การขาดวิตามิน D
Vitamin D deficiency is incredibly common in the US, but many Americans mistakenly believe they aren’t at risk because they consume vitamin-D- fortified foods (such as milk). There are very few foods that actually have therapeutic levels of vitamin D naturally and even fortified foods do not contain enough vitamin D to support your health needs. Despite its name, vitamin D is not a regular vitamin. It is actually a steroid hormone that you are designed to obtain primarily through sun exposure, not via your diet.
Just How Widespread Is Vitamin D Deficiency?
Before the year 2000, very few doctors ever considered the possibility that you might be vitamin D deficient. But as the technology to measure vitamin D became inexpensive and widely available, more and more studies were done, and it became increasingly clear that vitamin D deficiency was absolutely rampant. For example, according to one of the leading vitamin D researchers, Dr. Michael Holick:
- The Centers for Disease Control and Prevention (CDC) reported that 32 percent of children and adults throughout the US were vitamin D deficient — and this is grossly underestimated as they used vitamin D levels that were not consistent with optimal health.
- The National Health and Nutrition Examination Survey found that 50 percent of children aged one to five years, and 70 percent of children between the ages of six and 11, are deficient or insufficient in vitamin D
- Researchers such as Dr. Holick estimate that 50 percent of the general population is at risk of vitamin D deficiency and insufficiency
Researchers have also noted that vitamin D deficiency is prevalent in adults of all ages who always wear sun protection (which blocks vitamin D production) or limit their outdoor activities.1 People with increased skin pigmentation (such as those whose ancestors are from Africa, the Middle East, or India) are also at risk, as are the elderly.
It’s estimated that over 95 percent of US senior citizens may be deficient in vitamin D, not only because they tend to spend a lot of time indoors but also because they produce less in response to sun exposure (a person over the age of 70 produces about 30 percent less vitamin D than a younger person with the same sun exposure).
7 Signs You May Be Vitamin D Deficient
The only way to know for sure if you’re vitamin D deficient is via blood testing. However, there are some signs and symptoms to be aware of as well. If any of the following apply to you, you should get your vitamin D levels tested sooner rather than later.
1. You Have Darker Skin
African Americans are at greater risk of vitamin D deficiency, because if you have dark skin, you may need as much as 10 times more sun exposure to produce the same amount of vitamin D as a person with pale skin! As Dr. Holick explained, your skin pigment acts as a natural sunscreen, so the more pigment you have, the more time you’ll need to spend in the sun to make adequate amounts of vitamin D.
2. You Feel “Blue”
Serotonin, the brain hormone associated with mood elevation, rises with exposure to bright light and falls with decreased sun exposure. In 2006, scientists evaluated the effects of vitamin D on the mental health of 80 elderly patients and found those with the lowest levels of vitamin D were 11 times more prone to be depressed than those who received healthy doses.
3. You’re 50 or Older
As mentioned, as you get older your skin doesn’t make as much vitamin D in response to sun exposure. At the same time, your kidneys become less efficient at converting vitamin D into the form used by your body and older adults tend to spend more time indoors (i.e. getting even less sun exposure and therefore vitamin D).
4. You’re Overweight or Obese (or Have a Higher Muscle Mass)
Vitamin D is a fat-soluble, hormone-like vitamin, which means body fat acts as a “sink” by collecting it. If you are overweight or obese, you're therefore likely going to need more vitamin D than a slimmer person — and the same holds true for people with higher body weights due to muscle mass.
5. Your Bones Ache
According to Dr. Holick, many who see their doctor for aches and pains, especially in combination with fatigue, end up being misdiagnosed as having fibromyalgia or chronic fatigue syndrome. “Many of these symptoms are classic signs of vitamin D deficiency osteomalacia, which is different from the vitamin D deficiency that causes osteoporosis in adults,” he says. “What’s happening is that the vitamin D deficiency causes a defect in putting calcium into the collagen matrix into your skeleton. As a result, you have throbbing, aching bone pain.”
6. Head Sweating
According to Dr. Holick, one of the first, classic signs of vitamin D deficiency is a sweaty head. In fact, physicians used to ask new mothers about head sweating in their newborns for this very reason. Excessive sweating in newborns due to neuromuscular irritability is still described as a common, early symptom of vitamin D deficiency.
7. You Have Gut Trouble
Remember, vitamin D is a fat-soluble vitamin, which means if you have a gastrointestinal condition that affects your ability to absorb fat, you may have lower absorption of fat-soluble vitamins like vitamin D as well. This includes gut conditions like Crohn’s, celiac and non-celiac gluten sensitivity, and inflammatory bowel disease.
