Scientific studies (review articles) on the relationship between diet/nutrients and vegetarianism:
One swallow does not make a summer. A famous Dutch saying that could not be any more obvious. Just because one single scientific study about a certain topic makes certain claims, it does not necessarily mean it is true. On the other hand, a review article (a collection of scientific studies on a certain topic) of randomized, placebo-controlled double blind clinical trials (RCTs) will answer the following question:

Vegetarian diet has a protective effect against diabetes risk

Does a vegetarian diet reduce diabetes risk?

Study design:
This review article included 2 cohort studies and 12 cross-sectional studies.

Although the funnel plot showed a slight asymmetry, publication bias was not detected based on statistical tests such as the Egger’s [p = 0.465] and Begg’s tests [p = 0.584].

Results and conclusions:
The investigators found vegetarians had a 27.4% lower risk of having diabetes than omnivores [OR = 0.726, 95% CI = 0.608-0.867].