Plants do not have B12 unless fortified. Diets primarily or exclusively made of plants (e.g., vegan, vegetarian) often need vitamin B12 supplements.

Most people do not consume enough calcium-rich foods, regardless of the type of diet. There are several plant foods with bioavailable sources of calcium.

Most diets, including those with animal-sourced foods, are at risk for low vitamin D. Vitamin D is found in very few foods. It can be made from sunlight exposure; however, many people do not produce enough endogenously (e.g., darker skin, living in higher latitudes).

Regardless of diet type, infants 6-12 months, adolescents, pregnant, and lactating women tend to under-consume choline. [1] Requirements are higher during pregnancy and breastfeeding, and prenatal supplements typically lack adequate choline. [1]

Although only a small amount of omega-3 fats are needed in the diet, bioconversion of omega-3 fats to DHA and EPA is limited in the body. Diets low in fatty fish and fortified foods may need supplementation. 

Many diets during pregnancy may be at risk for low folate. Plant-based diets with ample fruits and vegetables are likely to meet folate needs. However, the critical nature of folate during conception should be stressed with all diets.

Many diets, especially during pregnancy and lactation, may lack adequate iodine. The iodine content of most plant foods depends on the soil's iodine content, which can vary dramatically.

Many diets may be low in iron, especially during pregnancy. The bioavailability of iron in plants is lower than in meats but can be improved with simple food pairings and culinary techniques.

Zinc bioavailability can be lower in some plant foods but may be improved with culinary techniques. 

Low vitamin A intake may occur in food insecure situations and with plant-exclusive diets that lack ample carotenoid-rich foods (e.g., betacarotene-rich fruits and vegetables).