The "Sunshine" Vitamin

One of the main sources of vitamin D₃ is from exposing skin to sunlight. However, this process can be limited by skin colour, sunscreen use, season and geographic location. People living close to the equator can easily produce vitamin D throughout the year, while those living farther away have to rely on foods and supplements for adequate vitamin D status.

Vitamin D₃ enhances calcium absorption and retention, a key nutritional function in supporting healthy bones and teeth. Decreased exposure to sunlight, a vegetarian diet and a low intake of vitamin D-fortified foods often contribute to inadequate vitamin D levels. Clinical studies involving vitamin D supplementation suggest the importance of both vitamin D and calcium for bone health. Calcium intake, when combined with sufficient vitamin D, a healthy diet and regular exercise, may reduce the risk of developing osteoporosis. Vitamin D supplementation alone also supports bone health. It promotes intestinal calcium and phosphorous absorption, and reduces urinary calcium loss, essential mechanisms for maintaining proper calcium levels in the body and healthy bone composition.

Vitamin D3 (the most potent form of vitamin D found in supplements) is found naturally in a limited number of foods, fish being the best source. For example, three ounces of rainbow trout or salmon typically contain 550-650 IUs of vitamin D, while there are roughly 40-50 IUs in one egg (in the yolk), three ounces of beef liver or tuna, or two sardines. Other foods that contain significant amounts of vitamin D because it is added (fortified) include cow milk, nut milks, orange juice, and breakfast cereals (read labels). Vitamin D2 (a vegetarian source of vitamin D and less potent than D3) is found primarily in mushrooms exposed to UV light. For example, a half cup of white mushrooms exposed to UV light contains 366 IUs of vitamin D2, while the same amount of portabella mushrooms contains only 4 IU.¹

References

1. NIH Vitamin D: Fact Sheet for Health Professionals  https://ods.od.nih.gov/factsheets/vitaminD-healthprofessional/ [Accessed August 25, 2022]