Nutrients from healthy foods are so crucial that public health departments may start doling them out like prescriptions. But for the vegetable-averse, there’s a certain allure to the idea of a vitamin pill — a single supplement to fulfill our nutrient needs. That sort of convenience would come at a cost: According to a paper released in the Annals of Internal Medicine on Monday, getting vitamins from a supplement just isn’t enough to help glean their protective effects.
The paper, authored by Fang Fang Zhang, Ph.D., a cancer epidemiologist at Tufts University, presents both good and bad news. First, the good news: some vitamins really do have positive effects on all-cause mortality. The bad news is that the positive effects depend on where you get those vitamins.
“Our results support the idea that, while supplement use contributes to an increased level of total nutrient intake, there are beneficial associations with nutrients from foods that aren’t seen with supplements,” said Zhang.
Food Versus Supplements
Adequate amounts of vitamin A and magnesium were associated with lower rates of death in Zhang’s cohort of 30,899 people. Vitamin A, vitamin K, zinc, and copper were also associated with lower rates of cardiovascular disease. But when Zhang asked her participants where they got their vitamins, the realized the effects were highly dependent on where nutrients came from.
Those who got those vitamins from the food they ate saw decreases in all-cause mortality and cardiovascular risk. But those who got their vitamins from supplements saw no reductions in their risk — even if they had an adequate amount of each vitamin or mineral in their diet. As Zhang explains, her results highlight the idea that it does matter where your vitamins come from, and in this case, getting those vitamins from food seems to be the way to go.
Being Health-Conscious Pays Off
According to a 2013 Gallup poll, about half of Americans take vitamins regularly. Zhang’s cohort seemed to reflect this, with 51.2 percent reporting that they used dietary supplements and 38.3 percent reporting that they took multivitamins or minerals within the past 30 days.
Supplements may not have the same nutritive value as actual food, but taking them was associated with some positive traits. In general, the people who took vitamins and supplements in Zhang’s cohort had, at baseline, a higher nutrient intake than those who didn’t supplement their diets. They also were less likely to smoke, drink heavily, or be obese, suggesting that they were already health-conscious to start with.
That level of health consciousness paid off, especially for people who got adequate amounts of vitamin K, vitamin A, zinc and magnesium. It just wasn’t the supplements that did it, according to Zhang’s analysis.
Caution About Calcium
In some cases, she pointed out, taking additional nutrients can have detrimental effects.
People who reported taking calcium supplements — more than 1,000 milligrams per day — actually had higher risks of cancer death than those who took less than adequate amounts of calcium, the paper reveals. Those supplements were associated with 62 percent higher rates of cancer death than those below that dosage — but only when the source was a supplement. Of all of Zhang’s participants, 38.6 percent reported using calcium supplements, which are were commonly taken in conjunction with vitamin D.
A dose of 1,000 milligrams may seem like a lot, but doses of 1,000 milligrams and higher are recommended by the NIH for adults over the age of eight.
While these results raise some concerns about calcium supplements, Zhang and her co-authors use the data to make a larger point about vitamins and minerals. It’s the source of the nutrient that really matters: In calcium’s case especially, the data suggest that calcium in supplements and in food seem to lead to different results. Further research may show that this is the case for other nutrients, as well.
Convenient as multivitamins are, Zhang’s work suggests they may not be providing the extra benefits that some hope they do. The paper makes one thing clear: When it comes to eating right, there are no shortcuts. But the benefits from trying to eat at least a vegetable or two continue to accumulate.
Background: The health benefits and risks of dietary supplement use are controversial.
Objective: To evaluate the association among dietary supplement use, levels of nutrient intake from foods and supplements, and mortality among U.S. adults.
Design: Prospective cohort study.
Setting: NHANES (National Health and Nutrition Examination Survey) data from 1999 to 2010, linked to National Death Index mortality data.
Participants:30 899 U.S. adults aged 20 years or older who answered questions on dietary supplement use.
Measurements: Dietary supplement use in the previous 30 days and nutrient intake from foods and supplements. Outcomes included mortality from all causes, cardiovascular disease (CVD), and cancer.
Results: During a median follow-up of 6.1 years, 3613 deaths occurred, including 945 CVD deaths and 805 cancer deaths. Ever-use of dietary supplements was not associated with mortality outcomes. Adequate intake (at or above the Estimated Average Requirement or the Adequate Intake level) of vitamin A, vitamin K, magnesium, zinc, and copper was associated with reduced all-cause or CVD mortality, but the associations were restricted to nutrient intake from foods. Excess intake of calcium was associated with increased risk for cancer death (above vs. at or below the Tolerable Upper Intake Level: multivariable-adjusted rate ratio, 1.62 [95% CI, 1.07 to 2.45]; multivariable-adjusted rate difference, 1.7 [CI, −0.1 to 3.5] deaths per 1000 person-years), and the association seemed to be related to calcium intake from supplements (≥1000 mg/d vs. no use: multivariable-adjusted rate ratio, 1.53 [CI, 1.04 to 2.25]; multivariable-adjusted rate difference, 1.5 [CI, −0.1 to 3.1] deaths per 1000 person-years) rather than foods.
Limitations: Results from observational data may be affected by residual confounding. Reporting of dietary supplement use is subject to recall bias.
Conclusion: Use of dietary supplements is not associated with mortality benefits among U.S. adults.