British Vegetarians have 30% Reduced Risk of Heart Disease
Released last week:
Heart disease rates of all vegetarians compared to all non-vegetarians were calculated for EPIC-Oxford from 1993 until 2009 (1). These participants were all thought to be free of heart disease at the beginning of the study. The results showed that vegetarians had a statistically significant, ~30% reduced risk of heart disease (.68, .58-.81). That is a fairly impressive finding for a nutrition study.
All results were adjusted for age, smoking, alcohol, physical activity, education, socioeconomic status, oral contraceptives, and hormone replacement therapy. The findings held after adjusting for body mass index (BMI) and removing the first two years of follow-up. (See the table in EPIC-Oxford: Heart Disease (2013) of VeganHealth.org for the relative risks.)
The researchers believed the difference in heart disease rates to be due mainly to the lower non-HDL cholesterol and systolic blood pressure of the vegetarians. The non-vegetarians had an average total cholesterol level of 222 mg/dl vs. 203 mg/dl for the vegetarians, while HDL was 52 vs. 50 mg/dl respectively. Systolic blood pressure was 134 for non-vegetarians and 131 mm Hg for vegetarians.
Given that vegetarians had cholesterol levels an average of 203 mg/dl – a full 33% higher than the 150 mg/dl, upper-end-of-healthy that many of the very low-fat doctors recommend – it might come as a surprise to learn that, in the authors’ words, “On the basis of the absolute rates of hospitalization or death from IHD [ischemic heart disease], the cumulative probability of IHD between ages 50 and 70 y was 6.8% for nonvegetarians compared with 4.6% for vegetarians.”
In other words, with cholesterol levels that high in both groups, you might think they would have a very high rate of heart disease, but, from what I can tell (see reference #2), their rates are relatively comparable to the general population of the United States (2).
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Reference
1. Crowe FL, Appleby PN, Travis RC, Key TJ. Risk of hospitalization or death from ischemic heart disease among British vegetarians and nonvegetarians: results from the EPIC-Oxford cohort study. Am J Clin Nutr. 2013 Jan 30. [Epub ahead of print] | link
2. Prevalence of Coronary Heart Disease — United States, 2006–2010
Morbidity and Mortality Weekly Report (MMWR) for October 14, 2011. Accessed February 3, 2013. | link (PDF)
February 3rd, 2013 at 8:29 pm
As you wrote, the author of the paper write that the difference in CHD rates is explained by the difference in non-HDL cholesterol and systolic blood pressure. The question is whether these differences are due to vegetarianism per se, namely due to the avoidance of meat? This question is not addressed by the authors, but in my opinion, the answer is no.
1. As far as I know, meat and fish do not increase blood pressure (in fact, omega-3 from fish decreases blood pressure). Therefore, the difference in SBP is due to other factors.
2. While meat and fish do increase non-HDL cholesterol (due to saturated fat and dietary cholesterol), their effect on LDL cholesterol is small, especially considering that the amount of meat and fish consumed by the non-vegetarians are small. According to a rough estimation, the meat and fish in the diet of the non-vegetarian explain a difference of 0.06 nmol/L, while the observed difference is 0.45 nmol/L.
3. The difference of 0.45 nmol/L is probably due to other factors, for example amount of dietary soluble fiber. In fact, the paper mentions that the vegetarian ate much more whole grains than non-vegetarian, which contain soluble fiber (and phytosterols).
February 3rd, 2013 at 8:53 pm
Dave,
The authors also wrote, “Vegetarians had a better lipid profile than did nonvegetarians, probably because of a higher ratio of polyunsaturated to saturated fat in their diet (22) and a lower BMI.”
> 2. While meat and fish do increase non-HDL cholesterol (due to saturated fat and dietary cholesterol), their effect on LDL cholesterol is small,
Really? That doesn’t seem to be the common view, from what I’ve read. And another study from EPIC showed that vegans had much lower intakes of saturated fat than the meat-eaters (at least for the men): http://www.veganhealth.org/articles/nutrientintakes
I’m surprised the authors didn’t mention fiber – I would also suspect it would explain some of the differences.
February 3rd, 2013 at 11:06 pm
According to the data from your link (Davey et al. 2003), the difference in SFA intake between non-vegetarian and vegetarian (including vegans) is small: 1% of energy intake for women, and 2% for men. According to http://ajcn.nutrition.org/content/77/5/1146.long , each 1% of SFA increases non-HDL cholesterol by 0.026 (mmol/L) compared to carbohydrates.
February 3rd, 2013 at 11:24 pm
Dave,
If saturated fat increases cholesterol levels independently, then absolute amounts of saturated fat would have to be considered. Are you sure that AJCN article is the most authoritative?
But of course it’s not some sort of essence of being vegetarian that reduces one’s risk of heart disease – it is a component (or components) of the diet, and whatever component(s) it happens to be can probably be manipulated on a non-vegetarian diet. If it’s the saturated fat, you can just find animal foods low in saturated fat, etc. So, I agree with you, it is not the “vegetarian diet” that protects vegetarians, but rather the components (or lack thereof) of these particular vegetarian diets compared to the components of the non-vegetarian’s diets.
February 3rd, 2013 at 11:54 pm
Jack , I’m not sure your high cholesterol comment makes much sense –
according to the 2nd link of the usa the overall risk in the 45-65 group is around 7.2 , That doesn’t strike me as such a big difference compared to 6.8 in this study and there is no group to understand how the IHD of 65-70 group is. As i understand this study was of a rather health conscience people and i think its probably to assume that these high cholesterol values are maybe lower then the average in USA .
February 4th, 2013 at 9:21 am
Idan,
My comment was not meant to suggest that there is no benefit to lowering cholesterol levels down to 150 mg/dl. I think it remains to be seen whether people without currently diagnosed heart disease should strive for cholesterol levels that low, but I am skeptical that its necessary and this study seems to provide some evidence that it’s not.
Vegans occasionally write me very worried that their cholesterol levels are around 180 mg/dl. My point is that with a heart disease risk of 4.6%, a cholesterol level of even 203 mg/dl does not seem to be a death sentence.
February 4th, 2013 at 7:21 am
Thanks for this, Jack. I think vegans are overreacting / overreaching.
1. This isn’t a study of vegans. Isn’t it the EPIC meta-study that showed actual vegans had higher (but non-statistically significant) mortality than vegetarians and fish-eaters? And the same as meat-eaters?
2. This seems to indicate that keeping your cholesterol down and blood pressure down is the key, not avoiding eating animals. Most people know / believe that already, but just don’t care (as they don’t care about getting optimal exercise, optimal sleep, or even flossing http://on.webmd.com/WTD2cK ). The majority of those who do / will care about heart disease will eat more (smaller) animals, regardless of what vegans claim.
In general, this study — and especially how vegans react — is something that makes those already veg feel superior, but isn’t something that will, overall, help animals.
February 4th, 2013 at 9:25 am
Bertrand,
> Isn’t it the EPIC meta-study that showed actual vegans had higher (but non-statistically significant) mortality than vegetarians and fish-eaters? And the same as meat-eaters?
It wasn’t EPIC, that came later, but the meta-analysis you’re referring to from 1999 showed the following all-cause mortality:
regular meat eaters 1.00
lacto-ovo vegetarians .84 (.74-.96)
vegans 1.00 (.70-1.44)