Are there any studies that show differences in health benefits between a low meat eater flexitarian and other vegetarians types?

Question

Reading this article, we are qualitatively informed about the health benefits and environmental impact of various types of vegetarianism. The summary:

• Vegan - clearly healthier on average than meat-eaters, most environmentally friendly
• Lacto Vegetarian - healthier on average than meat-eaters, still higher risks of certain diseases than vegans, environmentally friendlier than average
• Lacto-ovo Vegetarian - healthier on average than meat-eaters, still higher risks of certain diseases than vegans, environmentally friendlier than meat-eaters
• Flexitarian - if meat consumption is greatly reduced, healthier than average omnivores, environmentally friendlier than meat-eaters, but still support animal farming industry

I will define "cost" the total effort put by someone to adopt one of the styles defined above: financial, time, (almost) always taking care what you eat (stress).

I am interested in assessment of the most "cost" effective style in a Western society where vegetarianism is rather the exception (i.e. one of the countries listed here, with less than 5%). To simplify things, I want to reference this "cost" primarily against the health benefits and secondarily against environment impact.

The cost is clearly very subjective, but I think the health benefits can be studied.

Question: Are there any studies that show if there are major health benefits differences between a very low meat eater flexitarian and other types of vegetarians?

My feeling is that being a flexitarian who rarely eats some meat and has a balanced diet otherwise (no excess of dairy products) will still have many of the same health benefits as other types of vegetarians. But, I am interested in research results.

Answer 1

There are mixed results when comparing semi-vegetarians with lacto-ovo vegetarians, while vegans usually do best.

1. This study of Taiwanese Buddhists found that the vegetarians had lower rates of diabetes, even after controlling for several confounding factors, despite the fact that:

Overall, our study participants consumed a predominantly plant-based diet such that even the omnivores consumed little meat and fish

2. In this study, semi-vegetarians had less diabetes than vegetarians but more than vegans:

Cases of diabetes developed in 0.54% of vegans, 1.08% of lacto ovo vegetarians, 1.29% of pesco vegetarians, 0.92% of semi-vegetarians and 2.12% of non-vegetarians.

3. This study looked at blood pressure and cholesterol:

Only 16% of the vegetarians were confirmed to be hypertensive compared with 35.7% of the semi-vegetarians and 31.1% of the non-vegetarians.

The semi-vegetarians had lipid values intermediate to the vegetarian and non-vegetarian groups.

4. This study on blood pressure says:

the odds ratio of hypertension compared with omnivores was 0.37, 0.57 and 0.92, respectively, for vegans, lacto-ovo vegetarians and partial vegetarians. Effects were reduced after adjustment for BMI.

5. Finally, this study looking at all causes of death suggests that pescetarians are the healthiest, while vegetarians and semi-vegetarians are similar:

The adjusted hazard ratio (HR) for all-cause mortality in all vegetarians combined vs nonvegetarians was 0.88. The adjusted HR for all-cause mortality in vegans was 0.85; in lacto-ovo–vegetarians, 0.91; in pesco-vegetarians, 0.81; and in semi-vegetarians, 0.92 compared with nonvegetarians. Significant associations with vegetarian diets were detected for cardiovascular mortality, noncardiovascular noncancer mortality, renal mortality, and endocrine mortality.

It's important to always take findings like this with a grain of salt. The less meat or other animal products you eat, the more likely you are to have greater self-control when eating in general. No study can fully account for this, so observing health benefits in vegans and vegetarians is to be expected.