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The Effects Of Vegetarian Diets On Digestive Health

Last updated June 5, 2015

Approved by: Maulik P. Purohit MD, MPH

There are different types of vegetarian diets such as vegan, lacto-vegetarian, lacto-ovo- vegetarian, and ovo-vegetarian. All of these diets are mainly plant based and either exclude animal protein completely (vegan) or include it to varing degrees.

There are different types of vegetarian diets such as vegan, lacto-vegetarian, lacto-ovo- vegetarian, and ovo-vegetarian.  All of these diets are mainly plant based and either exclude animal protein completely (vegan) or include it to varing degrees. Lacto-vegetarian (dairy), lacto-ovo-vegetarian (dairy and eggs), and ovo-vegetarian (eggs) diets include animal protein products.

According to the American Heart Association, vegetarian diets that include essential nutrients (eg. protein, calcium, zinc, iron, vitamin D, and vitamin B12) can be nutritional and healthful. One way to ensure this is by consuming a wide variety of foods. Many studies have shown that vegetarian diets are associated with lower cholesterol, and they lower the risk of coronary heart disease, diabetes, and some cancers. A study published in the International Journal of Cancer in 1998 found that increased consumption of fruits and vegetables was associated with a reduced risk of stomach cancer. The National Cancer Institute supports this finding and promotes the consumption of cruciferous vegetables (eg. kale, radish, turnip) in the diet in order to fight cancer.

Vegetarian diets provide a good amount of fiber. Since fiber is bulky, it causes a feeling of fullness. A study published in the British Journal of Nutrition in 1986 studied the effects of dietary fiber and found that it has a buffering action on the stomach acid and has a variable effect on gastric emptying.  Excessive intake of fiber is sometimes associated with stomach cramps and diarrhea.

Vegetarian diets or diets that are low in proteins can cause hypochlorhydria, a condition characterized by insufficient secretion of hydrochloric acid in the stomach, which is essential for protein metabolism. Hypochlorhydria interferes with the absorption of certain minerals in the body and can cause improper digestion. This can lead to heart burn, gastritis, food allergies, and food sensitivity.

The Dietary Guidelines for Americans states "Vegetarian diets are consistent with the dietary guidelines for Americans and can meet the recommended dietary allowances for nutrients." Vegetarian diets help to fight against stomach cancer and ulcers due to their antioxidant activity.

In essence, the positive effects of a vegetarian diet are that they:

  • Provide a good amount of fiber
  • Give a feeling of fullness
  • Protect against stomach ulcers
  • Lower cholesterol
  • Lower the risk of heart disease
  • Have antioxidant, cancer fighting properties (example: stomach cancer)
  • In combination with some animal protein supplements, can meet the recommended allocation of nutrients

Although vegetarianism offers several advantages, they may also have some adverse health effects:

  • Vegetarians are more prone to the risk of developing nutrient and protein deficiencies
  • These diets can sometimes alter gastric acid secretions, leading to stomach related problems
  • Sometimes, certain vegetables could lead to Helicobacter pylori infection, which is the bacterium that causes stomach ulcers.

Taken together, several studies suggest that being a vegetarian is a good choice to make, provided care is taken to include some animal protein, in order to have a balanced diet that meets all nutritional requirements.


Vegetarian Diet. Retrieved from http://www.nlm.nih.gov/medlineplus/vegetariandiet.html

(2012 Jul 11). Vegetarian diet: How to get the best nutrition. Retrieved from  http://www.mayoclinic.org/healthy-living/nutrition-and-healthy-eating/in-depth/vegetarian-diet/art-20046446

(2014 Mar 19). Vegetarian Diets. Retrieved from https://www.heart.org/HEARTORG/GettingHealthy/NutritionCenter/Vegetarian-Diets_UCM_306032_Article.jsp

(2012 Jun 7). Cruciferous Vegetables and Cancer Prevention. Retrieved from http://www.cancer.gov/cancertopics/causes-prevention/risk/diet/cruciferous-vegetables-fact-sheet

Terry, P., Nyren, O., & Yuen, J. (1998). Protective effect of fruits and vegetables on stomach cancer in a cohort of Swedish twins. International Journal of Cancer, 76(1), pp.35-37. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/9533759

Tadesse, K. (1986). The effect of dietary fibre isolates on gastric secretion, acidity and emptying. British Journal of Nutrition, 55(3), pp. 507-513. Retrieved from http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=859004&fulltextType=RA&fileId=S0007114586000600

Hypochlorhydria (Low Stomach Acid). Retrieved from http://www.ndhealthfacts.org/wiki/Hypochlorhydria_%28Low_Stomach_Acid%29

Dietary Guidelines for Americans. Retrieved from http://www.health.gov/dietaryguidelines/dga95/9dietgui.htm

Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: June 5, 2015
Last updated: June 5, 2015