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The Sunshine Vitamin

by Dr. Thomas K. Lo, Advanced Chiropractic

Vitamin D, sometimes called the “sunshine vitamin,” is produced in your skin in response to sunlight. It is a fat-soluble vitamin in a family of compounds that includes vitamins D-1, D-2, and D-3.

Your body produces vitamin D naturally when directly exposed to sunlight. You can also get it through certain foods and supplements to ensure adequate levels of the vitamin in your blood.

Vitamin D has several important functions. Perhaps the most vital are regulating the absorption of calcium and phosphorus and facilitating normal immune system function. Getting a sufficient amount of vitamin D is essential for normal growth and development of bones and teeth, as well as improved resistance against certain diseases.

If your body does not get enough vitamin D, you are at risk of developing bone abnormalities such as soft bones (rickets in children and osteomalacia in adults) or fragile bones (osteoporosis). Muscles need it to move, nerves need it to carry messages between the brain and every body part, and the immune system needs vitamin D to fight off invading bacteria and viruses.

How Much Vitamin D Do I Need?

The amount of vitamin D you need each day depends on your age. Average daily-recommended amounts are listed in micrograms (mcg) and International Units (IU). Life Stage Recommended Amount: Birth to 12 months—10 mcg (400 IU); Children 1–13 years—15 mcg (600 IU); Teens 14–18 years—15 mcg (600 IU); Adults 19–70 years—15 mcg (600 IU); Adults 71 years and older—20 mcg (800 IU); Pregnant and breastfeeding women—15 mcg (600 IU).

What Foods Provide Vitamin D?

Very few foods naturally have vitamin D. Fortified foods provide most of the vitamin D in American diets.

Fatty fish such as salmon, tuna, and mackerel are among the best sources. Beef liver, cheese, and egg yolks provide small amounts, and mushrooms also provide some vitamin D. Almost all of the U.S. milk supply is fortified with 400 IU of vitamin D per quart, as are many of the plant-based alternatives such as soymilk, almond milk, and oat milk. Foods made from milk, like cheese and ice cream, are usually not fortified.

Can I Get Vitamin D From The Sun?

The body makes vitamin D when the skin is directly exposed to the sun, and most people meet at least some of their vitamin D needs this way. Skin exposed to sunshine indoors through a window will not produce vitamin D. Cloudy days, shade, and having dark-colored skin cuts down on the amount of vitamin D the skin makes.

People who avoid the sun or who cover their bodies with sunscreen or clothing should include good sources of vitamin D in their diets or take a supplement. Recommended intakes of vitamin D are set on the assumption of little sun exposure.

Am I Getting Enough Vitamin D?

Because vitamin D can come from sun, food, and supplements, the best measure of one’s vitamin D status is blood levels of a form known as 25-hydroxyvitamin D. In general, levels below 30 nmol/L (12 ng/mL) are too low for bone or overall health, and levels above 125 nmol/L (50 ng/mL) are probably too high. Levels of 50 nmol/L or above (20 ng/mL or above) are sufficient for most people.

By these measures, some Americans are vitamin D deficient, and almost no one has levels that are too high. In general, young people have higher blood levels of 25-hydroxyvitamin D than older people, and males have higher levels than females. By race, non-Hispanic blacks tend to have the lowest levels, and non-Hispanic whites the highest. The majority of Americans have blood levels lower than 75 nmol/L (30 ng/mL).

Certain other groups may not get enough vitamin D. These include breastfed infants, because human milk is a poor source of the nutrient. Breastfed infants should be given a supplement of 400 IU of vitamin D each day. Older adults, because their skin doesn’t make vitamin D when exposed to sunlight as efficiently as when they were young, and their kidneys are less able to convert vitamin D to its active form. People with dark skin have trouble because their skin has less ability to produce vitamin D from the sun. People with disorders such as Crohn’s disease or celiac disease who don’t handle fat properly, because vitamin D needs fat to be absorbed. Obese people, because their body fat binds to some vitamin D and prevents it from getting into the blood.

What Are Some Effects Of Vitamin D On Health?

Vitamin D is being studied for its possible connections to several diseases and medical problems, including diabetes, hypertension, bone disorders, cancer, and autoimmune conditions such as multiple sclerosis.

As we age, millions (mostly women, but men, too) develop, or are at risk of, osteoporosis, a condition in which bones become fragile and may fracture if one falls. It is one consequence of not getting enough calcium and vitamin D over the long term. Supplements of both vitamin D3 (at 700–800 IU/day) and calcium (500–1,200 mg/day) have been shown to reduce the risk of bone loss and fractures in elderly people aged 62–85 years. Many men and women supplement vitamin D (and calcium) as part of an overall plan to prevent or treat osteoporosis.

Can Vitamin D Be Harmful?

Yes, when amounts in the blood become too high. Signs of toxicity include nausea, vomiting, poor appetite, constipation, weakness, and weight loss. It can cause confusion, disorientation, and problems with heart rhythm. Excess vitamin D can also damage the kidneys.

The daily upper limit for vitamin D is 25 mcg to 38 mcg (1,000 to 1,500 IU) for infants; 63 mcg to 75 mcg (2,500 to 3,000 IU) for children one to eight years; and 100 mcg (4,000 IU) for children nine years and older adults, and pregnant and lactating teens and women. Vitamin D toxicity almost always occurs from overuse of supplements. Excessive sun exposure does not cause vitamin D toxicity because the body limits the amount of this vitamin it produces.

Are There Any Interactions With Vitamin D That I Should Know About?

Like most dietary supplements, vitamin D may interact or interfere with other medicines or supplements you might be taking. Here are some examples:

Prednisone and other corticosteroid medicines to reduce inflammation impair how the body handles vitamin D, which leads to lower calcium absorption and loss of bone over time.

Both the weight-loss drug orlistat (brand names Xenical® and Alli®) and the cholesterol-lowering drug cholestyramine (brand names Questran®, LoCholest®, and Prevalite®) can reduce the absorption of vitamin D and other fat-soluble vitamins (A, E, and K).

Both phenobarbital and phenytoin (brand name Dilantin®), used to prevent and control epileptic seizures, increase the breakdown of vitamin D and reduce calcium absorption.

Tell your doctor, pharmacist, and other healthcare providers about any dietary supplements and medicines you take.

If you are struggling with health issues, call the Advanced Chiropractic & Nutritional Healing Center at 240-651-1650 for a free consultation. Dr. Lo uses Nutritional Response Testing® to analyze the body to determine the underlying causes of ill or non-optimum health. The office is located at 7310 Grove Road #107, Frederick, MD. Check out the website at