Vitamin D Summary Sheet

Vitamin D Overview

• Vitamin D is a fat-soluble, steroid compound with two main forms: ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3)
• Ergocalciferol is present in dietary sources, while cholecalciferol is produced in the skin through sun exposure

Vitamin D Forms and Function

• The major circulating form of vitamin D is 25(OH)D (calcifediol)
• The active hormone form of vitamin D is 1,25(OH)2D (calcitriol), which is necessary for vitamin D to function in the body

Demographics and Recommendations

• The Estimated Average Requirement (EAR) for vitamin D is 400 IU (10 μg) for individuals aged 19-30 years old
• The Recommended Dietary Allowance (RDA) for vitamin D is 600 IU (15 μg) for individuals aged 19-30 years old
• The majority of Canadians have insufficient vitamin D intake, with 8% considered deficient

Vitamin D Deficiency and Toxicity

• 12.2% of individuals aged 19-30 are at risk of deficiency
• 2.5% are at risk of toxicity, with a Tolerable Upper Intake Level (UL) of 4,000 IU for all age groups

Food Sources

• Fatty fish and fish liver oils are the best dietary sources of vitamin D
• Small amounts of vitamin D are found in egg yolks, beef liver, and cheese
• Most dietary vitamin D comes from fortified foods, particularly dairy products
• Plant alternatives, such as soy, almond, or oat beverages, are often vitamin D-fortified

Roles and Functions

• Vitamin D helps the body absorb calcium
• Other functions of vitamin D include regulating inflammation, cell growth, glucose metabolism, immune function, and gene-encoding
• Vitamin D stimulates intestinal absorption of calcium (and phosphate) through active transport in the duodenum
• The body always prioritizes dietary calcium to maintain plasma levels, breaking down bone to meet needs if dietary calcium intake is low

Effects of Deficiency

• Vitamin D deficiency (hypovitaminosis D) is characterized by low levels of 25(OH)D