Archive for the ‘Protein’ Category

Best Study on Vegan Protein Intakes to Date

Sunday, January 31st, 2016

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 will 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 don’t 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

Ginny on Fire

Sunday, January 10th, 2016

In the last month, Ginny Messina, MPH, RD has put out a number of great articles for vegans to check out:

Vegan Diets and Orthorexia: How Should Activists Respond?

Lettuce and Bacon and the Environment: Some Thoughts for Vegan Activists

Will a Vegetarian Diet Make You Depressed?

Your Vegan New Year’s Diet: Don’t Forget the Protein

Amaranth is a Good Source of Plant-Based Protein

Thursday, April 2nd, 2015

A reader informed me that amaranth was a good source of protein–better than quinoa even. So I checked it out and found that she was correct.

Amaranth has 9 g of protein per cup (cooked) which is slightly higher than quinoa. One cup of cooked amaranth has 250 calories while one cup of cooked quinoa has 222 calories. This gives them about the same amount of protein per calorie.

Amaranth also has a decent amount of lysine, comparable to a serving of soy or other legumes.

I have added amaranth’s amino acid profile to Table 3: Protein & Amino Acids in Common Foods.


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Meat Alternatives Associated with Lower Hip Fracture Risk in AHS-2

Thursday, October 10th, 2013

Today was a good day: As longtime readers of this blog will know, I love getting good news about my “bad” habits. :)

A study came out that fits in well with past findings, is well-written, and supports my proclivity to eat and recommend soy meats!

It was a report from Adventist Health Study-2 (AHS-2), conducted among caucasian Seventh-day Adventists living in the USA, comparing the intakes of many different foods and hip fracture risk after 5 years of follow-up (1).

First, there was a bit of bad news in that vegans had the highest rates of hip fracture at 3.0 per 1,000 person-years compared to 2.0 for non-vegan vegetarians (including semi-vegetarians) and 1.6 for non-vegetarians. The paper didn’t report whether this finding was statistically significant, but it was not a great trend, obviously. Read on for how to reduce your chances.

Here are findings from the fully adjusted model (2):

– Meat alternatives once a day or more (compared to less than once per week) were associated with a 66% reduced risk of hip fracture in the vegetarians (.34, .12-.95).

– Eating legumes once a day or more (compared to less than once per week) was associated with an 82% reduced risk in non-vegetarians (.18, .06-.54) and an 55% reduced risk in vegetarians (.45, .22-.94).

– Meat more than 3 times per week was associated with a 45% reduced risk in the non-vegetarians (.55, .36-.83), compared to less than once per week.

– Dairy, nuts, soy milk, and “tofu & soy cheese” were not associated with a lower risk. The average amount of tofu & soy cheese per day was only .1 among the vegetarians. They did drink close to a cup of soymilk per day (or “soya milk” as the authors, who apparently think they live in Europe, call it).

The authors emphasize the need for vegans to eat legumes in order to get enough of the essential amino acid lysine:

“[A]n individual who adheres to a vegan diet, which excludes meat and dairy products, will need at least two cups of cooked beans [per day] to meet the recommended lysine intake requirement…Lysine and hydroxylysine are the main amino acids in the cross-linking process of bone collagen…Lysine can also influence bone health through its end product carnitine. Carnitine supplements have been shown to improve bone density in some animal and human studies.”

Note that the requirement for 2 cups of cooked beans assumes no other lysine sources in the diet, which isn’t the case. You can can read more on lysine needs and how to meet them in Protein.

They go on to say:

“Among our participants, intake of meat analogues of at least one serving daily reduced the risk of hip fracture by up to 49%…The main protein ingredients in meat analogues are soya, wheat, gluten, eggs and milk. A typical serving of meat analogues (1 serving ~73 g in AHS-2) contains at least 10 g of protein, but can vary from 9 to 18 g.”

Or 30 g as Tofurky Italian sausage has!

They point out that their finding for meat being protective is backed up by other research but not all. After a brief analysis of the research they suggest that meat intake is associated with bone health when protein intakes are low. And, finally:

“Protein is recognized for its ability to improve [calcium] balance, suppress parathyroid hormone, increase lean body mass and increase production of the bone growth regulator insulin-like growth factor-1.”

This study had something for everyone – low-fat proponents can relish in the findings for legumes and meat alternative eaters can smugly continue in their bad habits!

I have not yet updated the article, Calcium and Vitamin D, with this new study yet, but hope to do so in the next few days.


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1. . Lousuebsakul-Matthews V, Thorpe DL, Knutsen R, Beeson WL, Fraser GE, Knutsen SF. Legumes and meat analogues consumption are associated with hip fracture risk independently of meat intake among Caucasian men and women: the Adventist Health Study-2. Public Health Nutr. 2013 Oct 8:1-11. [Epub ahead of print] | link

2. *Adjusted for fruits and vegetables intake, age, height, weight, gender, energy intake, physical activity, smoking, health status and total calcium intake.

Does (Animal) Protein Leach Calcium from Bones?

Monday, February 25th, 2013

[Thank you for all the responses to my request for information on increasing bone mineral density! I received a lot of responses and am still working my way through them.]

Because I’m planning to write a more reader-friendly version of’s Bones, Vitamin D, and Calcium, I decided to check in on the research on protein and bone health. In so doing, I found a 2012 review from a group of researchers in France who declared having no conflicts of interest (1).

There has been an enormous amount of research on protein and bone health and their review had almost 4 pages of references. I will hit the highlights of what they found:

– Many clinical trials show that adding purified proteins to the diet increases calcium excretion through the urine.

– Phosphorus, in which meat and dairy are rich, counteracts the increase of calcium in the urine between 40 and 65%.

– Findings that older people in Western countries have higher hip fracture rates are confounded by the fact that people in Western countries live longer, protein intakes were not estimated for individuals, and there are ethnic differences in bone structure and lifestyles.

– High protein diets increase acid excretion in the urine, but this can be handled by the body’s acid buffer system without the need for calcium.

– Studies measuring whole-body calcium balance (as distinct from excretion) in relation to high protein diets have been mixed, but this might partly be due to the difficulty in measuring calcium balance and because high protein diets might reduce calcium balance when calcium intakes are particularly low.

– In low-calcium, but not high-calcium diets, higher protein intakes probably increase calcium absorption from the digestive tract causing an increase in calcium excretion in the urine.

– Fruits and vegetables are beneficial to bone health, probably due to their high potassium and magnesium content. This could cause confounding in protein studies because diets high in protein are often low in fruits and vegetables.

– As I describe in my post Protein Intake and Bone Health, Darling et al. (2009) found that a large majority of the cross-sectional surveys and cohort studies have reported either no association or a beneficial association between protein and bone mineral density.

– There is some evidence that a beneficial effect of protein on bones is only seen when calcium intake and vitamin D status is adequate.

– Maintenance of adequate bone strength and density with aging is dependent on adequate muscle mass which is dependent on adequate intake of protein.

– An increase in IGF-1 is most likely the mechanism for increased bone health with higher protein intakes.

They conclude, “Although HP [high protein] diets induce an increase in net acid and urinary calcium excretion, they do not seem to be linked to impaired calcium balance and no clinical data support the hypothesis of a detrimental effect of HP diet on bone health, except in the context of inadequate calcium supply.”

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1. Calvez J, Poupin N, Chesneau C, Lassale C, Tomé D. Protein intake, calcium balance and health consequences. Eur J Clin Nutr. 2012 Mar;66(3):281-95. | link

Pumpkin Seeds: Good Source of Lysine

Thursday, January 24th, 2013

Lysine is the limiting amino acid in most vegan diets. It is typically not hard for vegans to get enough lysine, but you have to eat three to four servings of high lysine foods each day. High lysine foods are legumes, seitan, quinoa, and pistachios.

The USDA lists pumpkin seeds in the same entry as other squash seeds and the entry for such seeds has listed high amounts of lysine. But I have not included them among the high lysine foods because it was not clear which seeds they are specifically talking about.

A reader decided to write the USDA Nutrient Data Laboratory and ask them about their entries. It turns out that three of the “pumpkin and squash seed” entries are for pumpkin seeds only.

According to the pumpkin seeds-only entry for roasted kernels (USDA nutrient #12016), a one-quarter cup of pumpkin seeds has 360 mg of lysine, which qualifies it as a high lysine food.

I have updated the Protein article at to reflect the addition of pumpkin seeds to the list of high lysine foods.

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Seitan – A High Lysine Food

Friday, November 2nd, 2012

Awhile back, a reader sent me a copy of a 2009 paper that analyzed the amino acid amounts in wheat gluten protein (1).

The USDA nutrient database does not give amino acid amounts for wheat gluten and it doesn’t include seitan at all. I have long suspected that seitan would be a good source of the amino acid lysine (which is generally the limiting amino acid in vegan diets), but I had no way to verify this until getting the 2009 paper.

Upon doing some calculations I estimate that White Wave seitan has approximately 656 mg of lysine per serving, making it one of the highest sources of lysine among plant foods. I have added this information to Table 3 of Protein at You can see more details about how I came up with this amount in the footnotes of the table, if interested.

There is one disconcerting thing about the 2009 paper – it has no amounts for tryptophan and no explanation as to why. And if you add up the amounts of the other amino acids in mg/g of protein, it comes to almost exactly 1 g, leaving no room for tryptophan. I have written the authors to find out why this might be.

The paper is rather technical and not being a laboratory scientist, I didn’t even understand most of it. If any readers would like to take a look at it, let me know through the contact form.

In any case, I feel confident now that seitan is a good source of lysine and I have added it to my protein recommendations as an option for getting your daily amount of lysine.

Addendum of November 7, 2012:

I have communicated with one of the paper’s authors, Dr. Ine Rombouts who told me that the protein in wheat is 80% gluten and that gluten is very low in tryptophan – that it only has negligible amounts. The other 20% of wheat protein is made up of albumins and globulins which have more tryptophan. This is why wheat has tryphtophan but wheat gluten does not.


1. Rombouts I, Lamberts L, Celus I, Lagrain B, Brijs K, Delcour JA. Wheat gluten amino acid composition analysis by high-performance anion-exchange chromatography with integrated pulsed amperometric detection. J Chromatogr A. 2009 Jul 17;1216(29):5557-62. Epub 2009 Jun 3. | link

VRG: Can a vegan diet provide enough protein to slow down age-related muscle loss?

Tuesday, May 15th, 2012

Good article from Christine Kasum Sexton of the Vegetarian Resource Group on preventing age-related muscle loss:

Can a vegan diet provide enough protein to slow down age-related muscle loss?

Protein, Lysine & Muscle Mass in Vegans

Monday, May 14th, 2012

Just added to the Protein page at

“A study out of Boston published in 2011 but performed using data collected during the 1980s, found that vegan and non-vegan, middle-aged women had similar levels of muscle mass despite differences in protein intake of 1.0 g/kg/day for vegans and 1.3 g/kg/day for omnivores (14). However, the muscle mass was not measured directly – rather it was estimated using formulas based on creatinine clearance (a byproduct of muscle metabolism). The researchers believed the formulas to be accurate, but since they have not been validated on vegans it should be viewed with some uncertainty.

At 30 mg/kg/day, the vegan women did not meet the RDA for lysine which is 38 mg/kg/day. However, the study showed the vegan women to be consuming only 1511 kcal/day vs. 1866 kcal/day for the omnivores, yet their body mass indexes were very similar at 20.0 and 20.7 respectively. This could indicate that food intake for the vegans was underestimated, possibly due to a lack of data on vegan foods.”

More commentary: This is one of only two studies that have looked at protein status in actual vegans, the other study being one that measured serum albumin levels (12). While not conclusive, it provides evidence that vegans generally have adequate protein status.


12. Haddad EH, Berk LS, Kettering JD, Hubbard RW, Peters WR. Dietary intake and biochemical, hematologic, and immune status of vegans compared with nonvegetarians. Am J Clin Nutr. 1999 Sep;70(3 Suppl):586S-593S. (Link)

14. Andrich DE, Filion ME, Woods M, Dwyer JT, Gorbach SL, Goldin BR, Adlercreutz H, Aubertin-Leheudre M. Relationship between essential amino acids and muscle mass, independent of habitual diets, in pre- and post-menopausal US women. Int J Food Sci Nutr. 2011 Nov;62(7):719-24. Epub 2011 May 16. (Link)

Protein Recommendations and Kidney Function

Wednesday, April 4th, 2012

I see that you advocate higher intakes of proteins, but what about renal function? In the ADA Position I read:

“Long-term high intakes of dietary protein (above 0.6 g/kg/day for a person with kidney disease not undergoing dialysis or above the Dietary Reference Intake for protein of 0.8 g/kg/ day for people with normal kidney function) from either animal or vegetables sources, may worsen existing chronic kidney disease or cause renal injury in those with normal renal function (185)”.

This is the reference:


This is a legitimate concern.

Someone with kidney disease should be careful about protein intake. My recommendations for protein (Table 1 in the article Protein) are generally lower than what the population normally consumes, though higher than what many vegans might consume, and should be safe for someone without kidney problems, especially since some studies have shown vegetable protein to be less harmful than animal protein.

My recommendations for older people are a range from .8 to 1.3 g/kg/day. If someone has kidney disease, they might want to stick to the lower end of the range, or even lower than that if indicated during monitoring by their physician. And vegans should focus on high lysine protein foods to make sure they get enough of the amino acid lysine.