How to Get an ‘A’ in Vitamin D

vitamin d facts
Dr. Geoffrey Harris, MD

Vitamin D: We know we need it, and most of us only know about getting it from the sun. Then we’re told it’s bad to get too much sun because you’ll get cancer and die.

It can make you hate science.

Don’t worry, we’ve got you covered.

Vitamin D Facts — The Basics

Vitamin D is important for immune system functioning, preventing osteoporosis, lowering blood pressure, regulating cholesterol levels, and may even protect against some cancers including breast and prostate cancer. One study has even identified an association between Alzheimer’s disease and vitamin D deficiency.

Almost all fungi, plants, and animals produce a form of vitamin D that absorbs ultraviolet light. In humans, ultraviolet light from the sun, along with special processes in the liver and kidneys, helps our bodies produce a usable, active form of vitamin D. We can also absorb it from supplements and the foods we eat. Experts consider the active form of vitamin D a hormone because it is similar in structure to the body’s steroid hormones like estrogen and testosterone. In this role vitamin D increases phosphorus and calcium absorption from the intestines and promotes bone mineralization for stronger bones.

History — Why’s It in My Milk?

During the industrial revolution, when families left their farms to live in the city and work in factories, there was an increase in two bone diseases, rickets and osteomalacia. Rickets is where bones in growing children do not mineralize properly and become weak, misshapen, and soft. Osteomalacia is similar, but affects the bones and muscles of adults.

Minimal sun exposure and poor diets led to an epidemic in vitamin D deficiency. Scientists in the late 1800’s discovered this, and figured out that giving children cod liver oil reversed rickets. By the 1930’s, the United States began fortifying milk with Vitamin D, which made rickets a rare disease in this country.

However, recent reports are showing a resurgence of rickets and vitamin D deficiency in the United States. The are many reasons for that.

Ten Common Reasons for Vitamin D Deficiency

1) Aging—Studies have revealed that aging can decrease the skin’s ability to create vitamin D.

2) Melanin—Higher melanin levels in dark-skinned individuals blocks ultraviolet light and limits the skin’s ability to create vitamin D.

3) Higher Latitudes and Seasonal Changes—In Northern cities like Boston, Massachusetts, skin can only produce vitamin D from March to October due to low levels of wintertime ultraviolet light reaching the ground.

4) Sunscreens and Clothing—Block ultraviolet light can interfere with the skin’s ability to produce vitamin D. Studies have shown that sunscreen with SPF of 8 or more will block the skin’s ability to make vitamin D, but it’s still important to wear sunscreen to prevent premature wrinkling, DNA damage to the skin, and skin cancer.

5) Glass—Blocks the UV-B light waves that the skin uses to make vitamin D.
(IMPORTANT: Glass does not block UV-A, which also has been associated with causing skin cancer and premature skin aging. UV-A does not create vitamin D in the skin.)

6) “9-to-5 Jobs”—Indoor work environments during peak sun hours prevent the skin from absorbing ultraviolet light to produce vitamin D.

7) Avoiding Dairy Products—Since milk is fortified with vitamin D, avoiding milk and milk products can lead to vitamin D deficiency. Vegetarians who do not drink milk or eat fish may be at the greatest risk if they do not take a supplement.

8) Breastfeeding—Vitamin D is not found in breast milk, so infants who exclusively receive it for a prolonged period of time without vitamin D supplementation can develop a deficiency.

9) Dermatologists and Skin Cancer Prevention—Since ultraviolet light exposure is associated with developing skin cancers, we are constantly “encouraged” to wear hats, long sleeves, and sunscreen. Avoiding ultraviolet light helps lower your risk of developing skin cancer and prevents premature skin aging, but it also necessitates taking a vitamin D supplement.

10) Sitting– Staying indoors, watching television, and playing video games does not help your skin create vitamin D. Light from a television set does not generate vitamin D.

This vitamin D deficiency is exacerbated by the fact that the natural food sources of vitamin D are not as prevalent in our modern diet. The Food and Drug Administration’s recommended daily amount of vitamin D for people under 50 years old is 200 IU per day. (A cup of vitamin D fortified milk provides half of this.) And, the required daily amount of vitamin D increases after age 50.

Food Sources of Vitamin D Include

Cod Liver Oil—contains 1,360 IU in one tablespoon
Salmon, cooked—contains 360 IU in 3.5 ounces
Mackerel, cooked—contains 345 IU in 3.5 ounces
Tuna Fish, canned in oil—contains 200 IU in 3 ounces
Sardines, canned in oil and drained—contains 250 IU in 1.75 ounces
Milk, vitamin D fortified—contains 98 IU in one cup
Egg (vitamin D is found in the yolk)—contains 20 IU in one egg

Many experts on vitamin D and nutrition are saying that the FDA’s recommendations are not enough and that people under 50 years old should try to get 400 to 800 IU per day, and people over 50 years old should get at least 1000 IU per day.

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