Vitamin D supplements are fat-soluble and should be taken with a meal for better absorption, reports WebMD. As of May 2010, a study proved that people who take their vitamin D supplement with the largest meal of the day get better absorption. Study participants showed a 50 percent increase.
Besides taking supplements, sunlight provides vitamin D, and it is also found in some foods, notes National Osteoporosis Foundation, including cereals, orange juice, tuna, salmon and wild-caught mackerel. Vitamin D is necessary to help the body absorb calcium, and it protects the bones. Those who lack vitamin D may lose bone density and easily break their bones.