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  • Writer's pictureDavid S Klein, MD

Reducing Cancer Risk with Vitamin D-3, Cholecalciferol

Updated: Sep 24, 2023

Why Vitamin D??? Well, for starters, Vitamin D-3 is not a vitamin at all.  Vitamin D is a family of steroidal hormones that the body needs to maintain an ever increasingly appreciated number of bodily functions. Vitamin D occurs in 3 morphologies- Vitamin D1, Vitamin D2 and Vitamin D3. 

Vitamin D-2 is made in the gut from the precursor, Vitamin D-1 (which is essentially inactive.) Vitamin D-3 is the active hormone, and requires sunlight to convert from Vitamin D-2.

As a moiety derived from cholesterol, low levels may be related to the use of cholesterol lowering medications, such as the statin family, and Vitamin D-3 is structurally similar to estrogen, testosterone and other adrenal hormones. 


Vitamin D-3, in doses of at least 2,000 IU/day will decrease the risk of breast cancer by 50%; reduce the risk of prostate cancer by 50%.  Getting therapeutic levels, as demonstrated by quantitative blood work, the typical dosage for adults is closer to 5000 IU per day.

  1. Pharmaceutical-grade Vitamin D-3 costs about $6 per month.

  2. It should be taken in the morning with a fish-oil capsule, to enhance absorption.

  3. It is absorbed best if pre-suspended or dissolved in olive oil.

  4. Higher doses are indicated in the presence of rheumatoid arthritis, M.S., and other auto-immune disease processes.


Vitamin D-3 (cholecalciferol) is being shown to help prevent multiple sclerosis, osteoporosis and even prostate cancer. (See Daily Health News, March 29, 2004 and July 26, 2005.) Now it turns out that it may do even more — vitamin D and calcium may help prevent premenstrual syndrome (PMS). In the Nurses’ Health Study II (a large study of nurses that has been ongoing since 1989), women who consumed higher levels of these two nutrients faced a lower risk of premenstrual symptoms such as fatigue, irritability, mood swings and stomach cramps.

Doses of Vitamin D-3 (2,000 IU) have been shown to reduce the risk of breast, prostate, colon and pancreatic cancer by as much as 50%.


Recent studies have shown that vitamin D deficiency is very, very common, indeed.  It may be a co-morbid factor in the development of chronic pain as well as contributory to the development of a host of auto-immune disease.


Who needs additional amounts of vitamin D?

  • Anyone with inadequate caloric or nutritional dietary intake or  increased nutritional requirements.

  • Older people (over 55 years), especially women after menopause. Pregnant or breast feeding women.

  • Those who abuse alcohol or drugs.

  • People who have recently undergone surgery.

  • People with recent severe burns or injuries.

The single best way to find out if you need supplemental Vitamin D-3 is to get a blood test through your doctor.

D (cholecalciferol/ergocalciferol)

Vitamin D-3 is the principal regulator of calcium homeostasis in the body.

  • Vitamin D-1 and Vitamin D-2 are the inactive precursors to the active Vitamin D-3.

  • It is essential for skeletal development and bone mineralization.

  • Vitamin D-3 is a selective estrogen blocker, which may be the action that results in protection from certain cancers.

  • Vitamin D is a pro-hormone with no hormone activity. It is converted to Vitamin D-3, if you have adequate Vitamin D-2 in your blood stream, and then you lay out in the sun. Vitamin D-3 is the form that has biological activity.

  • The active form of the vitamin is 1-25-dihydroxyvitamin D, usually referred to vitamin D-3. It is synthesized in the skin from 7-dehydrocholesterol via phytochemical reactions requiring UV light (sunlight).

  • Inadequate exposure to sunlight contributes to vitamin D deficiency. Adequate sun exposure, however, results in increase skin wrinkling and skin cancer.

  • Increasing evidence suggests that vitamin D may also contribute to antioxidant function by inhibiting lipid peroxidation.

  • The mechanism of the antioxidant effect is unknown.

Vitamin D-3 deficiency in adults can lead to osteoporosis, which results from an imbalance between bone resorption and bone formation. Decreased vitamin D levels result in decreased production of the active vitamin form, vitamin D3. Vitamin D enhances the efficiency of calcium absorption. Chronic vitamin D deficiency results in a decreased calcium absorption and secondary hyper-parathyriodism.

Vitamin D-3 has also been found to have anti-carcinogenic activity, including apoptosis in many types of cancer cells. It has also been useful in the treatment of psoriasis when applied topically. Vitamin D appears to demonstrate both immune-enhancing and immunosuppressive effects.

Supplemental vitamin D-3 is available, inexpensive, and avoids the ill-effects of daily sun exposure. For more information, click on the image, below:

David S. Klein, MD, FACA, FACPM

Stages of Life Medical Institute

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