The Science Behind Oatmeal and Diabetes

Before Insulin, There Was Oatmeal

Before the discovery of insulin, the lives of many people with diabetes were saved or prolonged by Carl von Noorden’s oatmeal diet. As I discuss in my video Is Oatmeal Good for People with Diabetes?, he published his findings in 1903, which were received with a great deal of skepticism. But the critics were overcome in the following years by the weight of the evidence.

Acclaimed doctor James B. Herrick began to try the oatmeal diet on his patients. Initially very doubtful, he became astonished by the results, which led to the 1909 proclamation that no case of juvenile or adolescent diabetes should be deprived of the benefits of the oatmeal cure.

The great Elliott Joslin, founder of the oldest and largest diabetes clinic in the world, described the effects of oatmeal as “sometimes magical,” calling the oatmeal cure an unsolved mystery, referred to back then as “one of the greatest puzzles in diabetes.” They did have some clues, though. They found that animal protein had to be strictly excluded, as it annihilates the favorable action of oatmeal-type diets.

And now we know, more than a century later, that, indeed, animal protein intake intensifies insulin resistance, which is the cause of prediabetes and type 2 diabetes, whereas plant-based foods enhance insulin sensitivity, which is the opposite.

Is Oatmeal Good for People with Diabetes?

We’ve long known that higher consumption of whole grains, including oats, is associated with a lower risk of diabetes. As I discuss in my video How Does Oatmeal Help with Blood Sugars?, more than a dozen randomized controlled trials found that oats significantly improved both short-term and long-term blood sugar control, in addition to lowering cholesterol levels.

We think the benefits arise from a fermentable fiber in oats called beta-glucan. We know one of the underlying cholesterol-lowering mechanisms of oatmeal consumption might be its microbiome-manipulating ability––in other words, having a beneficial effect on our intestinal bacteria.

What’s So Great About the Fiber in Oatmeal?

A little fiber goes a long way. Our good gut flora uses fiber to make short-chain fatty acids that have anti-inflammatory effects. There are dozens of randomized controlled trials showing the types of fiber found in oats and beans can improve long-term blood sugar control in people with diabetes. Why? Because the gut bacteria selectively promoted by dietary fiber intake can help alleviate type 2 diabetes.

The oat fiber itself has been shown to act as a prebiotic, boosting the growth of beneficial bacteria like Lactobacillus and Bifidobacteria. So, between the lack of animal protein, lack of animal fat, and bursting at the seams with prebiotic fiber, it’s no wonder that oatmeal diets grew to become part of the clinical routine in the treatment of diabetes.

How Soon Can You See Results?

As I discuss in my video Oatmeal Diet Put to the Test for Diabetes Treatment, several studies have suggested that a few days of eating oatmeal could have beneficial effects for about a month afterward. In a randomized, controlled, crossover trial, not only did insulin needs drop by about 40% in just two days, compared to just restricting calories alone with a hypocaloric diabetic diet, but a measure of long-term blood sugar control taken four weeks later reflected the benefit.

Other new studies have shown the same thing. Two days of oatmeal significantly reduced the required amount of insulin and improved blood sugar levels, with beneficial effects noted for up to four weeks. Consider this: Patients with uncontrolled type 2 diabetes on the two-day oatmeal diet experienced a 40% reduction of insulin dose, accompanied by almost normalization of average blood sugars. Although the intervention only lasted for two days, researchers observed a lasting significant reduction of insulin dosage and ameliorated mean blood sugars for weeks after the participants were dismissed from the study—and that was after they resumed their regular diets.

Put people on a diet packed with oats, beans, fruits, vegetables, and nuts, and the number of their gut fiber-feeders churning out beneficial short-chain fatty acids shoots up, and fasting diabetic blood sugars drop by about 25% within one month. The more fiber-feeders they fostered, the better their blood sugar control. When the fiber-promoted short-chain fatty acid producers were present in greater diversity and abundance, participants had better improvement in their hemoglobin A1c levels (which is a measure of longer-term blood sugar control).

Are There Any Downsides to Oatmeal?

If you try an oatmeal diet, your physician should be ready to rapidly deprescribe your blood sugar drugs or else you could become dangerously overmedicated. Oatmeal interventions should not be performed in patients who might have difficulties in reporting symptoms of low blood sugar. The downside of trying oatmeal days is that it may work a little too well, so it must be done under close medical supervision.

The Glycemic Index of Oatmeal

Whole grains are good, but intact whole grains are better. The wholiest of grains: groats.

Oat groats have their inedible outer husks removed during processing. They can then be sliced into two to four pieces to make steel-cut (also known as pinhead or Irish) oats, which are considered a low-glycemic-index food, averaging under 55.

Oat groats can also be coarsely ground into Scottish oatmeal or steamed and flattened into “old-fashioned” rolled oats, which have a glycemic index of 55.

Instant oats are steamed longer and rolled even more thinly. Scoring 79, it’s considered a high-glycemic-index food, but not as bad as some breakfast cereals, which can get into the 80s or 90s.

Jazzing Up Oatmeal

Oatmeal is a classic whole-grain breakfast, and there are plenty of ways to enjoy it.

• Of course, fruit and nuts are popular additions. A berry banana oatmeal bowl is quick and easy, and cinnamon baked apples make for a cozy breakfast. Assemble overnight oats or baked carrot cake oatmeal the night before to simplify your morning.
• To add another type of fiber for your gut flora, mash cannellini beans into your oatmeal—my friend Paul swears you can’t even see or taste them.
• I like to start my mornings with what I call my BROL bowl. BROL stands for barley, rye, oats, and lentils. I use oat groats (also called hull-less and hulled oats). I premix all the ingredients in a 1:1:1:1 ratio and then cook one scoop of dry BROL and two scoops of water in an electric pressure cooker. That makes a base with great texture. 

Once you have your BROL base, pick your toppings. When I feel like something sweet, my go-to is a chocolate-covered-cherry sensation. I make it with frozen dark red cherries, cocoa powder, dates, and walnuts or pumpkin seeds.

You can easily turn that BROL bowl savory; here’s a version made with sautéed greens. Google “savory oatmeal” for all sorts of interesting dishes involving mushrooms, herbs, curry, roasted vegetables—you name it!