A report from the German Nutrition Society asserts that a vegan diet may lead to nutrient deficiencies, particularly in vitamin B12. The report, which is cited on the German government’s website, states that vegans should “permanently” take B12 supplements and have their B12 levels checked regularly by a physician. The report goes on to state that, due to the increased risk of nutrient deficiencies, cutting out all animal products isn’t recommended for pregnant or nursing women, or children and teens of any age. In addition, it recommends that people of all life stages follow “a diet that includes all foods in the nutrition circle—including animal products.”
Not all health organizations support these recommendations. For example, the report cited three international nutrition organizations, the US Academy of Nutrition and Dietetics, the Australian National Health and Medical Research Council, and the Canadian Paediatric Society, which all hold the position that a well-planned vegan diet, one that includes food supplements and fortified foods, is nutritionally adequate and appropriate for everyone. The Portuguese National Programme for the Promotion of a Healthy Diet also supports veganism but recommends that vegan infants be breastfed for the first two years so they receive enough high-quality milk protein.
A spokesperson from the pan-EU Vegan Society reiterated these organizations’ position that going vegan requires a little extra knowledge and planning, but added that “. . . you can get everything you need from a vegan diet for great health.” As for specifically getting the B12 you need, some researchers and healthcare practitioners believe that plant sources don’t provide sufficient quantities of B12, although one study found that nori seaweed did contain substantial amounts of B12. If you're concerned about your B12 intake, speak with your healthcare practitioner who can recommend supplements or food sources to correct any deficiencies.