Vitamin D: The Sunshine Vitamin

Vitamin D is often referred to as the “sunshine vitamin” because the body can synthesise it after exposure to the sun’s ultraviolet rays. Author: Andrea Carpenter

The "Sunshine" Vitamin

Vitamin D is often referred to as the “sunshine vitamin” because the body can synthesize it after exposure to the sun’s ultraviolet rays. Apart from sunlight, other natural sources of Vitamin D include egg yolks and fatty fish (salmon, tuna, mackerel). In Canada, certain foods are fortified with vitamin D, including dairy products and dairy alternatives, juice, and margarine.

Why Do I Need It?

Vitamin D is needed to keep bones well mineralised and strong, improve muscle contraction, and for other cellular functions in the body. New research also suggests that Vitamin D may benefit the immune system, and have anti-inflammatory effects. Calcium and phosphorus are pulled from the bone when the body does not have optimal blood levels of vitamin D. Bones can become thin, brittle, or misshapen, and lead to osteopenia or osteoporosis. However, if vitamin D levels are too high, excess calcium may be deposited onto muscles and organs in the body. A balance of all these nutrients is required.

Vitamin D levels can be reduced in children and adults, even if they’re otherwise healthy, and they may not show any clinical signs of deficiency. A national study revealed that approximately 30% of American adults and children were vitamin D deficient. In Canada, the percentage is likely even higher where exposure to colder temperatures and natural sunlight is less. For this reason, it is recommended to maintain adequate vitamin D intake either through food or supplements, especially in areas with limited sunshine and during the cold winter months.

How Much Do I Need?

Vitamin D Supplementation

There are two forms of Vitamin D added to food, and available as supplements: Vitamin D2 (ergocalciferol) and Vitamin D3 (cholecalciferol). Vitamin D2 and D3 are considered to be equivalent, however Vitamin D3 may be more effective at higher doses. Vitamin D3 is the supplement form of Vitamin D available in Canada while Vitamin D2 is available in the US

Vitamin D in Health & Disease

  • Breastfeeding

Infants in their first year of life who are exclusively breastfed, partially breastfed, or on low volumes of infant formula, require Vitamin D supplementation of 400 IU, the RDA for their age. Human milk provides suboptimal Vitamin D to support infant’s needs. Formula is fortified with Vitamin D, so when infants take adequate volumes, their needs for Vitamin D will be met.

  • Older Adults

Older adults are at risk of vitamin D deficiency. Vitamin D needs increases with age, as the body’s ability to synthesize the vitamin decreases. Additionally, elderly people are less likely to spend much time in the sun, and they may have inadequate intake of the vitamin through food or supplements.

  • People with dark skin

Individuals with darker skin have greater pigment, which reduces the body’s ability to synthesize Vitamin D from the sun. Those who have darker skin, compared to those with lighter skin, are at greater risk of Vitamin D deficiency and often require additional Vitamin D intake.

  • Inflammatory bowel disease

Individuals with Inflammatory Bowel Disease (IBD) may limit their intake of dairy, which is a great source of Vitamin D. They may also not take enough Vitamin D supplements, since they have so many other medications to take. Active intestinal inflammation may also cause poor absorption of Vitamin D in the small intestine. Either by limiting Vitamin D intake, or experiencing intestinal inflammation, it can be hard for people with IBD to get the recommended amount. Recent literature suggests that nearly half of patients (adults and children) with IBD are Vitamin D deficient, and that Vitamin D levels were found to be lower in children with IBD than in their healthy peers.

  • Obesity

A BMI of above 30 has been linked to decreased blood levels of Vitamin D. It is not well documented, but obese individuals, compared to healthy weight individuals, may need higher amounts of the nutrient. Vitamin D ingested from food or supplements, and absorbed by the skin, is distributed into adipose tissue. General obesity does not affect the skin’s ability to absorb the vitamin, however the excess adipose tissue may affect the body’s ability to release it into circulation, so blood levels of the vitamin will be reduced.

What can you do? Tips to improve your Vitamin D status

  • Eat a healthy, balanced diet, including foods fortified with calcium and Vitamin D.
  • Take Vitamin D supplements (especially in the winter months) if you are not meeting the RDA for your age through a combination of food, multivitamins, or Vitamin D supplements.
  • Speak with a Registered Dietitian. They will provide strategies to help improve your Vitamin D status and bone health.

Source: Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: National Academy Press, 2010.

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