Being gluten-free or following the Paleo diet are among the most popular fad diets in the USA today. Paleo diet mythology proclaims that all grains are unnatural and, therefore, unhealthful food choices for human beings since grains were not consumed by our Paleolithic ancestors. This claim is likely incorrect, although it is likely whole grain intake was much lower for most human populations during the Paleolithic Period than it is in most modern human populations today. The Paleolithic Period coincides almost exactly with the Pleistocene epoch of geologic time, which lasted from about 2.6 million years ago to about 12,000 years ago. Also in the anti-whole grain camp are the proponents of Atkins and other low-carbohydrate diets, who have long declared that all foods high in carbohydrate (including whole grains) are largely responsible for promoting obesity, diabetes, cardiovascular disease (CVD), as well as numerous other ills. The gluten-free dieters and many in the Paleo diet movement blame wheat, barley, rye, and other grains containing gluten for "leaky guts,” inflammation, and numerous human ills. Of course, for those with celiac disease (a.k.a. gluten-sensitive enteropathy) the scientific evidence clearly shows that gluten does indeed cause numerous gastrointestinal problems and numerous other pathological changes. Aside from the perhaps 1-2% of people with celiac disease and the even smaller number of people with allergies to wheat or other grains, there is little credible evidence linking whole grains to any disease. Health professionals need to know what the scientific evidence actually does and does not show when it comes to health issues associated with the consumption of grains and other sources of carbohydrate. Any potential health benefits that may result from the removal of wheat and other grains and/or dramatic reduction in all high-carbohydrate foods needs to be scientifically established before any responsible health professionals would promote gluten-free, Paleo, and/or a low carbohydrate diet. These fad diet proponents claim that grains and/or other sources of dietary carbohydrate promote numerous adverse health effects such as weight gain, "leaky guts," inflammation, diabetes, and CVD.
Does the Scientific Evidence Support Reduced Grain and Carbohydrate Intake?
Contrary to the claims of the proponents of various fad diets including the Paleo diet, gluten-free diets, and low-carb diets, there is actually growing scientific evidence from both clinical trials and epidemiological studies showing that consuming more whole grains in particular actually improves insulin sensitivity (1), reduces inflammation (2), and improves blood lipids (3), and endothelial function (4) in human subjects.
A recent study investigated the impact of whole grain intake prospectively in 74,341 women from the Nurses’ Health Study (1984–2010) and 43,744 men from the Health Professionals Follow-Up Study (1986–2010). Data from these two large prospective cohort studies followed these health professionals since the mid-1980s through 2010 and examined the relative risk of premature death due to either CVD or cancer in initially young to middle-aged healthy men and women.
They found that the substitution of one serving of refined grains with a serving of whole grains each day was associated with an 8% reduction in mortality from CVD (pooled HR 0.92; 95% CI 0.88-0.97). They also reported based on substitution analysis that replacing one serving of red meat daily with a serving of whole grain reduced CVD mortality risk even more markedly by an average of 20% (pooled HR 0.80; 95% CI 0.75-0.86). By contrast, Dr. Sun and colleagues found no significant association between whole grain intake and the risk of dying from cancer. Dr. Sun also used the data to estimate that each additional serving of whole grains consumed daily was associated with a 5% (95% CI, 2%-7%) reduction in total mortality and a more marked 9% (95% CI, 4%-13%) reduction in deaths from CVD. Past studies have also noted a fairly consistent reduction in the risk for colorectal cancer, but the relationship between whole grain intake and other cancers has been inconsistent at best. The observation that increased dietary bran, but not germ, intake was associated with a reduced CVD mortality was a new and significant finding. Dr. Qi Sun observed an inverse association between wheat and other cereal bran intake and CVD mortality with a pooled HR of 0.80 (95% CI 0.73-0.87; P for trend < 0.001). By contrast, the increased consumption of wheat germ and the germ component of other cereals was not associated with a reduction in total or CVD mortality after adjusting for whole grain intake (5).
Bottom Line: The results of Dr. Sun's study are clearly at odds with the numerous but largely unsubstantiated health claims being made by the proponents of gluten-free, Paleo, and low-carb diets. It appears these fad diets are erroneously blaming the consumption of wheat, all grains, and/or all dietary carbohydrates for morbidity and mortality, despite the fact that the preponderance of prior research and now Dr. Sun's recent study clearly indicate that consuming more whole grains (mostly wheat in a US population) is actually associated with a significant reduction in both total and CVD mortality in both US men and women. Importantly, the reduction in CVD and total mortality was found to be independent of other dietary and lifestyle factors. The results of Dr. Sun's study reinforce current dietary guidelines that promote the consumption of more whole grains and reductions in refined grains, other refined carbohydrates, and red meat as likely to help reduce the risk of developing type 2 DM and CVD and possibly colorectal cancers too.
By James J. Kenney, PhD, FACN
- Piera MA, et al. Effect of whole grains on insulin sensitivity in overweight hyperinsulinemic adults. Am J Clin Nutr 2002;75:848-55.
- Adlercreutz H. Lignans and human health. Crit Rev Clin Lab Sci. 2007;44:483-525.
- Jenkins DJA, et. al. Viscous and nonviscous fibres, nonabsorbale and low glycaemic index carbohydrates, blood lipids and coronary heart disease. Curr Opin Lipidol. 2000;11:49-56.
- Katz DL, et.al. Effects of oat and wheat cereals on endothelial responses. Prev Med. 2001;33476-84.
- JAMA InternMed.doi:10Med.doi:10.1001/jamainternmed.2014.6283.
Stephanie Ronco has been editing for Food and Health Communications since 2011. She graduated from Colorado College magna cum laude with distinction in Comparative Literature. She was elected a member of Phi Beta Kappa in 2008.