The only scientifically proven way for vegans to reach these levels is by consuming B12-fortified foods or taking a vitamin B12 supplement. B12-fortified foods commonly include plant milks, soy products, breakfast cereals and nutritional yeast.
Some plant foods seem to naturally contain a form of vitamin B12, but there’s still debate on whether this form is active in humans (7, 8, 9, 10, 11, 12, 13).
What’s more, no scientific evidence supports depending on unwashed organic produce as a reliable source of vitamin B12.
Nutritional yeast only contains vitamin B12 when fortified. However, vitamin B12 is light-sensitive and may degrade if bought from or stored in clear plastic bags (14).
It’s important to keep in mind that vitamin B12 is best absorbed in small doses. Thus, the less frequently you ingest vitamin B12, the more you need to take.
This is why vegans who are unable to reach the recommended daily intake using fortified foods should opt for a daily supplement providing 25–100 mcg of cyanocobalamin or a weekly dosage of 2,000 mcg.
Those weary of taking supplements may find it reassuring to get their blood vitamin B12 levels checked before taking any.
But be aware that high intakes of seaweed, folic acid or vitamin B6 can falsely inflate markers of vitamin B12. For this reason, you may want to have your healthcare practitioner evaluate your methylmalonic acid status instead (15).
Interestingly, your ability to absorb vitamin B12 decreases with age. Therefore, the Institute of Medicine recommends that everyone over the age of 51 — vegan or not — consider fortified foods or a vitamin B12 supplement (16).
BOTTOM LINE:It’s extremely important that all vegans get enough vitamin B12. The only reliable way to achieve this is by eating fortified foods or taking a vitamin B12 supplement.
2. Vitamin D
Vitamin D is a fat-soluble vitamin that helps enhance the absorption of calcium and phosphorus from your gut (17).
This vitamin also influences many other bodily processes, including immune function, mood, memory and muscle recovery (18, 19, 20, 21).
The RDA for vitamin D for children and adults is 600 IU (15 mcg) per day. The elderly, as well as pregnant or lactating women, should aim for 800 IU (20 mcg) per day (22).
That said, there is some evidence that your daily requirements are actually far greater than the current RDA (23).
Unfortunately, very few foods naturally contain vitamin D, and foods fortified with vitamin D are often considered insufficient to satisfy the daily requirements.
This could partly explain the worldwide reports of vitamin D deficiency among vegans and omnivores alike (19, 24).
Besides the small amount you get from your diet, vitamin D can also be made from sun exposure. Most people likely make enough vitamin D by spending 15 minutes in the midday sun when the sun is strong — as long as they don’t use any sunscreen.
However, the elderly, people with darker skin, those living in northern latitudes or colder climates and those spending little time outdoors may be unable to produce enough (25, 26, 27).
Furthermore, because of the known negative effects of excess UV radiation, many dermatologists warn against using sun exposure to boost vitamin D levels (28).
The best way vegans can ensure they’re getting enough vitamin D is to have their blood levels tested. Those unable to get enough from fortified foods and sunshine should consider taking a daily vitamin D2 or vegan vitamin D3 supplement.
Although vitamin D2 is probably adequate for most people, some studies suggest that vitamin D3 seems more effective at raising blood levels of vitamin D (29, 30).
For this reason, you may want to try a vegan vitamin D3 option such as Vitashine or Viridian.
BOTTOM LINE:Vitamin D deficiency is a problem among vegans and omnivores alike. Vegans unable to maintain normal blood levels through fortified foods and sun exposure should consider taking a supplement.