Consequences of vitamin D deficiency include:

• Generalized bone pain or isolated bone pain (Osteomalacia)
• Muscle aches
• Weakened immune system
• Depression
  
• Osteoporosis
• Breast, ovarian, prostate, and colon cancer
• Leukemia in children
• Kidney disease or kidney stones
• High blood pressure
• Cardiovascular disease
• Autoimmune disease prevention (type I diabetes, MS)
• Weakened liver function

Research shows that activated Vitamin D inhibits cancer cell growth, so get your 2-3 hours of sun per week, or take your vitamin D!

Vitamin D is critically important for many functions in the body. Most people are aware of its necessity for healthy bones; it promotes proper calcium absorption in the gut, and maintains correct levels of calcium and phosphate in the blood for bone mineralization. It is also required for bone growth and remodeling, which is why a severe deficiency can cause rickets in children (and is still reported in the U.S. today.) What many people don’t know is that it also has important health implications in other body systems, such as nerve and muscle function, immune system function, and reducing inflammation in the body. ^1,2 Taking into consideration a rather widespread deficiency of adequate vitamin D, even in relatively affluent countries, an astonishing recent meta-analysis report showed a collective reduction in all cause mortality by 7% based upon 9 trials with supplementation of vitamin D in amounts varying from 300-2,000 I.U. per day.³

So how do we get vitamin D? Our main source is from exposure to UV light, which causes vitamin D to be synthesized in the skin. The form that we initially get from sun exposure and oral consumption of vitamin D is inert and must be converted twice in the body before it becomes its most active form: first in liver, then primarily in the kidneys. Vitamin D is not found naturally in many foods, but it is routinely fortified into products such as milk and other dairy products. Unfortunately, this is usually not enough to guarantee that requirements are being met for children or adults.

 In temperate climates, the winter months pose a particular challenge for getting an adequate supply of vitamin D. Reduced exposure to sunlight because of cold weather, as well as weaker UV penetration through the atmosphere during those months makes it difficult to get enough UV stimulation of the skin. Even in the warmer months, wearing sunblock, having darker skin tones, and spending more time indoors can greatly limit UV exposure. Furthermore, cloud cover and pollution reduce the ability of UV rays to penetrate the earth’s atmosphere.

Many cells in the human body, especially in the immune system, have receptors for vitamin D in their membranes. There is interesting research that vitamin D plays a role in defending our bodies from infection, by increasing the aptitude of certain immune cells called macrophages to attack invaded cells.⁴ Other research studies note that humans are most susceptible to respiratory diseases when exposed to a particular viral strain in winter months, as opposed to summer months. We already know that cold viruses and influenza infections peak in winter and early spring months in temperate climates, but tropical climates also have their seasonal peaks of viral respiratory infections⁵- they occur in the rainy seasons when UV light is partially blocked and people spend more time indoors.

Of even greater concern, we now know that vitamin D deficiency increases the risk of serious chronic disease, including: many common cancers, multiple sclerosis, rheumatoid arthritis, hypertension, cardiovascular heart disease, and type I diabetes.^6,7

Populations at increased risk of vitamin D deficiency:

1. Infants who are exclusively breastfed. In 2008, the American Academy of Pediatrics (AAP) issued a statement to recommend double the amount of vitamin D previously recommended for infants and adolescents, currently 400 IU. Most baby nutritional formulas and milk products are fortified to provide 400 IU per liter. So, children consuming less than this amount per day are recommended to supplement the difference, up to the limit of 400 IU.

2. The elderly and invalid. This population often gets less sunlight exposure, and their skin is less able to convert vitamin D.

3. People with digestive limitations. People who have conditions which limit their absorption of nutrients in general, and fats in particular, are at risk of becoming deficient. (vitamin D is a fat soluble vitamin.) This includes those with intestinal surgical interventions such as small bowel resection, those with inflammatory or autoimmune intestinal disorders such as Crohn disease or celiac, or pancreatic insufficiency.

4. Obese individuals. Since vitamin D is fat soluble, increased body fat may cause too much vitamin D to be stored in fat cells, and not enough to be available for general use.

5. Individuals using certain medications. Corticosteroids like prednisone inhibit calcium absorption and interfere with vitamin D metabolism, which is why people using these anti-inflammatory medications have an increased risk of developing osteoporosis. Weight loss drugs which inhibit fat and cholesterol absorption, and drugs used to control epileptic seizures such as phenobarbital and phenytoin can also interfere with vitamin D availability and metabolism.

General nutrition guidelines, IU’s per day**:

Infants, children, adolescents: 400 IU

Adults under age 50: 400-600 IU

Adults over age 50: 800- 1000 IU

 **these recommendations are modest increases over the current Adequate Intakes (A.I.). These are levels developed by the Food and Nutrition Board (FNB) at the Institute of Medicine of The National Academies (formerly National Academy of Sciences). “Adequate Intake (AI) is established when evidence is insufficient to develop an RDA and is set at a level assumed to ensure nutritional adequacy.”

 People who test low in serum vitamin D may be instructed by their physicians to take much higher doses until the deficiency is corrected.

Testing: Lab diagnosis to determine blood levels of 25(OH)D is generally the best reflection of vitamin D status. It will measure total vitamin D, including what is produced in the skin, as well as what is obtained from food and supplements.

Symptoms of deficiency can be subtle, but may include muscle pain and weakness.

How to get adequate vitamin D:

 1. Sun exposure. Suggestions vary, but one way is to try to get anywhere from 5-15 minutes of sun exposure to face, arms, legs and/or back between the hours of 10am and 3pm several times per week. (without sunblock.) Unfortunately, if you live at a latitude above 42 degrees north latitude (which is a line drawn approximately between the northern border of California to Boston), sunlight exposure will not be sufficient for producing vitamin D between the months of November and February.⁸ As an important side note, the benefits of exposure to sunlight without protection need to be balanced with the increased risk of skin cancer.

 2. Food.  The following table outlines food choices with the corresponding amounts of vitamin D. Cod liver oil is a particularly rich source of natural vitamin D, as well as fat soluble vitamin A.

Selected Food Sources of Vitamin D⁹

  3. Supplements: vitamin D supplements come in two forms: D₂ (ergocalciferol), and D₃ (cholecalciferol). Both forms have been shown to effectively prevent rickets, but they are each metabolized in different ways in the body. D₃ could be more than 3 times as effective as D₂ at raising serum 25(OH)D concentrations, and at maintaining those levels for longer times.

Symptoms of toxicity: headaches, weakness, nausea and vomiting, constipation, increased thirst, increased urination, and diarrhea. Vitamin D toxicity can lead to bone loss, kidney stones, and calcifications in various organs.

Toxic interactions: People taking digoxin/ digitalis need to use caution and check with their doctor before considering supplementation of vitamin D, as this combination can cause hypercalcemia.

1. Holick, M. “Vitamin D: important for prevention of osteoporosis, cardiovascular heart disease, type 1 diabetes, autoimmune diseases, and some cancers.” South Med J. 2005 Oct;98(10):1024-7.

2. Holick,M., Chen, T. “Vitamin D deficiency: a worldwide problem with health consequences.” Am J Clin Nutr. 2008 Apr;87(4):1080S-6S.

3. Holick, M. Sunlight and vitamin D for bone health and prevention of autoimmune diseases, cancers, and cardiovascular disease. Am J Clin Nutr. 2004 Dec;80(6 Suppl):1678S-88S.

4. Cannell, J., Vieth, R., Umhau J., et al. “Epidemic influenza and vitamin D.”Epidemiol Infect. 2007 Oct;135(7):1095-6; author reply 1097-8.

5. Shek, L., Lee, B. “Epidemiology and seasonality of respiratory tract virus infections in the tropics.” Paediatr Respir Rev. 2003 Jun;4(2):105-11.

6. Zitterman, A. Vitamin D in preventive medicine: are we ignoring the evidence? Br J Nutr. 2003 May;89(5):552-72.

7. Zitterman, A. Vitamin D and disease prevention with special reference to cardiovascular disease. Prog Biophys Mol Biol. 2006 Sep;92(1):39-48. Epub 2006 Feb 28.

8. Webb, A., Kline, L. Holick, M. Influence of season and latitude on the cutaneous synthesis of vitamin D3: exposure to winter sunlight in Boston and Edmonton will not promote vitamin D3 synthesis in human skin. J Clin Endocrinol Metab. 1988 Aug;67(2):373-8.