@honour.health: What oil is in your vitamin D3 supplement? Pretty much every vitamin D3 supplement will include a carrier oil in the formula to support absorption. But most brands use low quality vegetable oils in their formula, because they're cheap and they're not looked to as one of the main ingredients. If you're going to spend your money on a vitamin D3 supplement, our preference is always a D3 that includes a high-quality oil like MCT oil, coconut oil, or olive oil.