Vitamin D deficiency: a worldwide problem with health consequences

Abstract

Vitamin D deficiency is now recognized as a pandemic. The major cause of vitamin D deficiency is the lack of appreciation that sun exposure in moderation is the major source of vitamin D for most humans. Very few foods naturally contain vitamin D, and foods that are fortified with vitamin D are often inadequate to satisfy either a child's or an adult's vitamin D requirement. Vitamin D deficiency causes rickets in children and will precipitate and exacerbate osteopenia, osteoporosis, and fractures in adults. Vitamin D deficiency has been associated with increased risk of common cancers, autoimmune diseases, hypertension, and infectious diseases. A circulating level of 25-hydroxyvitamin D of >75 nmol/L, or 30 ng/mL, is required to maximize vitamin D's beneficial effects for health. In the absence of adequate sun exposure, at least 800-1000 IU vitamin D3/d may be needed to achieve this in children and adults. Vitamin D2 may be equally effective for maintaining circulating concentrations of 25-hydroxyvitamin D when given in physiologic concentrations.

Vitamin D and immune function: an overview

“…In particular, increasing numbers of studies have linked vitamin D insufficiency to increased risk or severity of autoimmune disease (132,133) . Low vitamin D status has been linked to type 1 diabetes (134,135) , and supplementation with vitamin D has been reported to protect against this disease (136) .…”

Maternal vitamin D status in Type 1 diabetic pregnancy: Impact on neonatal vitamin D status and association with maternal glycaemic control

“…Holick [4] suggests that for extraskeletal health, sufficiency is achieved at vitamin D levels .75 nmol/l. Hypovitaminosis D is commonly seen in both pregnant and non-pregnant women worldwide [5]; with many factors impacting on vitamin D status, including; exposure to sunlight, skin colour, season, latitude and obesity, among others [6].…”

Oral vitamin D supplementation has a lower bioavailability and reduces hypersecretion of parathyroid hormone and insulin resistance in obese Chinese males

“…The US Institute of Medicine (11) reports that a circulating 25(OH)D concentration equal to 50 nmol/l (20 ng/ml) meets the vitamin D requirements of 97·5 % of the population, and this threshold is widely accepted for hypovitaminosis D (10,(12)(13)(14) . Not satisfied with that basic requirement, many researchers claim that improvement of circulating 25(OH)D concentrations to much higher than 50 nmol/l can prevent a broad range of diseases (4,(15)(16)(17) .…”

“…The US Institute of Medicine (11) reports that a circulating 25(OH)D concentration equal to 50 nmol/l (20 ng/ml) meets the vitamin D requirements of 97·5 % of the population, and this threshold is widely accepted for hypovitaminosis D (10,(12)(13)(14) . Not satisfied with that basic requirement, many researchers claim that improvement of circulating 25(OH)D concentrations to much higher than 50 nmol/l can prevent a broad range of diseases (4,(15)(16)(17) .In addition, 25(OH)D ≤25 nmol/l (10 ng/ml) is considered to be 'severe vitamin D deficiency', 75-250 nmol/l (30-100 ng/ml) a 'sufficient or optimal' level and 50-75 nmol/l (21-29 ng/ml) an 'insufficient' level (12,13,18) , although these reference ranges are not defined by the Institute of …”