Читать книгу The Vitamin Cure - Monte Lai - Страница 23

 • Geography. The closer a place is to the equator, the stronger the intensity of ultraviolet light from the sun. Therefore, people who live closer to the equator have a lower risk of vitamin D deficiency compared to those who live farther away from the equator. Indeed, people who live at the 43rd parallel north and farther are more susceptible to vitamin D deficiency. In those regions, every year from October to April, ultraviolet light from the sun cannot reach the surface of the Earth, so the skin ceases to produce vitamin D, increasing the risk of deficiency.

 • Sun protection. Except beachgoers and those who love outdoor activities, most people try to avoid sun exposure. Sun umbrellas, hats, long sleeves, long pants, and sunscreen are common remedies to shun sun exposure. Excessive avoidance of the sun can cause vitamin D deficiency.

 • Infants fed with breast milk. The vitamin D content of breast milk is relatively low. Infants who are born to Asian and African families in the northern hemisphere are at especially high risk of vitamin D deficiency. A daily dose of 400 IU is recommended for infants to avoid vitamin D deficiency.

 • Obesity. Vitamin D is a lipid-soluble vitamin. Upon absorption in the intestines, vitamin D dissolved in chylomicrons (fat globules) is transported to the liver and other organs in the body. In the bloodstream, vitamin D binds to a vitamin D–binding protein, which is then absorbed by fat tissue. In other words, in obese individuals, vitamin D is mostly stored in fat tissue, while the rest of the body is devoid of vitamin D, causing vitamin D deficiency. Weight loss is the only way to release it from fat tissue and increase vitamin D levels.

 • Chronic kidney disease. An enzyme in the kidneys is required for final activation of vitamin D in the body, which creates the active form of vitamin D. Chronic kidney disease hinders the activation of vitamin D in the kidneys, resulting in vitamin D deficiency.

 • Enteritis (inflammation of the small intestine). Inflammatory bowel diseases—such as ulcerative colitis, Crohn’s disease, and fat malabsorption—may lower the absorption of vitamin D in the intestines, aggravating the risk of vitamin D deficiency.