**5. Vitamin D replacement in diet**

*Vitamin D Deficiency*

indicator of vitamin D status.

population (97.5%) [12].

hypercalciuria.

manner.

**4. Evidence-based review**

specific condition (e.g. epilepsy) were excluded.

made according to evidence-based protocols.

the intestinal calcium absorption to 40% and phosphorus to 80% (**Figure 2**, [10]). Vitamin D is transformed for activation through two hydroxylations in the body. Among the metabolic products or modified versions of vitamin include calcitriol (1,25-dihydroxyvitamin D3); the active form of vitamin D, with a 15-hour half-life; and calcifediol (25-hydroxyvitamin D3) with a 15-day half-life [10]. Vitamin D is bounded to specific receptors located throughout the body. Whilst serum 25(OH) D levels do not indicate the amount of vitamin D stored in body tissues, it is the best

When the level was 30 ng/mL or less, there was a significant decrease in intestinal calcium absorption that was associated with increased parathyroid hormone [10]. Further, there is strong support from reports that maternal vitamin D deficiency leads to overt bone disease (congenital rickets) from before birth to post-natal life [11]. Throughout the world, there has been widespread debate as to the serum 25(OH)D concentrations associated with deficiency (e.g. rickets), for optimal bone health and optimal overall health, and most cut points have not been developed by an agreed mutual scientific process. The US Institute of Medicine concluded that individuals are at risk of vitamin D deficiency at serum 25(OH)D concentrations <30 nmol/L (<12 ng/mL). However, some individuals are potentially at risk for inadequacy even at levels ranging from 30 to 50 nmol/L (12–20 ng/mL). The committee agreed with sufficient levels at ≥50 nmol/L (≥20 ng/mL) and that 50 nmol/L is the serum 25(OH)D level that covers the majority of needs of the

Further, hypovitaminosis D in its mild but especially in severe forms can exacerbate symptomatic hypocalcaemia following intravenous bisphosphonate (zoledronic acid) [13]. Even though this is rare, associated hypocalcaemia may be life-threatening and require immediate resuscitation and evaluation, often requiring hospitalisation to prevent additional morbidity and mortality risk from tetany, refractory hypotension, seizures or arrhythmias. Therefore it makes good sense to

Vitamin D toxicity can occur when blood 25(OH)D levels are 88 ng/mL or greater [15]. Symptoms may include sleepiness, vomiting, weakness, headache, nausea and constipation, and acute toxicity may cause hypercalcaemia and

Whilst there have been several treatment guidelines published, they are consensus-based rather than evidence-based [16–19]. This review seeks to address this issue and identify any gaps in research for vitamin D replacement, listing the types available including dietary, other supplementation and sunlight, for bone health (rickets, osteoporosis) as well as to address safety and efficacy in an evidence-based

Systematic search of MEDLINE, CINAHL and EMBASE for articles published rom September 2015 to August 2019 and the Cochrane Database of Systematic Reviews (most recent issue searched—Issue 2, 2019) was conducted by the author. Randomised controlled trials, meta-analyses and reviews of all aspects of vitamin D supplementation in humans were reviewed. Articles pertaining to osteoporosis in a

All studies were reviewed independently by the author, who recorded individual study results, and an assessment of study quality and treatment conclusions was

optimise vitamin D levels prior to administration of these agents [14].

**98**

Human beings require and source vitamin D from diet, dietary supplements and exposure to sunlight.

Whilst in particular for older people and those with restriction in diet, a diet rich in oily fish (which can theoretically improve 25-OHD levels and prevent vitamin D deficiency), in reality this is a challenge to achieve [24]. Only a few foods are a good source of vitamin D. These include fortified dairy products and breakfast cereals, fatty fish, beef liver and egg yolks.

Apart from the flesh of fatty fish (such as salmon, tuna and mackerel) and fish liver oils, very little foods contain vitamin D. Trace amounts of vitamin D can be found in egg yolks, cheese and beef liver. These foods contain vitamin D3 and its metabolite 25(OH)D3 [25]. Vitamin D2 is contained in some mushrooms [26, 27].

In the standard Western diet, fortified foods provide most of the vitamin D [26]. For example, US milk is fortified with 100 IU/cup. (In Canada, by law its milk is fortified with 35–40 IU/100 mL and its margarine at ≥530 IU/100 g.) However, other dairy products derived from milk, such as ice-cream and cheese, are generally not fortified. Some ready-to-eat cereals for breakfast often contain small amounts of added vitamin D, as do some brands of orange juice and yogurt. Some plant-based alternatives to mild (such as drinks made from oats, almond or soy) are sometimes fortified with vitamin D to the amount (about 100 IU/cup) found in fortified cow's milk. Several countries of the developed world (e.g. United States, Canada and Australia) mandate the fortification of infant formula with vitamin D, 40–100 IU/100 kcal in the United States and 40–80 IU/100 kcal in Canada; however, this is not practical especially in those who breastfeed and those countries which do not mandate fortification of their milk formulas.
