Excerpts from “Vitamin D: The Sunshine Vitamin,” by Barbra Wexler, MPH
Vitamin D
You know that old expression about something being worth more than its weight in gold? Well, what if I told you that there’s a substance in your body so important that one tenth of a millionth of a gram circulating in your bloodstream can make the difference between vibrant health and increased risk for numerous diseases? How much would that be worth?
Now, what if I were to tell you that you can get this remarkable substance for free? All you need is some cholesterol and sunshine and your body will do the rest.
But wait; haven’t we spent the last 30 years learning that cholesterol is bad and contributes to the development of heart disease and that sunshine can cause skin cancer? Is it time to toss the sunscreen and embrace a high cholesterol diet?
The simple answer is no. Using sunscreen protects the skin from potentially damaging radiation and reducing excess dietary cholesterol is still a heart-healthy choice. But, in part because we’ve changed our diets to minimize our consumption of cholesterol — an essential nutrient the body uses to naturally create hormones and other vital compounds — and have learned to stay out of the sun or slather on high SPF sunscreens, many of us just don’t make enough of this miraculous stuff naturally.
We’ll give you one guess to figure out what’s worth so much more than its weight in gold.
It’s vitamin D.
Who Is At Risk for Vitamin D Deficiency?
Practically anyone can suffer from vitamin D deficiency, from breast-fed infants to older adults. According to the NIH National Nutrition Monitoring System, men generally have higher vitamin D intakes than women, and children tend to have higher vitamin D levels than adults.
In general, leaner people have higher circulating concentrations of 25(OH)D (hydroxylated vitamin D) than heavier people. People with a higher body mass index generally have low plasma concentrations of 25(OH)D, and vitamin D levels appear to decrease as BMI increases. People over age 50 are also at increased risk of vitamin D deficiency. As we age, the skin is less able to synthesize vitamin D efficiently and the kidneys are less able to convert vitamin D to its active hormonal form.
People with little or no sun exposure may also have low vitamin D levels. These include people who are homebound; populations of the northern latitudes; women who wear long robes and head coverings for religious or cultural reasons; and workers in occupations that prevent sun exposure (for example, night-shift workers who commute in darkness and work indoors).
People with darker skin may have increased risk of vitamin D deficiency. This is because darker skin contains more melanin, a pigment that reduces the skin’s ability to produce vitamin D from sunlight. Researchers from the Centers for Disease Control and Prevention (CDC) report that older women with darker skin are at especially high risk of developing vitamin D deficiency.
Too Much of a Good Thing?
It is possible to have too much vitamin D and that condition is referred to as hypervitaminosis D. Abnormally high levels of vitamin D can cause abnormally high levels of calcium in the blood. Over time, high levels of calcium can damage bones, soft tissue and the kidneys. Typical symptoms of hypervitaminosis D include constipation, decreased appetite, dehydration, fatigue, irritability and vomiting; however, hypervitaminosis D can also cause mental confusion and heart rhythm abnormalities.
According to the FNB, the tolerable upper limits of vitamin D intake should not exceed 2,000 IU per day; however, the board concedes that its upper limit recommendations have not been revised since 1997 and are based on older studies. More recent research supports doses as high as 10,000 IU per day.
D is for Support Against Disease
Through its immune system action, vitamin D plays pivotal roles in insulin secretion and regulation, heart and blood pressure regulation, muscle strength and brain activity. Vitamin D plays an important role in reducing the risk of many chronic diseases. None of this is surprising when you consider that more than 36 different organs and tissues throughout the body (including the breasts, colon, intestines, kidneys, lungs, parathyroid glands, prostate, retina, skin, stomach, and uterus) respond to vitamin D.
Let the Sunshine Vitamin In!
During the past decade, tremendous strides have been made in vitamin D research. We have advanced beyond the notion that vitamin D receptor activation is only involved in the regulation of mineral metabolism and maintenance of bone mass and skeletal health. Inadequate vitamin D prevents children from attaining peak bone mass, contributes to osteoporosis in adults and causes osteomalacia. It is also is involved in a myriad of physiological functions, influencing the expression of hundreds of genes and acting on tissues throughout the body.
Vitamin D is vital for overall health and well-being. Emerging scientific evidence suggests it may help support the body when faced with cardiovascular disease, Parkinson’s disease, multiple sclerosis, some forms of arthritis, kidney disease, and depression.
Because vitamin D deficiency has reached epidemic proportions in the United States, many health professionals and scientists recommend routine annual monitoring of vitamin D status, which can be performed with a simple blood test. The primary cause of vitamin D deficiency is the fact that moderate sun exposure is the major source of vitamin D for most humans, and many of us do not get enough. Very few foods naturally contain vitamin D, and foods that are fortified with vitamin D generally are not consumed regularly or in adequate quantities to satisfy vitamin D requirements.
