**11. Recommended daily allowances and supplementation**

The Institute of Medicine (IOM) concluded that there is sufficient evidence to support a role for vitamin D in maintaining skeletal health, but a lack of evidence to support beneficial effects on non‐bone‐related health outcomes [19]. The Endocrine Society also does not recommend screening for vitamin D deficiency in individuals who are not at risk for vitamin D deficiency [16].

The recommended dietary intake (RDI) of vitamin D is 400 IU/d for 0–12 months, 600 IU/d for ages 1–70 years, as well as for pregnant and lactating women, and 800 IU/d for ages 71 years and older [16, 20, 71, 72]. Measurement of 25(OH)D serum level is the best indicator for overall vitamin D status in the clinical setting, since it has a longer half‐life (10–27 days after admin‐ istration) [21].

Vitamin D can be found in foods such as oily fish (salmon, sardines, and mackerel—400 UI/ 3.5 oz), cod liver oil (400 IU/tsp), egg yolk (20 IU), fortified milk, orange juice, cereals, cheese, and mushrooms. (100 IU/8oz) [3, 10, 15–17].

In terms of supplements, for every 100 IU of vitamin D ingested, blood 25(OH) level increases by around 1 ng/ml (2.5 nmol/l).

Vitamin D supplementation has dose‐dependent side effects, which are fairly rare, such as hypercalcemia, hypercalciuria, renal calcification, and increased bone resorption. Significant increase in triglyceride has also been described [62].
