First, it is important to distinguish between the forms of Vitamin D. The two major forms are vitamin D2 and vitamin D3. Vitamin D2 is largely human-made and added to foods, whereas vitamin D3 is synthesized in the skin of humans from the sun and is also found in certain animal-based foods.
However, while the sun is the primary source of Vitamin D, a variety of factors from busy lifestyles, pollution and skin sensitivity can make it extremely difficult to get your daily dose of Vitamin D from the sun.  Furthermore, because there are a few naturally occurring food sources of Vitamin D, a deficiency of this vitamin can occur regardless of diet. Regardless, studies looking at vegetarian and vegan intakes have suggested that those consuming a plant-based diet may indeed consume less Vitamin D in their diet compared to their omnivore counterparts, and may, therefore, be at an increased risk of developing a deficiency .
Therefore, if eating a predominantly plant-based diet, it is advisable to get your daily dose of Vitamin D from a supplement, as this is the easiest and most reliable way to avoid developing a deficiency. [4,5]
When it comes to selecting a Vitamin D supplement, there two main things to consider:
- The origin of Vitamin D - Vitamin D2 is derived from plant sources (fungi & yeast) while Vitamin D3 can be found in animal sources (typically wool or cod liver oil) or plant sources (lichens).  It’s worth noting that while studies have shown that supplements deriving their Vitamin D from cod liver oil are effective, these also contains toxic levels of Vitamin A.[7,8] Therefore, a safe and equally effective alternative to supplement Vitamin D3 is derived from plant lichens.
- The form of Vitamin D - A recent Systematic Review & Meta-Analysis found that Vitamin D3 is superior to D2 in raising Vitamin D levels in the blood. 
For these reasons, although plant-based versions of Vitamin D2 are cheap and easy to come by, we have formulated our Essential 3 with plant-based Vitamin D3 that has been ethically sourced from plant lichen. Our plant-based Vitamin D3 is supplied by Vitashine™, the world’s only Vegan Society & Vegetarian Society registered company producing plant-source Vitamin D3. Their Vitamin D3 was developed after working with Independent expert laboratories making it the perfect choice for those wishing to increase their Vitamin D intake without consuming fish oils.
 Crowe FL E al. Plasma concentrations of 25-hydroxyvitamin D in meat eaters, fish eaters, vegetarians and vegans: results from the EPIC-Oxford study. - PubMed - NCBI n.d. https://www.ncbi.nlm.nih.gov/pubmed/20854716 . Website n.d. https://www.ncbi.nlm.nih.gov/pubmed/22552031