A new understanding of vitamin D

Topics covered in this article:

Once these insightful researchers set aside the old assumptions about vitamin D and began to ask new questions, a new wave of information arose. This information promises to revolutionize the way medicine looks at, and uses, vitamin D. New perspectives include awareness that:

We evolved outdoors, exposed to abundant sunlight, with attendant “high” vitamin D blood levels. For hundreds of thousands of years, humans evolved in open sunlight, producing high levels of vitamin D on a regular basis. For example, scientists calculate that human societies that spend most of their lives outdoors at lower latitudes have naturally high vitamin D blood levels, at, or above, the high end of “normal” for the current, standard laboratory range. These levels are maintained without any toxic effects; in fact, considerable data suggest health-promoting effects of these naturally occurring high vitamin D levels.
The optimal, health-promoting level of vitamin D is much higher than expected. For nearly 100 years it was thought that all humans needed was the tiny amount of vitamin D required to prevent rickets. Now science clearly documents that we need much higher levels of vitamin D for the prevention of a wide range of degenerative diseases. Today the “optimum” blood level of vitamin D is held to be that at the high end of the normal range, with current research suggesting an ideal level of 50–70 ng/mL vitamin D as measured by the 25(OH)D test.In regard to bone health, the current thinking holds the minimum appropriate level of vitamin D to be that level which favorably normalizes parathyroid hormone (a hormone which you want to be in the low normal range to prevent osteoporosis). Research suggests the blood level of vitamin D needed for this is 40 ng/mL or greater. Interestingly, the two well-accepted studies showing osteoporosis fracture prevention with vitamin D and calcium supplementation reported that the mean vitamin D concentration of subjects after supplementation exceeded 40 ng/mL, measured as 25(OH)D.
Humans use and need much more vitamin D than ever imagined. Whether our vitamin D comes from sunlight, food, or supplements, researchers find we use and need substantially more vitamin D than previously thought. Dr. Robert Heaney of Creighton University and colleagues have documented that we use between 3,000 and 4,000 IU of vitamin D daily. Depending on many factors, including one’s sunlight exposure, skin pigmentation, weight, age, and existing vitamin D body stores, maintaining an adequate level of vitamin D can require anywhere from a few hundred to 4,000 or more International Units (IUs) of vitamin D daily. The need for supplemental vitamin D can vary a great deal from individual to individual and blood testing for vitamin D level is the best way to insure appropriate dosing.
Our government’s recommendations for oral vitamin D intake are too low. The renowned osteoporosis researcher, Dr. Robert Heaney, who was a member of the 1997-2002 US Food and Nutrition Board which set the official vitamin D intake guidelines, now reports, however, that his new research suggests these government recommendations were far too low. In an encouraging sign, the Food and Nutrition Board in Nov 2010 did issue new recommendations that doubled or tripled the existing ones. These, however, are still too low. In fact, Dr. Heaney now calculates that our typical diet combined with the current recommended supplemental D intake (which is only 600 IU, rising to 800 IU for 71 years and older) would only provide for a small percentage of an ideal vitamin D blood level. Dr. Heaney himself now classifies the US Food and Nutrition Board recommendations as “falling into a curious zone between irrelevant and inadequate.” For individuals with extensive sunlight exposure, the governmental intake recommendations add little to their daily vitamin D production, and for those without ultraviolet exposure the recommended levels are insufficient to ensure desired 25(OH)D blood levels.
The best way to determine vitamin D need and adequacy and to assure the safety of higher dose supplement use is to measure the blood level of the vitamin D metabolite known as 25(OH)D vitamin D. The only real way to know if you are receiving an adequate and/or safe dose of vitamin D is through a blood test for 25(OH)D. Be sure your physician tests for the more stable form of vitamin D known as 25-hydroxyvitamin D (25[OH]D). The 1,25-dihydroxyvitamin D active form of vitamin D should not be used to test for a vitamin D adequacy. Follow-up vitamin D tests done 2 months after the start of supplementation, or after changing your dose, will help ensure that you are not getting too high or too low a dose of vitamin D. Experts also recommend initially testing your vitamin D level twice a year, at the end of summer and mid-winter. This way your health care guide can help you establish a year round vitamin D supplementation program.
Vitamin D is much safer than previously thought. Being fat soluble, vitamin D can accumulate in the tissues and become toxic. Documented toxicity, however, is rare and often involves either individuals with specific vitamin D hypersensitivity or accidental misuse of the substance. As vitamin D authority, Dr. Reinhold Veith, reports, vitamin D toxicity is always accompanied by serum 25(OH)D levels greater than 88 ng/mL.3 In clinical practice we see that the need for supplemental vitamin D varies from person to person. While vitamin D researchers suggest that most people would obtain an adequate level with 2,000 IU vitamin D per day, some need more, and a few others might need less (see www.grassrootshealth.org). Everyone’s biochemistry is different, so it is wise to have your vitamin D levels tested.
While most of our vitamin D comes from ultraviolet solar radiation, in northern latitudes the winter sunlight is so indirect that the body cannot produce vitamin D from sunlight. In latitudes 40 degrees or more either way from the equator (a northern parallel around Philadelphia or Lisbon), the slant of the sun is such that during winter months we produce very little, if any, vitamin D, even with sunlight exposure. In the winter, those in northern climates depend on vitamin D stores accumulated in the summer and on supplemental vitamin D. If such stores are inadequate because of lack of exposure, northern residents will be deficient — and many are.
Vitamin D deficiency and inadequacy are more common than expected worldwide.By current standards, it is estimated that at least one billion people worldwide have inadequate vitamin D levels. Even using the traditional standards for vitamin D adequacy, nearly half of US African-American women ages 15 to 49 were recently found to be vitamin D deficient. Further, 30% of African-American women who were given more than 2,000 IU of vitamin D from supplements were still found to have low vitamin D levels. In another study, 34% of Canadians surveyed had inadequate vitamin D levels. In a Boston study of elderly people who took vitamin D supplements or drank 2–3 glasses of vitamin D-fortified milk, 80% were overtly or borderline vitamin D-deficient at the end of winter. (For other interesting statistics on vitamin D deficiency worldwide, see my article, “Vitamin D: Its benefits are more than ever imagined.”)
Vitamin D is more than just a bone nutrient. Receptors for vitamin D have been found all over the body, from bone and brain to thymus and uterus. While there is still much to learn, strong evidence suggests that vitamin D is also important as an immune enhancement, anti-cancer, cardio protective, and joint protective agent, as well as being a potent antioxidant. For further information on the protective roles of vitamin D, see the vitamin D section in our 20 key nutrients for bone health article, and the regularly updated vitamin D websites listed at the end of this article.
Types of vitamin D supplements. There are two common forms of vitamin D supplements. One, known as vitamin D3 (cholecalciferol), is a natural form of the vitamin. D3 is most commonly derived from sheep’s wool lanolin and can also be produced from fish oil. The second common form of vitamin D is known as vitamin D2 (ergocalciferol). D2 is a synthetic form of the vitamin. Recent research suggests it is only half as potent as natural vitamin D3. For this reason D3, cholecalciferol, is the preferred supplement form.

Variables influencing vitamin D requirements

Sunlight exposure
Skin pigmentation
Baseline vitamin D level
Intestinal absorption rates
Type of vitamin D supplement (D3 is 3 times more potent than D2)
Age (with increased age, there is a reduced photoconversion of 7-dehydrocholesterol to vitamin D)
Genetic variation in vitamin D receptor activity

The Better Bones Perspective on Vitamin D Supplementation

Ask your doctor to test your blood 25(OH)D level at base line and then after at least four weeks of supplement use, adjust dose accordingly, and retest as necessary.
Do not use D supplements without your doctor’s instructions if you have kidney problems, kidney stones, high blood calcium (hypercalcemia), hyperparathyroidism or the diseases of sarcoidosis, tuberculosis, non-hodgkins lymphoma, oatcell carcinoma or leukemia which can make you hypersensitive to vitamin D.
Supplement with vitamin D3; do not use supplements composed of vitamin D2.

Stay tuned for the “third wave” of vitamin D awareness (2009 and beyond)

The “first wave” of vitamin D awareness gifted humans with a cure for rickets, a major devastating bone disease. The recent “second wave” of awareness has shown vitamin D to be universally important to many body systems and more powerful than we ever expected. The “third wave” of vitamin D awareness we are now entering in early 2009 is generated by a multitude of new scientific studies linking adequate levels of vitamin D to disease resistance and showing that low levels are related to increased disease incidence and mortality. In regards to bone health, my review of the literature suggests that osteoporotic fractures can be reduced by 50 to 60% with the attainment of therapeutic vitamin D levels. (For a link to my published scientific article rethinking the fracture reduction potential of vitamin D, click here.)

For more information, see these vitamin D websites:

Click here to return to page 1.