Why is vitamin D important?

  • Vitamin D can be found in foods such as fish, liver and egg yolks.
  • Milk are fortified with vitamin D, this began in the 1930’s when it was noted that the there was a significant incidence of bone problems secondary to vitamin D deficiency.
  • Vitamin D is produced when your skin is exposed to the sun’s UVB rays, cholesterol is used in this process.
  • It is important to note that UVB does not penetrate glass.
  • Cloud cover and smog can decrease the bodies production of vitamin D as it block some of the UVB waves.
  • Vitamin D is one of the fat-soluble vitamins.
  • Fat soluble vitamin also includes vitamins A, E and K.
  • Vitamin D is important for calcium  and phosphorus absorption which is needed for bone health.
  • “Helps regulate blood pressure in the kidney
  • Helps regulate blood sugar levels in the pancreas
  • Vitamin D acts as a hormone, regulating more than 200 genes throughout the body” John Hopkins 

Vitamin D supplements

Two forms of vitamin D are used in supplements,

  • Vitamin D2 -Also known as ergocalciferol
  • Vitamin D3  -Vitamin D3 is similar to vitamin D that is produced in our body. Vitamin D3 is also known as cholecalciferol.

Who benefits from vitamin D supplements

The Agency for Healthcare Research and Quality recently reviewed the effectiveness and safety of vitamin D on outcomes related to bone health (Cranney 2007). The report suggests that vitamin D supplementation has positive effects on bone health in,

  • Postmenopausal women
  • Older men.

How much vitamin D do we need?

  • The recommended daily intake is usually around 400-800 IU. Reference Institute of Medicine.
  • The Institute of Medicine concluded that people who are at risk of vitamin D deficiency when their serum level of  25(OH)D concentrations  is lower than 30 nmol/L (<12 ng/mL).
  • Currently, there is a debate as to how much vitamin D people need each day, these numbers may be too low.  Reference CDC
  • The American Academy of Pediatrics (AAP) recommends that exclusively and partially breastfed infants receive supplements of 400 IU/day of vitamin D shortly after birth and continue to receive these supplements until they are weaned and consume ≥1,000 mL/day of vitamin D-fortified formula or whole milk.


  • Although blood tests can tell you if there is vitamin D is does not mean that the body is using it correctly.
    • Serum concentration of 25(OH)D  is felt to be the best test for vitamin D deficiency.
    • Circulating 1,25(OH)2D can also be tested but  is not recommended as the level can change rapidly in the face of calcium, phosphate and parathyroid hormone levels.

Vitamin D Deficiency

  • It is estimated that 40% of Americans are deficient in Vitamin D.  Reference CDC
  • Other reports show up to 70% of Americans are deficient in vitamin D.

Diseases associated with low vitamin D 

vitamin D informationRickets

  • Rickets is a condition where the bones do not calcify properly leading to deformed bones and or fractures.
  • Rickets is caused by a deficiency in vitamin D, calcium or phosphorus.


  • Osteoporosis is a condition where the bones thin leading to a higher risk of fractures.
  • In elderly or postmenopausal women, vitamin D deficiency may exacerbate osteoporosis.
  • Rizzoli R1, Boonen S, Brandi ML, Bruyère O, Cooper C, Kanis JA, Kaufman JM, Ringe JD, Weryha G, Reginster JY.  Curr Med Res Opin. 2013 Apr;29(4):305-13. doi: 10.1185/03007995.2013.766162. Epub 2013 Feb 7.

There is a lot of literature about vitamin D

  • There is no definite evidence that taking a supplement will reduce heart attacks.
  • The Agency for Healthcare Research and Quality reviewed data from nearly 250 new studies published between 2009 and 2013, Their conclusion was it was not possible to specify a relationship between vitamin D and health outcomes other than bone health.
  • More research is needed.
  • I have listed some of the articles below.

Vitamin D and cardiovascular disease

  • The Health Professional Follow-Up Study checked the vitamin D blood levels in nearly 50,000 men who were healthy.
  • The participants were followed for 10 years
  • Men who had vitamin D deficiency were more likely to have a heart attack.
  • Reference Giovannucci E, Liu Y, Hollis BW, Rimm EB. 25-hydroxyvitamin D and risk of myocardial infarction in men: a prospective study. Arch Intern Med. 2008; 168:1174-80.
  • Vitamin D may play a role in controlling blood pressure and preventing artery damage which would help decrease the risk of heart attacks.
  • Reference Holick MF. The vitamin D deficiency pandemic and consequences for nonskeletal health: mechanisms of action. Mol Aspects Med. 2008; 29:361-8.
  • More research is needed in this area.

Vitamin D and infections

  • Some studies suggest that people who have higher vitamin D levels are less likely to get head colds and the flu.
  • Additional studies are needed
  • Urashima M, Segawa T, Okazaki M, Kurihara M, Wada Y, Ida H. Randomized trial of vitamin D supplementation to prevent seasonal influenza A in schoolchildren. Am J Clin Nutr. 2010 91:1255-60. Epub 2010 Mar 10.

Vitamin D and cancer

  • Vitamin D may reduce the risk of certain cancer such as colorectal cancer, further studies are needed.
  • “Improving calcium and vitamin D nutritional status substantially reduces all-cancer risk in postmenopausal women.”
  • Am J Clin Nutr. 2008 Mar;87(3):794.
  • Garland CF, Gorham ED, Mohr SB, Garland FC. Vitamin D for cancer prevention: global perspective. Ann Epidemiol. 2009; 19:468-83.
  • The National Institute of Health states  “studies to date do not support a role for vitamin D, with or without calcium, in reducing the risk of cancer.”

Vitamin D and bone loss

  • Several studies link low vitamin D levels with an increased risk of fractures in older adults, and they suggest that vitamin D supplementation may prevent such fractures if taken in a high enough doses.
  • Boonen S, Lips P, Bouillon R, Bischoff-Ferrari HA, Vanderschueren D, Haentjens P. Need for additional calcium to reduce the risk of hip fracture with vitamin d supplementation: evidence from a comparative metaanalysis of randomized controlled trials. J Clin Endocrinol Metab. 2007; 92:1415-23.
  • Researchers found that high intakes of vitamin D supplements—of about 800 IU per day—reduced hip and non-spine fractures by 20 percent, while lower intakes (400 IU or less) failed to offer any fracture prevention benefit.
  • Reference-Bischoff-Ferrari HA, Willett WC, Wong JB, et al. Prevention of nonvertebral fractures with oral vitamin D and dose dependency: a meta-analysis of randomized controlled trials. Arch Intern Med. 2009; 169:551-61.

Muscle strength and vitamin D

  • “Vitamin D supplementation increases upper and lower limb strength.”
  • Further research should focus on its effect on muscle power, endurance and maximal strength.”
  • Reference Tomlinson PB1, Joseph C1, Angioi M2J Sci Med Sport. 2015 Sep;18(5):575-80. doi: 10.1016/j.jsams.2014.07.022. Epub 2014 Aug 11

Vitamin D and diabetes

  • Vitamin D may reduce the risk of diabetes
  • Reference Gillespie KM. Type 1 diabetes: pathogenesis and prevention. CMAJ. 2006; 175:165-70.

Multiple Sclerosis and Vitamin D

  • The rates of multiple sclerosis are higher further away from the equator.
  • The rates of multiple sclerosis also appear higher in people who have low vitamin D levels.
  • There is not a definite cause and effect.
  • More studies are needed.
  • Reference Munger KL, Levin LI, Hollis BW, Howard NS, Ascherio A. Serum 25-hydroxyvitamin D levels and risk of multiple sclerosis. JAMA. 2006; 296:2832-8.

Vitamin D and depression

  • “Vitamin D supplementation may be effective for reducing depressive symptoms in patients with clinically significant depression; however, further high-quality research is needed.”
  • Reference Shaffer JA1, Edmondson D, Wasson LT, Falzon L, Homma K, Ezeokoli N, Li P, Davidson KW.  Med. 2014 Apr;76(3):190-6.

Too much vitamin D

  • Too much vitamin D has been associated with an increased risk of fracture.
  • Sanders KM, Stuart AL, Williamson EJ; et al. Annual high-dose oral vitamin D and falls and fractures in older women: a randomized controlled trial. JAMA. 2010;303:1815-1822.
  • Serum concentrations >125 nmol/L (>50 ng/mL) are associated with potential adverse effects including decreased appetite,  kidney stones, and heart arrhythmias.
  • Reference-National Institute of Health

What are the risk factors for vitamin D deficiency

  • Darker skin because they do not produce as much vitamin D
  • Elderly people
  • Living far from the equator where there is limited sun exposure.
  • People who are over weight. Fat cells absorb vitamin D and prevent it from circulating in the blood stream.
  • Certain diets will increase the risk of vitamin D deficiency-People who are lactose intolerant, have milk allergies or those who are  vegetarians.
  • Medical conditions such as inflammatory bowel disease or gastric bypass surgery for weight loss may lead to inadequate absorption of vitamin D.
  • Medications such as steroids and anti-seizure medicines can decrease vitamin D metabolism.
  • Weight loss medications can reduce fat soluble vitamin absorption.

Vitamin D in our foods

  • Fish such as cod, salmon and tuna.
  • Mushrooms

Spend time outside

  • “Getting about 10 minutes of moderate summer sun exposure can supply you with 3,000 to 5,000 IU of vitamin D. You would have to drink approximately 30 glasses of milk to match that amount”. John Hopkins
  • Even in the colder months you can spend some time out doors doing yard work or taking a walk.


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