I just read an interesting paper from March 2011 (sent my way by Dave of TheVegetarianSite.com). It was a cross-sectional study on semi-vegan, Buddhist nuns from Korea. The study was done by German researchers studying how the nuns’ B12, folate, and iron intakes were affecting their blood cell size (1).

The nuns’ blood cells appeared fine, indicating that either they were getting plenty of vitamin B12 for the purposes of their blood cells, or that they were getting enough folate to mask a B12 deficiency. I should also point out that there are two types of B12 deficiency – one that causes blood problems (which can be masked by high intakes of folate) and one that causes nerve problems (that cannot be masked by high folate intakes).

For me, the more interesting part of the paper was how strongly the researchers suggested that nori (also known as laver) is a reliable source of vitamin B12.

The semi-vegan Buddhists ate some dairy, but it was not very much according to their diet diaries (only 21 grams per day on average). If you assume they were drinking milk, 21 grams would be only about .1 µg of B12 per day. That is not enough to keep vitamin B12 levels at the 360 pmol/l that they averaged, indicating they either were eating more animal products than reported or were getting their B12 elsewhere, such as from nori.

The nuns ate 1.3 g of nori per day. According to previous studies, nori contains anywhere from about 1.5 to 20 µg of B12 analogue per 30 g. That would mean 1.3 g of nori would contain .05 to .6 µg. If we generously assume the nori had the very highest amount of B12 and add the .6 to the .1 µg from dairy products, you get .7 µg of B12 per day in the best case scenario. That still does not seem to be enough to explain such high B12 levels.

However, the semi-vegans did eat other sea vegetables and many sea vegetables are known to have B12 analogues. Generally, blood B12 levels of people who eat significant amounts of sea vegetables cannot be considered reliable, because the testing methods cannot discern between active and inactive B12 analogues.

There have been quite a few studies measuring the vitamin B12 content of nori. But only one has actually tested the seaweeds’ effect on methylmalonic acid (MMA) levels. MMA is the only marker that can determine true vitamin B12 activity as it is not impacted by high folate intakes. When there is not enough active B12 in the blood, MMA levels rise. The one study on nori that measured nori’s effects on MMA levels found that it increased MMA levels, though the increase was statistically significant for only dried nori and not from raw nori. This means that dried nori had anti-B12 activity, while the raw nori did not improve nor harm B12 status. Most nori eaten in the U.S. is dried.

This current study on semi-vegan Buddhist nuns in Korea could have at least partially solved this whole question of B12 sufficiency by testing MMA levels. Although it would not necessarily have meant that the nuns’ were getting most of their vitamin B12 from nori, healthy MMA levels would have at least indicated if most of the B12 in their blood was active.

The study that really needs to be done is to take some willing vegan participants in the Western world and have them avoid all B12 supplementation until their MMA levels increase above normal. Then feed them nori purchased in stores in the U.S. and see what it does to their MMA levels and how much is needed. If their MMA levels improve, then the same study should be performed a few different times on different people and with different batches of nori. Three successful studies like this would satisfy me that nori is a reliable source of vitamin B12 for vegans. Until these studies are done, choosing nori instead of B12-fortified foods or supplements could result in vegans harming themselves.

In countries where vitamin B12 fortification or supplements are not readily available, it makes perfect sense that researchers would hope that B12 would be in an available food such as nori. And, while I am quite skeptical of its reliability, I certainly hope nori turns out to be a reliable source of vitamin B12.

While I would be very happy to see a new source of vitamin B12 for vegans, especially in developing countries, this would not therefore prove that a vegan diet is “natural”. That question is answered by the fossil evidence as to whether Homo sapiens ate animal products throughout our evolution, and not whether plants could theoretically provide all the nutrients necessary for sustaining human life.

Humans have always had a rich, vegan source of vitamin B12 close by – our feces. Human feces contain much active vitamin B12. However, that does not mean that anything that gets contaminated with the bacteria from human feces is, therefore, also a rich source of vitamin B12. I have yet to see convincing data that human feces contamination on food, in water, or just in the soil can produce enough vitamin B12 to sustain humans, much less keep their homocysteine at a healthy level.

Reference

1. Lee Y, Krawinkel M. The nutritional status of iron, folate, and vitamin B-12 of Buddhist vegetarians. Asia Pac J Clin Nutr. 2011;20(1):42-9. Link

The Survey on Vegans’ Nutrient Intakes that I wrote about yesterday is only for people living in the United States. I’m sorry for any inconvenience that may have caused you.

Hear ye, hear ye – another cross-sectional study on vegans has been released!

This time, it’s from Brazil (1). The main focus of the study was to determine how fast various lipids (triglycerides and cholesterol) were removed from the blood.

21 vegans were compared to 29 omnivores. The vegans had lower intakes of calories, saturated fat, and total fat. Vegans had similar triglyceride removal to omnivores, but they had faster cholesterol removal. Vegans also showed a lower rate of transferring cholesterol to HDL particles which is, apparently, a good thing.

The authors conclude that these findings, along with the vegans’ lower LDL cholesterol levels, puts vegans at a lower risk for atherogensis (fatty build up in the arteries).

Reference

1. Vinagre JC, Vinagre CG, Pozzi FS, Slywitch E, Maranhão RC. Metabolism of triglyceride-rich lipoproteins and transfer of lipids to high-density lipoproteins (HDL) in vegan and omnivore subjects. Nutr Metab Cardiovasc Dis. 2011 Sep 19. Link

Update: This survey is only for people living in the United States.

Kelly Blanco, a graduate student in the Department of Dietetics & Nutrition at Florida International University in Miami, is conducting a research study to examine the intake of calcium, vitamin D, and phosphorus in vegans.

She is requesting that vegans fill out this on-line survey, which will take 20 to 30 minutes of your time:

https://fiu.qualtrics.com/SE/?SID=SV_0diJiK2fuPuXurW

Thank you to anyone who decides to take part!

In my post of yesterday about the semi-vegetarians in Chad, I said that there is a steady flow of cross-sectional studies on semi-vegetarians from developed countries and their cardiovascular disease markers. Today I’m reporting on another one that can roughly go in that category, although the subjects were actual vegetarians (171 males) from a temple in China (1). They were mostly vegan, though some occasionally eat eggs and milk. They were compared to 129 omnivores.

Intima-media thickness is a measure of the thickness of the artery wall that has been shown to predict cardiovascular disease. To make a long story short, the vegetarians had thinner carotid intima-media indicating less atherosclerosis.

Other results were all over the board. For example, even though vegetarians had lower BMI, they had higher waist to hip ratios. Surprisingly, the vegetarians had much lower homocysteine levels, but the homocysteine levels for both groups were “off the charts” at 76 and 125 µmol/l respectively. I’ve never heard of homocysteine levels so high (normal is between 6 and 12 µmol/l) and it makes me think their measuring methods were not calibrated to other studies’ methods.

One final tidbit: Total cholesterol for vegetarians and omnivores was 164 and 193 mg/dl.

The take home message: Make sure you have a reliable source of vitamin B12. (Just kidding!)

1. Yang SY, Zhang HJ, Sun SY, Wang LY, Yan B, Liu CQ, Zhang W, Li XJ. Relationship of carotid intima-media thickness and duration of vegetarian diet in Chinese male vegetarians. Nutr Metab (Lond). 2011 Sep 19;8(1):63. Link

Warning: Lots of biochemistry discussed below. Hopefully the general ideas of the article will make sense even if you skim over the more technical parts.

A study just came out with a scary title, “Vegetarianism produces subclinical malnutrition, hyperhomocysteinemia and atherogenesis.” The abstract shows that the cross-sectional study measured homocysteine levels (among other disease markers) of a rural population of men living in Chad who were supposedly vegetarian (1). They found homocysteine levels to be elevated and therefore concluded that the men might be at risk for cardiovascular disease. Except for the provocative title, there was nothing particularly interesting in the abstract, and I decided not to pursue it further as there is a steady flow of cross-sectional studies on semi-vegetarians from developed countries and their cardiovascular disease markers.

But a number of people contacted me about it and so I changed my mind. I’m glad I did, as the paper was much more interesting than the abstract, though still not very relevant to vegetarians in developed countries.

Here is a summary. Twenty-four apparently healthy men from a rural part of Chad, a country in Africa, were compared to 15 men from a nearby urban part of Chad. The rural men ate very little animal products and less than their urban counterparts. There is no indication that this was due to any sort of “vegetarianism,” but rather simply because of the food available to them in their area.

Protein intakes for the rural men were an average of 50 g per day compared to 63 g per day for the urban men. The RDA for meat-eating men of that height would be 51 g and the recommended protein intake for vegan men that height would be 57 g. That would put these rural men at a “probably adequate” protein level, in my opinion. However, their average intake of the sulfur amino acids methionine and cysteine was only 10.4 mg/kg while the RDA is 19 mg/kg.

The rural men were marginally suffering from an indicator of protein malnutrition, known as prealbumin (aka as transthyretin), which was at an average level of 176 mg/l (compared to 292 mg/l for the urban men). The lower limit of a healthy prealbumin is listed by most sources as 180 mg/l, while the upper limit of healthy is listed as anywhere from 300 to 400 mg/l.

The B12 levels of the rural vs. urban men were 174 vs. 269 pmol/l. Homocysteine levels of the rural vs. urban men were 19 vs. 11 µmol/l.

Some background: Homocysteine is a byproduct of methionine metabolism and is considered to be a risk factor for heart disease and stroke (among other diseases). Generally, homocysteine is raised by either vitamin B12, folate, or vitamin B6 deficiency. Vegetarians and vegans who do not supplement with vitamin B12 typically have elevated homocysteine levels. A level of 8 µmol/l or below is ideal, whereas greater than about 12 µmol/l is associated with increased risk of disease.

In the past, some people have thought that elevated homocysteine was caused by high levels of methionine in the diet, although this was put to rest some years ago.

Now, here is the interesting part of this study (if you happen to find the folate/methionine cycle interesting). Because the rural men were not technically deficient in vitamin B12, but were marginally protein malnourished, the researchers thought it was not vitamin B12 deficiency that was causing the elevated homocysteine but rather marginal intakes of the amino acid methionine. Their theory is that when you are deficient in methionine, the body produces excess homocysteine from cysteine so that it can then create methionine and, in turn, s-adenosylmethionine (SAMe) which is an important methyl donor for many reactions throughout the body.

My take on this is somewhat different. Although the vitamin B12 levels in the rural men were technically not in the deficiency range, they were not ideal for homocysteine levels. Selhub (2) suggests a minimum vitamin B12 level of 300 pmol/l for minimizing homocysteine levels and this is born out in the current study in that even the urban men with a B12 level of 269 pmol/l had a slightly elevated homocysteine of 10.8 µmol/l while getting plenty of protein.

Despite the title of the study saying that vegetarianism produces atherogenesis, there was no mention of this in the paper. In fact, the cholesterol levels of the rural and urban men were at relatively low levels of 154 and 166 mg/dl respectively (which is not a direct measure of atherogenesis, but low cholesterol levels are often associated with low atherogenesis).

A press release published in SFGate.com did a write-up on the study (which is what caught some people’s attention): Vegetarian Diet Might Increase the Risk of Cardiovascular Diseases, According to a Recent Study, Says Nutri-Med Logic Corp. While I would not describe their release as terribly inaccurate, they fail to mention that the study was of semi-vegetarians in Chad who were arguably malnourished. Their suggestion of supplementing with alpha-lipoic acid to combat what is either B12 or protein malnutrition is a stretch.

The take home message from this study is: People who limit animal product consumption need a regular source of vitamin B12. People who follow a vegetarian diet due to a lack of food in an area with low amounts of available plant protein could become protein malnourished and this could possibly exacerbate elevated homocysteine levels. Vegans in developed countries can easily avoid these problems by supplementing with vitamin B12 and getting enough protein.

References

1. Ingenbleek Y, McCully KS. Vegetarianism produces subclinical malnutrition, hyperhomocysteinemia and atherogenesis. Nutrition. 2011 Aug 26. [Epub ahead of print] Link

2. Selhub J, Jacques PF, Dallal G, Choumenkovitch S, Rogers G. The use of blood concentrations of vitamins and their respective functional indicators to define folate and vitamin B12 status. Food Nutr Bull. 2008 Jun;29(2 Suppl):S67-73. Review. Link

Ginny has once again set the record straight with her article, Vitamins B12 and D: Monitoring versus Supplementing.

I would merely add that if you are going to the doctor to get tests done anyway, it wouldn’t hurt to add vitamin D to the panel just to know where it is.

Bill Clinton, are you listening?!

VeganHealth.org update to Bones, Vitamin D, and Calcium:

In 2011, a follow-up (1) of an earlier study on vegan Buddhist nuns (2) was released. After two years, the vertebrae of 88 vegans and 93 omnivores were examined using x-rays. Ten women (five vegans and five omnivores) had sustained a new vertebral fracture after two years; there was no significant difference between the two groups.

Rates of bone mineral density (BMD) change were examined at the lumbar spine and femoral neck with a variety of associations found. Lumbar BMD increased with age, lean body mass, and vegetable fat; and decreased with vegetable protein and steroid use. The authors suggested that the increase in BMD of the lumbar spine was possibly due to osteoarthritis and, therefore, not a healthy phenomena.

As for the femoral neck, BMD increased with both lean and fat body mass; and decreased with age, animal fat, and ratio of animal protein to vegetable protein. This would indicate that animal protein had a negative impact on bone. To make this even a bit more complicated, the food questionnaires used by the researchers indicated that the vegans were only eating an average of 1,093 calories, 36 g of protein, and 360 mg of calcium per day. The estimated energy requirement for women their age and size is about 1,600 calories which indicates that the food intake of the vegans was possibly underestimated by one-third. The non-vegan nuns had intakes of 1,429 calories, 62 g of protein, and 590 mg of calcium per day which seems more likely.

In summary, compared to non-vegetarian Buddhist nuns, vegan nuns had a similar rate of vertebral fractures, but it is not clear how accurate were the associations with changes in BMD.

Commentary not added to VeganHealth.org:

Ten fractures in 181 women in two years seemed high to me, so I did a bit of searching and found a study (3) that indicated that in Hong Kong and Japan, the rate of vertebral fracture in women over 65 is 594/100,000 person-years. I calculate the person-year fracture rate in this Buddhist nun study to be 2,762/100,000. That’s obviously quite a bit higher, but it should be noted that the fractures in the Buddhist nun study were determined by giving an x-ray to each subject, rather than reporting a bone break, and would likely find more fractures than the study determining the 594/100,000 rate.

1. Ho-Pham LT, Vu BQ, Lai TQ, Nguyen ND, Nguyen TV. Vegetarianism, bone loss, fracture and vitamin D: a longitudinal study in Asian vegans and non-vegans. Eur J Clin Nutr. 2011 Aug 3. [Epub ahead of print] Link

2. Ho-Pham LT, Nguyen PL, Le TT, Doan TA, Tran NT, Le TA, Nguyen TV. Veganism, bone mineral density, and body composition: a study in Buddhist nuns. Osteoporos Int. 2009 Apr 7. [Epub ahead of print] Link

3. Bow CH, Cheung E, Cheung CL, Xiao SM, Loong C, Soong C, Tan KC, Luckey MM, Cauley JA, Fujiwara S, Kung AW. Ethnic difference of clinical vertebral fracture risk. Osteoporos Int. 2011 Apr 2. [Epub ahead of print] (Abstract) Link

I’ve been reviewing the scientific literature on protein and bone health. As many readers know, there has been a theory that animal protein, by way of increased sulfur amino acids, causes calcium excretion leading to osteoporosis. This theory was always on shaky ground and more recent evidence has contradicted the theory. I just read a meta-analysis on the subject and added the following to the article, Bones, Vitamin D, and Calcium, on VeganHealth.org:

“Another 2009 meta-analysis found that among five well-designed studies measuring calcium balance, net acid excretion was not associated with either decreased calcium balance or a marker of bone deterioration (48).”

The paper had an interesting list of cohort studies in the discussion:

“First, during 8 yr of follow-up, fracture risk was not reduced among a cohort of 36,217 postmenopausal women who consumed either lower protein or lower NAE [net acid excretion] diets (37). Second, wrist fracture risk was highest among 1865 peri- and postmenopausal women who consumed the lowest protein intakes over 25 yr of follow-up (38). As well, a recent 2-yr trial in 276 postmenopausal women either supplemented with potassium citrate (expected to neutralize the acid of the Western diet) or encouraged to consume increased fruit and vegetables showed that these interventions did not reduce bone turnover or decrease bone loss (36).”

The take home message, which I’ve written about before, is that not eating animal protein does not protect you from osteoporosis. Make sure you get enough calcium, vitamin D, and even (plant) protein.

References

36. Macdonald HM, Black AJ, Aucott L, Duthie G, Duthie S, Sandison R, Hardcastle AC, Lanham New SA, Fraser WD, Reid DM. Effect of potassium citrate supplementation or increased fruit and vegetable intake on bone metabolism in healthy postmenopausal women: a randomized controlled trial. Am J Clin Nutr. 2008 Aug;88(2):465-74. (Link) Free article available.

37. Dargent-Molina P, Sabia S, Touvier M, Kesse E, Bréart G, Clavel Chapelon F, Boutron-Ruault MC. Proteins, dietary acid load, and calcium and risk of postmenopausal fractures in the E3N French women prospective study. J Bone Miner Res. 2008 Dec;23(12):1915-22. (Link) Free article available.

38. Thorpe DL, Knutsen SF, Beeson WL, Rajaram S, Fraser GE. Effects of meat consumption and vegetarian diet on risk of wrist fracture over 25 years in a cohort of peri- and postmenopausal women. Public Health Nutr. 2008 Jun;11(6):564-72. Epub 2007 Aug 9. (Link) Free article available.

48. Fenton TR, Lyon AW, Eliasziw M, Tough SC, Hanley DA. Meta-analysis of the effect of the acid-ash hypothesis of osteoporosis on calcium balance. J Bone Miner Res. 2009 Nov;24(11):1835-40. (Link)

Ginny Messina: Tips to help Bill Clinton get the most out of his vegan diet