The so-called “lentil effect” or “second meal effect” describes the remarkable effect of beans to help control blood sugar levels hours or even the next day after consumption.
Image thanks to PNNL - Pacific Northwest National Laboratory via Flickr.
We've known for decades that beans have an exceptionally low glycemic index. You give someone cooked beans, peas, or lentils and you don't even get half the blood sugar spike that you get with the same amount of carbs in the form of bread, pasta, or potatoes. So if you're going to eat some high glycemic food like white rice, consider having some beans with it and the more beans the better. Check it out, as your bean to rice ratio increases from left to right from more rice with some beans to more like beans-with-some-rice you can see these trends towards improving cardiometabolic risk factors. "Substituting one serving of beans for one serving of white rice was associated with a 35% lower risk of metabolic syndrome, or pre-diabetes."
Why do beans have such a low glycemic index? Maybe it's because they've got so much fiber that absorption is just slower or something, but it was this next study that blew people's minds.
Started out same as before. Give someone bread for breakfast, and get a big spike in blood sugar and insulin levels, but give the same amount of carbs in lentil form and you blunt the effect. OK, but now let's follow through to lunch.
At breakfast, same as before, big spike with bread, small spike with lentils but then for lunch both groups got the same meal. Both got bread, and those that had lentils four hours earlier for breakfast had less of a glycemic reaction to the bread. At the time they called it the, lentil effect, but chickpeas appear to work just as well, so it has since been dubbed the second meal effect. Eat lentils for dinner and then for breakfast, even if forced to drink sugar water, you have better glycemic control. Beans moderating your blood sugar not just at the meal you eat them but even hours later or the next day.
How is that even possible? The mystery has since been solved. Remember what our gazillions of gut bacteria do with fiber? They produce compounds like propionate with it, which gets absorbed into our system and slows down gastric emptying, slows the rate at which food leaves our stomach so we don't get as much of a sugar rush. It's like symbiosis. We feed our good bacteria and they feed us back. So, you have a bean burrito for supper and by the next morning it's time for your gut bacteria to eat that same burrito and the by-products they create which may affect how our breakfast the next morning is digested. They figured this out by giving people rectal infusions of the amount of propionate your good bacteria might make from good burrito and you can see the stomach relax within minutes. So I guess if you forgot to eat any kind of beans for supper and need to blunt the effect of your breakfast doughnut, it's theoretically not too late, but in general I encourage people to administer their food orally.
To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Ariel Levitsky.
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But what about the gas? Check out my blog post Beans and Gas: Clearing the air.
What other superpowers do beans posses? They are packed with potassium (Preventing Strokes with Diet), mad with magnesium (Mineral of the Year—Magnesium), and a preferred source of protein (Plant Protein Preferable). They improve breast cancer survival (Breast Cancer Survival and Soy), reduce hot flashes (Soy Foods & Menopause), delay premature puberty (The Effect of Soy on Precocious Puberty), and they're a great bargain to boot (Eating Healthy on a Budget).
Lentils for breakfast? Well, the Brits like baked beans on their toast but I've started using a handful of sprouted lentils in my breakfast smoothie (see A Better Breakfast and Antioxidants Sprouting Up)
The propionate video I reference is Fawning Over Flora with a follow-up Boosting Good Bacteria in the Colon Without Probiotics.
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