A cross-sectional study was released today describing habits of men age 45-69 in California. Highlights from the abstract:

“Vegetarians accounted for 1.4% (736/51,901) of [white, non-hispanic men] and 20.4% (124/602) of Asian-Indians. Age was not associated with diet among Asian-Indians, but among [white, non-hispanic men], vegetarian diet was associated with younger age (< 55) (45.1% vs. 31.6%, p < 0.001). "Compared to non-vegetarians, vegetarians more often reported healthier behaviors including a lower fat diet, higher fruit and vegetable intake, more physical and less sedentary activity." Reference

1. Ghai N, Van Den Eeden S, Jacobsen S, Ahmed A, Quinn V. PS1-02: Health Behaviors in Asian-Indian and White, Non-Hispanic Vegetarian Males in the California Men’s Health Study (CMHS). Clin Med Res. 2012 Aug;10(3):144. | link

A new meta-analysis on vegetarian mortality and cancer has been released (1). It found a statistically reduced rate for vegetarians in terms of ischemic heart disease mortality and cancer incidence. It did not find a difference for all cause mortality or stroke.

Comments I have added to Disease Rates of Vegetarians and Vegans on VeganHealth.org:

“Although the 2012 meta-analysis by Huang et al. (1) is more recent, it may not be as reliable as the 1999 meta-analysis [by Key et al.] because it includes a 1984 study on Zen priests (2) who were mostly semi-vegetarian and which used a standardized mortality ratio (comparing all the Zen priests to the greater population rather than comparing the “vegetarians” to non-vegetarians within the same group). The Heidelberg Study results were also included and its control group was semi-vegetarians, which means there were semi-vegetarians in both the “vegetarian” and “non-vegetarian” group in the 2012 meta-analysis; while this is not ideal, it should have biased the results against finding a beneficial effect of a vegetarian diet. In its favor, the 2012 meta-analysis includes data from EPIC-Oxford that was not available for the 1999 meta-analysis.”

There is a table with the confidence intervals at the link above.

Reference

1. Huang T, Yang B, Zheng J, Li G, Wahlqvist ML, Li D. Cardiovascular Disease Mortality and Cancer Incidence in Vegetarians: A Meta-Analysis and Systematic Review. Ann Nutr Metab. 2012 Jun 1;60(4):233-240. (Link)

2. Ogata M, Ikeda M, Kuratsune M. Mortality among Japanese Zen priests. J Epidemiol Community Health. 1984 Jun;38(2):161-6. (Link)

The results of a survey from Western Washington University on current and former “animal product limiters” has been released in the journal Appetite.

With a cross-sectional survey that is not randomly selected, it is pretty hard to draw any strong conclusions, but I thought there were some interesting findings:

More details can be seen in the abstract.

Reference

Haverstock K, Forgays DK. To Eat or Not to Eat: A Comparison of Current and Former Animal Product Limiters. Appetite. 2012 Mar 1. Epub ahead of print. | link

Here’s something I’ve been mentioning in my talks lately. A 2000 study measured the percentage of calories as fat in the diet as well as cholesterol levels in a subset of EPIC-Oxford vegan and non-vegan men. Here is what they found:

Vegans ate 30% of their calories as fat compared to 34% for meat-eaters. Not a huge difference and many people would be horrified at such a high fat intake on behalf of the vegans. Yet, their cholesterol levels were well below what is commonly considered the danger zone.

What accounts for this? The vegans’ much lower intake of saturated fat probably explains a lot. But the vegans’ 20% fewer calories also probably accounts for much of their lower cholesterol levels. Addendum 1/27/12: Additionally, higher fiber intake and zero or near-zero cholesterol intake all likely contribute to the vegans’ lower cholesterol levels. Clarification 1/30/12: People who exercise a lot can eat more calories without cholesterol levels increasing as long as they are not eating so much that they gain body fat (thanks, Ginny).

Some people might point out that ideal cholesterol levels are actually less than 150 mg/dl, so 158 mg/dl is too high. While many clinical trials in people with heart disease (and normally on cholesterol-lowering medication) show a benefit to getting levels below 150 mg/dl, I have not seen evidence that this is ideal, or even desirable in people without diagnosed heart disease or normally high cholesterol. Instead, the observational studies I’ve seen measuring cholesterol levels and mortality have not shown a benefit from cholesterol levels less than 160 mg/dl.

I would not completely rule out the idea that studies have not shown reduced mortality in people with cholesterol levels less than 160 mg/dl because they have not included enough people with cholesterol levels that low and who do not have such low levels due to undiagnosed disease. But “not completely ruling out something” is a far cry from saying there is good evidence that it is true.

The reason I think this is particularly important is anecdotal evidence that people on long-term, low-fat diets can find them hard to stick with. I know there are some exceptions – people who find them easy to stick with, but I sense that there are more who find it difficult. When people crave meat, they tend to think they are craving the protein. But meat is also about 50% fat on average and it would not surprise me if such people are often craving fat as much or more than protein. Eating a diet closer to 30% fat might prevent such cravings.

Yes, lots of qualifiers above that I’m not 100% certain of everything I’m saying. But I think there is enough evidence that I should share it with readers rather than just keeping it to myself until “further studies” are done.

Reference

Allen NE, Appleby PN, Davey GK, Key TJ. Hormones and diet: low insulin-like growth factor-I but normal bioavailable androgens in vegan men. Br J Cancer. 2000 Jul;83(1):95-7. Link

In 2009, preliminary cross-sectional data on blood pressure rates among various diet groups were reported from Adventist Health Study 2. Just today, a more thorough report was posted at PubMed. The 2012 report only included whites and the results did not appear to be adjusted. But, in any case, vegans had a 63% reduced risk of having high blood pressure, as compared to regular meat-eaters, which was highly statistically significant. Lacto-ovo vegetarians had a 43% reduced rate, which was also statistically significant. More details can be seen in Table 12 of Disease Markers of Vegetarians at VeganHealth.org.

Body mass index was able to account for most of the differences in blood pressure between the diet groups, though other factors probably play a small role, such as higher potassium and lower sodium intakes, and lower insulin levels and blood viscosity.

Reference

Pettersen BJ, Anousheh R, Fan J, Jaceldo-Siegl K, Fraser GE. Vegetarian diets and blood pressure among white subjects: results from the Adventist Health Study-2 (AHS-2). Public Health Nutr. 2012 Jan 10:1-8. [Epub ahead of print] Link

On December 5, the Vegetarian Resource Group (VRG) released results of their latest poll of the number of vegetarians in the United States. Here is my quick analysis:

VRG found that 5% of adults “Never eat meat, fish, seafood, or poultry.” The margin of error was approximately 3%, meaning the real number could be from 2 to 8%. This continues a long trend of VRG polls showing the percentage of vegetarians in the United States to be steadily increasing. However, none of these polls, going back to 1994, has shown an increase greater than the margin of error above the 3% of the population in the U.S. that did not eat chicken at the time.

It should be pointed out, though, that even keeping up with the increase in the U.S. population is impressive. In 1994, the population of the U.S. was 260 million. In 2011, it is almost 312 million. So even to keep the percentage of vegetarians at 3% would be an increase of 1.5 million vegetarians. If it has really gone from about 3 to about 5%, then the increase has been 7.8 million people. And this does not count all the semi-vegetarians or people who have become opposed to factory-farming in the past 15 years.

It is slow progress, but lately it seems to be picking up momentum. With the hard work of organizations like Vegan Outreach, those trends will continue.

Did I mention Vegan Outreach is having an end of the year fundraising drive in which your donation can be doubled? 🙂 Click here to donate. Thank you!

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

I was reading the latest issue of the Vegetarian Nutrition Dietetic Practice Group’s newsletter and saw that there had been a review article published in 2009 that listed data from the Adventist Health Study-2 that has not been reported elsewhere to my knowledge. It is cross-sectional data that showed vegans to have a 75% reduced risk of high blood pressure compared to non-vegetarians.

More details can be seen in Table 11 of Disease Markers of Vegetarians.

Because this is cross-sectional data, it does not mean a vegan diet reduces the risk of high blood pressure by 75%. It could be that people with high blood pressure are less likely to become vegan. And the results were not adjusted for smoking.

Prospective data from AHS-2 should help clarify how much is from the vegan diet in the coming years.

Metabolic syndrome is a cluster of disorders that are associated with an increased risk of diabetes and cardiovascular disease. The disorders generally include high blood pressure, triglycerides, waist circumference, blood sugar, and low HDL cholesterol.

Cross-sectional data of 773 subjects from the Adventist Health Study-2 (AHS2) showed that, when compared to regular meat-eaters, vegetarians (those eating meat or fish less than 1 time per month) had a 56% lower rate of metabolic syndrome (0.44, 0.30-0.64). Adjustments were made for age, sex, ethnicity, smoking, alcohol intake, physical activity, and caloric intake.

Semi-vegetarians (defined as consuming fish at any frequency but consuming other meats ≥ 1 time per month but < 1 time/week), had an intermediate rate (specific data not reported).

It was somewhat disturbing (though not completely surprising given a previous report from the AHS2) to see that although the vegetarians had the lowest average body mass index of the three groups, even theirs would be considered overweight at 25.7 kg/m² (healthy is considered to be 20.0 to 25.0).

Thanks, Matt and Dima.

Reference

Rizzo NS, Sabaté J, Jaceldo-Siegl K, Fraser GE. Vegetarian Dietary Patterns Are Associated With a Lower Risk of Metabolic Syndrome: The Adventist Health Study 2. Diabetes Care. 2011 Mar 16. (Link)