Where does terrible diabetes diet and lifestyle advice come from?
Recently I saw a clickbait headline, claiming magical benefits for one mystery ingredient, and I felt inspired to chase it down the rabbit hole.
The headline: “Type 2 diabetes: Eat this fruit three times a day to lower your blood sugar levels.”
The newspaper: The Daily Express, the British tabloid.
To be sure, one shouldn’t mistake this newspaper for a bastion of serious journalism. The banner on the top of the page links mostly to stories about soap opera twists and spats between footballers’ wives. But it’s a popular paper, with a long history and many, many subscribers, and it’s likely that many of their readers take their reporting seriously.
The claim: “According to research presented at the American Diabetes Association’s 72nd Annual Scientific Session, eating raisins three times per day may reduce post-meal sugar spikes significantly.”
Plenty of readers will immediately recognize that the claim is nonsense. If you have diabetes, we hope you already know that there is no fruit that reduces blood sugar. It just doesn’t work that way. Raisins, like all dried fruits, are extremely carbohydrate dense. Grapes themselves have very little protein or fat, so once you remove most of the water content, you’re basically left with condensed carbohydrate bombs. And carbohydrates invariably cause blood glucose to rise.
One of those small red boxes of Sun-Maid raisins, for decades a mainstay of ‘healthy’ bagged lunches, has 32g of carbohydrates. That’s same number of carbs as a chocolate frosted donut with sprinkles from Dunkin’ Donuts.
How on earth could such a carb-heavy treat actually reduce your blood sugar? The answer, of course, is that it can’t.
Whether it was through sheer ignorance or intentional exaggeration, The Daily Express badly misstated the reality of the study in question. Here’s the study (PDF), published in 2015 in a journal named The Physician and Sports Medicine. And here’s the actual conclusion, stripped of tabloid puffery: “raisins may be a healthy alternative to processed snacks.”
Raisins did not lower anyone’s blood glucose. They lowered blood glucose in comparison to junk food. This more modest claim is both expected and unexciting. No wonder The Daily Express decided that it should jazz up the researchers’ findings.
… Based on Industry-Backed Science
To run this experiment, the scientists chose a list of sweet and starchy foods with essentially no nutritional value (“illustrative competitor snack examples included Keebler Cheez-It Crackers, Nabisco Honey Maid Cinnamon Roll Thin Crisps, and Pepperidge Farm Goldfish Baked Snack Crackers”), and asked twenty people with Type 2 diabetes to eat them three times a day. Another group with Type 2 ate raisins three times a day. Then they compared the results. The raisin group saw their glucose levels drop, the junk food group saw their glucose levels rise.
Initially, I saw no reason to doubt the conclusions of the study; after all, it seems natural to accept that raisins are indeed healthier than Cheez-Its and Goldfish crackers. Many people with diabetes have found that simple starches raise their blood sugar more dramatically than the more complex carbohydrates from whole foods. But as I read the actual text of the article, I began to realize that the study itself was extremely shaky.
First of all, we have no idea what these people were eating beforehand. The people that began eating raisins seemed to get healthier, but we have absolutely no clue what their usual snacking habits were before the study began.
Even worse, the two groups under consideration, supposedly randomized, were actually very poorly matched. The group that was assigned raisins had a fasting glucose of 162 mg/dL and an A1C of 7.62%, while the group that was assigned “alternative processed snacks” had a fasting glucose of 140 and an A1C of 7.08%. The raisins group also had a higher body-mass index (i.e., they were probably fatter). Simply put, the raisin-eaters were meaningfully less healthy across the board.
Because the two groups were so poorly matched, this study doesn’t actually measure anything. There’s no baseline from which to make a comparison. The two groups had different starting points, and we don’t even know what those starting points were.
There were other potential confounding factors on top of these central flaws. The two groups had very different racial makeups and very different gender ratios. Some of the patients were using insulin, and some were not, about which no details were reported. The participants were also given diet and exercise instruction (which the less-healthy raisin-eating cohort would naturally stand to benefit from more).
Keep reading, and the details get even weirder. Eight members of the raising-eating group complained of gastrointestinal distress (diarrhea, nausea), compared to only one from the snack-eating group. Two of the raisin-eaters withdrew from the study “due to intolerance of raisins.” Maybe eating raisins three times a day isn’t actually a great idea? But these details were omitted from the conclusion, which heartily recommended raisin consumption.
At this point it should come as absolutely no surprise that the study was funded by Big Raisin. More amusingly, the specific funders are the California Raisin Marketing Board. That’s right, this science was brought to you by the same group that 30 years (and one minor name change) ago brought a lovable group of Motown-singing Claymation raisins onto America’s TV sets, and into America’s hearts:
The point is not that raisins are poisonous or that they’re junk food. Given the choice, I’d rather my children eat raisins than Goldfish crackers. Perhaps the same study, even if properly executed, would have led to the same conclusions. Or perhaps not.
Trust Your Glucose Meter
My purpose was to investigate the origin of a bit of advice in the newspaper that was so wildly misleading as to be dangerous. When journalists inflate and exaggerate scientific claims, they are failing their responsibility to the public and their commitment to truth. When those claims involve practical health advice, they are putting their readers at risk.
But the newspaper isn’t alone to blame. This misleading clickbait story was based on a scientific study funded and subsequently propagated by a team of marketers. It’s very easy to imagine the raisin marketers applauding the type of creative misinterpretation practiced by The Daily Express.
It’s critical for everyone with diabetes to understand that this kind of lazy magical thinking has no place in serious management of the condition. Luckily, we all carry with us a finely tuned B.S. detector: the glucose meter. Think raisins will lower your blood sugar? Eat a little red box, test your blood sugar, and find out for yourself.