Serum levels of the circulating form of vitamin D3, 25-hydroxycholecalciferol [25-(OH)D3], were determined in 59 university students, 26 males and 33 females, aged 18 to 26 yr and in 24 elderly subjects, 13 males and 11 females, with a mean age of 62 +/- 13 yr. The level of 25-(OH)D3 was significantly lower in the elderly persons (p less than 0.001) than in young students of both sexes, and was significantly higher in females than in males. Serum levels of 1, 25- and 24, 25-dihydroxycholecalciferol were measured in adult males and found to be within the normal range. A group of elderly patients were exposed to natural uv light, and the circulating levels of 25-(OH)D3, serum phosphorus, and alkaline phosphatase were determined both before and 1 day after the last exposure. The exposure to natural uv light resulted in a 2 1/2-fold increase in the level of 25-(OH)D3 and a significant decrease in the activity of alkaline phosphatase, but no significant change in serum phosphorus concentrations was observed. It is concluded that the low vitamin D3 status in Saudis is mainly due to avoidance of sunlight exposure and other factors discussed below.

Serum levels of the circulating form of vitamin D, 25-hydroxyvitamin D, and calcium were measured in 104 Saudis, 44 Jordanians, 17 Egyptians and 10 other subjects aged between 18 and 23 years. All subjects were male university students living in Riyadh for more than 2 years. 25-Hydroxyvitamin D levels were (mean ± SD) 12.8 ± 6.3, 11.0 ± 5.8, 11.9 ± 6.9 and 11.9 ± 5.0 ng/ml, respectively. The percentages of subjects with serum 25-hydroxyvitamin D levels below 10 ng/ml were 35, 45, 53 and 50% for normal Saudis, Jordanians, Egyptians and others, respectively. All subjects had normal serum calcium concentrations. There was no correlation between 25-hydroxyvitamin D and serum calcium levels in the subjects investigated. This study indicates a tendency for a low vitamin D status among residents of Saudi Arabia, in spite of abundant sunlight all the year round.

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SummaryVenous blood was obtained from 100 consecutive and unselected Saudi Arabian mothers and their neonates within 48 h after delivery. Plasma levels of 25-hydroxyvitamin D (25-0HD) and total calcium were measured in paired samples. Fifty-nine mothers and 70 neonates had subnormal (less than 10 ngJml) 25-OHD levels. Plasma Ca concentrations were low in 61% of the mothers and 59% of the newborns consisting of 10 preterm and 38 full term babies. There were significant correlation between the plasma levels of maternal and neonatal 25-0HD (r = 0.54; P = 0.0001), maternal 25-0HD and Ca (r = -0.22; P = 0.03), neonatal 25-0HD and Ca (r =-0.28; P =0.0009), and maternal and neonatal calcium levels (r = 0.46; P = 0.0001). Nevertheless, maternal 25-0HD was not invariably higher than that in the infant. Normocalcemia was observed in 29 neonates and 26 mothers (20 mother/baby pairs) in the presence of subnormal maternal 25-0HD. Twenty babies and 16 mothers including nine mother/baby pairs had hypocalcemia in the presence of normal levels of 25-0HD. This indicates that vitamin D plays a crucial, but not exclusive, role in calcium homeostasis during pregnancy.This study revealed that vitamin D deficiency is very prevalent during pregnancy in Saudi Arabia. It also showed that asymptomatic hypocalcemia in full term babies is far commoner than is generally appreciated. It is considered that vitamin D deficiency is primarily due to lack of exposure to sunlight. Encouragement to obtain sunlight exposure and fortification of food are the only alternative measures. Abbreviation 25-0HD, 25-hydroxyvitamin D Saudis, especially women, avoid exposure to sunlight due to cultural and traditional beliefs. Ultraviolet light has been shown to produce changes in circulating 25-0HD equivalent to those produced by a daily dose of 10,000 IU i.e. several times the recommended daily adult intake in food (21). Second, the dietary intake of vitamin D by Saudi Arabians has been shown to be far below the amount recommended by FAO/WHO, in the United States and in the United Kingdom (20,24).In spite of abundant sunlight throughout the year, several vitamin D deficiency diseases have been reported in Saudi Arabia, including rickets (8,9), fractures of the head of the femur in the elderly, and osteomalacia (24). We have noticed a strikingly high incidence of hypocalcemia in full term infants delivered at King Abdul Aziz University Hospital. In view of the wide pre". alence of vitamin D deficiency diseases, we sought to define the role of this vitamin in the pathogenesis of neonatal hypocalcemia. Since 25-0HD is the major circulating form of vitamin D and since its plasma concentrations directly reflect its status (6), we opted to measure this metabolite and total calcium concentrations in mothers and their neonates. PATIENTS AND METHODS Clinical.A 5-ml sample of venous blood was taken from each of 100 unselected mothers and 2 ml from their corresponding babies, within 48 h of delivery at King Abdul Aziz University Hospital for estimation of plasma 25-0HD ...

The existence of nutritional deficiency rickets among infants in sunny Riyadh was confirmed radiologically. Most of the rachitic infants were breast-fed, some received unsupplemented infant feeding formulae, and all live in an environment that is devoid of sunlight. Their mean age at the time of onset was 10.5 months. 25-Hydroxyvitamin D (25OHD) levels were found to be low in mothers of the rachitic infants. This maternal deficiency as a factor in pathogenesis of rickets in the infant is discussed. Proposals are made to prevent the occurrence of rickets on this scale.