One of the answers at Which essential amino acids are the most likely to be deficient in a vegan diet? suggests beans are the best source of essential amino acids requirements in vegan diets.

Is there a bean or combination of beans that would be the best from a nutritional view in a vegan diet?

  • best in terms of amino acids? in terms of completeness or quantity? or just all-round "best" (which is maybe too broad)?
    – Zanna
    Feb 10 '17 at 9:40
  • @Zanna amino acids are the key in beans and vegs diet discussion. Feb 10 '17 at 9:47
  • Are you interested in beans specifically, or would you consider pulses like peas, lentils, and chickpeas?
    – Nic
    May 14 '18 at 1:04
  • 1
    I was thinking just beans. May 14 '18 at 9:46

The best bean is variety

The main concerns with bean are that many are incomplete proteins: they are relatively low in Lysine and Methionine.

However, there are some exceptions. Most notably Soy is a complete protein with high levels of Methionine so Soymilk, Tofu, Edamame, and Natto are all good protein sources. Similarly, Chickpeas (garbanzo) are higher in Lysine than most beans, while not complete for essential amino acids there easier to complement. Not strictly beans but Quinoa, Buckwheat, and Quorn are all complete protein sources too.

Another consideration is that Methionine and Lysine are plentiful in other foods and easy to complement. Eating beans with Rice, Wheat, or Couscous would get you your full set of amino acids in one meal. Note that Corn is also Lysine deficient which is a problem in some diets.

The best approach to complete proteins is variety, then you ensure you get a variety of other nutrients (vitamins, minerals), and get to eat interesting things instead of the same thing everyday. Soy has become the de facto vegetarian protein substitute for good reasons but a health diet is a balanced one and there's no reason not to give other beans a try.

  • Fruits (including tomatoes) and dairy are also high in lysine so V*gan TexMex is also possible with complete (complementary amino acids) protein.
    – Tom Kelly
    Feb 11 '17 at 22:24
  • Beans are high in lysine relative to all other plant-based foods. You might want to specify what you're comparing beans against.
    – Nic
    May 17 '18 at 21:48

The soy bean provides more protein (and lysine) than other beans.

On a comparison of protein per gram, soy beans excel with 36 grams protein (of which 2.7 grams lysine) per 100 grams of beans. The next runner-up is mung beans which provide 24 grams protein (of which 1.7 grams lysine) per 100 grams beans. By this comparison soy beans have 50% more protein than any other bean.

Or when comparing protein per calorie, soy beans still win with 8.2 grams protein (of which 0.6 grams lysine) per 100 kcal. The next runner-up is mung beans again with 6.9 grams protein (of which 0.5 grams lysine) per 100 kcal. It's impressive that soy beans still win even though they contain more fat than most beans.

Soy beans provide more of the essential amino acids because the total protein content is so high.

Okay, but other than soy?

Mung beans (aka green gram) and kidney beans are pretty much tied for second place with very slight differences in the amino acid profiles between them.

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