Fat people will frequently need to swallow 5,000 IU vitamin D3 softgels every day instead of swallowing 2,000 IU vitamin D3 softgels every day in order to get their blood vitamin D level, which is called, 25(OH)D, into the ideal range of 26 to 34 nanograms per milliliter [that's exactly the same as 65 to 85 nanomols per liter]. Keeping our blood level of 25(OH)D within this optimal range will minimize our risk of developing heart disease, cancer, Osteoporosis, and a weakened immune system. The farther our blood level of 25(OH)D goes higher than or lower than this optimal range, the higher our risk of developing heart disease, cancer, Osteoporosis, and a weakened immune system. People who aren't fat should swallow only 2,000 IU of vitamin D3 softgels every day in order to achieve a blood level of 25(OH)D that is within this optimal range. To save money, swallowing three 5,000 IU vitamin D3 softgels per week would successfully achieve the same result as swallowing seven 2,000 IU vitamin D3 softgels per week. Doctor's Best is the only brand of vitamin D3 softgels that contains extra virgin olive oil, which is extremely healthy for us to consume, instead of other vegetable oils, all of which are much less healthy for us to consume. Mushrooms are high in vitamin D1, vitamin D2, and vitamin D4. Wild ocean fish are high in vitamin D3. Exposure to sunshine creates inside of our bodies a form of vitamin D3 that is safer against overdoses than the vitamin D3 contained in softgels, which is derived from lanolin, which is the waxy coating on sheep's skin. The healthiest form of vitamin D is vitamin D4 because only vitamin D4 can increase our blood levels of calcium. Vitamin D2 and vitamin D3 are about equally healthy for us. However, vitamin D2 is slightly safer to use than vitamin D3 because vitamin D2 is absorbed slightly less well than vitamin D3 at extremely high, overdose levels. At levels under 10,000 IU per day, vitamin D2 is absorbed just as well as vitamin D3