Nutritional Status of Vegetarian Patients Before and After Bariatric Surgery: a Monocentric Retrospective Observational Case-Control Study

The obesity pandemic is associated with an increasing number of bariatric surgeries which allow improvement in obesity-related comorbidities and life expectancy but potentially induce nutritional deficiencies. Vegetarianism becomes more and more popular and exposes as well to vitamin and micronutrient deficiencies. Only one study has explored the impact of vegetarianism on the preoperative nutritional status of eligible patients for bariatric surgery, but none in postoperative care.

Materials and methods: We conducted a retrospective case-control study in our cohort of bariatric patients, matching 5 omnivores for each vegetarian. We compared their biological profile regarding vitamin and micronutrient blood levels before and 3, 6, 12, and 30 months after surgery.

Results: We included 7 vegetarians including 4 lacto-ovo-vegetarians (57%), 2 lacto-vegetarians (29%), and one lacto-ovo-pesco-vegetarian (14%). Three years after surgery with equivalent daily standard vitamin supplementation, the two groups showed a similar biological profile including blood levels of ferritin (p = 0.6), vitamin B1 (p = 0.1), and B12 (p = 0.7), while the total median weight loss at 3 years was comparable (39.1% [27.0-46.6] in vegetarians vs 35.7% [10.5-46.5] in omnivores, p = 0.8). We observed no significant difference between vegetarians and omnivores before surgery regarding comorbidities and nutritional status.

Conclusion: It seems that, after bariatric surgery, vegetarian patients taking a standard vitamin supplementation do not show an increased risk of nutritional deficiencies compared to omnivores. However, a larger study with a longer follow-up is needed to confirm these data, including an evaluation of different types of vegetarianism such as veganism.