Lentils vs Beans: Comparing Gas, Protein, and Nutrition


When you switch to a more plant-based diet, it’s a big change.

Protein is a bit harder to come by, the gas can be crazy at first, and you need to consider where you’re getting your nutrients from.

While lentils are legumes, just like all other beans, most tend to think of them as their own sort of food. They share a lot of similarities with beans, but also have some fairly big differences.

I’ll walk you through the most important differences so that you can get the most from your diet.

Do Lentils or More Beans Give You More Gas?

There are 2 main reasons why legumes give people gas:

  • High fiber content
  • High oligosaccharide content

While you’ll eventually get used to the fiber, a large increase in fiber intake will cause stomach issues for most.

Let’s look at the numbers:

Legume Fiber (g) in a Cup (cooked)
Lentils 15.6
Navy beans 19.1
Black beans 15
Kidney beans 11.3
Soybeans 10

It varies a lot based on the type of bean you’re looking at. But other than soybeans, lentils have more (or as much) fiber as any common bean.

That’s the first part of the picture, now what about oligosaccharides? This is actually the bigger issue, since you’ll get used to the fiber pretty quickly.

Oligosaccharides are a type of sugar that’s hard to digest. So instead of easily getting absorbed in the stomach or small intestine, they mostly don’t break down until the large intestine. The fermentation process that breaks down these sugars in the large intestine emits gas.

It’s not quite as easy to see data for this, but I found a few studies that had some.

First, this study found that both pardena (brown) lentils and soybeans both have about the same amount of oligosaccharides.

However, red lentils have about 30 percent more oligosaccharides. If you’re worried about gas, avoid red lentils.

Another study found that lentils had the least amount of oligosaccharides (they didn’t look at soybeans in this one), followed by:

  • Common white bean
  • Red beans (e.g., kidney beans)
  • Fava beans
  • Chickpeas

Basically, soybeans and brown lentils should give you the least gas.

Want to Reduce Gas Further?

If you’re really having stomach issues, you should be soaking your beans.

Soaking reduces not only oligosaccharides, but also “antinutrients,” which bind to certain nutrients and prevent you from getting the full nutritional value from your legumes.

The second study from above looked at the effect of soaking legumes for 16 hours. Here are the results we’re interested in:

oligosaccharides in legumes

After soaking, oligosaccharide content went down:

  • About 38% in lentils
  • 67% in white beans
  • 40% in fava beans
  • 32% in red beans
  • 16% in chickpeas

For most legumes, the change was around 30-40%, but white beans respond particularly well to soaking, while chickpeas don’t.

Protein Comparison of Lentils and Beans

Legumes are every vegan’s main source of protein.

Here’s how much protein you get in a cup of a variety of cooked legumes:

Legume Protein (g) per Cup (cooked)
Soybeans 28.60
Lentils 17.86
Kidney beans 15.35
Black beans 15.24
Navy beans 14.98
Chickpeas 14.53
Fava beans 12.92

Excluding soybeans, which most people don’t eat directly (rather in tofu form), lentils are better than every other type of bean when it comes to protein.

Considering you might eat 3-4 cups of legumes, that could be an extra 15-20 grams of protein, which is nothing to sneeze at.

The amino acid profile for beans and lentils are quite similar for the most part. Soybeans have the most balanced profile, but again, aren’t a common bean in most recipes.

Nutritional Value of Lentils and Beans

All legumes are fairly nutritious, and just a few cups can exceed the recommended daily value for many nutrients.

Take a look at this comparison table for the main types of legumes:

  Lentils (% DV) Black Beans (% DV) Kidney Beans (% DV) Navy Beans (% DV)
Thiamin 22% 28% 19% 29%
Vitamin B6 18% 6% 11% 13%
Folate 90% 64% 58% 64%
Iron 37% 20% 22% 24%
Magnesium 18% 30% 19% 24%
Phosphorus 36% 24% 24% 26%
Potassium 21% 17% 20% 20%
Zinc 17% 13% 12% 12%
Copper 25% 18% 19% 19%
Manganese 49% 38% 38% 48%

While it’s not a huge margin in most cases, lentils give you the most vitamins and minerals.

Summary: Lentils and Beans Compared Head-to-Head

For the most part, lentils and beans share most things in common.

Personally, I just try to get a good variety of legumes.

However, if you’re trying to pick one legume to focus on, the winner is lentils.

Factor Takeaway
Gas Lentils have fewer oligosaccharides, and will likely give you the least gas.
Protein Lentils are clearly the best choice unless you eat soybeans.
Nutritional Value Lentils win most categories, including iron, but not by a huge amount

Let me know if you have any questions in the comments below.

You might also be interested in my comparison of legumes vs nuts.

About the author

Dale C.

Your friendly neighborhood vegan from Toronto. Chemical engineer turned semi-professional soccer player and freelance writer. Trying to do my small part in making the world better by writing about the wonderful world of veganism.

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