Costs and Benefits of a Vegetarian Diet

Originally published December 2012, updated February 2015

Vegetarians live on a diet of grains, nuts, seeds, vegetables and fruits. A strict vegetarian or vegan does not eat or use animal products, including honey, milk or eggs.  In between, there are ovo-vegetarians, lacto-vegetarians, ovo-lacto-vegetarian who exclude or include various foods.  (There are even pescetarians or pesco-vegetarians who eat only fish.) Well-balanced vegetarian diets can have advantages over omnivorous diets (plants and animals), while excessively restrictive (such as macrobiotic and fruitarian diets) or poorly planned vegetarian diets can compromise health, especially for pregnant women and children.    

According to a Gallup poll, 5 percent of American adults consider themselves vegetarians and 2 percent consider themselves vegans.[1]  These diets have been found to have varying degrees of cardio-protective effects:  

  • In general, vegetarians have lower cholesterol.[2]  A study of nearly 7,000 Taiwanese men and women found that an ovo-lacto vegetarian diet was effective in lowering low density lipoprotein (LDL) “bad” cholesterol for males.[3]  Using the same study, researchers also compared the lipid profiles among pre- and postmenopausal women on vegan, ovo-lacto-vegetarian and omnivorous diets. Vegan diets lowered HDL, whereas an ovo-lacto-vegetarian diet (compared to an omnivorous diet) significantly lowered HDL and LDL (the “bad” cholesterol) among premenopausal women.
  • In a separate six-month controlled trial, 63 overweight and obese individuals were randomly assigned to vegan, vegetarian, pesco-vegetarian (fish only), semi-vegetarian or omnivorous diets. Participants on the vegan diet had significantly greater improvement in most macronutrients, including fat, saturated fat, and cholesterol, as compared to the other diet groups.[4]
  • In another study, researchers found that a vegetarian diet was associated with lower levels of triglycerides, total cholesterol and LDL as compared to an omnivorous diet.[5]
  • Vegetarian diets can lower blood pressure.[6] 

Vegetarian diets have other healthful benefits.   Vegan diets can provide adequate amounts of key nutrients for bone health[7] and they seem to offer additional protection for obesity, hypertension, type-2 diabetes, and cardiovascular mortality.[8]   Vegetarian diets also confer protection against some cancers and total mortality.  

On the other hand, overly restrictive or poorly planned vegetarian diets can have their weaknesses.  In 2012, researchers evaluated the nutritional quality of diets for 1,475 participants, including vegans, vegetarians, semi-vegetarians, pesco-vegetarians, and omnivores. Vegetarians, semi-vegetarians and pesco-vegetarians were mostly better in nutrient quality than the omnivores. The most restricted diet (i.e., vegan) had the lowest total energy intake, better fat intake profile, lowest protein and highest dietary fiber intake in contrast to the omnivorous diet. Typical aspects of a vegan diet (high fruit and vegetable intake, low sodium intake, and low intake of saturated fat) contributed substantially to its nutritional quality. However, vegan calcium intake was below national dietary recommendations.[9]

Vitamin B12 is most readily found in meats, milk and milk products and eggs. That is because animals produce vitamin B12 after consuming microorganisms and cobalt from soil and plants. As a result, Vitamin B12 deficiency has been found in 62% of vegetarian pregnant women, 25% to 86% of vegetarian children, 21% to 41% of vegetarian adolescents, and 11% to 90% of vegetarian elderly.  

Vitamin B12 is important for metabolizing fatty acids and amino acids into nerve, blood and other cells.  Since the body stores 3 to 5 years of vitamin B12, there is a time lag between low dietary intake and onset of deficiency symptoms - symptoms such as moodiness, confusion, depression, delusions and psychoses.  Long-term vitamin B12 deficiency results in pernicious anemia – a disease where large, immature, megaloblasts (the forerunners of red blood cells) circulate in the blood, yet do not function as red blood cells.  Pernicious anemia results in irreparable nerve damage and death.

If the Vitamin B12 deficiency is caused by an animal-free diet, then one of the best natural plant sources of Vitamin B12 is dried purple laver, otherwise known as nori which is a breakfast staple in Japan.[10]  Trace amounts of B12 can also be found in tofu, soy sauce and other products that contain yeast.  Alternatively, supplements that use yeast-based sources are another option.  Since the adult Recommended Daily Allowance of 3 micrograms per days is microscopic, resolving deficiencies can take a week or less with mega doses, and there seems to be no risk of taking too much.[11] 

The bioavailability of iron and zinc in vegetarian diets is poor due to the absence of flesh foods and higher levels of absorption inhibitors.  Iron is important for red blood cell and muscle cell production, and zinc is critical for protein and DNA synthesis.  Vegetarians can eat fortified cereals to boost iron and zinc or fermented soy foods.  Experts also believe that iron and zinc supplements may be necessary for children following strict vegan diets.[12]

A well-planned vegetarian diet can boost health.  If embarking on a vegetarian diet, then consulting with a physician or certified dietician is advised.  If already a vegetarian, then physicians should regularly test for iron, B12 , folic acid, and conduct other basic lab tests to determine if any nutritional deficiencies are occurring.  

Vitamin and minerals supplements may play an important role in strict vegetarian diets or when vegetarian diets lack a balanced nutritional profile.  Depending on the dietary or nutritional deficiency, it may be necessary to take individual vitamin or mineral supplements, a multivitamin, or a mineral complex.  Always consult with and inform the physician of any supplement use.    

[1]  Frank Newport, “In U.S., 5% Consider Themselves Vegetarians,”  July 26, 2012, < > (accessed December 14, 2012)

[2] Barnard ND, “The lipid-lowering effect of lean meat diets fall far short of that of vegetarian diets,” Archives of Internal Medicine, February 2000: 395-396.

[3] Jian HZ, Chiang YC,  Lung CC, et al, “Vegetarian diet and cholesterol and TAG levels by gender,”< > (accessed February 12, 2015)

[4] Jian ZH, Chiang YC,  Lung CC, et al, “Vegan diet and blood lipid profiles: a cross-sectional study of pre and postmenopausal women”, Boston Medical Center Women’s Health 2014, 14:55 (April 8, 2014)

[5]De Biase SG, Fernandes SF,  Gianini RJ, Duarte JL,  “Vegetarian diet and cholesterol and triglycerides levels” January 2007, <  > (accessed February 12, 2015)

[6] Pettersen BJ, Anousheh R, Fan J, Jadeldo-Siegl K, Fraser GE, “Vegetarian diets and blood pressure among white subjects: result from the Adventist Health Study-2 (AHS-2),” Public Health Nutrition, October 15, 2012: 1909-16.

[7] Mangels AR, “Bone nutrients for vegetarians”, The American Journal of Clinical Nutrition”, June 4, 2014.

[8] Le LT and Sabate J, “Beyond meatless, the health effects of vegan diets; findings from the Adventist cohorts”, Nutrients, May 27, 2014

[9] “Comparison of nutritional quality of the vegan, vegetarian, semi-vegetarian, pesco-vegetarian and omnivorous diet”, Nutrients, March 2014

[10] Watanabe F, Yabuta Y, Bito T, and Teng F, “Vitamin B12-Containing Plant Food Sources for Vegetarians”,  Nutrients, May 2014

[11] Kaltenbach G1, Noblet-Dick M, Andrès E,  et al, “Early response to oral cobalamin therapy in older patients with vitamin B12 deficiency”,  Annales de Medicine Interne, March 2003

[12] Gibson RS, Health AL, Szymiek-Gay EA, “Is iron and zinc nutrition a concern for infants and young children in industrialized countries?”, American Journal of Clinical Nutrition, May 28, 2014.