If there is one lesson we should have learned from the last decade of nutrition recommendations and research, it’s that there is no demon food group.

Dietary fat was nutrition’s ugly stepchild for decades. But, finally, we have come to terms with the idea that fat isn’t so terrible. In fact, certain types and amounts of fat are necessary for optimal health.

Still, we can’t leave well enough alone. Now we’re after carbs with our torches and pitchforks. Carbohydrates are blamed for all kinds of evil. Weight gain! Inflammation! Bad skin!

But not all carbs are created equal.

A new study by researchers at Harvard’s T.H. Chan School of Public Health suggests certain carbohydrates, like some fats – namely whole grains - can be beneficial to your health.

The research published this month in the British Medical Journal reviewed data from 45 previously published studies including over 700,000 study subjects. The research found that “whole grain intake is associated with a reduced risk of coronary heart disease, cardiovascular disease, and total cancer, and mortality from all causes, respiratory diseases, infectious diseases, diabetes, and all non-cardiovascular, non-cancer causes.”

You read that right. Heart disease, cancer, diabetes, respiratory disease and all-cause mortality are all lower in people who eat more whole grains.

It is important to note that this is an epidemiologic study. This means it looked at what large groups of people chose to eat of their own free will. It didn’t assign groups to eat more or less of any type of food. So people who freely chose to eat whole grains may have made other lifestyle choices they perceived to be healthy. Or it could be that the whole grains don’t really improve anything, it’s just that whatever they replaced is particularly bad for health. I’m looking at your highly processed and refined grains and sugars.

Nutrition research is difficult. It’s hard to study enough people for a long enough time, with confounding factors controlled, to get useful results. The researchers did control for these in factors, in retrospect, as much as the data allowed. It’s about as much as we can ask for in the nutrition world. It certainly supports the USDA recommendations to increase whole grain consumption.

This leaves us with the question of why whole grains have this effect. It probably comes down to the difference between refined grains and whole grains. The process of refining grains breaks them down into highly digestible components. This means they are rapidly absorbed into the blood stream after consumption. This causes a surge in blood glucose – or sugar – levels, and a corresponding bump in insulin. This causes all kinds of havoc on the body.

Whole grains, however, are rich in fiber. It is theorized that this slows the absorption of sugars following a meal. The slower absorption allows for a smaller bump in glucose and insulin levels.

This research represents another baby step away from an era of food experimentation where we tried to outsmart Mother Nature and ended up damaging our own health. The more research we do, the more we understand that a diet composed of a variety of unprocessed, or minimally processed, foods is the simplest and most direct path to good health.