Direct from GoPrimal Website:
Vitamin D3 provides a large number of benefits for the human body
- Boosting your immune system
- Prevents osteoporosis
- Maintains a normal bone/tooth health
- Lower risk of fractures after a fall
- Might help against depression
- Indispensable during pregnancy for embryonic development
- Recent studies have shown that a Vitamin D deficiency may encourage diseases like cancer, Diabetes Typ2, cardiovascular disease, autoimmune disorder or multiple sclerosis
Vitamin D3 from other sources
Spending 20 minutes under direct sunlight is releasing D3 synthesis in the skin (around 400 IU, which is not enough for your daily supply)), but this is only working in midsummer around lunch time, without sun protection like sunscreen and who wants to risk older looking skin or skin cancer at worst case?
Besides that, in wintertime sun rays are not strong enough to release D3 synthesis.
In nutrition you can find Vitamin D in the oil made from tuna liver or halibut, to get a sufficient supply you have to eat at least 800 gramm.