OK, I think we all understand that “links” and “associations” are not the same things as “causes,” let’s proceed.
A number of reputable, good-sized studies (including the Nurses Health Study) have observed an association between whole grain consumption and lower risk of certain serious health conditions. However, researchers have yet to establish cause and effect in almost all cases.
Scientists acknowledge that people who include whole grains in their diet tend to have other healthy behaviors that may contribute to a lower rate of the disease or health conditions being studied. The trick is to try to figure out which healthy behavior (whole grains, or otherwise) is responsible. So far, those attempts have been inconclusive.
Cardiovascular Disease (Including Heart Attack and Stroke)
- Whole grains that are rich in soluble fiber (oats and barley) lower LDL cholesterol. Yet the most-consumed grain in the United States (and by study participants) is whole wheat, which is rich in insoluble fiber.
- Studies examining whether whole grains improve insulin metabolism (which plays a role in heart health) have been positive, but have involved too few participants to be reliable. More, and larger, studies need to be done.
- Whole grains are rich in antioxidants and other substances that may protect the heart, but no research has yet identified what exactly these substances do inside the body that gives that protection.
Type 2 Diabetes
- Soluble fiber slows absorption of carbohydrates into the bloodstream, but again, most of us are eating insoluble fiber.
- Whether a grain is refined does not affect it’s glycemic index as much as whether it is finely ground. Thus, whole wheat flour has nearly the same glycemic index as refined flour.
Other Health Conditions
- The positive effect of whole grains on bowel function appears clear, but evidence linking whole grains (and other food sources of fiber) to a lower risk of colon cancer is far from clear.
- Obesity has so many contributing factors that results of studies linking higher whole grain consumption to a lower body weight are not strong enough to show cause and effect. Once again, the presence of other healthy behaviors muddies the waters.
Even though the research so far has some serious limitations in terms of pinning down what, if any, credit whole grains deserve for lowered disease risk and better health, most health experts encourage people to replace refined grains with whole grains. Do I think this is a bad thing. Not necessarily. But the issue is not as cut and dried as you might think.
I am unfortunately taking a short hiatus from writing in order to attend to some urgent personal business. But I have lots more to say about whole grains, and how to look at them from a balanced perspective, instead of buying wholesale into the “healthy whole grains” propaganda. I hope to have something new for you early next week. Stay tuned!