By Kelly Kwiatkowski
It is well-known that vitamin D is essential in maintaining healthy bones.
However, research over the past 10 years has shown that vitamin D is essential for overall health and disease prevention. In fact, several studies have linked vitamin D deficiency to a variety of chronic diseases.
Vitamin D is a fat-soluble prohormone that helps regulate calcium absorption and bone metabolism. Evidence from cell-culture and animal studies shows that vitamin D also plays a role in regulating cell metabolism, insulin production, the immune system and inflammation –
factors that contribute to a host of chronic diseases, including cancer, diabetes, high blood pressure, cardiovascular disease and many autoimmune disorders such as MS and inflammatory bowel disease.
Sources of Vitamin D
About 90 percent to 100 percent of vitamin D intake comes from the sun and the rest comes from natural and fortified dietary sources like oily fish, vitamin D-fortified foods such as milk and orange juice, and vitamin supplements.
Conditions associated with
suboptimal vitamin D status |
Autoimmune
- Multiple Sclerosis
- Systematic Lupus Erythematosus
- Crohn’s Disease
- Rheumatoid Arthritis
Cardiovascular
- Hypertension
- Cardiovascular Disease
Dermatologic
Endocrine
Gastrointestinal
Musculoskeletal
- Osteoporosis
- Osteoarthritis
- Osteopenia
- Osteomalacia
- Rickets
- Fractures
- Fibromyalgia
Neurologic
- Parkinson’s Disease
- Schizophrenia
- Seasonal Affective Disorder
Oncologic
- Colon cancer
- Breast cancer
- Ovarian Cancer
- Prostate Cancer
- Cervical Cancer
- Bladder Cancer
- Endometrial Cancer
|
Vitamin D Deficiency
Despite a generally available source (sunlight), researchers argue that vitamin D deficiency remains prevalent. Factors contributing to vitamin D deficiency include: 1) the modest amount of vitamin D in fortified foods; 2) the reduction in milk consumption; 3) socioeconomic differences in milk and fortified cereal consumption; and 4) the avoidance of sun exposure due to the great concern about skin cancer as well as skin damage.
Classic vitamin D deficiency results in rickets (in infants) and osteomalacia (in adults). These are painful bone diseases that can lead to growth deficiencies and fractures. Thus, dietary sources of vitamin D are especially important for individuals more at risk for vitamin D deficiency. Individuals with darkly pigmented skin, those who are obese, elderly people, infants who are exclusively breastfed, people who get little or no sun exposure, and individuals with fat malabsorption conditions (e.g., celiac disease) are at higher risk for vitamin D deficiency.
Dietary reference intakes for vitamin D are based solely on the dietary intake that is adequate to prevent bone disease (i.e., rickets or osteomalacia), but there is overwhelming evidence that vitamin D is essential in maintaining overall cellular health and plays a role in other diseases. Based on this research, some researchers are calling for a revision of the recommended intakes for vitamin D. Experts propose that the recommended daily allowance of vitamin D be increased to 1,000 IUs per day during times when sun exposure is insufficient. Note that the 2005 U.S. Dietary Guidelines for Americans now recommends an increased intake of vitamin D of 1,000 IU for at-risk populations – older adults, people with dark skin and people exposed to insufficient UVB light. This is not yet reflected in the current dietary reference intakes for vitamin D.
Food Sources of Vitamin D |
Source |
Amount Obtained |
Fish; fatty, cold-ocean |
100-500 IU/serving |
Milk |
400 IU/quart |
Orange Juice |
400 IU/quart |
Bread |
In process of being determined |
Solar UVB |
0 IU (winter in north) to 10,000 IU per day |
Artificial UVB |
10 minute tanning session yields 2,000-4,000 IU |
Supplements |
200-1,000 IU per pill |
Table adapted from Grant WB & Holick MF. Benefits and requirements of vitamin D for optimal health: a review. Altern Med Rev, 2005;10(2):94-111. |
Vitamin D From the Sun
For most people, 10-20 minutes of sunshine can yield approximately 10,000 to 20,000 IUs of vitamin D each day, depending on the time of year and your geographical location. At high latitudes, sun exposure isn’t enough to produce vitamin D between the months of October and April. The amount of vitamin D from the sun can vary greatly depending on other factors, including time of day, pollution, cloud cover, sunscreen, skin color, age and weight. Here are some of the statistics:
- Sunscreens as low as SPF 18 decrease vitamin D synthesis by 97.5 percent.
- During winter, sunlight provides no vitamin D to the skin at latitudes above 35 degrees.
- Older adults have approximately 25 percent of the capacity to produce vitamin D compared with young, healthy adults.
- African-Americans require 5-10 times longer sun exposure than Caucasians to produce similar amounts of vitamin D in the skin.
Safe sun exposure is important when considering vitamin D for health. The Food and Nutrition Board recognizes the importance of sun exposure to achieve vitamin D requirements, and says that between 10-15 minutes of sun exposure (without sunscreen) per week is adequate for most individuals. It also recommends that individuals use a sunscreen with an SPF of at least 15 for any exposure beyond that time.
Other Considerations
If your patients express a concern about getting enough vitamin D, here are a few considerations to share when addressing their vitamin D requirements:
- Vitamin D3 (cholacalciferol) is the preferred form of vitamin D for therapeutic and nutritional uses, as it generates a 70 percent higher serum vitamin D level compared to the same amount of vitamin D2 (ergocalciferol) in humans.
- Vitamin D toxicity can cause serious health problems so it’s important for your patients to discuss vitamin D status and intake with you, their doctor.
- Although vitamin D toxicity from sun exposure has never been reported, excessive sun exposure causes skin cancer, so you should limit your sun exposure and wear protective clothing and sunscreen to avoid overexposure.
Kelly Kwiatkowski has worked as a communications professional and project manager in the academic and corporate health care research sectors for the past seven years. She is currently a scientific writer for a whole foods supplement company in Palmyra, Wis. |