Concerned about your protein intake on a vegan diet? Are plant-based sources really inferior to animal sources? Limiting factors may exist on a vegan diet, but once you know what they are, you can work around them like a pro.
If you’ve ever attempted a vegan diet while weight training, it probably won’t take long for people to infiltrate your social media feeds with warnings of impending doom.
“You know your muscles are going to fall off, right?”
Jokes aside, there’s a lot of confusion when it comes to optimizing protein intake in the absence of animal foods. In order to demystify this concept, let’s provide a bit of background on what protein actually is.
Amino Acids (AA) are the building blocks of proteins; not only within the protein you consume, but also within the protein stored in your body as lean tissue. There are 20 different AA that are crucial for muscle protein synthesis (MPS, a fancy term for “building muscle”). Luckily, our bodies can produce 11 of these amino acids on its own, so they are categorized as “non-essential.”
The remaining nine AA cannot be produced by the body, making them “essential” amino acids (EAA) – they’re essential to consume through the diet in order to promote MPS.
This may come as a surprise, but the recommendation to eat “enough total protein” to promote MPS is a bit misguided. Protein as a whole is the vehicle to deliver AAs, but the actual requirements to be met are for specific AAs, not for protein.
Simple analogy: you’re building a house, and you need 100,000 pounds of material to construct it. You need different amounts of brick, plaster, drywall, wood, etc., which all add up to the total. But if you simply tell your supplier to give you 100,000 pounds of random material without making specifications, chances are you’ll be left with a pretty janky looking house at the end of the day.
It may be helpful to consider total protein as a means to an end, but the true goal is to cover each AA requirement.
Sounds tedious, right? Luckily, it’s not too hard in practice.
The key is to consume “complete” protein sources; protein sources that contain sufficient amounts of EAA to support human needs. Most complete proteins are animal products, but some plant protein sources fit the bill as well.
Despite people claiming the opposite, all plant protein sources contain every EAA. However, plant-based protein sources tend to have low amounts of one or more EAA. The lacking EAAs are known as “Limiting Amino Acids,” which is why these protein sources are considered to be incomplete.
While it might be simpler to meet your EAA requirements by including animal products in your diet, it can be accomplished all the same by prioritizing complete plant-based protein sources and tactically combining incomplete sources to cover your bases.
So now that we understand what EAAs are and their function, there’s still a major question to address: what’s the optimal EAA requirement?
Unfortunately, most literature examines EAA requirements to support the “average human” need in day to day life. If you find yourself reading this information in the first place, I highly doubt you’re the “average human” who doesn’t care about training and sits on the couch for hours a day. It stands to reason that hard-charging individuals who actually use their muscles have higher requirements in order to promote performance and recovery.
The first thought that came to mind was to adjust the AA profile of plant-based sources to the ones of good animal protein sources that have been shown to support MPS efficiently. But different animal sources differ in EAA composition as well.
Chicken, beef, egg whites and cottage cheese (representing dairy) all have different EAA compositions. It’s also unclear whether there’s an “optimal source” that’s superior to the others due to the fact that no long-term research exists examining MPS in relation to only one protein source. Simple observation would suggest otherwise, as countless lifters have gained plenty of muscle with a wide variety of protein sources for decades.
Without a clear-cut frontrunner from the animal kingdom, that still leaves us to speculate on what to base our EAA targets of.
For this reason, I shifted my focus to the EAA composition of human muscle. You know, that stuff we’re actively trying to build. Could matching our intake with the EAA composition of muscle be the key?
When comparing EAA content of 100 grams of various animal proteins to human muscle, the results are all over the map.
Sources like cottage cheese and chicken have more than enough leucine and threonine but come up relatively short in isoleucine and the sulfur-containing AAs. Based on these calculations, you’d need to consume roughly 130 grams from a mix of animal protein sources in order to build 100 g of the human muscle.
As for plant-based sources, they generally contain ~16% fewer EAA than animal sources, so vegans should consume at least 16% more protein (>150 grams) compared to omnivores in order to match the EAA composition of muscle.
Of course, this is all highly theoretical. It would be a godsend if every morsel of EAA you ate only contributed to building muscle, but if that were the case, we’d all be professional bodybuilders by now (…sigh…). The body uses EAA for many purposes outside of stimulating MPS, such as producing enzymes, hormones and even glucose in the absence of sufficient carbohydrate intake (a process known as gluconeogenesis).
Even if the optimal EAA target remains speculative, there are other considerations to make to determine sufficient protein and AA intake on a vegan diet.
It is commonly believed that Branched-Chain Amino Acids (BCAA), three of the nine EAAs that are heavily implicated in muscle growth, are almost completely lacking in a vegan diet. But as with most cliché’s in the fitness industry, the data paint a different picture.
BCAA content in plant proteins are generally not much lower than what’s found in animal protein or even human muscle. You can easily compensate by slightly increasing the total amount of protein you eat.
Of the three BCAAs, leucine likely reigns supreme. Leucine not only serves as a building block for tissue, but it also has the unique ability to independently signal MPS. A vegan meal that nets ~1 gram of leucine, which can be as little as 17 grams of total protein, is sufficient to maximize MPS for young lifters. For older individuals (> 65 years), the leucine requirement per meal more than triples, which makes fewer meals with higher total protein intakes (53 grams +) the prudent choice.
While leucine gets all the attention, it doesn’t actually seem to be an issue. However, leucine’s partner in crime, isoleucine, is relatively lower in plant protein sources. It would be wise to incorporate chia seeds and sunflower protein on a vegan diet to prevent any deficiencies.
BCAAs may not be the limiting AAs in a vegan diet, but research has shown that three other culprits in the EAA family may actually be too low to maximize MPS: lysine, as well as the sulfur-containing AAs methionine and cysteine.
Composition of animal sources rival that of muscle, but not all plant-protein sources do. Many plant sources seem to favor one or the other: pea protein, soy products and lentils contain nearly as much lysine as animal proteins but strongly lack the others, while cereal grains pose the opposite problem.
For this reason, it’s crucial to not only get enough protein when following a plant-based diet, but to also pay particular attention to the right combination of sources that will result in adequate amounts of EAA intake.
As a rule of thumb, vegan lifters should err on the side of caution and consume 50% of their protein from legumes (pea protein, soy products and lentils), 25% from seeds (hemp, chia and sunflower seeds) and 25% from grains (rice and wheat protein).
Even when applying this level of protein disparity, a total protein intake should still be recommended in order to give you a tangible landmark. Based on my calculations, vegans should get at least 2.4 g protein per kg bodyweight (or 1.1 g per lb) to optimally support muscle gains and overcome almost any limiting factor due to the AA composition of plant proteins.
Since lysine intake appears to be one of the hardest limiting factors to overcome, supplementing with it directly can actually reduce your recommended daily intake to about 2.1 g/kg/day (~.95 g/lb/day).
The amount of lysine you supplement with depends on your body weight; a petite 45 kg /100 lbs bikini athlete would require one gram while a big 136 kg / 300 lbs powerlifter would require three grams.
You can calculate the amount of lysine you need by using the following formula:
GRAMS LYSINE = 0.0221 x body weight (in kg***) – 0.0046
***Conversion: Kg = lbs/2.2
In my opinion, the greatest potential benefits of lysine supplementation are its safety and its ability to save you lots of calories from protein intake that you can utilize in the form of carbs of fats in order to create a more balanced diet. For me personally, it saves 20 g protein a day.
Does all this theory make your head spin and you still don’t know what to eat?
If so, check out one of my previous meal plans below to get some ideas and inspiration. This is the meal plan I followed a few months ago while preparing for my bodybuilding competition, so simply copying this structure to the letter isn’t advisable for those of you who have different levels of advancement, different training programs and different goals. It isn’t even the plan I follow at the moment, either. View this plan as an example of how to pull together the principles and theories presented in this article in order to efficiently promote muscle gain, but it’s not gospel. It worked for me before, but it doesn’t work for me now and there’s absolutely no guarantee that it’ll work for you.
I trained twice daily and consumed most of my protein around my workouts. My workout in the evening was more challenging, so I ate more protein in the evening.
Meal 1 – protein from legumes (after waking, before my first training session):
Chocolate pea protein mousse with strawberries containing 24 g protein. I ate 24 g protein in this meal due to the research finding that consuming 0.4 g protein/kg pre- and post-workout optimizes muscle growth. For me, that was 24 g.
Meal 2 – protein from seeds and grains (post-workout meal 1):
Protein bread consisting of sunflower protein and vital wheat gluten with a protein amount of 27 g. In addition to the protein bread I ate 300 g veggies that kept me full and satisfied.
Meal 3 – low protein meal (when I get hungry around lunchtime): about 300 g vegetables, mostly eggplant, zucchini and mushrooms with paprika spread or tomato sauce.
Meal 4 – protein from legumes (before my second training session):
Chocolate pea protein mousse with strawberries containing 24 g protein (same as meal 1).
Meal 5 – protein from legumes, seeds and grains (post-workout meal 2, which was also my dinner)
Meal 5 would be the largest meal of the day. I usually ate protein bread consisting of wheat flour, pea protein and vital wheat gluten that contains 34 g protein. In addition, this meal also contained most of my fat sources, 300 g veggies and chia seeds. Chia seeds are a fat source and a seed protein source at the same time. I also added two grams of supplemental lysine to this meal.
Meal 6 (pre-bed meal) – A snack made with sunflower protein. This meal supplied me with protein before sleep to support MPS and allowed me to get more protein from seeds to reach my target protein intake and the desired AA ratio for the day.
On days I didn’t train twice, I usually had only four meals a day, as the optimal meal frequency per day seems to be within the three to five range. However, when I went through periods of intense training for contest prep, I increased meal frequency to aid recovery.
In total, I got about 64 g protein from legumes, 30 g protein from grains and 30 g protein from seeds per day. The vegetables I ate with my meals added some more protein to my total daily intake, so that I hit my protein intake of 2.1 g protein/kg body weight per day pretty easily.
[Editor’s Note: In addition to certain limiting factors pushing the recommendations for protein intake higher on a vegan diet, some research suggests that higher fiber intakes can also reduce the digestibility of protein when eaten at the same time. If you notice your fiber intake greatly exceeds the recommended intake of about 25-38 grams/day due to your higher intake of plant-based foods, you may consider pushing your protein intake as high as 2.7 g/kg/day without lysine supplementation or 2.4 g/kg/day with lysine supplementation to compensate for this effect.]
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Scientific content creator: Anastasia Zinchenko, Ph.D.
Editor: Joe Flaherty, B.Sc., Certified Bayesian and NASM Personal Trainer, Joe's page