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Switching to whole grains may reduce body fat and aid heart health, according to scientists at the University of Copenhagen who reported their work in the Journal of Nutrition. In a twelve-week, randomized clinical trial, they asked 79 overweight or obese postmenopausal women to eat a calorie-restricted diet the grain part of which incorporated either 480 calories of reﬁned grain foods or the same amount of whole grain foods. Those eating the diet with whole grains lost more weight (3.6kg vs 2.7kg) and saw a more signiﬁcant decrease in body fat (3% reduction vs 2.1%) compared to those eating reﬁned grains. Cholesterol levels increased 5% in the reﬁned group, highlighting the heart beneﬁts of choosing whole grains instead of reﬁned.
Much of the earlier evidence for whole grains was derived from epidemiological studies, in which associations are documented between one factor and another. It’s important to remember that associations don’t prove cause, however. If an epi study (as they’re often called) shows that people who eat whole grains are thinner, we don’t know if it’s because of the whole grains they ate, or because they all jog daily, or because they eat more veggies. Epi studies are a great way to generate hypotheses, but it’s always reassuring when a randomized clinical trial backs up the epi research, as this one does. Randomized clinical trials (RCTs) are often viewed as the gold standard in research, and there’s a lot to be said for dividing people randomly into groups and comparing the eﬀects of just one diﬀerent variable.
That said, clinical trials are not real life. Total diet includes lots of diﬀerent variables, and often it is our choices over long periods of time and the interactions and synergies between diﬀerent foods, that aﬀect our health. So the controlled environment of an RCT and its short time frame (RCTs are expensive, and you can’t make people eat a limited diet for that long, so they’re almost always relatively short-lived) also have their limitations. That’s why we need to continue gathering data about whole grains and health from both epidemiological studies and clinical trials. (You can check out our great collection of whole grain health studies here.)
That’s why we also need to keep an eye on the common-sense argument for whole grains and health. Every once in a while we run into someone – often respected academics – who says, “The evidence for whole grains and health is not yet ironclad. Yes, the epi evidence for whole grains is stronger than for any other food group, but a few RCTs have been inconclusive.”
Our answer to that? If there were two versions of apples – one with all the nutrients originally found on the tree, and one with 25% to 75% or more of various nutrients removed, which one would be healthier for you? Which one would you eat, and which one would you buy for your family? I’m not sure we need dozens of additional studies to realize the logic of enjoying foods with all of the goodness originally bestowed on them by nature. Enjoy your whole grains! (Cynthia)