What’s the deal with legumes?

I live in Spain where one of the traditional dishes is a simple lentil soup with vegetables and meat. It’s nothing too fancy, but it’s a very savory and nourishing dish. The typical Spanish way of cooking lentils usually includes a bit of “chorizo”, a kind of cured meat which adds a very special taste. It might also be a small trick parents use to get their children to eat vegetables. In Spain, people have traditionally eaten other kinds of legumes, such as chickpeas and beans.

Legumes are a staple in the diet of many Mediterranean cultures. Lentils, chickpeas and fava beans originally came from regions in the middle east, whereas the common bean, scientifically called Phaseolus vulgaris, was originally cultivated in Central America. From there, it spread north and south, becoming a staple in the diet of many indigenous cultures of the Americas. Different types of common bean include kidney beans, pinto beans and navy beans. Of course, there are also well know types of Asian beans such as mung, soy and adzuki beans.

Recently I’ve been learning about blue zones, small areas on the planet where people tend to live exceptionally long lives. There’s a few all over the world which experts on longevity have identified, such as the island of Sardinia, the peninsula of Nicoya in Costa Rica, and the islands of Okinawa, Japan. One of the things I’ve found interesting is that legumes are one of the fundamental foods in the diet of these cultures.

I wanted to investigate a little more on the nutritional benefits of legumes, so here it goes!

Benefits of legumes

Legumes are widely considered a healthy and nutritious food. The U.S. Dietary Guidelines recommends about three cups a week . Also, the DASH eating plan of the National Heart, Lung and Blood Institute recommends about four or five half-cup servings a week.

In a nutshell legumes are a great and inexpensive nutrient dense food, containing protein, vitamins, complex carbohydrates and fiber. Two important vitamins many legumes have are vitamin B1 (Thiamine) and vitamin B9 (Folate). They are also rich in minerals such as iron, magnesium, phosphorus and potassium.

1. Legumes are satiating (and they can help you lose weight)

Eating legumes makes you feel satiated and this can prevent unhealthy snacking. The fiber in legumes slows down digestion, and this may contribute to the feelings of fullness.

All legumes are considered “slow carbs”, which means they are digested slowly and glucose enters the blood at a steadier pace. Instead of getting a spike of energy, as with white pasta or rice, “slow carbs” sustain you for a longer period of time.

All legumes have a low glycemic index, which measures how quickly the body digests carbohydrates (and how much a particular food affects blood sugar). Lentils, for example, have a low glycemic index of 22 on a scale of 100. Anything below 55 is considered a “slow carb”. Because of this, and the fact that they are low in calories, some nutritionists believe legumes and specially lentils are a good choice for losing weight.

2. They promote digestive health

Not all starches are rapidly digested and turned into glucose in the small intestine. There is also “resistant starch”, which was discovered in the 1980’s by two English researchers. Resistant starch passes into the large intestine where it is used as food by healthy bacteria. Surprisingly, almost half the starches in legumes are resistant starches.

Legumes also contain soluble and insoluble fiber. Insoluble fiber can’t be digested by the body and the gut bacteria can’t brake it down either. It acts as a bulking agent and it reduces constipation. Soluble fiber is broken down by the gastrointestinal fluid, producing a liquid which is then used by gut bacteria. Much of the fluid is converted by bacteria into short-chain fatty acids (SCFA), which are essential for the health of cells lining the colon.

3. Legumes will help your cardiovascular system

Fiber can also help your cardiovascular system. Researchers believe that fiber binds with certain cholesterol molecules and eliminates them from the body. A meta-analysis of 11 clinical trials found that legumes lowered LDL (“bad”) cholesterol by 6% and increased HDL (“good”) cholesterol by 2.6%.

Even more important, legumes are packed with minerals that take care of the cardiovascular system. For example, magnesium and potassium help regulate blood pressure and electrical nerve impulses. Legumes also contain vitamin B9 (folate or folic acid) which, together with vitamins B6 and B12, neutralize harmful homocysteine molecules. A high level of homocysteine molecules is associated with risk of heart disease.

A cohort study which used data from about 9500 people found out that after 19 years, those that consumed legumes 4 times or more a week had 22% less risk of heart disease and 11% less risk of heart attack or stroke.

4. They may help prevent diabetes type 2 and regulate blood sugar

The American Diabetes Association recommends eating beans several times a week. A 2015 report by Rani Polak, from the Institute of Lifestyle Medicine, says:

“A diet rich in plant-based foods, including legumes, and lower in refined grains, sugar-sweetened beverages, and processed meats has been shown to lower the risk of developing type 2 diabetes and, for those who have diabetes, to improve both glycemic and lipid control”

In the report, they cite a couple of studies where legumes were effective in lowering blood sugar levels. However, in an article from Harvard School of Public health, they say it’s not completely clear weather legumes can help prevent diabetes type 2 or lower blood glucose. They cite an older study from 2000, where no difference was noticed in women who ate a lot of legumes and women who ate few.

A couple of bonus ideas

Big epidemiologic studies can give us an idea of the benefits of a certain food. However, only you know what is best for your body, and that can only be learned with experience. If you usually don’t eat legumes, try including some and see how you feel. Everyone’s body responds in a slightly different way to different foods!

That being said, legumes are a very inexpensive source of nutrients. There are a couple of curious things to keep in mind when it comes to legumes.

A) Combine them with rice for a whole protein

Amino acids are what proteins are made of, and each protein in your body is made of 20 amino acids. 11 of those are produced by the body, but the other 9 your body can’t make, and you must get them from food. The combination of rice and beans is called a whole protein because it provides those other 9 essential amino acids.

Other types of complete proteins are eggs, fish, chicken, beef, pork, dairy and whole sources of soy (tofu, edamame, tempeh, miso)

Combine beans with brown rice for an extra nutritious meal. Brown rice has more fiber and nutrients than white rice. Here’s a simple and tasty recipe.

B) The “soaking” question

Traditionally people soaked beans before cooking to make them more digestible and increase nutrient absorption.

The argument for soaking: legumes contain phytic acid which is considered an anti-nutrient. Soaking them basically gets rid of the phytic acid. The idea is that phytic acid can cause loss of mineral absorption (especially iron and zinc) and also damage the intestinal tract.

However, Dr. Alan Christianson believes there is evidence proving phytic acid can have positive effects. He says there’s been large population studies which show that phytic acid cuts the risk of various types of cancer. In addition, it works as a detoxifier of heavy metals and can lower the risk of diabetes.

He’s arguments on the article that I linked (click on his name) are pretty convincing. However, I wouldn’t completely ignore the fact that traditionally many cultures have soaked beans before cooking them.

So, we’ve got a bit of a problem here haven’t we? I have stopped getting frustrated reading about nutrition. There are so many theories reading studies on food can feel like falling through an endless rabbit hole.

My recommendation: experiment with soaking, but don’t worry too much about it. Find the way you prefer cooking and eating beans the most. For some people soaking makes beans less tasty, so they skip it. Sometimes I just want a quick nutritious meal, and canned beans come in handy.

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