If You Don't Want Older Bones, Don't Be Low In Vitamin D - How To Make Sure You're Getting Enough of The Sunshine Vitamin
Those with the greatest need of vitamin D typically have the lowest intakes. If you are a woman, you need to pay special attention to your vitamin D status to protect your bones. Using state-of-the-art technology, researchers from the University Medical Center Hamburg in Germany, and the University of California, Berkeley found that vitamin D deficiency was associated with less mineralization on the surface of the bone, as well as structural characteristics of older and more brittle bone.
"Vitamin D deficiency [...] creates a paradox," wrote the researchers, led by Bjorn Busse. "The mineralized tissue ages despite an endocrine state that promotes high turnover and resorption of old bone. Because of the coating of the bone with resorption-resistant osteoid [the un-mineralized, organic portion of the bone matrix], vitamin D deficiency causes aging of the tissue and compromises its structural integrity and resistance to fracture.
"Well-balanced vitamin D levels are essential to maintain bone's structural integrity."
In an accompanying Focus article in the same journal, Lorenz Hofbauer and Christine Hamann from the Dresden Technical University Medical Center in Germany stated that the new study provides a rationale to continue vitamin D supplementation in people with osteoporosis.
"Nearly 90% of elderly persons or patients who are institutionalized or in the hospital for a prolonged time have vitamin D deficiency, many with levels below 10 ng/ml," they wrote.
"Moreover, with aging the efficacy of the skin and kidney to synthesize or activate vitamin D is declining. Thus, vitamin D supplementation has been a well-established baseline therapy for patients with osteoporosis. In practical terms, vitamin D deficiency needs to be corrected before embarking on specific osteoporosis therapy [...] Apart from preventing osteoporosis and bone fractures, vitamin D promotes muscle strength and thus reduces the propensity to fall down."
The Sunshine Vitamin
Vitamin D refers to two biologically inactive precursors - D3, also known as cholecalciferol, and D2, also known as ergocalciferol.
Both D3 and D2 precursors are transformed in the liver and kidneys into 25- hydroxyvitamin D (25(OH)D), the non-active 'storage' form, and 1,25-dihydroxyvitamin D (1,25(OH)2D), the biologically active form that is tightly controlled by the body.
Vitamin D deficiency (<20 ng/mL) can cause a number of health issues, including rickets and other musculoskeletal diseases. Recently, data has also suggested that vitamin D deficiency and vitamin D insufficiency (between 21-29 ng/mL) may be linked to cancer, autoimmune diseases, infectious diseases, type 2 diabetes and cardiovascular disease."
There is unfortunately a large emphasis in current vitamin D research that overstates the benefits of vitamin D supplementation on the conclusions of studies conducted on UV exposure from the sun. Such disparities in reporting have obviously increased the supplement market for this valuable nutrient, however vitamin D from sunlight exposure and supplementation may not be interchangeable in terms of effectiveness.
Busse and his co-workers analyzed bone samples from 30 participants (half of whom were deficient in vitamin D), and used state-of-the-art technology, including synchrotron radiation-based micro computed tomography, to characterize bone quality on the smallest of size scales, from nanometers to micrometers.
While vitamin D deficiency was associated with less mineralization on the surface of the bone, the researchers found that, underneath, bone was actually more heavily mineralized. The data also indicated structural characteristics of older and more brittle bone.
Islands of mineralized bone were found to be surrounded by a collagenous boundary, which prevented them from being properly remodeled. Cut off from a supply of cells which remodel bone (osteoclasts), these islands of mineralized bone begin to age, while overall bone mineralization decreased from a lack of calcium, said the researchers.
"We suggest that local tissue aging is a key cause of increased fracture risk in vitamin Dâ€“deficient osteomalacia [softening of bones caused by flawed bone mineralization], contrary to previous beliefs that the increased osteoid volume was the main contributor associated with weakening of the bones," they wrote.
How Do You Make Sure You're Getting Enough Vitamin D?
Sunlight contains ultraviolet (UV) rays that come in three different lengths: UV-A, UV-B, and UV-C.
UV-B rays are the ones that are capable of producing vitamin D in your body by acting on cholesterol found in your skin.
To make vitamin D, you need UV-B rays to come into direct contact with your skin. UV-B rays cannot penetrate glass, so you don't make any vitamin D while you're sitting in a car or by a window at work or at home.
But creating enough vitamin D in your body isn't as simple as getting a certain number of minutes of sunlight exposure every day because the number and intensity of UV-B rays that reach your skin and lead to vitamin D production is affected by a number of different factors, the main ones being:
Your Skin Color
Lighter skin color allows deeper penetration by UV-B rays, which decreases the amount of sunlight exposure needed for adequate vitamin D production. If you have darker skin, it's harder for UV-B rays to penetrate your skin and create vitamin D, which means that you need greater exposure to sunlight than someone with lighter skin.
If you live above 35 degrees latitude north or below 35 degrees latitude south, you receive little to no UV-B rays from some point in autumn to some point in spring. During this time, your body has to rely on the vitamin D that it has created during warmer months, or on intake of vitamin D through food and supplements.
Altitude and Latitude
The further north or south you live from the equator, the less exposure you have to UV-B rays.
The higher you live above sea level, the greater exposure you have to UV-B rays.
Pollution and Clouds
Both decrease the number of UV-B rays that reach you.
With each passing year, natural degenerative changes that occur in your skin make it harder for UV-B rays to convert cholesterol in your skin into vitamin D. It's a known fact that elderly people need to rely more on food sources than sunlight for their vitamin D. At 70 years of age, the average person has approximately 30% of the capacity to generate vitamin D from sunlight that a 20-year old has.
How Much Vitamin D Do You Need for Your Best Health?
Based on all of the most recent research that I have reviewed on this matter, I feel that an optimal range is somewhere between 50 and 60 ng/ml (125 to 150 nmol/l). To convert ng/ml to nmol/l, simply multiply by 2.5.
Unfortunately, the only way to know where you're at is to ask your doctor to include 25 (OH) D, also known as 25-hydroxy D, with your blood work during your next checkup. Some labs test for 1,25 hydroxy D, which isn't as accurate a marker of your vitamin D status as 25 hydroxy D, so be sure to specifically ask for 25 hydroxy D.
You want your 25 hydroxy D level to be at least 30 ng/ml (75 nmol/l), but again, based on the research that I have reviewed, mainly that of Dr. Michael Holick, the optimal range appears to be 50 to 60 ng/ml. Some prominent physicians and vitamin D experts feel that one can go even higher, even up to 80 ng/ml. But my suggestion is to err on the side of caution and aim to be in the 50 to 60 range.
The 50 to 60 range is based on numerous studies that show strong relationships between these levels and reduced risk of a wide variety of chronic diseases and increased lifespan. This range is also based on the 25 hydroxy D levels of healthy people living in areas of the world (tropical and subtropical regions) where it's quite common to receive more than enough sunlight exposure to ensure regular vitamin D production.
But here's an important point that you want to keep in mind: When sunlight creates vitamin D in a healthy person and that person's 25 hydroxy D is in the optimal range, that person is almost certainly benefiting from other natural compounds that are generated with sunlight exposure. Dr. Holick calls these other compounds "photo products," and he and his team are currently researching the makeup and benefits of these photo products.
Put another way, establishing optimal vitamin D status mainly via healthy sunlight exposure may provide more health benefits than establishing optimal vitamin D status mainly via foods and supplements. Correct usage of foods and supplements only gives you the right amount of vitamin D - they don't generate the photo products that sunlight does. As more information about these photo products becomes available, I'll be sure to provide an update.
At the same time, it's worth remembering that even responsible exposure to sunlight comes with some undesirable effects, like premature aging of skin and possibly increased risk of non-melanoma skin cancers, depending on your history of sunlight exposure.
Testing Vitamin D
An increase in testing may result from recent scientific reports that a growing percentage of the global population has low vitamin D status, in combination with fresh research to link insufficient vitamin D with higher risks of certain diseases such as diabetes, heart disease, multiple sclerosis, osteoporosis and certain cancers. New tests tend to overestimate vitamin D deficiency.
There are a number of different companies that have approval to perform vitamin D testing, but the gold standard is DiaSorin. Their radioimmunoassay (RIA) method for measuring total vitamin D levels has become the gold standard, not because it’s more accurate than the others, but because it’s the one used in almost every major vitamin D study, on which the recommended blood levels for clinical efficacy are based.
Therefore, in order for any other testing method to offer clinically relevant results, the test values must agree with DiaSorin RIA results, since those were used to establish the recommended levels.
Vitamin D status is measured by looking at blood levels of 25-hydroxyvitamin D3. There are three common methods used for measuring vitamin D3:
1. LC-MS/MS -- This test measures 25-hydroxyvitamin D2 and D3 separately
2. RIA (DiaSorin) -- Developed in 1985, it accurately measures total 25-hydroxyvitamin D (It does not separate D2 and D3)
3. Liaison (DiaSorin) -- a more recently developed automated immunoassay by DiaSorin that has largely replaced the RIA
The LC-MS/MS (liquid chromotatography-mass spectrometry) method is the preferred method for many labs, including the Mayo Clinic, Quest Labs, Esoterix, ZRT, and others, while Liaison is favored by other testing labs like LabCorp.
Since the DiaSorin assay (RIA) was used in the major clinical studies that led to the recommended vitamin D levels, any lab using the LC-MS/MS method need to make sure their test correlate with the RIA test values in order to accurately determine your vitamin D status.
Mae Chan holds degrees in both physiology and nutritional sciences. She is also blogger and and technology enthusiast with a passion for disseminating information about health.