Doctor, do I have to take Vitamin D pill everyday?

There was an article (“Effects of vitamin D supplementation on musculoskeletal health”) recently published on Lancet Diabetes and Endocrinology; it was a meta-analysis report reviewing 81 studies. The conclusion is that normal individuals taking vitamin D supplements doesn't prevent fracture or fall and may increase the risk of kidney stone.

I gave a talk (to a Taiwanese community) on vitamin D some years ago, in which I mentioned the statement of Institute of Medicine (IOM, now called the National Academy of Medicine, is part of the National Academy of Sciences, Engineering, and Medicine) in November 2011.

Vitamin D is still important for bone health, I believe
The following is from the Power Point of my talk. The IOM analyzed more than 1,000 studies and interviewed the experts of various fields and its conclusion “found evidences to be mixed and inconclusive” using vitamin D on various conditions such as cancer, hypertension, cardiovascular diseases, diabetes, metabolic syndrome, immune responses, falls, neuro/psychological functions, physical performance, pre-eclampsia and reproductive function.

Power Point of my talk

But IOM says “current evidence supports vitamin D a role in bone health."  IOM is known to be very conservative, having 10 or more members. American doctors respect, but not necessarily follow its recommendation, Just like Mark Twain says of classic, “a book which people praise and don't read.”

Vitamin D comes with many forms: Those come from foods are D2, skin (with help of sun) D3; both are converted to 25(OH)Vitamin D in liver, then to 1,25(OH)2 Vitamin D in kidney (this is the active form). Level of 25(OH)Vitamin D reflects vitamin D store, so when we check vitamin D level, we measure blood 25(OH)Vitamin D level.

The best source of vitamin D is your skin and sunlight (UVB)

It is the ultraviolet B (UVB) in the sunlight that helps skin make vitamin D, general speaking 10AM to 3PM is the better time to have more UVB. In certain areas such as Boston, there is practically no UVB reaches the earth in winter time (November to February). Skin color also determines the efficiency, fair (white) skin has the best efficiency, the dark skin (containing more melanin) the least effective as the melanin competes for UVB with the vitamin D-making cells. General speaking, it is enough to have 10% of body expose to sunlight for 10 minutes a day for the fair skin.

Of note, vitamin D2 (from food) is only 30% as effective as vitamin D3 (from sun) in maintaining 25(OH)Vitamin D level, that is why we sing “you are my sunshine” with enthusiasm and admiration. Keep in mind, the vitamin D store declines as we age. Ability of vitamin D synthesis from skin also declines with age. We are led to believe that vitamin D deficiency may lead to or accelerate osteoporosis (骨質疏鬆症), even though the Lancet Diabetes and Endocrinology says otherwise.

No consensus for normal blood vitamin D level among professional organizations

The problem comes from the fact that there is no consensus opinion on the normal vitamin D level among various professional organizations.

IOM says the blood vitamin D level is 20 ng/mL or above, but National Osteoporosis Foundation, International Osteoporosis Foundation and American Geriatric Society all say 30-70 or even 30-100 ng/mL. Most physicians go by the “30 to 70 or even 100” normal value.

The best source of vitamin D is your skin and sun; few foods contain vitamin D. Sea shells contain vitamin D, but not all sea foods do (salmon, tuna and mackerel are exceptions) Cheese, egg and yogurt have some vitamin D; this is why we have vitamin D fortified milk, orange juice and cereals.

The following table gives you some idea as to the food sources of vitamin D:

Our body cannot make vitamins, vitamin D is the only exception. Sometime I wonder what is the God's purpose? It is either God knows few of our foods contain vitamin D or vitamin D is more important than any other vitamins.

There is an ongoing vitamin D and Omega-3 trial (VITAL), a large study (more than 25,000 participants) investigating whether vitamin D and omega-3 supplements can lower the risk of cancer, heart disease or stroke; the jury is not out yet.

If one googles Internet, one will find innumerable articles that vitamin D is good for almost all diseases of all organ systems, ranging from cancer to Alzheimer disease, 而且有病治病，無病防身。對於這些報導我是姑且聽之. But for bone health, I go by the normal vitamin D level of 30 ng/mL or above (some say >50 may be detrimental). If one cannot maintain the normal value with one's diet, then vitamin D supplement is the way to go, especially during the winter time.

It is of importance to maintain normal vitamin D level if one has osteoporosis

In case of having osteoporosis, in addition to the specific treatments (bisphosphonates, Prolia, Forteo, Tymlos, Evista, etc.) One needs to strive to maintain normal vitamin D level and to ensure adequate calcium intake.

Power Point of my talk

An article in 2014 British Medical Journal says “People with low vitamin D levels were more likely to die from cancer, heart disease and to suffer from other illnesses.” However, in 2014 the United States Preventive Services a Task Force (USPSTF—a federal government agency) advised doctors not to do “routine” as the benefits of taking vitamin D supplement in a healthy individuals are not proven. 我買了一大瓶 vitamin D 要給 Katy吃，我道她沒有每天認真吃，我也睜一眼 閉一眼。因為我也不確知她到底要不要吃。Some experts warn that taking vitamin D supplement may increase risk of kidney stone or calcification of the blood vessel wall. I believe this may be a concern only for those taking excessive or mega doses of vitamin D.

How much vitamin D supplement one should have everyday?

Institute of Medicine: for those age 1 to 70: 200-600 IU a day; age 71 or above: 400-800 IU a day.

National Osteoporosis Foundation: 800-1000 IU a day.

Endocrine Society (of endocrinologists): 1500-2000 IU a day.