Study of Taiwanese Vegetarians vs. Omnivores

[Dean Pomerleau]

All,

 

Al Pater posted a study [1] that compared the effects on biomarkers of health for various types of vegetarian diets vs. omnivores in a group of Taiwanese men and women of all ages. The study divided subjects into four groups: vegan, lacto-vegetarians, ovo-lacto-vegetarians, and omnivores, as ascertained via a 26 element food frequency questionnaire, and explicit questions about how they self-classify their diet. They matched each of the 10,000 vegetarians in the study with five omnivores of the same age and sex.

 

 

Here are the main findings comparing all the vegetarians as a group against the omnivores:

 

With adjustment for age, sex, physical activities, alcohol consumption and education, vegetarians had significantly lower abnormalities [i.e. values in the unhealthy range as defined by health authorities - DP] in WC [Waist Circumference], BMI, SBP [systolic BP] DBP [Diastolic BP], FBG [Fasting Blood Glucose],TC [Total Cholesterol] and LDL as well as in TC:HDL ratios, with OR ranging from 0·37 to 0·90, but higher abnormality in HDL [i.e. low HDL] (OR ranged from 1·17 to 1·52), when compared with non-vegetarians cross-sectionally. <snip>

 

Overall, we observed lower values for WC, BMI, SBP, DBP, FBG, TC, HDL and LDL, along with lower TC:HDL ratios, in vegetarians compared with non-vegetarians, which replicated the findings of previous Taiwanese studies(9,22,23). Except for [lower] HDL and [higher] TAG [triglycerides] values in lacto-ovo-vegetarians [only], the vegetarian diets showed significant beneficial effects on metabolic traits, which may be partly due to the lower BMI of vegetarians.

 

<snip> 

 

With additional adjustment for BMI (Table 3), the beneficial effects for blood pressure and blood glucose were partly attenuated, whereas the effect on lipids remained consistent.

 

<snip>

 

Lacto-ovo-vegetarians appeared to eat more carbohydrates and fructose, which could be one of the main causes for TAG elevation in this group.

 

<snip>

 

Whether the lower HDL in vegetarians can be regarded as a risk factor may require further study, as vegetarians generally had better TC:HDL ratios. In addition, previous studies have found that low HDL due to reduced fat intake was not associated with poor cardiovascular health(25,26).

 

Strangely, they apparently didn't ask the subject about smoking habits, and therefore didn't control for it.

 

Here are the two main tables of results comparing the various types of vegetarians to the omnivores (click to enlarge):

 

 

They also tried doing a longitudinal analysis of the data, but the results weren't too informative, and for most of the subjects (63%) they only had one (baseline) measurement. Most of the baseline differences remained significant and mostly improved for those people who remained vegetarians at follow-up visits.

 

Comparing the various types of vegetarians vs. omnivores, it appears that lacto- and lacto-ovo-vegetarians had a slight advantage over vegans across most of the health markers when compared with omnivores, both before and after adjusting for BMI (see Tables 2 and 3 above). Besides the obvious difference between consumption of eggs and dairy, the biggest difference in the vegan food intakes relative to the other two vegetarian groups were they consumed less beans, less "sweet breads" and less fried vegetables. Perhaps a poorer B12 status or lower bean intake could explain the less advantageous health markers of the vegans vs. the other two types of vegetarians (but all three vegetarian types were better than omnivores).

 

So overall, vegetarians of all types appeared to do better compared with omnivores in all of the commonly acknowledged biomarkers markers of health, except for lower HDL and higher triglycerides among the lacto-ovo-vegetarians. This is pretty much consistent with previous studies, such as the Epic Oxford and Seventh Day Adventists.

 

--Dean

 

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[1] Br J Nutr. 2015 Oct;114(8):1313-20. doi: 10.1017/S0007114515002937. Epub 2015 Sep

10.

 

Cross-sectional and longitudinal comparisons of metabolic profiles between

vegetarian and non-vegetarian subjects: a matched cohort study.

 

Chiu YF(1), Hsu CC(1), Chiu TH(2), Lee CY(1), Liu TT(3), Tsao CK(3), Chuang

SC(1), Hsiung CA(1).

 

 

Several previous cross-sectional studies have shown that vegetarians have a better metabolic profile than non-vegetarians, suggesting that a vegetarian dietary pattern may help prevent chronic degenerative diseases. However, longitudinal studies on the impact of vegetarian diets on metabolic traits are scarce. We studied how several sub-types of vegetarian diets affect metabolic traits, including waist circumference, BMI, systolic blood pressure (SBP), diastolic blood pressure, fasting blood glucose, total cholesterol (TC), HDL, LDL, TAG and TC:HDL ratio, through both cross-sectional and longitudinal study designs. The study used the MJ Health Screening database, with data collected from 1994 to 2008 in Taiwan, which included 4415 lacto-ovo-vegetarians, 1855 lacto-vegetarians and 1913 vegans; each vegetarian was matched with five non-vegetarians based on age, sex and study site. In the longitudinal follow-up, each additional year of vegan diet lowered the risk of obesity by 7 % (95 % CI 0·88, 0·99), whereas each additional year of lacto-vegetarian diet lowered the risk of elevated SBP by 8 % (95 % CI 0·85, 0·99) and elevated glucose by 7 % (95 % CI 0·87, 0·99), and each additional year of ovo-lacto-vegetarian diet increased abnormal HDL by 7 % (95 % CI 1·03, 1·12), compared with non-vegetarians. In the cross-sectional comparisons, all sub-types of vegetarians had lower likelihoods of abnormalities compared with non-vegetarians on all metabolic traits (P<0·001 for all comparisons), except for HDL and TAG. The better metabolic profile in vegetarians is partially attributable to lower BMI. With proper management of TAG and HDL, along with caution about the intake of refined carbohydrates and fructose, a plant-based diet may benefit all aspects of the metabolic profile.

 

PMID: 26355190

[nicholson]

As a contrast to these results I recall from several years ago that the EPIC study found no material differences in health status between vegetarians and *health conscious* omnivores.

 

Clearly all vegetarians appear to be health conscious, whereas the vast majority of omnivores we know are not.  So if you really want to tease out the benefits of vegetarianism *specifically* in its various forms, it would be necessary to have a control group of health-conscious omnivores.

 

IIRC the Epic study recruited people through their use of 'health food' stores. 

 

Based largely on the EPIC finding, I do not think becoming a vegetarian or vegan would further benefit my health or longevity.  But I do not eat a lot of meat, and almost zero beef.  I eat modest amounts of animal products once or twice a week, including chicken breast, shrimp, fin-fish, and occasionally pork tenderloin.

 

Rodney.

[nicholson]

Here is a link to one of the EPIC papers:

  ===============================

Am J Clin Nutr. 2009 May;89(5):1613S-1619S. doi: 10.3945/ajcn.2009.26736L. Epub 2009 Mar 18.

Mortality in British vegetarians: results from the European Prospective Investigation into Cancer and Nutrition (EPIC-Oxford).

Key TJ¹, Appleby PN, Spencer EA, Travis RC, Roddam AW, Allen NE.

Author information

Abstract

BACKGROUND:

Few prospective studies have examined the mortality of vegetarians.

OBJECTIVE:

We present results on mortality among vegetarians and nonvegetarians in the European Prospective Investigation into Cancer and Nutrition (EPIC-Oxford).

DESIGN:

We used a prospective study of men and women recruited throughout the United Kingdom in the 1990s.

RESULTS:

Among 64,234 participants aged 20-89 y for whom diet group was known, 2965 had died before age 90 by 30 June 2007. The death rates of participants are much lower than average for the United Kingdom. The standardized mortality ratio for all causes of death was 52% (95% CI: 50%, 54%) and was identical in vegetarians and in nonvegetarians. Comparing vegetarians with meat eaters among the 47,254 participants who had no prevalent cardiovascular disease or malignant cancer at recruitment, the death rate ratios adjusted for age, sex, smoking, and alcohol consumption were 0.81 (95% CI: 0.57, 1.16) for ischemic heart disease and 1.03 (95% CI: 0.90, 1.16) for all causes of death.

CONCLUSIONS:

The mortality of both the vegetarians and the nonvegetarians in this study is low compared with national rates. Within the study, mortality from circulatory diseases and all causes is not significantly different between vegetarians and meat eaters, but the study is not large enough to exclude small or moderate differences for specific causes of death, and more research on this topic is required.

 

PMID:  19297458

  ==============================

 

The mortality rates in this study were lower than the national averages *because* they acquired their subjects from those who frequented health food stores, and thereby were defined as 'health conscious'.

 

This paper is free full text so, with luck, Dean will be able to elaborate on anything really important  :  ^  )))

 

Rodney.

[Mary Robinson]

The lower BMI and WC for the vegetarians imply a lower energy intake - so that is a confounder. 

[Dean Pomerleau]

Mary,

 

The authors controlled for BMI and waist circumference in their analysis, but you are right, it may not have fully controlled for their effects (or the implied lower calorie intake).

 

--Dean