How Food Order Impacts Blood Sugar Control
We've known for some time that the sequence of food consumption affects blood sugar control in people with type 2 diabetes.
For example, in a small trial, patients with type 2 diabetes showed a 54% reduction in their peak glucose level after eating when they consumed protein and vegetables first, compared to when they ate carbohydrates first.
Furthermore, studies have shown that when patients adhere to this pattern for months, or years, they experience significant improvements in fasting blood sugar, HbA1c, and postprandial glucose excursions (meaning how much blood sugar fluctuates after eating).
But what exactly drives this phenomenon? And are these findings relevant to individuals with healthy blood sugar regulation?
This Week’s Research Highlights
🍽️ Consuming vegetables or protein before carbs results in better blood sugar control in people with prediabetes.
Researchers affiliated with Weill Cornell Medical College recruited 15 adults who had prediabetes (meaning higher than normal blood sugar but not high enough to be diabetic). The research team had the participants visit the lab on three different occasions. At each session, they were presented a standardized meal with the exact same foods, but the order in which the components of the meal were consumed varied at each visit, like so:
- In the carb-first condition, subjects ate bread, waited ten minutes, then consumed a salad and skinless chicken breast.
- In the vegetable-first condition, participants ate the salad, waited ten minutes, then ate the chicken breast and bread.
- Finally, in the protein- and vegetable-first condition, participants ate both the salad and chicken breast first, then ate the bread after the ten minute interval.
Blood samples were taken before the meal, and then repeatedly at 30-min intervals, to see how each pattern of consumption affected the way that their body dealt with the blood sugar load. So what happened? Well, what we see is that the total amount of glucose in the blood over 180 minutes was not different across all conditions, as you would expect (all of the meals contain the same amount of carbohydrates). However, the carb-first pattern exhibited greater glycemic variability, with a sharp peak at the 60 min mark and then a "crash" at 180 minutes. In contrast, researchers found that the salad-first and protein- and vegetable-first conditions both resulted in significantly lower postprandial glucose and insulin excursions. Compared to carb-first, the protein- and vegetable-first condition resulted in 39% lower blood sugar levels at the 30 and 60 min mark, and the vegetable-first pattern was 23% lower. The big early spike in blood sugar with the carb-first condition also demanded more insulin — the total amount of insulin in the blood for the vegetable-first condition was 44% lower, versus carb-first.
🍽️ Consuming salad before rice results in less glycemic variability in healthy adults with normal blood sugar.
So we see that altering meal order can flatten glucose spikes in people who are already experiencing problems with blood sugar control (diabetes or prediabetes). But what about healthy folks? In a new experiment, researchers in Tokyo recruited 13 healthy middle-aged men with normal HbA1c, and had them visit the clinic on three different occasions. At each visit, they were presented with one of three meals, with blood samples taken at baseline and then repeatedly at regular intervals. However, these researchers also wanted to investigate the role of dietary fiber. Accordingly, the meals for this trial looked like this:
- Rice + Vegetable: 150 g of rice consumed in 5 min, followed by 175 g of cabbage-based salad with 30 g of dressing eaten in 10 min
- Vegetable + Rice: Salad consumed in 10 min, followed by rice consumed in 5 min
- Vegetable Juice + Rice: Salad (including dressing) macerated with solids removed, consumed in 5 min, followed by rice consumed in 5 min
When they analyzed the blood samples, they found that serum glucose levels were significantly lower at the 45 and 60 min mark when the participants ate vegetable + rice, compared to rice + vegetable. However, as you can see from the graph below, the peaks were considerably lower in these healthy participants, compared to the prior study in those with prediabetes. No significant difference was seen with the vegetable juice, which is a bit surprising. The researchers attribute this to a reduction in dietary fiber relative to the salad, as well as poor transfer of bioactive compounds like polyphenols into the juice. It's possible that a higher quality juice would have produced better results, because more water-soluble fiber and polyphenols (both of which are linked to improved blood sugar control) would have transferred into the liquid.
🍽️ Eating vegetables first in a meal leads to reduced blood sugar spikes, possibly through the action of incretin hormones.
So we see that the sequential order of food components can affect postprandial blood sugar and insulin excursions. But why? To explore causal mechanisms, researchers in Singapore recruited 16 healthy adults of Chinese descent, and put them through a similar protocol to those described above, but they also measured levels of incretins. Incretins are a class of metabolic hormones that stimulate changes in blood glucose, and that are triggered differentially by certain macronutrients and food components. In random order, subjects visited the lab on five different occasions, and consumed the following meals at these sessions:
- 1) vegetables first, then meat (skinless chicken breast) and rice together
- 2) meat first, then vegetables and rice together
- 3) vegetables first, then meat second, then rice third
- 4) vegetables, meat, and rice mixed together and consumed simultaneously
- 5) rice first, then vegetables and meat together
Compared with consuming rice first, all of the other food intake sequences resulted in a lower peak postprandial glucose level. The best results, in this respect, were observed when participants ate the vegetables first, then the other components (conditions 1 and 3 listed above). This was accompanied by a greater GLP-1 response. The hormone GLP-1 is known to delay gastric emptying and attenuate blood sugar spikes, which would certainly explain these findings. GLP-1 is also associated with satiety, which would be a major added bonus.
So what can we do with these findings? One thing you could try is simply to eat a salad before the main course (lots of people do that anyway). You could also snack on some raw vegetables, or drink a green smoothie, prior to eating dinner. Since consuming protein beforehand seems to attenuate glycemic responses as well, adding in some protein powder might not be a bad idea as well.
Random Trivia & Weird News
🐌 Venomous sea snails use insulin as a weapon.
Most of us think of snails as being fairly innocuous creatures (immortal snail assassin notwithstanding). However, cone snails are a different story. All cone snails are venomous, and some species emit a toxin that can even be fatal to humans.
Some species of cone snails secrete a form of rapid-acting insulin. When this chemical is released around nearby fish, they experience a sudden drop in blood sugar. Crippled by hypoglycemic shock within seconds, the fish become easy prey.
As you might imagine, the speedy action of this toxin has made it a target of research.
Image credit: Jason Biggs and Baldomero Olivera
Podcasts We Loved This Week
- Alan Flanagan & Danny Lennon: Does time of day impact hunger, appetite, and satiety? Via Sigma Nutrition Radio.
- Seirian Sumner: Why you should thank your local wasp. Via Science Friday.
Products We Are Enjoying
This fiber blends really easily into beverages, smoothies, sauces, baked goods, etc with no discernible flavor. But what really sets oat fiber apart is that it is a rich source of beta-glucan, which is associated with improvements in glycemic control, much like what we see in the studies described above.
humanOS Catalog Feature of the Week
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This week, we’d like to highlight one of the courses from our Ideal Weight Program, developed by our good friend Stephan Guyenet. Simple food is exactly what it sounds like - food that is prepared and consumed as close as possible to its natural state, with limited added fats and sugars. These types of food enable you to stay satisfied and stave off hunger, while lowering energy density.
In this course, Stephan breaks down the scientific rationale for the Simple Food Diet, what to eat, vital food preparation tips, and other information crucial to lasting success on this plan. For more information, please refer to our How-to Guide for the Simple Food Diet, and the other materials from the Ideal Weight Program.