Leucine for Vegans – Food Sources, Supplementation, Meal Plan

March 1, 2022

Leucine is an essential amino acid that might be slightly more challenging for vegans to consume through the diet.

You may have come across this amino acid when looking at different sports supplements.  Leucine is one of the three branched-chain amino acids (BCAAs) involved in building muscle.

In this article we take a look at leucine for vegans – food sources, supplementation and how much you need each day.

 

What are amino acids?

Proteins are made up of amino acids.

There are 20 different amino acids, nine of which are considered essential. This means that our bodies cannot produce them and they must come from our diet. 

Within the nine essential amino acids are three branched-chain amino acids. Leucine falls within this category, alongside isoleucine and valine. 

Every protein-containing food has a unique ‘amino acid profile’. Most animal-based proteins are considered complete proteins as they have an amino acid profile that is not limited by lacking one or more amino acids. 

On the other hand, many plant-based proteins are considered incomplete. This means that the protein source is lacking in one or more amino acids.

For example, legumes are often low in methionine and grains are low in lysine. 

Protein synthesis can only occur to the extent that the most limiting amino acid allows. So if you have 20g of protein with a complete amino acid profile, the body is able to use that full protein amount to its greatest potential. However, if that same 20g is now lacking in methionine, the body will only make protein until the methionine has run out. 

 

What is leucine?

Of the branched-chain amino acids, leucine is the most critical for optimising muscle protein synthesis (the creation of new muscle tissue). This is because leucine actually triggers the process. 

If you do not have enough leucine within a protein dose, muscle protein synthesis won’t be able to happen.

Think of it like driving a car. Muscle protein synthesis is the car, the fuel in your tank is the pool of amino acids and leucine is the car key. Even if you have a full tank of gas, without the car key, you aren’t going anywhere. 

The only difference is that leucine’s ability to trigger muscle protein synthesis happens on a sliding scale. 

If you have some leucine (but not an optimal amount), your body will be able to start the process of muscle protein synthesis a little bit.

You can’t really just start your car a little bit because you have some of your car key, so this is when the car analogy starts to fall apart.

Either way, to get the most out of your protein intake, you want to have an optimal amount of leucine several times per day. 

Unfortunately, vegan protein sources are notoriously low in leucine

 

amino acids vegan

 

How much do you need per day 

The amount of leucine required for optimising muscle protein synthesis is 2.5-3g per protein dose. 

This number is more relevant to those who are looking to build muscle, retain muscle in a calorie deficit, improve recovery, or meet other athletic or body composition goals. 

For a regular person focused on health and wellness, ensuring you are having adequate protein from a variety of sources is the most important thing. For these people, starting the car a little bit but not the whole way is fine and won’t result in any negative health consequences. 

Now when it comes to optimizing muscle protein synthesis, having adequate leucine is only one piece of the puzzle.

 

In order of priority, you will also need to ensure that you are:

  1. Having an adequate amount of protein daily
  2. Splitting this protein intake into 4-6 doses per day 
  3. Using protein-combining strategies or having complete proteins at each protein dose to avoid the issue of rate-limiting amino acids
  4. And then ensuring there is 2.5-3g of leucine per protein dose

 

It is also likely beneficial for vegan athletes to aim for the higher end of this range as plant-based proteins are not as well digested as animal proteins. 

 

Leucine deficiency 

Whilst leucine is important for things outside of improving lean mass and recovery such as wound healing, deficiency is unlikely. 

The most important thing to consider here is to avoid protein deficiency in general by having at least 1g/kg body weight of protein daily.

You can further optimise that by having your protein from a variety of sources and including food high in leucine such as soy food and legumes. 

A focus on leucine may also be more important for maintaining skeletal muscle in elderly vegans who may be experiencing muscle wasting. 

 

Where can you get leucine on a vegan diet?

Leucine is found mostly in red meat, poultry, fish, eggs and dairy. 

Therefore, vegans tend to have lower blood levels of leucine than meat-eaters and even vegetarians who get some leucine from eggs and dairy. 

 

Soy 

The best source of leucine on a vegan diet is soy.

When it comes to vegan proteins in general, soy definitely reigns supreme. 

Unlike many plant proteins, soy has an amino acid profile similar to animal products and therefore rarely has an issue with rate-limiting amino acids. 

In certain forms such as tofu and especially soy protein isolate, the digestibility of the protein is one of the highest amongst plant proteins. 

Tofu has around 1.7g of leucine per 100g so you would need 150-200g of tofu for an optimal leucine dose. 

Soy protein isolate typically has 2-2.5g per standard 30g serve.

Other soy foods such as edamame beans, tempeh, textured vegetable protein, bean curd and soy milk are likely to have a similar leucine content per gram of protein.  

Leucine can also be found in decent amounts in some legumes such as lentils and navy beans. However, there is only ~1.6g of leucine in a full cup of lentils so you would be eating a lot of lentils to get your 3g of leucine at each meal if you were relying solely on legumes. 

 

soy is the best option for leucine for vegans

 

Leucine content in vegan protein powders

Choosing a vegan protein powder can be a minefield. Just like plant-based milks, you can make almost anything into a protein powder these days. From soy and pea to almond and hemp, it can be difficult to make a good decision. 

There are two great options for vegan protein powders from the perspective of digestibility, amino acid profile and leucine content and they are:

 

1. Soy Protein Isolate

Soy naturally has a more complete amino acid profile and high leucine content. Supplementation with soy protein isolate has even been shown to be as effective as building lean mass as whey protein where total protein intake and leucine is matched. 

Soy protein isolate typically has 2-2.5g per standard 30g serve which can be increased by pairing with soy milk or slightly increasing the serving size. 

 

2. Pea & Rice Protein Blend

Pea and rice proteins use the concept of protein combining to improve the amino acid profile. However, the leucine content of each protein blend can differ between brands. Most companies will list the amino acid profile on the back of the packet. 

Find leucine on this list to compare it to the recommendation of 2.5-3g per protein dose. Most of these protein powders have a leucine content between 1.7-2g. Again, you can increase the leucine amount by pairing the protein powder with a glass of soy milk, increasing the serving size or even by adding additional leucine. 

 

protein powders can be a great option for leucine for vegans

 

Do vegans need to supplement?

Generally, most vegans will not need to individually supplement with leucine. As long as you are meeting your protein requirements, you will not suffer from a leucine deficiency.

It is recommended that you simply aim to have a variety of protein foods in your diet including soy and legumes often. 

For vegans looking optimise muscle building, leucine supplementation may be worthwhile. Although we don’t have the research to back this up yet.

But since you need to have ~3g of leucine 4-6 times per day (with every main protein dose), supplementation may make this easier.

For example, you could have 2-3 protein doses per day that are coming from mostly soy protein (and therefore have a decent amount of leucine naturally) and then supplement non-soy-based meals/snacks with leucine.

But supplementing several times a day, every day is quite a burden so I would only recommend it to those who are prioritising muscle building and are highly motivated such as a vegan bodybuilder in comp prep. 

If you cannot eat soy due to interactions with medication, an allergy or intolerance, supplementation several times per day with meals would be useful for building muscle mass and improving recovery. 

Otherwise, you could trial a day on a plate similar to the example below.

 

A leucine-rich vegan diet optimised for muscle building may look like:

 

Breakfast

Banana Smoothie: 1 banana, oats, 1 cup of soy milk, 1 tbsp hemp seeds, 30g soy protein isolate & maple syrup 

Lunch

2 slices whole grain bread + 170g of hard tofu + 2 cups of mixed vegetables 

Dinner

Vegan bolognese made with 40g textured vegetable protein (made from soy) & lentil pasta 

Snacks

200g of soy yogurt with berries & granola + 2g leucine mixed into the yogurt

 

The goal isn’t to have a certain total amount of leucine per day but to have 2.5-3g of leucine every 3-4 hours to optimise muscle protein synthesis. 

 

High leucine vegan recipes

 

The bottom line

Leucine is important for triggering the process of muscle protein synthesis. This is particularly relevant for vegans with athletic and/or body composition goals. 

You want to aim for ~3g of leucine 4-6 times per day or every 3-4 hours. You can do this by having a large focus on soy-based food in your diet or individually supplementing leucine with high protein meals. 

For the general vegan who isn’t too concerned about gaining as much muscle mass as possible or recovering from intense and frequent training sessions, simply getting adequate protein is absolutely fine.

Having greater leucine doses for vegans is really only helpful when building and retaining lean mass is a priority. 

If you are finding it challenging to build muscle on a vegan diet, you are welcome to book a free discovery call with one of our dietitians at the PNW Clinic to discuss options for nutrition coaching.

 

This article was written by Sports Dietitian Leah Higl.