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April 18, 2006
Tough meat for vegetarians to swallow
Based on my considerable reading of the medical literature it seems as if everyone bends over backwards to put a healthy face on vegetarianism. A recent issue of Atherosclerosis, however, contains an article that goes against the herd.
Researchers in China recruited 57 healthy post-menopausal women who had been vegetarians for an average of a little over 10 years and age matched them with 61 healthy omnivores to study cardiovascular risk and carotid artery atherosclerotic disease.
To fulfill the criteria of apparently healthy subjects, women with any of the following conditions were excluded: a history of diabetes mellitus or fasting blood glucose over 126 mg/dL; hyperlipidemia (cholesterol level ≥240 mg/dL or triglyceride level ≥200 mg/dL); regular alcohol drinking or smoking; any treatment that might affect lipid metabolism; history of CVD, hypertension (systolic blood pressure (SBP) ≥160 mmHg or diastolic blood pressure ≥95 mmHg), or use of anti-hypertensive medication; or serum creatinine level ≥125 μmol/L; thyroid disease; and malignancy of any kind. Vegetarians were defined as exclusive consumption of a vegetarian diet void of meat, fish, and poultry for at least 5 years.
After an overnight fast the subjects provided blood samples that were evaluated for lipids, homocysteine, vitamin B12, and a host of other parameters. The researchers evaluated the presence and degree of any carotid artery disease present in the subjects using ultrasonography.
After the results were tabulated it turns out that vegetarians have significantly increased levels of homocysteine along with decreased levels of vitamin B12. The low levels of vitamin B12 would be expected because vitamin B12 is found only in foods of animal origin, which is one of the primary indicators that humans have evolved eating meat. Homocysteine, a substance thought to be toxic to the arteries, is involved in the metabolism of methionine and is reduced with folic acid, vitamin B12 and vitamin B6. The interesting thing about the findings in this study is that when patients have elevated homosysteine levels they are usually advised to eat more fruits and vegetables to increase their intake of folic acid and to reduce their intake of meat, which provides large amounts of methionine, the precursor of homocysteine. In the case of the subjects in this study, they were already eating large amounts of fruits and vegetables while avoiding meat altogether, yet ended up with more homocysteine than those subjects consuming meat. (These findings are not unusual; most studies on vegetarians find this same phenomenon.) What this proves--at least to my satisfaction--is that vitamin B12 is more potent at reducing homocysteine that the combination of folic acid and vitamin B6. Another surprising finding was that the folic acid levels were the same in both groups.
Another finding in this study was that the vegetarians had elevated levels of soluble vascular cell adhesion molecule-1 (sVCAM-1), an inflammatory substance implicated in the development of atherosclerosis. After some statistical legerdemain, however, the researchers discounted these findings.
This study demonstrates a significant association between levels of Hcy [homocystene] and sVCAM-1, and between vegetarians and sVCAM-1; however, these relationships were attenuated after adjustment for associated covariates.
As you would expect, the vegetarians had both lower LDL and lower HDL levels than the omnivores, which goes to show that if you want your HDL to go up, you've got to eat meat (or at least fat).
Ultrasonography showed no difference in carotid artery thickness between vegetarians and omnivores, which the authors of the study reported as showing no difference in degree of arterial disease. Surprisingly, one of the factors that was different between the two groups the researchers didn't mention at all: pulse pressure.
The data clearly shows a difference in pulse pressure between the two groups that appears to be statistically significant (I say appears because all the data to make such a determination wasn't provided--only the 'p' factor). An increased pulse pressure indicates that arteries are less compliant, which is an indicator of increased rigidity and, consequently, more disease. And the vegetarians had a pulse pressure of 56.6 compared to 52.6 in the omnivores. I would love to have seen this disparity at least mentioned, if not discussed, in the paper.
What did the researchers think of their findings?
In the present study we showed that CA [carotid atherosclerosis] was not significantly different between vegetarians and omnivores in apparently healthy postmenopausal Chinese women. However, we found that plasma Hcy and sVCAM-1 were elevated and plasma Vitamin B12 was lower in vegetarians as compared with omnivores, which seemed to be contradictory to the common belief that a vegetarian diet is beneficial to CVD.
We could not demonstrate any significant beneficial effects of vegetarian diets on CA in this study.
The authors add this caveat:
Thus, all the evidence and inference should be under careful scrutiny.
Which, of course, means, hey, we know our data goes against what we all know to be true, i.e., that fruits and vegetables are good for us and meat is bad. And even though are data shows differently, these data need to be looked at with a jaundiced eye.
I wouldn't be surprised if the 'peers' who reviewed the article made the authors tack that line on as a condition of having the paper published.
Pass this post along to anyone you know who is a vegetarian for health reasons because it ain't all that healthy. And for those misguided souls who persist in believing that vegetarianism is our natural state on this planet, just enunciate the words VITAMIN-BEE-TWELVE to them clearly. It's like sticking a cross in a vampire's face.
Posted by mreades at April 18, 2006 03:20 PM
Comments
I could never be a vegetarian. I simply ADORE cheeseburgers. :)
This is very interesting. I have an aquaintance who wants to become vegan, but I think it's for ethical reasons rather than health.
I think humans were created to eat anything and everything - which is why out species has done so well - and cutting out anything (other than junk) just isn't smart.
Posted by: Victoria at April 18, 2006 09:40 PM
I tried vegetarianism when I was newly graduated from college and realized for the first time just how much of a dent meat puts in your grocery budget. After three days of lightheadedness and then nearly passing out in a store, I realized that it wasn't for me and I've never looked back. Anyway, what was I thinking? I adore beef, chicken and pork in all of its forms and let's face it, aside from the occasional helping of refritos properly made with lard (back when I lived in AZ), I've never cared much for beans. LOL, can't you just see Dr. Ornish and CSPI's Michael Jacobson clutching their chests at the very thought of lard in beans? Oh, the horror! Saturated fat! But I digress.
And I have to laugh at all the nay-sayers who proclaim that it's not healthy to cut out a entire food group when it comes to grains and other starchy foods and then turn around and say in their next breath that being a vegetarian/vegan is the healthiest diet of all. Heck doesn't that entail cutting out a whole food group?
Posted by: Esther Hoff at April 19, 2006 01:05 PM
Mike, interesting article.
Although the authors defined what *they* considered a vegetarian diet for the purposes of their study ("exclusive consumption of a vegetarian diet void of meat, fish, and poultry for at least five years"), we all know there is no single vegetarian diet. I prefer meatless to describe my own basic vegetarian menus, because I've always included fish, dairy products, and eggs--things which the religion I was raised in doesn't consider 'meat.' Others make different choices...meatless diets can run the gamut from people who only eat raw foods to people who, like me, aren't going to debate whether fish is meat or not based on religious traditions.
So while I appreciate that the researchers defined their dietary criteria, even that definition doesn't really tell anyone what the subjects WERE using for protein sources, and in what quantities. It is possible to get sufficient protein as a vegetarian from eggs, dairy products, wheat gluten and minimally processed fermented soy (if you can tolerate those things--I do it for periods as long as a month or more, and I know it's not only possible to do, but possible to sustain. Others' mileage may vary. ;)
But the best (IMO) vegetarian method cookbooks, like the ones in my library from the mid-70s, always advised vegetarians of the importance of getting adequate protein, didn't restrict fats like butter for ovo-lacto diets or olive and nut oils for vegans, and the importance (especially for vegans) of supplementing vitamin B-12. I don't supplement B-12, but even my ovo-lacto days appear from my journal stats and bi-weekly bloodwork to be providing enough from diet.
My first thought on reading the article you linked and your comments is that there is no single vegetarian diet...and actual mileage will vary. As for the 'disclaimer,' yep...sounds like a peer-reviewer caveat. In "The Devil Wears Prada," the heroine Andrea refers to this syndrome of equivocating as "the 'Runway Paranoid Turnaround,' applied whenever criticism of her lunatic boss surfaces in a moment of complete frustration." Or maybe it's a weird manifestation of "The Stockholm Syndrome" and too many people, including researchers, are still hostages of the prevailing attitudes. ;)
Also
Posted by: Gaelen at April 20, 2006 06:28 AM
Notwhithstanding, a person that decides to become a vegetarian, or more correctly, who decides not to eat meat but include dairy and eggs can still become a 'responsible' vegetarian if he/she is aware of the deficiencies that are most common. Supplmenting with B12, and other micronutrients that are lacking on a vegetarian diet may still be better than just deciding to go vegetarian on the erroneous notion "because it's healthier", which as we know, is anything but responsible.
Posted by: Gabriel E. Guzman, Ph.D. at April 20, 2006 06:39 AM