Vitamin D3 is found naturally in some foods, as well as in dietary supplements. The best natural sources of Vitamin D3 are
Fatty fish - Salmon & Tuna,
Fortified food, drinks, cereals,
Sunlight is also an essential source of Vitamin D3. When you are exposed to UV light, your body produces Vitamin D3. However, you should limit your exposure to the sun and wear sunscreen when outside, as too much UV light can damage your skin.