Which nutrients are at high risk of deficiency for adults on vegetarian or vegan diets?

• A. Vitamin C, potassium, iodine, magnesium
• B. Calcium, zinc, iron, and vitamin B12
• C. Protein energy deficiency
• D. Iodine only

Answer: (B)

When adults follow vegetarian or vegan diets, certain nutrients are more likely to fall short because the most reliable sources are animal products or fortified foods. Calcium, zinc, iron, and vitamin B12 are the nutrients most commonly at risk.

Calcium tends to be lower without dairy, so intake depends on fortified plant milks, calcium-set tofu, and leafy greens. However, absorption varies among foods (for example, spinach has calcium that isn’t absorbed well due to oxalates), so careful planning helps meet needs.

Zinc in plant foods can be less available because phytates inhibit absorption. Beans, lentils, nuts, seeds, and whole grains are good sources, but getting enough may require attention to variety and preparation (soaking, fermentation) to improve bioavailability.

Iron from plants is non-heme iron and isn’t absorbed as efficiently as heme iron from animals. Consuming iron-rich plant foods (beans, lentils, fortified cereals, seeds) with vitamin C-rich foods at the same meal can boost absorption, while limiting tea or coffee at meals helps as well.

Vitamin B12 is not reliably present in plant foods, so vegans must rely on fortified foods or supplements to prevent deficiency.

While iodine and other nutrients can be concerns in some cases, the combination above best captures the nutrients most at risk across typical vegetarian and vegan diets. Protein adequacy is usually maintained with sufficient calories and varied protein sources in a well-planned vegan diet.