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 â‰¥240 mg/dL or triglyceride level â‰¥200 mg/dL); regular alcohol drinking or smoking; any treatment that might affect lipid metabolism; history of CVD, hypertension (systolic blood pressure (SBP) â‰¥160 mmHg or diastolic blood pressure â‰¥95 mmHg), or use of anti-hypertensive medication; or serum creatinine level â‰¥125 Î¼mol/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.