Changes in gastrointestinal symptoms and bowel movements with vegan and meat-rich diets Original paper

In this randomized controlled trial, adopting a vegan diet or meat-rich diet had similar effects on gastrointestinal symptoms and defecation habits.

The effects of a vegan diet, compared to a meat-rich diet, on gastrointestinal symptoms and defecation habits.

The outcomes assessed were gastrointestinal symptoms, fecal incontinence, stool consistency, and defecation frequency, all of which were assessed using different questionnaires. Nutrient intake (i.e., macronutrients, fiber, calcium, potassium, sodium, iron, magnesium, phosphorus, and zinc) was also assessed.

65 students at a German university (average age of 23; 60% men, 40% women) without apparent health conditions.

All of the participants reported consuming omnivorous diets before the study. Potential participants who reported consuming a plant-based diet, a flexitarian diet, or infrequent meat consumption (<3 times per week) were excluded.

In this 8-week randomized controlled trial, the participants were assigned to consume a vegan diet (which excludes all animal products) or a meat-rich diet (at least 150 grams of meat daily, not including fish). All of the participants received nutrition counseling, diet books, and cooking and shopping guidance for their assigned diet, as well as a weekly newsletter on micronutrients.

All of the participants were instructed to consume a diet in line with the recommendations from the German Nutrition Association 1 week before the intervention diets. Three-day weighed food diaries were completed by the participants at baseline and the end of the study.

Changes in gastrointestinal symptoms and defecation habits did not differ between groups.

The intake of certain nutrients differed between groups at the end of the study:

• Protein intake was higher in the meat group (102 vs. 76 grams per day).
• Calcium intake was higher in the meat group (653 vs. 525 milligrams per day).
• Sodium intake was higher in the meat group (2,850 vs. 2,040 milligrams per day).
• Phosphorus intake was higher in the meat group (1,081 vs. 721 milligrams per day).
• Zinc intake was higher in the meat group (9 vs. 5 milligrams per day).
• Fiber intake was higher in the vegan group (35 vs. 23 grams per day).

There were 12 adverse events reported, 9 of which were in the meat group and typically involved postprandial (postmeal) abdominal pain, although there were 2 gastrointestinal infections involving diarrhea and vomiting.

All of the outcomes examined were secondary outcomes. The primary outcome (i.e., changes in neutrophil count) was reported in a separate publication. As such, the findings should be considered exploratory.