Best Study on Vegan Protein Intakes to Date

I just updated the Protein page at with a new section, Intakes and Plasma Amino Acid Levels in Vegans, based on a recent study from EPIC-Oxford.

The new research cannot substitute for a nitrogen balance or protein synthesis study on vegans, which I have been hoping to see, but for now it’s what we have.

The takeaway message is that vegans, and particularly vegan women, should continue to make sure they eat plenty of lysine-rich foods, and that if you do, you should be covering all your protein needs.

I have reproduced the new section below.

Intakes and Plasma Amino Acid Levels in Vegans

A 2015 report from EPIC-Oxford analyzed the dietary intakes and blood levels of amino acids in various diet groups in adult men (15). The study included 98 men for each diet group (vegan, lacto-ovo, pesco, and meat-eater). The authors say, “[T]his is the largest study to date of amino acids in the circulation or in the diet by habitual diet group, and on average participants had followed their diet for several years.”


The study didn’t compare the intakes of the various diet groups to the US RDA for amino acids, but I have done so in Table 4 below.


Vegan men met the RDA for all essential amino acids.

This study bolstered the idea that lysine is the limiting amino acid in vegan diets, with vegan men surpassing the RDA by the lowest amount–9%. Methionine, the amino acid of second most concern, surpassed the RDA at the next lowest level of 33%.

The 95% confidence interval for lysine was 2.69-2.95 g/day; with the lower margin coming in at 104% of the RDA. The people on the lower end might have been the people who weighed less (and thus had a lower RDA than the average vegan).

The RDA for protein and amino acids is the same for women as it is for men (based on a percentage of their body weight). Male vegans in EPIC-Oxford were found to eat 10.7% more protein than female vegans (62 vs. 56 g per day; link). If you assume female vegans eat the same percentage of high-lysine foods as men, their average lysine intakes would be only 98.7% of the RDA.

Given that women have a lower percentage of lean body mass on average, it might seem curious that they have the same RDA for protein (and amino acids). In determining the RDAs, the Institute of Medicine says (Ref 2, p. 644):

Although the data indicate that women have a lower nitrogen requirement than men per kilogram of body weight, this was only statistically significant when all studies were included, but not when the analysis was restricted to the primary data sets. This difference may be due to differences in body composition between men and women, with women and men having on average 28 and 15 percent fat mass, respectively. When controlled for lean body mass, no gender differences in the protein requirements were found. However, in view of the uncertain significance of the difference between the genders, the same protein EAR [i.e., Estimated Average Requirement, a foundation for the RDA] on a body weight basis for both men and women is chosen.

Another consideration is that the vegans in the UK may eat lower amounts of protein than those in the U.S. Adventist Health Study-2 found an average protein intake of 71 g/day for men and women combined, considerably more than in EPIC-OXford (link). It seems safe to assume that Seventh Day Adventist woman are likely getting plenty of lysine and other amino acids.

Finally, according to the authors, “[T]he validation of the [food frequency questionnaire] showed that protein intake was particularly difficult to estimate.”

Blood Levels

In comparing blood levels of amino acids between diet groups, vegans had lower levels of lysine, methionine, tryptophan, and tyrosine, and higher levels of alanine and glycine.

Interestingly, arginine, a dietary concern for vegans with herpes virus, was actually lower in the blood of vegans, but not significantly. It was also lower in the diet (3.92 g/day for vegans vs. 4.13 g/day for meat-eaters; lacto-ovo vegetarians had the lowest intake at 3.36 g/day).

The authors didn’t seem alarmed by any of the differences found between diet groups. I decided to take things a bit further and compare the plasma levels found in this study to the reference ranges given by the U.S. National Library of Medicine in Table 5 below.


In comparing the vegan’s blood levels to the reference range:

  • Alanine, glutamate, glycine, leucine, ornithine (a non-protein amino acid), phenylalanine, and serine are higher.
  • Aspartate is also higher, but the reference range is curiously low.
  • There is no reference range for tryptophan, with no explanation as to why.
  • There is a reference range for cystine (which is two cysteine molecules combined), but EPIC-Oxford didn’t list plasma levels for cystine or cysteine.

It is not clear what any of this means and the U.S. Library of Science notes that these numbers are dependent on the specific laboratory methods used.


The above research is not a great substitute for a nitrogen or protein synthesis study on vegans, but for now it’s what we have. The takeaway message is that vegans, and particularly vegan women, should continue to make sure they eat plenty of lysine-rich foods. There is no reason to think that the vegans in this study were aware of lysine or trying to increase their lysine intakes, so any vegan who does so should be well covered.


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2. Dietary Reference Intakes: Macronutrients. National Academy of Sciences. Institute of Medicine. Food and Nutrition Board. DRI table for carbohydrate, fiber, fat, fatty acids and protein. | PDF

15. Schmidt JA, Rinaldi S, Scalbert A, Ferrari P, Achaintre D, Gunter MJ, Appleby PN, Key TJ, Travis RC. Plasma concentrations and intakes of amino acids in male meat-eaters, fish-eaters, vegetarians and vegans: a cross-sectional analysis in the EPIC-Oxford cohort. Eur J Clin Nutr. 2015 Sep 23. | link

16. Plasma amino acids. Medline Plus. U.S. National Library of Medicine. Accessed January 30, 2016. | link

14 Responses to “Best Study on Vegan Protein Intakes to Date”

  1. Ari Says:

    Hi Dr. Jack Norris!

    being lysine necessary for the synthesis of collagen in the body, low lysine intake could be the reason why this vegetarians had a -10% lower collagen in one study? do meat eaters produce too much collagen? should vegans worry about it? (sorry about the english typos, i’m not american)

    the study:

  2. Jack Norris RD Says:


    I’ve never seen that study or heard about slow collagen synthesis in vegetarians. I’ll check it out.

  3. Ella Says:

    Thank you Jack Norris!

    You are a voice of sanity in the vegan community. Yes, I followed the Campbell/McDougall, etc. recommendations not to worry about getting enough protein, and I felt AWFUL. Now I focus on plenty of lysine containing protein, and I feel better than I did when I was an omnivore.

    Please get the word out. So many people give up veganism because they are not getting enough good protein – I am absolutely, totally convinced of that.

    Please continue getting the word out on protein. As a woman over 60, I’m convinced I need more than I did 20 years ago. The more plant protein I eat (particularly legumes), the better I feel, so my main focus is on that now.

    God bless.

  4. Ella Says:

    ..sorry, I meant CARNIVORE.

  5. Ari Says:

    I just asked you cause this study makes no sense in real life, right?

    i know this people in the study are “vegetarian”. but in real life the vegans i know look younger than they are, some have really good looking skin and have no problem at all growing muscle (even for bodybuilding). Even the raw vegans that consume very little lysine rich foods have good skin and muscle. The older vegans have no problem too..So i guess there is something wrong with this study or it simply isn’t important, because of all the extra antioxidant we consume. And maybe 10% less its still good enough anyway, or we need to consume 10% more of protein. what are your thoughts about it?

  6. Jack Norris RD Says:


    I’m not an expert in gene expression or collagen synthesis, but this study seems to be a very indirect way to measure whether vegetarians produce enough collagen. Basically, they found that vegetarians had a lower expression of collagen synthesis-associated genes. I’d be pretty surprised to find out that vegetarians don’t produce enough collagen, but it doesn’t appear to have been studied in any direct way.

  7. Consistency Says:

    Sufficient Vitamin D and leafy greens for collagen.

    Regarding the study. They could of been deficient in Niacin(Vitamin B3) since niacin is required to raise growth hormone levels.

  8. Alex Says:

    8 months vegan and i get less cold-sores than before. Although I do still get them, I have food triggers, coffee (which I have given up) and nuts, (which I have not) but i am digging into the mangoes and papaya and I find that helps a lot. I am following my own version of the 80/10/10 or rather I am a fruitarian and I am hoping that by being one this will eventually starve the virus out. I may need to give up nuts for a few years and all other argining foods, but I really hate this virus so it may end up happening – but will see… I love nuts btw.

  9. Brenda W. Says:

    Jack, This ‘thank you’ is long overdue, but I just wanted to add my personal experience and thanks to your always sound and useful recommendations, especially in regard to your protein aticle specifically (

    This has made a world of difference for me. I am a 63 year old female, vegan since 1980. Up until a year ago or so, I felt great all the time. My pasttime of choice is hard-core hiking … doing tough, off trail climbing, bushwhacking, and exploring in our western NC mountains.

    About a year ago, I noticed that after about only a couple hours, my muscles would begin painfully aching, feeling like they do when there’s lactic acid built up and I’d have to stop completely. I got really concerned when an easy 2 mile, flat hike on a clear trail left me in the same condition.

    Talking to my doc, who knows and supports my vegan lifestyle, after ruling out some other things, asked about my protein intake, saying that my hard core type of hiking certainly required plenty of protein to rebuild those muscles.

    That’s when I started researching and re-read your protein article and suddenly realized my diet was all but absent of lysine. Except for the occasional peaunut butter sandwich, I was eating no high lysine foods. My diet consisted mainly of lots of veggies, fruits, pasta, and bread.

    Given that I was both a very physically active person, and over 60, I immediately changed what I was eating every day, and after a short period of experimentation found that for my needs, I needed to take in a minimum of 3000mg lysine each day.

    Since I’ve been doing that, I’ve had zero recurrance of my aching muscles episodes, and have been able to get back to participating in the recreation I find so enjoyable. Beans are a regular daily food EVERY day, along with tofu and soymilk.

    Your blog has always been a superb source of info and scientific reference. Thank you for your efforts and service to the vegan community!!

  10. Jack Norris RD Says:


    Thank you for your kind words, I’m so glad my nutrition work helped you!

  11. canis Says:

    Dear Jack,

    As I have suffered from injury at my younger time, it caused serious osteropr in my head. Should I need more lysine foods in my diet? How many should be idea’s quanitity a day? Normally how many protein should be taken for woman for 46 years old a day? I have bloating for bean’s digestion. How I solve it? As your article, supplements with D3 (how much quanitity?), DHA/EPA, multi-vitamin and B12 must be taken for vegen. Is it correct? Any more supplement should be taken? I am too thin, only 80 lbs with 164cm height. How can I gain weight? More protein ?

  12. Jack Norris RD Says:

    Hi Canis–

    To find a high-lysine food other than beans, I’d try seitan, quinoa, tofu, tempeh or another processed, high-protein soy product.

    Here is a list of my daily recommendations for all vegans:

    If you need more help, I would suggest that you get personal nutrition counseling which I’m not able to offer at this time. Here’s a list of registered dietitians who are well-versed in vegan nutrition and who do personal counseling:

  13. Daniel Says:

    If someone eats a vegan diet of only fruits, vegetables, legumes, and potatoes, but no grains or seeds, can one get enough of every essential amino acid? Are there any amino acids in grains that one can’t get enough of in legumes? Are there even any other nutrients in grains that one couldn’t get enough of in legumes?

  14. Jack Norris RD Says:


    It’s certainly possible—probably even easy—unless you’re eating a very high percentage of your diet as fruit. You could get an idea by adding up the amino acids using the charts here:

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