? Sure, an apple a day might keep the doctor away, but is it just the vitamins we get out of the apple, or is the complex interplay of vitamins and other components of the apple that confer benefit?
Also, why cancer as a whole? We should really look at specific cancers, but even that is difficult considering the extreme variation in causes and types of cancer just within one category.
And while we're at it, why not other diseases? Vitamins might not stave off pancreatic cancer, for example, but maybe it can help mitigate depression or delay arthritis. (I'm just pulling these diseases out of a hat, I haven't looked for vitamin studies in these patients.)
I am not 60 years old, nor am I in a cardiovascular disease study. Does this mean vitamins have a chance of working for me? When I go to Whole Foods, the other people in the supplement aisle all look fit, healthy and young to middle-age. We could be spending money to alleviate our imaginary fears, and the supplement makers are cashing in on our placebo paranoia. Someone out there should conduct a study that follows the people I see buying the products - who knows, if they find an effect, they could make billions. In the meantime, I'm okay with my kidneys filtering out my hard-earned money - just in case...
Isn't this likely because the people most likely to spend their money on supplements are people who care about their bodies in general (e.g., eat well, exercise, etc.)?