Vegan Complete Protein Ratios

One of the most ubiquitous combinations of food found in indigenous cultures around the world is rice and beans. Rice (high in lysine) and beans (high in methionine) provide the body with all the essential amino acids necessary to build protein that would otherwise be lacking from a vegan diet. For a great cheat-sheet listing vegetarian foods that provide the highest concentrations of lysine and methionine amino acids per 100g serving, checkout my post on The Methionine and Lysine Complete Protein Cheat Sheet.

But this begs the question: how much rice do I combine with how much beans to achieve a complete protein without wasting any amino acids? 1 cup rice with 1 cup beans? Or more on the beans? Or more on the rice? What about hummus? Should I have equal parts of tahini and garbanzo to achieve that perfect lysine/methionine ratio for a complete protein?

In this post I will investigate these questions. I'll provide links to the sources I used for nutritional information, and show my calculations to determine what volume of lysine-rich food A should be combined with what volume of methionine-rich food B to achieve that golden ratio to form a complete protein.

Disclaimer: I am not a dietitian. I have no formal education in any of this. These numbers were pulled from the Internet and the calculations done by an untrained hand. I reasonably believe them to be correct, but please do not blindly follow my advice without first consulting your doctor or dietitian.

The Ratio

According to wikipedia's article on a Complete Protein, the ratio needed between lysine and methionine (which actually includes cystine, another amino acid) is 51:25. That means that, in order for your body to utilize most of the amino acids received from a ~24 hour period, you should have roughly twice the amount of lysine as you do the combined amount of methionine + cystine by weight.

For example (multiplying by 20 for realistic numbers for a small meal), if a you're eating a bowl of rice and beans such that there's a total of 51*20=1020 mg of lysine and 25*20=500 mg of the sum of the methionine and cystine, your body will (in theory) use every amino acid to build protein. If you had a different ratio of rice/beans, then some of the amino acids will be unused/wasted, and you may get less protein for the day than expected.

Update: Many people have commented on this article stating that you don't need to have this "perfect ratio" of lysine-rich food and methionine-rich food in the exact same meal. To be clear, this is correct. To avoid leaving undigested amino acids, you have to get this "perfect ratio" in the same day. For example, if you eat rice in the morning, you'll need to eat beans sometime within 24 hours to be able to use all of the methionine amino acids that you ate in the rice. If you ate rice and didn't eat beans within ~24 hours, you will not be able to get the protein you expected for the day.

If you're a lazy vegan like me, I highly recommend just combining lysine-rich foods with methionine-rich foods in the same meal. This way you don't have to track what to eat for the next meal based on what you ate in the past 24 hours. And, besides, rice and beans go so well together!

The source

All of these figures were pulled from nutritiondata.self.com. I am in no way affiliated with this website, but their database is wonderful to use for nutritinal data for common foods. I have no idea how accurate it is.

The combos

Now I'll describe popular combinations of foods, show my sources, my calculations, and end with the ideal theoretical volumetric combinations of lysine-rich item A to methionine-rich item B to achieve that golden ratio for a complete protein.

Black Beans & Long-grain Brown Rice

Starting with my #1 favorate combination. I eat this more times than I'd like to admit--usually in a latin-american stir-fry of some kind (cumin, chipotle peppers in adobo, apple cider vinegar, lots of veggies, and long-grain brown rice with black beans is my go-to).

I usually buy black beans dry, cook them in big batches, fill them into jars, add salt, and store them in the fridge until needed.

According to Self's DB, boiled black beans with salt have 1046 mg of lysine, 229 mg of methionine, and 165 mg of cystine per 1 cup (195 gram) serving According to Self's DB, cooked long-grain brown rice has 193 mg of lysine, 113 mg of methionine, and 60.5 mg of cystine per 1 cup (172 gram) serving.



Maybe one day I'll write a script for this, but my current approach is brute-force. First, let's assume we should combine exactly 1 cup of cooked rice with 1 cup of cooked beans. We'll run the calculations, and determine if there's excess lysine or methionine.

1046 mg lysine in 1-cup beans + 193 mg lysine in 1-cup rice = 1239 mg total lysine

229 mg methionine + 165 mg cystine in 1-cup beans + 113 mb methionine + 60.5 mb cystine in 1-cup rice = 567.5 mg total methionine/cystine

Since we need (a little more than) twice as much lysine as the methionine+cystine to meet our golden ratio of the complete protein, we'd need approximately 1135 mg lysine to match our 567.5 mg total methionine/cystine.

With equal-parts by volume, we have a difference of 1239-1135=104 mg from the ideal ratio. That's pretty damn close to ideal.

Conclusion: When combining black-beans and long-grain brown rice, use equal parts (by cooked volume).

Hummus

While rice and beans is probably the most popular combination of lysine-rich and methionine-rich foods to achieve a complete protein, the second-runner is likely hummus.

Garbanzo beans (chickpeas) are high in lysine, and sesame seeds are crazy high in methionine. Sesame seeds are usually ground into a paste similar to peanut-butter and added to hummus to make this delicious spread a complete protein.

But how much tahini should you add to your garbanzo beans to create a complete protein that meets that golden ratio?

It's generally common-knowledge to add equal parts of rice & beans to achieve a complete protein. So, naturally, I assumed it made sense to combine equal parts of garbanzo beans and tahini to have a fully utilized complete protein. But most recipes only call for 1-4 tablespoons of tahini per 1 cup of cooked garbanzo beans. Does that little tahini leave wasted lysine in your digestive tract?? I spent hours researching this question to no avail, so I ran the numbers (note I'm using 100-g rather than 1-cup since data for 1-cup of tahini isn't provided by the source):

According to Self's DB, boiled garbanzo beans with salt have 593 mg of lysine, 116 mg of methionine, and 119 mg of cystine per 100 gram serving.

According to Self's DB, roasted & ground sesame seeds (tahini) has 545 mg of lysine, 561 mg of methionine, and 343 mg of cystine per 100 gram serving.

First, let's assume 50% garbanzo beans and 50% tahini by weight.

593 mg lysine in the garbanzo beans + 545 mg lysine in the tahini = 1138 mg total lysine

116 mg methionine + 119 mg cystine in the garbanzo beans + 561 mb methionine + 343 mb cystine in the tahini = 1139 mg total methionine/cystine

Holy crap, that's a lot of tahini! Honestly, I think if you dipped your pita into a humus with 50% tahini, you'd probably respond the same way. Again, we need roughly half the amount of combined methionine and cystine as the lysine. In this calculation, we actually have more methionine (1139 mg) than lysine (1138 mg). That's just way too much, and your body probably won't use most of that tahini to build protein.

Let's try again, this time sticking to a common recipe that calls for 1 cup of garbanzo beans and just 1 tablespoon of tahini

According to Self's DB, boilded and salted garbanzo beans has 973 mg of lysine, 190 mg of methionine, and 195 mg of cystine per 1 cup.

According to Self's DB, tahini has 81.7 mg of lysine, 84.1 mg of methionine, and 51.5 mg of cystine per 1 tablespoon == 15 gram serving of tahini

973 mg lysine in the garbanzo beans + 81.7 mg lysine in the tahini = 1054.7 mg total lysine

190 mg methionine + 195 mg cystine in the garbanzo beans + 84.1 mb methionine + 51.5 mb cystine in the tahini = 520.6 mg total methionine/cystine

We need (slightly more than) twice as much lysine as methionine+cystine. 520.6 mg of methionine/cystine * 2 = ~1041.2 mg of lysine needed. This combination gave us 1054.7 mg of lysine. That's slightly more than twice as much lysine (13.5 mg), which is pretty perfect.

Conclusion: When combining garbanzo beans and tahini to make hummus, use 1 tablespoon of tahini per 1 cup of cooked garbanzo beans.