Vitamin D

Vitamin D (cholecalciferol) is a fat-soluble vitamin naturally produced when the skin is exposed to sunlight. It aids in the absorption of calcium and helps maintain healthy bones. Vitamin D deficiency causes various bone disorders, such as rickets in children and osteomalacia in adults.

Sunlight is the primary source of vitamin D (cholecalciferol), since very few foods contain significant amounts of the nutrient. It is also available as a health supplement, and many foods are vitamin D-fortified. However, vitamin D supplements must be taken in moderation because it can be toxic in large doses. This guide offers basic information on vitamin D (cholecalciferol) and tips on using supplements.

1. Recommended intake

Unlike other nutrients, vitamin D has no general recommended dietary allowance (RDA). Instead, an Adequate Intake (AI) for each age group has been established. The AIs are 200 International Units (IU) for ages 19 to 50, 400 IU for ages 51 to 69, and 600 IU for people aged 70 and up.

2. Who needs vitamin D supplements?

People who get limited sunlight need supplements or fortified foods to meet their AIs. These include people living in the northern latitudes, women who wear full body covers for religious reasons, and those who spend much of the day working indoors. Infants who are exclusively breastfed also need vitamin D (cholecalciferol) supplements because breast milk is low in vitamin D.

Because it is fat-soluble, vitamin D can be used for conditions that cause fat malabsorption. These include Crohn’s disease, cystic fibrosis, sprue, liver disease, small bowel disease, pancreatic enzyme deficiencies, and surgical removal of all or part of the stomach.

3. Side effects and safety

Vitamin D can be toxic in high doses. Symptoms of vitamin D toxicity are nausea, vomiting, constipation, weakness, poor appetite, and weight loss. It can also raise calcium levels in the blood, which can cause heart problems, confusion, and calcinosis, or the buildup of calcium and phosphate in the liver and kidneys.

Vitamin D overdose is commonly caused by supplements rather than food sources alone. People taking cod liver oil for cholesterol reduction are particularly at risk, because a dose can exceed the daily limit of vitamin D to reach beneficial levels of omega-3 (the substance that reduces cholesterol).

IMPORTANT: Some vitamin D (cholecalciferol) supplements contain potentially harmful chemicals such as silica, gluten, starch, and sugar. Choose only GMP-compliant supplements to make sure your supplements are free of such additives. Avoid products added with artificial flavors and colors.