I try to read as much as I can about health. Much has been written about vitamin D, and at one point it seemed to be the “miracle” solution for every ailment.
By Peter N. Landless and Allan R. Handysides
I try to read as much as I can about health. Much has been written about vitamin D, and at one point it seemed to be the “miracle” solution for every ailment. Is this so? I am seeing some conflicting reports in some recent articles.
Vitamin D, also known as the “sunshine vitamin,” plays a key role in calcium metabolism and bone strength and formation. It’s actually a hormone produced in the body that depends on the exposure of our skin to the ultraviolet (UV) rays of the sun (hence the name “sunshine vitamin”).
Initially, vitamin D was thought to be mainly a nutrient that helps to prevent the childhood disease known as rickets. Rickets is a disease in which softening and weakness of the bones occurs because of vitamin D deficiency and the resultant abnormality in calcium metabolism. When this occurs in adults, bones become decalcified and less dense (or strong). This condition is known as osteomalacia, the condition that precedes osteoporosis.
Vitamin D increases the absorption of calcium in the small intestine. It also influences the bone cells to release calcium into the blood to maintain normal blood calcium levels and to stimulate growth. Bone is a dynamic tissue that undergoes change and strengthening all the time; this process is termed “remodeling,” and is especially important in the healing and repair of bone fractures. Research has shown that most of the cells in the human body have receptors for vitamin D, where vitamin D attaches and triggers certain processes in the cells.
Vitamin D has a very complex metabolism and numerous related compounds. The substance produced in the skin (and also available in food and supplements) is converted in the liver to 25-hydroxyvitamin D, or calcidiol. This is converted in the kidneys to the active form of vitamin D, 1,25-dihydroxyvitamin D3. Vitamin D is fat-soluble and requires fat for absorption. It can be stored for those times we do not have sun exposure (depending on climates, seasons, dress, sunscreen use).
We get vitamin D mainly from sunshine and metabolism in the skin. Only a few foods—oily fish, cod liver oil, egg yolks, and some forms of mushrooms (shitake)—naturally contain vitamin D. Our main dietary sources are fortified foods, such as milk, some soymilks, dairy or soy yogurt, cheese, orange juice, margarine, breakfast cereals, and infant formula.
If you are tested and found to be low in vitamin D after “loading” supplemental doses are given, a typical maintenance dose would be between 800–2000 IU (international units) daily. This must be done under medical supervision; each individual may respond differently to these doses. Follow-up tests are needed to ensure correct dosing.
Exposure to sunlight varies around the world and even within communities. There is also the risk of skin cancer related to excessive sunlight exposure.
The following factors may contribute to low vitamin D levels:
- less sun exposure in some regions, especially in winter
- darker skin (reduces UV penetration)
- decreasing ability of the skin to produce vitamin D as one ages
- sunscreens (although important in preventing skin cancers, sunscreens can reduce vitamin D production by up to 99 percent)
- low intake of fortified foods
- obesity (vitamin D may become trapped in fatty tissue)
- bowel disorders or surgery
- certain medications
- impaired liver or kidney function
Along with bone health, numerous observational studies have connected other diseases and their outcomes to low vitamin D levels. These diseases include asthma, arthritis, various cancers, dementia, depression, coronary artery disease, hypertension, Parkinson’s, and infections. Several large, controlled clinical trials are under way, and the Institute of Medicine is predicting that we will have more definitive answers in 2017. In the meantime, discuss your personal situation and needs with your health advisor.
May God guide you in making wise health choices!
Peter N. Landless, a board-certified nuclear cardiologist, is director of the General Conference Health Ministries Department.
Allan R. Handysides, a board-certified gynecologist, is a former director of the General Conference Health Ministries Department.