By David Musnick MD

Vitamin D, known biochemically, as 1,25 dihydroxycholecalciferol has been associated  for a while with calcium and bone health.  It is accurate that vitamin D is essential for calcium metabolism and bone health but there are other very valuable roles for this nutrient in your body.  It is first important to understand where vitamin D comes from and how essential it is for bones.  This article will then inform you of other uses for vitamin D.

Your skin is one tool that your body uses to make vitamin D, via 7-dehydrocholesterol, a cholesterol precursor. This form of the vitamin must be modified in your liver and kidneys to become the active form of vitamin D.  During summer and late spring and very early fall you can produce enough vitamin D by exposing your arms and face to the sun for 10-15 minutes a day—less than the time that it would take to get a sunburn.  Your body can make as much as 10,000 units from sun exposure.    You can store vitamin D in your fat stores.

So why do many people get deficient in this vitamin? The angle of the sun is too low at northern latitudes to provide the necessary energy to make vitamin D from sun exposure.  Many people get very little sun exposure even if they live at lower latitudes because they use sun screen or are covered with clothes.  It is not healthy to get sun exposure that will make your skin red or that will lead to tanning because of increased risk of skin cancer.  For healthy bones, it is a good idea to take vitamin D daily as a supplement.

Vitamin D and Your Bones
Vitamin D helps your body absorb and regulate calcium and phosphorous. If your dietary intake of calcium is inadequate, calcitriol in combination with parathyroid hormone can mobilize calcium stores from your bones. This can lead to bone loss.  It is important for women of all ages to build bone density and to prevent bone loss.  It is especially important for a woman who is perimenopause and post menopausal to take supplemental vitamin D with 1500mg of calcium per day.  Maintaining healthy bones is also important for men because men can get osteoporosis when they age as well.  Remember that more than vitamin D and calcium are recommended for healthy bones—magnesium and boron are also important.  There are bone formulas available that contain all of the nutrients known for healthy bones.

Vitamin D, Strength and Preventing Falling
There is a study to support that vitamin D may help prevent falling and reduce the likelihood of hip fractures.  This may occur because vitamin D may be involved in increasing muscle strength (by increasing muscle protein synthesis) as well as bone density.  The standard dose of 400 units does not seem to be enough to accomplish this and 800-1000 units may be needed for this purpose.  It is likely that calcium, along with vitamin D, is necessary for fall prevention.

Pay Special Attention
If you are dark skinned you may not be able to make enough vitamin D, even at lower latitudes.  This includes Native Americans, people of African origin, Asians and other dark skinned people. If you are older than 60 your skin or kidneys may not be as efficient at making vitamin D as when you were younger.  Also, vitamin D receptors may decrease with aging. As was mentioned above, if you live in Canada or the Northern US or northern Europe you are not able to use the sun to make vitamin D during the fall, winter or spring months. Obesity can decrease a person’s ability to make enough vitamin D from sunlight.  In obese people, the vitamin D that they make can be sequestered in fat stores and not be available in quantities high enough for their body’s needs. If you take prednisone or have taken it for more than a few months for arthritis or an autoimmune disorder, you may need more vitamin D. If you are in one of these groups you will need to take vitamin D supplements daily.

Can Food Supply It?
Some foods such as soy and certain dairy products are supplemented with vitamin D, but you can’t rely on these foods to get enough. Breast milk may not supply enough vitamin D for infants. 

How About a Blood Test?
Yes, there is a blood test for vitamin D and it is a good idea to get your levels checked.  It is an especially good idea if you are in any of the groups listed under “Pay Attention” above.

Vitamin D is Found in Many Cells
Vitamin D receptors have been found on many cells of the body. These include immune cells (lymphocytes), cells of the brain, heart, pancreas and colon.  These cells are not involved with bone health therefore vitamin D must have other effects in your body.

Symptoms of Vitamin D Deficiency
Vitamin D deficiency can cause muscle aching, a sensation of heaviness in the thighs and legs.   It may cause a feeling of weakness and fatigue in the muscles of the hips and buttocks.  Vitamin D deficiency may cause muscle pain and difficulty with climbing stairs and getting off and on a chair.  Low vitamin D levels may cause diffuse pain in the bones.

Vitamin D May Help to Prevent Type 1 Diabetes
There is a theory that the development of type 1 diabetes in children or teenagers is an autoimmune reaction.  Supplementation with vitamin D might inhibit an autoimmune reaction of the beta cells in the pancreas that can lead to diabetes. 

Multiple Sclerosis and Vitamin D
It is known that multiple sclerosis (MS) has a much higher incidence in men and woman living in northern latitudes. MS is an autoimmune disease with damage to the myelin sheaths that insulate and speed transmission in nerves. There is some evidence that vitamin D in high enough levels may inhibit the autoimmune processes that lead to MS.  In patients that already have MS, taking adequate oral vitamin D is important to decrease or minimize flare-ups of the disease. The exact dosage is not known and it is important to have one’s blood level checked.

Vitamin D and Cancer Prevention
Having low levels of vitamin D may put women at risk for cancer of the breast and colon, and men at risk for cancer of the colon and prostate.  This is evidence that adequate vitamin D may limit growth of these cancers.

Vitamin D and Your Mood
Low levels of vitamin D may contribute to depression, seasonal affective disorder (SAD) or simply a low mood.  The low mood of SAD may be an effect of both low light and low vitamin D levels.   It is especially important to take supplemental levels of vitamin D in the winter as well as to get more exercise and more light exposure.

Dosages
Most of the recommended daily values for vitamin D are based on prevention of bone loss.  Generally, 400 units are recommended per day.  In older adults (>70) 600 units are recommended.  For MS or cancer prevention, doses of 600-1000 units per day are being used.   The dose to have all of the health benefits has not been determined at the time of writing.   The author thinks that one should take at least 400 units in the morning. You may add to this by increasing your morning dose depending on what you are using it for.  Avoid daily doses of 2000 units or more—1000 units per day for adults appears safe.

References