Glycemic response to legumes weighs their place for those who are dieting; are the chickpeas in hummus and the lima beans in succotash fattening? Can you enjoy lentils for vegetable protein without guilt about adding to your waistline?
Many of us are seriously confused about the role of starch in obesity. There are so many diets fingering bread and potatoes, and peas and beans as the cause of our steadily growing waistlines. Is it true, or is it fake news?
This page was last updated by Bernard Preston on 11th August, 2019.
You are probably concerned when you read reports that twice as many people on the planet are dying from obesity as from starvation; that's not fake news but solid fact. Life is good and you really have no desire for it all to end ten or more years before it should.
Add to that those aching knees and feet and you have a deep sense that all is not well in the state of Denmark.
Can you eat green peas, or can't you? It is all in the glycemic response to legumes. This is especially important if your doctor has told you that you have become insulin resistant. If you're not sure find out more from our page about legumes?
Let's look at some basic biochemistry.
Starches consist of long chains of glucose molecules; some are quickly digested in our very long small intestine, compared to the other primates, but others pass right through to the colon where they are slowly fermented to form healthy short chain fatty acids rather than sugars.
Those like boiled potatoes, white rice, bread rolls and chocolate cake that are quickly digested in the small intestine give a sharp rise in blood sugar, a high glycemic response, which must be counteracted by the pancreas which gives a squirt of insulin, and that glucose is quickly stored as adipose.
High blood glucose is very dangerous for the arterial lining; allowed to continue it causes inflammation and leads to blindness and loss of limbs as the blood doesn't get through to the organs. So the body stores it as adipose.
The problem arises when your body either cannot produce the hormone, called type 1 diabetes, or you have become insulin resistant. Blood sugar rises and is a real threat to both the quality and length of your life. At least 10% of folk in Western countries fall into one of these two categories, and the numbers are rising fast. At least half are walking the streets undiagnosed and unaware that their very lives are threatened; sudden death from heart attack or stroke lie in wait. Could you be one of them?
You've probably read that if you are overweight, that you quite likely could be one of them; a simple blood test will answer the question. However, interpretation of the results of those tests widely differs from one doctor to another.
So, you know you have a problem, and chocolate cake and colas are verboten, but what is the glycemic response to legumes? Are peas and beans also banned? Can you enjoy hummus on your green salad?
Glycemic response to legumes considers whether the obese should avoid beans and peas and other protein rich vegetables like limas, favas and lentils.
Legumes are sometimes sneered at, being called the poor man's meat. Like all half truths that is partially correct; peas, beans and lentils are a much cheaper source of protein than meat; but are beans very starchy is the oft heard cry.
The other half of the truth, though, is that they are a much better form of protein and, in any case, because of cost, within fifty years the population explosion means that only the very rich will be able to afford much red meat.
Just like the wealthy in Indonesia died from beri-beri from eating white rice, but the poor had to rely on healthy brown rice, so the rich in the Twenty-First Century are already dying from the diseases of so-called civilization.
The point for this page on the glycemic response of legumes though, is that foods like chickpeas are not only a good source of vegetable protein, but also of slow release carbohydrate. They have a higher proportion of amylose which, because of its helical structure, forms 'resistant starch.' Much passes through the small intestine undigested, reaching the colon, giving it bulk and a healthy short chain fatty acid called butyrate; these are the two most important markers of a healthy large intestine.
So, what is the glycemic response to legumes? Harvard Med school says the index for chickpeas, kidney beans and lentils are all around 30; the one exception is fava beans which is surprisingly high. For the rest there is no insulin rush, and no instant deposit of glucose as adipose.
I would be reluctant to exclude fava beans for many other reasons, but rather use the small-seed varieties like Gobik and Goral which have a significantly higher resistant starch content, making them less digestible by enzymes in the small intestine; they then reach the colon for fermentation by the microbiota.
Favas, also known as broad beans, are the only known source of L-dopa and are vitally important in the management and possibly prevention of Parkinson's disease. They also have the greatest amount of vegetable protein (25%) of all legumes.
Legumes are banned in various dietary protocols like Banting, Adkins and Paleo. That is partly because of their starch content, despite the fact it gives no abnormal postprandial rise in blood sugar in normal people.
It needs to be stressed that the glycemic index of starches, how quickly they are digested and absorbed in the small intestine, have all been tested on 'normal' people, whoever they are. Diabetics and those who are insulin resistant may respond very differently; in fact they probably do, as the glucose transporters in the blood and the liver ensure higher levels of blood glucose.
The Paleo diet goes so far as to call them anti-nutrients, because of their phytate content.
All three of these diets recommend high red meat consumption; even if the total exclusion of all legumes was effective in losing weight, there would be a far greater risk of getting a malignancy.
Personally I'm convinced the very low glycemic response of legumes, other than fava beans nutrition, far outweighs any deleterious effect of the starch for those dieting. Cooked with onions and chillis, ginger and garlic they are simply delicious.
Best of all, legumes have a very high satiety factor; they don't leave you feeling famished mid-morning.
Read more about glycemic index.
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