Vitamin D — Why It’s Easy to Be Deficient

Have you ever seen pictures of children with extremely bowed legs? It’s a condition called rickets and it’s from low levels of vitami
D, causing the bones to become soft and weak.

Vitamin D is crucial for bone health. It helps your body keep a good balance of calcium and phosphate in the blood. With low vitami
D levels, children can develop rickets and adults can develop osteomalacia, a condition in which weak bones cause bone pain, fractures, and muscle weakness.
Vitamin D also has many other functions in the body. It helps control the growth of your cells, improves your immunity, provides nerve and muscle strength, and reduces disease-causing inflammation in your body.

Some studies suggest it may help with type 2 diabetes, weight loss, multiple sclerosis, high blood pressure, depression, heart disease, colon cancer, and other types of cancer.

Nursing home residents seem to have significantly fewer falls when they start a daily vitami
D supplement.

While the jury is still out on all of the studies related to vitami
D, we know it is essential that you have enough but not too much so that it becomes harmful. Simply put, you need to have optimal levels of vitami
D.

How Do You Get Enough Vitamin D?

There are 3 ways for you to get vitami
D.

1.Your skin makes vitami
D through sunlight.
2.You can get vitami
D from food.
3.You can take a vitami
D supplement.

Let's start with the sun on your skin.

As a general rule, exposure of the face, hands, arms, and legs to sunlight 2 to 3 times a week may produce enough vitami
D to stay healthy. Exposure should be about 1/4 of the amount of time it takes for you to get a mild sunburn.(1) Depending on your skin color, this can mean from 5 to 30 minutes of sun exposure betwee
10 am and 3pm.(2)

It is the ultraviolet B radiation in sunlight that helps your skin make vitami
D. Complete cloud cover reduces this radiation by about 50%. Shade, including the shade from severe pollution, reduces this ultraviolet B radiation about 60%.

How about food?

Surprisingly, there are not too many foods that are naturally high in vitami
D. The following list includes the foods highest in vitami
D:

Vitamin D (IUs)

Cod liver oil, 1 tablespoon (1,360)
Swordfish, cooked, 3 ounces (566)
Salmon (sockeye), cooked, 3 ounces (447)
Mackerel, canned, 3 oz (214)
Sardines, canned, 3 oz (197)
Tuna fish, canned in water, drained, 3 ounces (154)
Orange juice fortified with vitami
D
1 cup (check product labels, as amount
of added vitami
D varies) (137)
Milk, vitami
D-fortified, 1 cup nonfat, reduced fat, and whole (115-124)
The abbreviatio
IU stands for "international unit" and is what you will find on food and supplement labels.

The third source of vitami
D is from supplements.

In general there are two different forms of vitami
D on the market: ergocalciferol (also known as vitami
D2) and cholecalciferol (also known as D3). I will discuss their effectiveness in the following section.

How Much Vitamin D Do You Need?

Well, if you can get enough sun on your skin as described above, you really do not have to worry about getting more vitami
D from food and supplements.
On the other hand, food and supplements can provide a healthy dose of vitami
D if you have any (or a combination) of the following risk factors for low vitami
D:

• You do not spend enough time outdoors, especially in the sun.
• You live in a northern latitude, especially north of the Philadelphia-San Francisco line. For example, in Boston, there is not enough sunlight to make vitami
D in your skin for about 4 months of the year. If you go further north to Edmonton, Canada, your skin cannot make vitami
D for 5 months of the year.(3)
• You have been following your dermatologist's suggestion of liberally using sunscreen to protect yourself from the sun's radiation.
• You have darker skin. Skin pigment reduces the skin's ability to absorb the ultraviolet radiation in the sun. In a bathing suit, a light-skinned person spending 10-12 minutes under peak July sun in Boston can make 10,000 to 20,000 international units of vitami
D. It will take an Asian Indian person, who has darker skin, about 30 minutes to make as much vitami
D. It will take an African American with very dark skin about 120 minutes to make the same amount of vitami
D.
• You are obese. Fat cells hoard vitami
D. This reduces the circulating vitamin in your blood.
• Your have a medical condition such as Crohn's disease, celiac disease, and cystic fibrosis that impairs your gut's absorption of vitami
D.
• You are a strict vegetarian.
• Your kidneys are impaired so they cannot activate the vitami
D you have.
• You are older tha
65. This means your skin makes less vitami
D, your gut may not absorb nutrients as efficiently, and your kidneys may not activate vitami
D as effectively. Even in sunny South Florida, as many as 40% of older people have low vitami
D levels.(4)

If you have any of these risk factors, how many international units of vitami
D should you aim for a day?

This depends on whom you talk to. In recent years, various scientific authorities came up with different amounts of vitami
D that they consider good for your daily intake through food and supplements.

To spare you the confusing numbers and arguments, here is the bottom line.

If you are an adult, aim for 600 to 2000 IUs of vitami
D a day from your food and supplements.

And if you get vitami
D from supplements, keep in mind that unit for unit, cholecalciferol (vitami
D3) is better used by your body than ergocalciferol (vitami
D2).
In general, vitami
D3 is about 3 times more powerful than vitami
D2.(5)

How Do You Know if You are Vitamin D Deficient?

If you are low on vitami
D, you may have bone pain and muscle weakness. But often the symptoms of low vitami
D are very subtle. And even without any clear symptoms, low vitami
D can badly affect your health in different ways.

Your doctor can order a simple blood test, 25-hydroxy vitami
D, for you. Again, the normal range for vitami
D also varies according to different authorities. But here is what you need to know: a level of 30 to 50 ng/mL is considered optimal for bone health and overall health.

If your blood test suggests that you are very low on circulating vitami
D, your doctor may give you a prescription for high-dose treatment for a period of time. Make sure you follow his or her directions.

Can You Get Sick From Too Much Vitamin D?

Yes you can!

Too much vitami
D in your body can make you not want to eat, lose weight, urinate excessively, and have abnormal heartbeats. Even more seriously, it can make your blood calcium level too high, resulting in damage to your heart, blood vessels, and kidneys.

Unless you are under close monitoring by you doctor, do not take over 4000 international units of vitami
D from food and supplements a day. Exceeding this dose will increase your risk for having a toxic overload of vitami
D.

On the other hand, your skin will not make too much vitami
D from sunshine. Your body is such a marvelous creation that when you get too much sun, your skin actually rids itself of the extra vitami
D automatically.

References

1.Holick MF. Vitamin D: importance in the prevention of cancers, type 1 diabetes, heart disease, and osteoporosis. Am J Clin Nutr 2004;79:362-71.
2.Holick MF. Vitamin D deficiency. N Engl J Med 2007; 357:266-281;July 19, 2007.
3.Engelsen O, et al. Daily duration of vitami
D synthesis in human skin with relation to latitude, total ozone, altitude, ground cover, aerosols and cloud thickness. Photochem. Photobiol. 2005;81:1287-90.
4.Levis S, et al. Vitamin D deficiency and seasonal variation in an adult South Florida population. J Clin Endocrinol Metab. 2005;90:1557-62.
5.A
as LAG, et al. Vitamin D2 is much less effective than vitami
D3 in humans (abstract OR22-2). The Endocrine Society 86th Annual Meeting, June 16-19, New Orleans, LA.