Illustrations by Lauren Giordano / The Atlantic.
Multigrain is a genius approach to selling both white bread and righteousness. The term crept under the umbrella of health quietly. It wasn’t clear why, exactly. (The grain part? Or the multi?) At least it wasn’t white bread, right?
As many eaters of bread came to understand that white bread is a nutritional equivalent of Pixy Stix—the nutritious, fibrous shell of the wheat having been removed, leaving us with only the inner starch, which our bodies almost instantly turn into sugar—it needed some rebranding.
Multigrain is now often used to imply wholesomeness, a virtue to which it often has no claim. Containing the flour of multiple grains does not mean containing whole grains. When millers leave the grain intact before milling, this is whole grain flour. It contains fiber, appeasing the pancreas and microbes that demand it for optimal performance. So, the term to look for is 100 percent whole wheat. (Or whole grain, though the grain is usually wheat.)
It’s a valuable piece of health knowledge to have, more so in light of findings from an expansive analysis released in 2016 from the Harvard School of Public Health: Eating at least three servings of whole grains per day is associated with lower risk of death from cancers, heart disease, and stroke.
This is especially relevant, too, at a time when many people are needlessly avoiding gluten, or simply think that carbs are bad.
“There is still some misconception about the role of carbohydrates in a healthy diet,” said Frank Hu, a professor of epidemiology and nutrition at Harvard, and one of the study’s authors. “Some people still believe that all carbohydrates are bad, and some people still promote a very low carbohydrate diet without strong scientific support.”
Hu sees this study as further evidence that the type of carbohydrate is “very important.”
Published in the American Heart Association’s journal Circulation, the Harvard study is an analysis of 12 prior studies, as well as previously unpublished results drawn from the National Health and Nutrition Examination Survey. The combined studies involved 786,076 people and 97,867 total deaths.
This is a correlation, an epidemiological study—so people in Facebook timelines and comment threads will predictably shout that correlation is not causation. While true, the accusation is misplaced. Epidemiology may well be the most important type of research at our disposal to understand the role of food in chronic disease.
In many areas of science, the gold-standard approach is a randomized controlled trial. This works very well, for example, when testing drugs for short-term effectiveness and side effects. The effects of our food, though, tend to be too expansive to lend themselves well to the same studies. Chronic diseases (as the name implies) manifest not over weeks or months, but decades—longer than most research institutions can keep thousands of subjects adhering to any particular diet. And longer than most people would be willing to take part.
(Would you help us please by using only white bread for the rest of your life, and see what diseases you get or don’t get? Actually, wait, you can’t know that it’s white bread or that will ruin the experiment. Wear these dark sunglasses always? And let us cauterize your tongue?)
So it is reliable and worthwhile to know that long-lived, healthy people tend to eat a lot of whole grains.
The study did not, however, differentiate between milled grains and whole grains that tend to be eaten whole—quinoa, farro, amaranth, and the like. I asked Hu what the deal was there.
“That's a really good question,” he said. “We don't have a sufficient amount of data to address it.” But, like any good scientist, he was willing to speculate: “When whole grain is milled and becomes whole-wheat flour, the digestion and absorption process is still fast. And that can induce higher insulin responses. Theoretically, that kind of product is less beneficial compared to whole grains that are minimally processed, or not processed at all.”
Those insulin responses correspond with a measure known as glycemic index, essentially the speed at which glucose enters our blood upon eating. Pixy Stix are high, and broccoli is low. Eating a lot of foods with high glycemic indices is known to be associated with diabetes, obesity, heart disease, and even liver damage. (A randomized clinical trial in JAMA suggested otherwise in 2014, but that study lasted just five weeks.) It’s not a perfect metric, but an interesting one.
In this case, it’s relevant because white Wonder bread and whole wheat bread have the same glycemic index. According to Harvard’s website, they are identical. Both are high (even higher than Coca Cola). Ever since I first saw that a couple years ago, I’ve wondered why—and what would make whole wheat pasta healthier than white pasta, if not a mitigated sugar surge. (Because I love them both, and I’d like to feel good about eating both.)
Hu clarified that glycemic index “depends mainly on the particle size of the food. So, when whole grains are milled, the particles are similar in size to those of white flour.”
It can even depend on the structure final product. Furio Brighenti, a professor of nutrition at the University of Parma in Italy, has studied in great detail—perhaps predictably—pasta. He explained to me how food structures affect the absorption of starches into sugars, which he has seen through studies of various types of pastas. Even though they are made of the same thing, we absorb them differently.
Total meal surface area (after chewing) may partly explain differences in the body’s response to different pastas, Brighenti explains. The thickness of pasta alone is a variable. In his findings, thicker penne has a lower glycemic index than thinner.
Pastas left al dente (really, the only way to cook pasta) also have lower indices than those left to mush like so much cafeterial nonsense.
He layers on complexity in diagraming for me that different pasta shapes tend to be eaten with different amounts of oils and sauces, and this changes the way the body absorbs the food—not just the glycemic index, but the rate at which the stomach empties. He cannot explain, though, why whole-wheat pastas have a glycemic index similar to white pastas.
“Glycemic index is just one of the factors that goes into the quality of a high-carbohydrate food,” Hu emphasizes. “The amount of fiber, minerals, antioxidants, and phytochemicals are also very important. Really, the whole is greater than the sum of the parts.”
This is a fundamental tenet of wisdom in nutrition. The grain is a microcosm. Take the exact same flour, and make it into pasta or bread, and it functions differently inside us:
Adapted from Giacco et al., British Journal of Nutrition.
The variables are many, but the takeaway is not complex: Eat whole grains instead of just their starchy white endosperm whenever possible, and a person’s odds of health increase. Hu and every other scientist I’ve spoken to on the subject are confident in that. This has long been true. A very similar, large meta-analysis will be coming out in another major medical journal later this week, and its findings are much the same. It tends to be the convention-upending studies that make news, though, so these studies may not.
What makes nutrition confusing is not the science, but the news cycle, the fad diet books warning against gluten and carbs, and the marketing of meaningless things like multigrain bread. When someone asks if you’d like white bread or multigrain, suggest that they are doing damage to the health of the public by perpetuating a false dichotomy. Or, simply, “multigrain this.”