What is Vitamin D?
Vitamin D is not a vitamin. Instead, this supplement is a group of fat-soluble prohormones that are precursors to hormones usually with little hormonal activity without Vitamin D. Two major forms of vitamin D important to humans are vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Vitamin D2 is made naturally by plants. Vitamin D3 is made naturally by the body when the skin is exposed to ultraviolet radiation in sunlight. Vitamin D2 and vitamin D3 can also be manufactured and taken as supplements. Vitamin D3 is the preferred form of the supplement.
What is the relationship between Vitamin D and health?
Low Vitamin D levels are associated with fatigued muscles, compromised immune function, chronic inflammatory conditions, poor calcium absorption, and inadequate blood levels of minerals such as calcium and phosphate. Research indicates that Vitamin D deficiencies are linked to health challenges such as high blood pressure and cardiovascular disease, diabetes, osteoporosis, autoimmune diseases, infectious diseases, and certain types of cancer.
Studies indicate that most people have insufficient levels of Vitamin D. This is a widespread health problem and a correctable one.
Since every tissue in the body has receptors for Vitamin D, including the brain, heart, muscles, and immune system, proper levels of this nutrient are necessary for healthy functioning. The following highlights include only some of the many health benefits of Vitamin D.
- Regulates genes
- Improves muscle strength
- Improves the immune system
- Reduces inflammation
- Promotes the intestinal absorption and metabolism of calcium and phosphorus
- Regulates reabsorption of calcium in the kidneys
- Helps maintain adequate blood levels of calcium and phosphate needed for bone formation, mineralization, growth, and repair, including governing the transport of calcium into bone
- Regulates thyroid and parathyroid function
What are some specific health benefits of Vitamin D in cancer patients?
- Supports anticancer activity
- Induces cell differentiation
- Inhibits cancer cell cycle
- Promotes programmed cancer cell death through apoptosis
- Inhibits invasion, angiogenesis, and metastasis in cancer animal models
- Plays a role in blood sugar regulation and insulin sensitivity2
Other studies suggest that Vitamin D supports cancer prevention.
What is the appropriate Vitamin D dose and target range?
Vitamin D supplementation levels should be customized based on blood tests and recommendations from a qualified provider. Different providers may suggest different doses and target ranges. Many integrative cancer care practitioners or providers recommend a target range of 70-100 ng/ml achieved with 2,000-10,000 IU depending upon each person’s Vitamin D deficiency levels. The same amount applies to those with heart disease, and for others the serum levels should be between 50-70 ng/ml.
Vitamin D3 (the preferred form of the supplement) should be taken with fat if possible since Vitamin D is fat-soluble. Levels should definitely be checked in the winter and summer since Vitamin D may vary due to light exposure. Since Vitamin D is a hormone and fluctuates for everyone differently, you may also consider having it checked more frequently such as every 3 months.
What are some natural sources of Vitamin D and supplied levels?
Although some foods provide some Vitamin D, it is generally not possible to consume adequate amounts of Vitamin D through foods.
- Cod liver oil—1,460 IU in a tablespoon
- Salmon—360 IU in 100 grams
- Mackerel—345 IU in 100 grams
- Sardines—270 IU in 100 grams3
Sunlight provides Vitamin D, but most people cannot receive adequate levels of Vitamin D through natural light exposure. Many factors also influence the rate of Vitamin D formation in the skin creating variability with sunlight recommendations for each person. Some research indicates that twenty to thirty minutes of midday sunlight exposure provides 8,000 to 10,000 IU of Vitamin D. People with dark skin may need 5 to 10 times more sunlight compared to light-skinned people for Vitamin D production.
What is the difference between blood 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D?
Vitamin D obtained from sun exposure, food, and supplements is biologically inert and must undergo two hydroxylations in the body for activation. The first occurs in the liver and converts vitamin D to 25-hydroxyvitamin D (calcidiol). The second occurs primarily in the kidney and forms the physiologically active 1,25-dihydroxyvitamin D (calcitriol).
Some people take Vitamin D supplementation and their 25-hydrovitamin D does not increase. If this occurs, 1,25-dihydroxyvitamin D must be measured, and if elevated, Vitamin D supplementation is not advisable.
For More Information
- Life Over Cancer by Keith Block, MD
- Anticancer by David Servan-Schreiber MD, PhD
- The Definitive Guide to Cancer, 3rd Edition: An Integrative Approach to Prevention, Treatment, and Healing by Lise Alschuler, ND and Karolyn A. Gazella