Vitamin D3 increases the absorption of calcium and phosphorus from food as well as promoting the re-absorption of calcium from the kidneys into the bloodstream. The presence of vitamin D stimulates bone cells to make new bone tissue, increasing bone density.

Numerous studies indicate the link between healthy vitamin D levels and a strong immune system. A group of immune cells, known as T-cells, are critical for immune defence and are dependent on adequate levels of vitamin D in the blood. When a T-cell is exposed to a foreign bacteria and/or virus, if vitamin D is not present, it will remain dormant and unable to attack the bacteria/virus.

Vitamin D receptors exist in the brain. Studies have shown that vitamin D increases serotonin levels in the brain, improving mood and a sense of wellbeing.

A study has suggested that people suffering moderate to severe pain demonstrated poor vitamin D status. It has been shown that vitamin D turns off a signalling mechanism within cells that promote an inflammatory response. People suffering from inflammatory conditions such as arthritis have benefitted from vitamin D supplementation.