Beans reduce insulin response

If you've been reading our columns for a while, you probably know that the fiber content of a food contributes to your feeling more satisfied after you eat it. It also helps prevent heart disease, improves your cholesterol scores, and may even help you gain less weight as you get older.

Fiber is important for diabetics, as well, as higher fiber intake has been associated with a lower fasting insulin score. Like whole grains such as brown rice and whole wheat bread, legumes are an excellent source of fiber - but they're also a good source of protein and other nutrients. A team at University of California at Davis (Appetite 2017;118:75-81) wondered if a meal containing beans would be more satisfying, both subjectively and in terms of digestive hormones, than a meal containing a non-legume protein. Essentially: was one source of fiber better than another?

In their pilot study the authors recruited 6 men and 6 women, all overweight or clinically obese, to participate in their feeding study. Once per week for three weeks the participants came to the lab and ate one of three different breakfasts, which were served to them in random order. Each breakfast contained the same amount of fiber, but the main source of the fiber was different: the control breakfast used a couscous-based pasta, while a second breakfast contained black beans along with the couscous-based pasta, and a third included the couscous-based pasta and was supplemented with a non-legume-based fiber. All three breakfasts also contained the same amount of protein.

The participants responded to appetite and mood questionnaires before and after the meal as well as every hour after the meal for 5 hours. Blood was drawn every hour as well so that the researchers could track appetite hormones as well as glucose and insulin levels. After leaving the lab the participants kept detailed records of everything else they ate that day and turned those records in to the lab.

The results are rather surprising. Regardless of which meal they consumed, the participants ate about the same amount after leaving the lab: the authors had expected that consuming the bean-containing meal would mean they ate later in the day than when they consumed either the control meal or the added fiber meal. Similarly, although the bean meal caused greater digestive hormone response than the other two meals, the participants did not feel more satisfied - the added fiber meal had the greatest effect on the participants' feelings of how much they thought they would eat at the next meal. Blood glucose levels were also about the same for all three meals. That said, the bean meal caused a much lower insulin response than the control meal or the added fiber meal: about 50% lower.

What this means for you

This is important for those who might be pre-diabetic: not all sources of fiber are equal. Clearly fiber from beans is superior to other fiber sources when you're concerned with your insulin levels. And far tastier! Here are some legume-containing recipes for you to add to your high-fiber repertoire:

References:

Elizabeth J. Reverri, Jody M.Randolph, C. Tissa Kappagoda,EunyoungPark, Indika Edirisinghe, Britt M.Burton-Freeman. Assessing beans as a source of intrinsic fiber on satiety in men and women with metabolic syndrome. Appetite 2017 (118:75-81)

First posted: November 8, 2017