I thought I'd start a topic here since this question comes up for me again and again whenever I see discussion in the realm of supplementing when you're on a vegan (and vegetarian) diet. B-12 gets mentioned a lot, which, of course it should, since it's either only available through animal proteins or via supplementation. Of course supplementation is the best route since animals only get their B-12 through supplementation themselves. But D3 seems to get left out a lot, so I'm curious why that is. (My assumption is people think D3 is easily accessible so does not require supplementation and thus doesn't get mentioned as a necessary supplement for veg*ns.) I understand your body can produce D3 via sun exposure, however there have been studies that show that sun exposure is not a reliable method. (Often people either live in hemispheres too far away to get the right amount of exposure, or they're stuck indoors all day avoiding winter, or, there comes a risk of skin cancer from sun exposure - and sun block renders sun exposure for D3 ineffective. There was also a study a while ago that showed that even people living in Hawaii had inadequate D3, so even sun exposure in optimal conditions seems to be pretty unreliable.) Mushrooms contain trace amounts of D3, but you'd probably have to consume unrealistic quantities of them to get enough (I see conflicting studies on these). Otherwise you're relying on foods fortified with D3 like plant milks and tofu, and I guess it depends on the person - maybe some people eat those fortified foods every single day and get enough D3 that way. In any case, I have to supplement D3. Even when I was lacto-ovo vegetarian I didn't get enough D3 (blood tests revealed this). So, maybe my case is just anecdotal, but I'd think as vegans we should be recommending not only B-12 but D3 to those transitioning over. Appreciate your thoughts on this.