Measuring Your Vitamin D Levels: Your Most Important
By John Cannell, MD and Alex Vasquez, D.C., N.D.
Our children need help. Many of them are suffering from unrecognized and untreated vitamin D deficiency. A recent June 2004 study from Harvard
found 24 percent of healthy adolescents had vitamin D levels less than 15 ng/ml and 42 percent had levels less
than 20 ng/ml.
Many adults need help, too. Several studies have documented that vitamin D deficiency among adults is an
epidemic, not only on a national level, but also worldwide.
However, the problem is much worse than that because a wide variety of diseases and unhealthy conditions are
associated with vitamin D levels less than about 40 ng/ml--more than 70 percent of adolescents in the above study
had 25(OH)D levels less than 40 ng/ml. Remember that 25(OH)D blood levels are technically difficult to perform and
significant variation occurs from lab to lab and from the past literature to present literature. However, as
Reinhold Vieth has pointed out, one must proceed with the literature, and the variation, as that is all that is
So how do we know what our vitamin D blood levels
(25(OH)D) should be?
1.The most commonly used rationale for optimum vitamin D levels is the level that maximally suppresses parathormone
(PTH) levels. PTH is the emergency hormone the body uses to maintain calcium blood levels and high levels are
associated with a number of chronic illnesses, not just osteoporosis. Therefore, the thought is the lower your PTH the
better. A study shows 25(OH)D was highly inversely correlated with PTH and at concentrations of 25(OH)D below 36
ng/ml (90 nmol/l), an increase in PTH was observed. The data from elderly adults indicates even higher 25(OH)D
levels are needed as suppression of PTH does not plateau until 25(OH)D is 44 ng/ml.
2.When vitamin D levels fall below 35 ng/ml, calcium absorption in the intestine falls with it. That is, calcium
absorption is maximized by keeping vitamin D levels above 35 ng/ml.
3.Deaths from cardiovascular disease are more common in the
winter, more common at higher latitudes and more common at lower altitudes, observations that
are all consistent with vitamin D deficiency contributing heart disease. People with 25(OH)D levels above 35 ng/ml
were half as likely to have a heart attack than those whose level was less than 35 ng/ml.
4.One-hour glucose and area under the glucose curve during a standard 75-g oral glucose tolerance test are
inversely associated with the serum concentration of 25(OH)D. Extrapolation of recent graphic data for healthy
young adults showed that improvements in 60-minute, 90-minute and 120-minute postprandial glucose levels and
insulin sensitivity appeared to plateau when subjects reached vitamin D levels above 35 ng/ml.
5.Framingham data showed osteoarthritis of the knee progressed more rapidly in those with vitamin D levels lower
than 36 ng/ml (90 nmol/L). Another study found that osteoarthritis of the hip progressed more rapidly in those with
vitamin D levels lower than 30 ng/ml (75 nmol/L).
6.In an eight-year prospective study of 25,000 subjects, colon cancer was reduced by 80 percent in those with
vitamin D levels above 33 ng/ml.
7.Hollis and Wagner have reported that lactating women need 4,000 IU of vitamin D3 a day to maintain both their and their infants
vitamin D levels. Such supplementation is associated with vitamin D levels of about 40 ng/ml. (Hollis and Wagner
have answered an old and puzzling question, "Why is almost all human breast milk deficient in vitamin D?"
Answer: "Because almost all the mothers are deficient in vitamin D.")
8.A study published in July 2004 showed that people over the age of 50 with higher vitamin D levels have less
evidence of periodontal disease. There is a significant inverse relationship between periodontal disease and
vitamin D levels. Those with levels greater than 34 ng/ml had the least risk.
The Optimal Level for Vitamin
Perhaps the most compelling reason to keep our vitamin D levels above 40 ng/ml is a naturalistic one. Humans have
spent about 2 million years on the earth, almost all that time we were naked in equatorial Africa. Vitamin D levels
of American lifeguards (almost naked in the sun) and humans living in high agricultural societies near the equator
(Brazil) both have vitamin D levels in excess of 40 ng/ml.
Therefore, the normal human vitamin D level is above 40 ng/ml and any argument to accept lower levels would have
to be based on compelling new research. So far, nothing--not one article in the literature--gives any reason to
accept anything less than 40 ng/ml in children and adults.
There is a wide variety of evidence that tells us we should keep our vitamin D level above 40 ng/ml. Based on
our extensive review of the research, which will soon be published in Alternative Therapies in Health and Medicine,
we have proposed that optimal vitamin D levels are between 40-65 ng/mL--these levels are high enough to reduce the
risk for disease, yet are low enough to avoid complications and adverse effects. (Dr. Mercola believes the range should be 40-55 to avoid toxicity risk).
Treatment and testing needs to be supervised by a doctor, and 25(OH)D needs to be performed along with
measurement of serum calcium to ensure that treatment is safe and effective.
Our conclusion in our review article is that, "Until proven otherwise, the balance of the research clearly
indicates that oral supplementation in the range of 1,000 IU per day for infants, 2,000 IU per day for children and
4,000 IU per day for adults is safe and reasonable to meet physiologic requirements, to promote optimal health, and
to reduce the risk of many serious diseases."
Dr. Mercola has shown with his clinical experience that microemulsified vitamin D in the product "Bio-D-Mulsion"
(400 IU per drop) has been the most effective form of supplementation for optimizing blood levels of vitamin D. The
new "Bio-D-Forte" will provide 2,000 IU of vitamin D per microemulsified drop for more convenient dosing in
children and adults.
Measuring your vitamin D levels with 25(OH)D may be the single most important blood test you, and your children, can have. Vitamin D
supplementation (or prudent sun exposure) is crucial for significantly reducing the risk for many illness
•17 varieties of cancer
•Type 1 and type 2 diabetes mellitus
•Other autoimmune diseases
Testing for and treating vitamin D deficiency must be considered a crucial component of health promotion and
preventive health care.