Psychology Department

Health Psychology Home Page

Papers written by students providing scientific reviews of topics related to health and well being

  HomeWeight LossAlternative Therapy | Supplements | Eating Disorders | Fitness | About this Page |


Are vegan diets healthy, or do they lead to malnourishment or nutritional deficiencies? Are vegans healthier than omnivores?

Stacy Clark

October 10, 2008



Veganism, the avoidance of all foods with animal products, has come into vogue in the past few decades. While most websites promote veganism for ethical reasons, they also say that vegans are healthier than people who consume animal products.



What specific claims are they making?

Vegan Action cites the American Dietetic Association in claiming that vegans have lower rates of cardiovascular disease, colon and lung cancer, osteoporosis, diabetes, kidney disease, hypertension, and obesity, because vegan foods are low fat and cholesterol free. The website also claims that vegans can obtain all necessary nutrients thorough vegan foods: “With planning, a vegan diet can provide all the nutrients we were taught as schoolchildren came only from animal products.” They assert that vitamin B12 can be obtained through supplements; thus, a vegan diet is nutritionally sound, and even healthier than a diet with animal products (, a project of Vegan Outreach, echoes many similar claims, which they use several research studies (published in reputable journals) to support: lower risk of high blood pressure, diabetes, arthritis, certain types of cancers, and lower mortality rates in general. Several of the major factors that they said led to vegans having higher life expectancies than non-vegans include the healthfulness of the diet and the lower body weight of vegans (  Vegan Outreach goes a step further, claiming that, “Well-planned vegan … diets are appropriate for all stages of the life cycle, including during pregnancy, lactation, infancy, childhood, and adolescence” ( also claims that veganism leads to better health outcomes than regular diets and provides all of the body’s necessary nutrients, without harmful substances such as saturated fat and cholesterol. They link osteoporosis, Alzheimer's, asthma, male impotence, a lowered immune system, and various chronic diseases with animal products, arguing that vegetarian (and by extension, vegan) children are healthier and smarter than their peers ( VEGAN echoes many of these ideas, claiming that veganism is healthy, even for children, if a person takes B12 supplements (

Web Overview

These websites claim that veganism is a healthy and nutritionally sound diet that leads to better health outcomes than an omnivorous diet.  They say that veganism is healthy for adults and children- with minor exceptions, such as the need for vitamin B12- according to nutritional authorities such as the American Dietetic Association and studies published in reputable medical journals. Veganism is healthy, according to such sources, because it provides the necessary nutrients for a body without poisoning it with fat and cholesterol. Although the main aim of these websites is to discourage cruelty to animals, as many are sponsored by or linked with animal rights groups, the writers seem acutely aware of the skepticism surrounding veganism and go to great lengths to establish that such a diet is healthy and nutritionally sound.


What does the evidence say about these claims?



Low Bone Mineral Density (Osteoporosis) and Fracture

Annabelle Smith (2006) conducted a meta-analysis of studies of calcium and vitamin D deficiencies in vegan diets and the relationship to low bone mineral density (or osteoporosis) and risk of fracture.  She found that vegans were shown to have lower than recommended calcium and low BMD, but the evidence surrounding vitamin D and fracture conflicted among the studies.  She concluded that vegans have lower BMD than non-vegans, remarking, “this fact alone supports the need for further investigation of vegan diets/lifestyles” (305). Possible drawbacks of her study, which she acknowledges, include the small sample sizes of the studies she used and the use of homogenous populations (older Caucasian women). However, the meta-analysis included studies of geographically diverse populations, which would indicate that vegans probably do have lower BMD than non-vegans. 

Appleby et al. (2007) found that vegans had a higher risk of fracture than vegetarians and those who consume meat, which they attributed to a lack of calcium in the vegan diet. Their prospective cohort study measured fracture rates in meat eaters, fish eaters, vegetarians, and vegans. The study included 7,947 men and 26,749 women, 20–89 years old, who were followed for an average of 5.2 years to determine the rate of fracture among the groups.  A survey of eating habits was given to determine how to classify the subjects, and a follow-up questionnaire was sent about 5 years later asking if they had experienced fractures. Cox regression was applied to the data, controlling for various factors, such as age. Calcium intake was found to be the lowest in vegans, but vegans with a high calcium intake were not found to have a higher risk of fracture.  Other factors, such as protein intake, could not account for the difference in fracture risk among vegans. The authors found that vegetarians, omnivores, and fish eaters had a similar risk for fracture, but “The higher fracture risk in the vegans appeared to be a consequence of their considerably lower mean calcium intake” (1400).  The authors suggest that vegans must be careful to get enough calcium.  This study appears to be very well designed. 


Problems for Pregnant and Nursing Mothers

Dror and Allen (2008) conducted a meta-analysis of studies of the neurological effects of vitamin B12 deficiency in infants, generally caused by maternal veganism or pernicious anemia. They looked at 48 studies, mostly case studies, of infants with B12 deficiencies, compiling the data about symptoms and treatment.  They note that “there is remarkable similarity between the neurological symptoms of infants raised by mothers with pernicious anemia (in which vitamin B12 is the only deficient nutrient) and those whose mothers were vegans or had very low intake of animal-source foods (who may have other nutrient deficiencies, in addition to vitamin B12)” (251). They found that infants with B12 deficiencies began to recover quickly when B12 was provided, but often suffered long-term problems. They discuss the possible mechanisms by which B12 deficiencies cause problems, including a lack of myelin, altered S-adenosylmethionine:S-adenosylhomocysteine (SAM:SAH) ratio, cytokine imbalance, and lactate accumulation; they conclude that multiple processes probably are at work. This study indicates that maternal veganism can have permanent detrimental effects on infants, particularly the lack of B12 in utero and throughout lactation.  The large sample of studies and the high correlation of symptoms indicate that their conclusion about B12 and infants is likely to be valid.

Specific Problems with B12 Deficiency

Waldmann et al. (2005) found that vegans have lower levels of LDL and high homocysteine

and Lp(a) concentrations, related to vitamin B12 deficiency, which can lead to a higher probability of coronary heart disease. This cross-sectional study looked at 154 German vegans to determine their cardiovascular risk profiles. The researchers found sufficient folate and favorable cholesterol and LDL profiles, which would be atheroprotective, but low HDL and elevated homocysteine and Lipoprotein(a) concentrations, related to vitamin B12 deficiencies, which could lead to increased risk for coronary heart disease. Participants took two food frequency questionnaires, one in autumn and one in spring, and underwent various tests by physicians. The authors conclude that “Overall, these results confirm the notion that a vegan diet is deficient in vitamin B12, which may have an unfavorable effect on CHD risk” (371). Thus, B12 deficiency can have a negative impact on a person’s risk for heart problems. One potential drawback of the study is that there were no control groups, which the authors note.


Support for Veganism as Healthy

Majchrzak et al. (2006) found that vitamins B2 and B12 were lacking in strict vegan diets, but vegans were otherwise healthy. Researchers measured the level of various B-vitamins, including folic acid, and homocysteine in omnivores, vegetarians, and vegans. Vegans had sufficient thiamine and the highest levels of folate, but lower levels of B1 and B12 and therefore higher levels of plasma homocysteine.  The study included 118 people of similar BMI: 40 omnivores, 36 vegetarians and 42 vegans, and various statistical tests were used to determine the results. The authors concluded that with attention to B2 and B12, vegan diets that “incorporate the principles of adequacy, balance and moderation can be nutritious and healthy” (491). One potential problem with this study is that the vegans in the study were younger than the other groups, but overall, the study seems sound.


Dewell et al. (2008) found that vegan diets were linked to lower rates of chronic disease. The authors of the study randomly distributed 93 early stage prostate cancer patients into two groups: one followed a very low fat vegan diet including exercise and stress management, and the other remained on normal treatment by their physicians. A year later, levels of protective dietary factors (fiber and lycopene) and pathogenic dietary factors (cholesterol and saturated fat) were measured, and various statistical methods were applied. Researchers found that “a very-low-fat vegan diet can be useful in increasing intake of protective nutrients and phytochemicals and minimizing intake of dietary factors implicated in several chronic diseases” (347). They concluded that a vegan diet increased protective factors and decreased factors linked with chronic disease. In addition, no nutritional deficiencies in the vegan patients were reported, and the levels of many nutrients increased, as compared to the control group.

Goff et al. (2004) found vegan diets to be “cardioprotective” (291). The authors of the study matched 24 vegans and 25 omnivores in a case control study based on BMI, gender, and age; there were also no differences in activity level, waist measurement, body fat percentage, or energy intake. They wanted to determine whether vegans were more sensitive to insulin than omnivores and whether this related to IMCL (intramyocellular lipid) levels.  After documenting dietary habits for a week and measuring insulin sensitivity, beta-cell function, IMCL levels, and body fat content using various techniques, the authors concluded that, “Vegans have a food intake and a biochemical profile that will be expected to be cardioprotective, with lower IMCL accumulation and beta-cell protective” (291).  They noted lower triacylglycerol levels, fasting glucose concentrations, cholesterol, and blood pressure in vegans than the omnivores. They did not find that insulin sensitivity increased among vegans, but beta-cell function improved, indicating a protective effect against diabetes. Possible drawbacks of this study are the relatively small sample size and the fact that the subjects were all Caucasian, but the study does seem to indicate health-protective effects of vegan diets.


Conclusion: Are vegan diets healthy? Are they healthier than omnivorous diets?

The evidence surrounding veganism appears to be mixed: while vegans tend to have lower cholesterol and LDL levels and blood pressure, and seem to be at lower risk for chronic disease, vegan diets have been shown to lead to B12 deficiencies, lower bone density, and elevated homocysteine levels, which can lead to various health problems. There seems to be a consensus that it is difficult for vegans to maintain proper levels of nutrients such as B12 and calcium, but the diet is basically healthy, if carefully executed. A person who follows a balanced vegan diet will not likely be malnourished, but might suffer from isolated nutritional deficiencies. This does not seem to be the case for pregnant and nursing mothers; veganism, contrary to at least one of the websites, has been shown to have lasting negative effects on infants, through a lack of vitamin B12.

Veganism has a positive impact on health in the sense that it seems to decrease the likelihood of chronic diseases such as diabetes, CHD, and other diseases related to obesity and high BMI.  Overall, veganism is healthier than an omnivorous diet with respect to chronic diseases, but may lead to nutritional deficiencies, lower bone density, and higher homocysteine levels; a balanced vegan diet with supplements for B12 and calcium would likely be healthy for anyone other than pregnant and lactating mothers, who should consider introducing animal products until their children finish nursing. The claims about vegan diets being healthier than omnivorous diets thus are thus partly true, but not entirely; serious side effects can occur, especially when a vegan diet is not well balanced. 
















Web Sources


Academic References


Appleby, P, et al. “Comparative Fracture Risk in Vegetarians and Non-Vegetarians in EPIC- Oxford.” European Journal of Clinical Nutrition 61 (2007): 1400-1406.


Dewell, Antonella, et al. “A Very-Low-Fat Vegan Diet Increases Intake of Protective Dietary Factors and Decreases Intake of Pathogenic Dietary Factors.” Journal of the American Dietetic Association 108 (2008): 347-356.


Dror, Daphna K, and Lindsay H Allen. “Effect of Vitamin B12 Deficiency on Neurodevelopment in Infants: Current Knowledge and Possible Mechanisms.” Nutrition Reviews 66.5 (2008): 250-255.


Goff, LM, et al. “Veganism and its Relationship with Insulin Resistance and Intramyocellular Lipid.” European Journal of Clinical Nutrition 59 (2005): 291-298.


Majchrzak, B., et al. “B-Vitamin Status and Concentrations of Homocysteine in Austrian Omnivores, Vegetarians and Vegans.” Annals of Nutrition and Metabolism 50 (2006): 485–491.


Smith, Annabelle M. “Veganism and Osteoporosis: A Review of the Current Literature.” International Journal of Nursing Practice 12 (2006): 302–306.


Waldmann, A., et al. “German Vegan Study: Diet, Life-Style Factors, and Cardiovascular Risk Profile.” Annals of Nutrition and Metabolism 49 (2005): 366-372.




Psychology Department

The Health Psychology Home Page is produced and maintained by David Schlundt, PhD.


VuLogoVanderbilt Homepage

Return to the Health Psychology Home Page
Send E-mail comments or questions to Dr. Schlundt