“Vegan diets are deficient / unsafe”

Evidence quality

The evidence is high for the general conclusion that an appropriately planned vegan diet can be nutritionally adequate in adults because this conclusion is supported by a current professional position paper and systematic reviews of intake and nutritional status (Raj et al., 2025; Bakaloudi et al., 2021; Neufingerl and Eilander, 2021). Certainty is lower for specific long-term outcomes and some life stages because available studies are often observational, concentrated in high-income countries, and heterogeneous in food choices, supplement use, and fortification exposure (Bakaloudi et al., 2021; Neufingerl and Eilander, 2021).

Professional positions

The Academy of Nutrition and Dietetics' 2025 position states that appropriately planned vegetarian and vegan dietary patterns can be nutritionally adequate for adults and can offer long-term cardiometabolic benefits (Raj et al., 2025). That paper is explicitly limited to adults and emphasizes nutrient balance and individualized guidance (Raj et al., 2025).

The existing stub's broader life-stage statement accurately reflects the Academy's 2016 position, which stated that appropriately planned vegetarian, including vegan, diets were appropriate during pregnancy, lactation, infancy, childhood, adolescence, older adulthood, and for athletes (Melina et al., 2016). The 2025 paper replaced that position with an adult-scoped statement, so the older all-life-stages wording should be identified by date rather than presented as the scope of the current Academy paper (Raj et al., 2025).

Nutrient profile

A systematic review of 48 mostly European studies found that vegan diets were commonly lower in vitamin B12, vitamin D, iodine, zinc, calcium, and selenium intake, with protein intake lower than in comparison diets (Bakaloudi et al., 2021). It did not find vegan diets generally deficient in vitamins A, B1, B6, C, or E, iron, phosphorus, magnesium, copper, or folate, and it cautioned that low intake does not always establish impaired health status (Bakaloudi et al., 2021).

A broader systematic review of 141 studies found that people following plant-based diets generally consumed more fiber, polyunsaturated fat, folate, vitamins C and E, and magnesium than meat-eaters, while intake or status of vitamin B12, vitamin D, iron, zinc, iodine, calcium, EPA, and DHA was generally lower (Neufingerl and Eilander, 2021). It also found potential inadequacies among meat-eaters, including fiber, alpha-linolenic acid, folate, vitamin D, vitamin E, calcium, and magnesium (Neufingerl and Eilander, 2021). These findings support a nutrient watch list but do not support the claim that vegan diets are inherently deficient (Neufingerl and Eilander, 2021).

Vitamin B12

Vitamin B12 is the nutrient requiring the clearest nonoptional planning in a vegan diet (Melina et al., 2016; Pawlak et al., 2013). A review of 18 studies using methylmalonic acid, holotranscobalamin, or both reported B12 depletion or deficiency across age groups and locations, with higher rates in vegans than in other vegetarians (Pawlak et al., 2013). The 2016 Academy paper consequently specified that vegans need reliable B12 sources such as fortified foods or supplements (Melina et al., 2016).

What “adequate” means

Adequate does not mean automatic. Diet quality, total energy intake, food variety, fortification, supplement use, geography, sun exposure, and life stage can alter nutrient intake or status (Bakaloudi et al., 2021; Neufingerl and Eilander, 2021). The same reviews show that poorly planned diets can occur under vegan, vegetarian, and meat-containing patterns, although the nutrients most likely to require attention differ among them (Neufingerl and Eilander, 2021).