Supplement Studies: Sorting Out the Confusion To consumers,
keeping track of the research on vitamin supplements can be an
exercise in frustration. Different studies on the same vitamins
often present conflicting information. Why the contrary
findings? A closer look at the study design often reveals the
cause of these discrepancies. Next time you read a news story
about a vitamin trial, keep the following questions in mind,
since the answers may help you put conflicting results into
context: 1. What vitamin dose did study participants take—and
for how long did they take it? The most obvious source of
conflicting findings is the fact that different studies test
different doses of vitamins, for different lengths of time. Take
vitamin D as an example. Studies have found that it protects
against fractures at doses of 700 to 800 IU a day, (1) but that
400 IU a day has less benefit. (2) A short vitamin supplement
trial may not show any benefit simply because it takes a long
time for a disease to develop or for the