Like the sun, Vitamin D is hot right now. Recent studies reveal it is more than just a factor in calcium absorption, but a nutritional powerhouse with wide-ranging health benefits, way beyond our bones.

We know Vitamin D controls more than 200 genes (directly or indirectly), and has an impact in reducing many chronic illnesses. Cardiovascular disease, infectious disease, autoimmune disease, common cancers, glucose imbalance, inflammation, poor muscle performance, mental illness and more are influenced by its activity.

It seems high circulating serum levels of Vitamin D, measured as 25-hydroxyvitamin D (25-OHD), are associated with a decreased risk of deadly cancers and other diseases. Those living at higher latitudes where Vitamin D exposure is lower, are at increased risk for many of these diseases–Hodgkin’s lymphoma, cancers of the colon, pancreas, prostate, ovarian and breast, type 1 diabetes, multiple sclerosis, Crohn’s disease, rheumatoid arthritis and osteoarthritis, hypertension and cardiovascular disease.

In addition to latitude, various factors inhibit the absorption or manufacture of Vitamin D and contribute to its deficiency. Sunscreen use, high melanin skin pigmentation, advanced age, clothing, glass, season, altitude, cloud cover, time of day, obesity, hyperthyroidism, liver and kidney diseases, malabsorption syndromes, smoking status, and certain medications all can impede Vitamin D reaching its destination organ or tissue. Many Americans are chronically deficient, so it is wise to test patient levels.

Currently, there is no consensus on normal serum levels of 25-OHD. But most experts agree levels below 20 nanograms per ml (ng/ml) indicate deficiency, and 40 to 80 ng/ml are optimal. Recent epidemiological data show levels above 50 ng/ml reduce breast cancer risk.

Optimum levels of Vitamin D have wide-ranging benefits. Deficiencies are very common, putting patients at risk for many chronic diseases and poor bone health. Patients can be checked via a serum 25-hydroxyvitamin D and, if levels are sub-optimal, exposed to sensible sunlight or supplemented up to 10,000 iu a day with little risk of toxicity. Certain medical conditions will require more careful monitoring to avoid serum calcium and phosphorus excesses.


  • Available from three sources — the sun, nutritional supplements and food.
  • Comes in two forms—D2/ from plants and fungi, and D3/ cholecalciferol from animals. Being animals ourselves, D3/ cholecalciferol, is the preferred and more absorbable form.
  • Few foods provide sufficient quantities to meet our daily D needs (unless you enjoy blubber).
    In late fall to early spring, no vitamin D3 is made in New Jersey, or at latitudes north of 37 degrees. It is important to monitor levels at this time, and supplement as needed.
  • In summer, exposure of 10-30 minutes of sun, without sunscreen, between 10 AM & 3 PM on arms and legs (daily to twice weekly) provides adequate D3 in caucasians. Those with darker skin need 3 to 10 times longer exposure.
  • 10,000 iu a day is seen as the safe upper limit of vitamin D3/ cholecalciferol by many researchers, with 4,000 to 5,000 iu a day (or more) suggested to bring levels up to optimum.



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Lips P, Vitamin D physiology, Prog Biophys Mol Biol, 92(1), 4-8, Sep 2006.

Prieto-Alhambra D, et al, Vitamin D threshold to prevent aromatase inhibitor-induced arthralgia: a prospective cohort study, Breast Cancer Res Treat, 1075-9, 28 Jul 2010.

Ross AC, et al, Dietary Reference Intakes for Calcium and Vitamin D, report brief, Institute of Medicine, 1-4, Nov 2010.

Sardi B, A Return To The Dark Ages, Knowledge of Health, Inc, 1-7, Vitamin D Council website, 30 Nov 2010.

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