CHAPTER 12
Vitamin D: Let The Sun Shine In
PART 1
Running Low on Vitamin D
A study released in March, 2011, by the CDC indicated that about a quarter of the U.S. population is low on Vitamin D, and about 8% at risk for a full-blown deficiency. Around the world, surveys have found that between 40% and 90% of people have less-than-optimal levels, and that includes those living in sunny climates. READ MORE
Vitamin D deficiency can be asymptomatic, and the only way to know for sure whether your levels are low is to have a blood test. Those most likely to need Vitamin D supplements include seniors, breastfed infants, people with dark skin, and people with certain conditions including liver diseases, cystic fibrosis, and Crohn’s disease. People who are obese or have had gastric bypass surgery may also need a boost.
The D’s We Need
| Chemical Name | Derived From | Characteristic | |
| Vitamin D3 | Cholecalciferol | UV-B rays | Biologically synthesized in the skin |
| Vitamin D2 | Ergocalciferol | plants | Available directly from plants and via animal foods |
| Synthetic Vitamin D | - | laboratories | Vitamins D2 and D3 can be synthesized commercially and used as food additive |
| Transitional form | Calcidiol or 25-hydroxyvitamin D or 25(OH)D | D3 and D2 | D3 and D2 after being modified in the liver. Next it travels to the kidneys. |
| Biologically active form | Calcitriol or 1,25-dihydroxyvitamin D | 25-hydroxyvitamin D | Made after transitional form is modified in the kidneys. Ready for use throughout the body. |
LESS
PART 2
The Calcium Connection
Glance at those polysyllabic chemical names for the D-family vitamins — cholecalciferol for D3, ergocalciferol for D2 — and you’ll see a calci root. Vitamin D’s prime responsibility is to help the body absorb calcium. READ MORE
Overproduction
The simpatico between Vitamin D and calcium is mirrored in cases of vitamin excess, which are uncommon and more likely to occur from overuse of supplements than from eating too many fortified foods. What makes Vitamin D excess toxic is the resulting surplus of calcium. Calcium deposits left in soft tissues of the heart contribute to heart-rhythm abnormalities; too much calcium in the bloodstream can cause kidney problems and mental confusion.
Super D
If any vitamin deserves a letter on its chest and a flowing cape, it’s probably Vitamin D. Essential functions include improving muscle strength and bolstering the immune system to fight off invasions by bacteria and virus. It also carries messages along nerve pathways from the brain to every part of the body. In concert with its sidekick, calcium, Vitamin D helps minerals to form and strengthen bones, playing heroic roles in the development of the fetal skeleton and the prevention of osteoporosis in the elderly. LESS
PART 3
Balancing Sun Exposure and D Needs
Health authorities scratch their heads about how to recommend we get enough sunlight since UV exposure is the leading cause of skin cancer. Once you sort out the mixed messages, the upshot is that a little UV without protection — to the tune of two half-hour periods in the sun per week — is probably adequate, with Vitamin D supplies to be topped off by fortified foods. The amount of D that you derive from sunlight should be qualified by what you know about your own susceptibility to skin cancer, paying attention to risk factors such as skin type, geographical location, and family history.
PART 4
Vitamin D vs. The Big C
The potential for supplementary Vitamin D to help reduce the risk of cancer or slow its spread has generated a lot of news and mobilized funds for research. The results of studies to date can be characterized as cautiously optimistic; definitive studies of cause and effect are ongoing. READ MOREHere’s a snapshot of study results shared by the National Cancer Institute:
- Colorectal cancer Some epidemiological (large scale) studies have indicated higher levels of D intake is associated with reduced risk.
- Breast cancer Conflicting results.
- Prostate cancer Conflicting results. Some studies correlating cancer prevalence to geographical location suggest that men exposed to higher levels of sunlight may have a lower risk.
- Pancreatic cancer Conflicting results. In one 16-year study, subjects with higher dietary Vitamin D had progressively lower risk; in another, subjects with the highest blood Vitamin D levels had twice the risk of those with normal levels.
The mechanism by which Vitamin D may affect cancer cells is not completely understood, but the vitamin appears to promote cellular differentiation, slow the growth of cancer cells, and stimulate apoptosis (sometimes referred to as “cell suicide”).
Adding to the complexity, it’s difficult for researchers to distinguish the effects of Vitamin D and calcium since the two are so biologically intertwined. New trials need to be carried out, and researchers are still trying to determine appropriate doses of D with which to work.
Elderly Concerns
Elderly people tend to have lower levels of Vitamin D. It makes you wonder: If they’re not getting sun, what are they all doing in Florida?
The tendency to be deficient actually appears to result from a few age-related changes. In older adults, the skin does not make Vitamin D as efficiently. Also, the kidneys are not as capable in converting Vitamin D into its active form. Dietary changes may also account for lower levels in some people.
Declining levels are something of a one-two punch for the elderly, since aging and Vitamin D deficiency are both associated with cognitive decline and the development of dementia. The risk factors for osteoporosis also include both aging and D deficiency. With a physician’s approval, those with low levels can take Vitamin D supplements.
Photo courtesy of Joe Schlabotnik LESS