'Vitamin' D not a vitamin, but necessary for health

<p>Humans were made to live naked on the equator. Physically, our bodies miss those direct UVB rays, and if we don't supplement adequately, we are most likely deficient in a very important hormone: calcitriol. Between the months of November and February, it is impossible for anyone north of Atlanta to get enough UVB rays for adequate amounts of calcitriol.</p><p>Hormones like estrogen, testosterone and calcitriol are biologically active substances that are produced by the endocrine glands of the body. When secreted into body fluids, they have specific life-supporting effects on vital organs.</p><p>The hormone calcitriol has multiple effects. Its first action is to enable absorption of calcium from our diet. If there is not enough calcitriol to facilitate calcium absorption, the body will simply compensate by taking all the calcium it needs from our bones. This weakens the bones and can cause pain, skeletal deformities, osteoporosis and rickets.</p><p>If we have enough calcitriol left over after dietary calcium needs are met, the hormone goes on to target other organs throughout the body. We now know that lack of calcitriol contributes to many health problems. A partial list includes Type I diabetes, hypertension, congestive heart failure, schizophrenia, depression, multiple sclerosis, dental caries and psoriasis. Cancers proven more likely to occur in people with calcitriol deficiency include Hodgkin's lymphoma, and colon, pancreatic, prostate, ovarian and breast cancers.</p><p>Part of the problem is a long-term misunderstanding about calcitriol, its sources and our minimum needs. This hormone is produced by the liver and the kidneys working together using an ingredient that is often lacking in modern-day humans. The necessary ingredient is D3. Early humans who lived on the equator had a constant supply of D3 provided by the UVB rays of the sun. But migration into northern latitudes led to chronic insufficiency.</p><p>A harmful and common misconception is that high levels of D supplements are toxic. D was thought to be a "fat-soluble vitamin" that could harm us if we took too much. But we now know that it is not a vitamin, and we can take at least 4,000 international units (IU) every day for five months without any indication of toxicity. Breastfeeding mothers can safely take more.</p><p>Recently the American Academy of Pediatrics changed their recommendations for D supplements for children. They recommend all children, from birth through adolescence, get at least 400 IU of D each day. Since most breast milk only contains 20 IU in each liter, either the mother or the baby needs to ingest more in order to reach the minimum daily requirement.</p><p>"25-hydroxy-D" is a test for levels of calcitriol in the blood. Adding this simple test to prenatal panels can easily identify those who are low and at risk. If pregnant women increased their levels so their developing babies get enough calcitriol even before they are born, there would be fewer pregnancy complications and healthier newborns.</p><p>Checking 25-hydroxy-D as part of regular preventive health care visits, and supplementing to bring levels above 30ng/ml (ng/ml=nanogram per milliliter) would have considerable positive effects. For many, adequate supplementation requires daily doses of 5,000 IU or alternatively, weekly doses of 50,000 IU.</p><p>It is important to change our long-standing assumptions about "vitamin" D:</p><p>D is not a vitamin. It is a hormone substrate.</p><p>We rarely get enough from sun exposure. Even summer sun may not provide enough, depending on skin tone and exposure. SPF 15 blocks 99 percent of D.</p><p>Doses larger than previously recommended are not toxic and may actually be necessary for optimum health.</p><p>Breastfed babies need 400 IU daily supplements. Alternatively, breastfeeding mothers can consider taking 6,400 IU daily to provide the required amount for their babies.</p><p>Get your 25-hydroxy-D checked and make sure you have enough calcitriol, even if you think you spend plenty of time in the sun. Make sure your kids get at least the recommend 400 IU each day. Your body and theirs will thank you.</p><p>Dr. Stacey Kerr, a longtime Sonoma County family physician, graduated from UC Davis Medical School and is certified in her specialty by the American Board of Family Medicine. Her columns are not intended as a substitute for hands-on medical advice or treatment. Consult your health care provider before adhering to any recommendations in this column. E-mail comments to drkerr@the-doctors-inn.com.</p>