Factors in human vitamin D nutrition and in the production and cure of classical rickets

Abstract

Vitamin D reaches the body from two totally dissimilar sources, first by cutaneous synthesis under the action of ultraviolet light and secondly in the diet. The relative contribution of these sources to human vitamin D nutrition is uncertain; this paper will examine some of the factors which determine their efficacy and the ultimate production of rickets. Our studies have also provided evidence for an action of vitamin D on renal tubular phosphate reabsorption in healing rickets.The natural vitamin D, cholecalciferol, is produced in skin by the action of ultraviolet light on the physiological precursor 7dehydrocholestero1, which in man is concentrated in the Malpighian layer of the epidermis (Wheatley & Reinertson, 1958). Diets contain cholecalciferol (and probably a significant amount of 25-hydroxycholecalciferol(25-HCC)) and in addition may be fortified, especially in the USA and Canada, with the yeast vitamin product, ergocalciferol. With the exception of oily fish, natural foods are surprisingly deficient in vitamin D, considering the usual connotations of the word 'vitamin'. We rely heavily on eggs as a natural source of vitamin D but they too are fortified with vitamin D, or rather the food of the battery hen is.Vitamin D from dietary and cutaneous sources is metabolized in liver to form 25-hydroxy-vitamin D (25-OHD), the major circulating form of the vitamin (DeLuca, I 974a, 6). We have used a precise radio-competitive protein-binding assay for 25-OHD (Haddad & Chyu, 1971) which measures together the equally effective 25-hydroxy derivatives of both ergocalciferol and cholecalciferol. Isotopic tracer studies with radioactive cholecalciferol and comparisons between measured z5-OHD levels and bioassayable anti-rachitic activity indicate that, under physiological conditions, vitamin D circulates almost exclusively as its hydroxylated derivatives (Stamp, 1973). Plasma levels of 25-OHD are therefore a precise measurement of nutritional status.During a study of possible sex and age differences in plasma 25-OHD, we noted apparent inconsistencies as the months progressed, with new control populations giving different results from those already established. Eventual comparison of several populations within single assays led us to demonstrate a marked seasonal variation in plasma z5-OHD regardless of age or sex : this is shown in Table I. at https://www.cambridge.org/core/terms. https://doi

Multiple sclerosis and vitamin D: an update

“…Currently, there is no consensus on what represents an optimal serum 25OHD concentration. An increasing number of reports is available on 25OHD serum levels both in healthy and unhealthy populations, from which it has become apparent that serum 25OHD levels vary from winter to summer, with lower levels in winter (Stamp, 1975;Bouillon et al, 1987;Lips et al, 1988: McKenna, 1992Scharla et al, 1996;Scharla, 1998). Here we focus on two of these reports (Bouillon et al, 1987;Scharla, 1998).…”

A phase 2 trial exploring the effects of high‐dose (10,000 IU/day) vitamin D3 in breast cancer patients with bone metastases

“…29,30 However, because exposure to sunlight can provide an adult with vitamin D in an amount equivalent to daily oral consumption of up to 10,000 IU/ day, [15][16][17][18] this dose would appear to be intuitively safe. A review of the toxicities of vitamin D has shown that except in patients with conditions causing hypersensitivity, there is no evidence of adverse effects with serum 25-hydroxyvitamin D concentrations equivalent to 10,000 IU/day.…”

“…[15][16][17][18] Furthermore, toxicities have been described at doses of 20,000 IU for 12 weeks 20 ; therefore, a 4-month duration at a dose of 10,000 IU was conservatively chosen as an optimal balance between likelihood of response and expected toxicity profile. Selfreported compliance was assessed at each follow-up visit by individual investigators.…”

“…[15][16][17][18] Furthermore, a review of data from vitamin D supplementation studies reveals a dose-response curve for vitamin D that is relatively linear up to 10,000 IU of vitamin D 3 per day, suggesting that this dose may be a physiologic upper limit. 19 The present study aimed to assess the effects of a high physiological dose of vitamin D (10,000 IU per day) on both palliation and bone turnover in women with bone metastases from breast cancer.…”

Bone mineral density and its relationship to skin colour in Caucasian females

“…Furthermore, only small amounts of sunlight exposure are required to maintain normal vitamin D levels, and vitamin D can be stored in fat and muscle to be used at times of shortage. Although it has been shown that white skins are more efficient at producing vitamin D than black skins [I 11, it has also been demonstrated that blackskinned people can still produce enough vitamin D from sunlight exposure to maintain normal levels throughout the winter if given enough sunlight exposure at northern latitudes [12].…”