Vitamin D Bioavailability: State of the Art

Abstract

There has been renewed interest in vitamin D since numerous recent studies have suggested that besides its well-established roles in bone metabolism and immunity, vitamin D status is inversely associated with the incidence of several diseases, e.g., cancers, cardio-vascular diseases, and neurodegenerative diseases. Surprisingly, there is very little data on factors that affect absorption of this fat-soluble vitamin, although it is acknowledged that dietary vitamin D could help to fight against the subdeficient vitamin D status that is common in several populations. This review describes the state of the art concerning the fate of vitamin D in the human upper gastrointestinal tract and on the factors assumed to affect its absorption efficiency. The main conclusions are: (i) ergocalciferol (vitamin D2), the form mostly used in supplements and fortified foods, is apparently absorbed with similar efficiency to cholecalciferol (vitamin D3, the main dietary form), (ii) 25-hydroxyvitamin D (25OHD), the metabolite produced in the liver, and which can be found in foods, is better absorbed than the nonhydroxy vitamin D forms cholecalciferol and ergocalciferol, (iii) the amount of fat with which vitamin D is ingested does not seem to significantly modify the bioavailability of vitamin D3, (iv) the food matrix has apparently little effect on vitamin D bioavailability, (v) sucrose polyesters (Olestra) and tetrahydrolipstatin (orlistat) probably diminish vitamin D absorption, and (vi) there is apparently no effect of aging on vitamin D absorption efficiency. We also find that there is insufficient, or even no data on the following factors suspected of affecting vitamin D bioavailability: (i) effect of type and amount of dietary fiber, (ii) effect of vitamin D status, and (iii) effect of genetic variation in proteins involved in its intestinal absorption. In conclusion, further studies are needed to improve our knowledge of factors affecting vitamin D absorption efficiency. Clinical studies with labeled vitamin D, e.g., deuterated or (13)C, are needed to accurately and definitively assess the effect of various factors on its bioavailability.

Supplementation of Merino ewes with cholecalciferol in late pregnancy improves the vitamin D status of ewes and lambs at birth but is not correlated with an improvement in immune function in lambs

“…25-hydroxyvitamin D 3 is known to be more potent than, and has an increased bioavailability compared with cholecalciferol, and, thus, supplementation with 25-hydroxyvitamin D 3 is recognised to be between 4.2 and 5 times more effective at improving the vitamin D status of an individual than supplementation with cholecalciferol (Cashman et al 2012;Borel et al 2015). Supplementing ewes with 25(OH)D 3 during late pregnancy may therefore be more effective at boosting the vitamin D status of ewes and fetal lambs than supplementation with cholecalciferol.…”

Cardiac tissue oxidative stress and inflammation after vitamin D administrations in high fat- diet induced obese rats

“…Vitamin D as a nutrient contained in natural foods, after intake, requires skin exposure to ultraviolet B (290–315 nm) radiation and a series of sequential biochemical reactions occurring in the liver and kidneys to convert 7-dehydrocholesterol into a bio-functional form of vitamin D, which is called vitamin D3 or calcitriol (1,25-dihydroxycholecalciferol) [19]. …”

Correlation of Vitamin D3 (Calcitriol) Serum Concentrations with Vitamin B12 and Folic Acid in Women Undergoing in vitro Fertilisation/Intracytoplasmatic Sperm Injection

“…Although many influences were eliminated, some might still persist, such as the variable bioavailability of vitamin D3 in different sorts of alimentation [39]. As a matter of fact, vitamin D is lipo-soluble and hence absorbed in the intestine similarly to fatty acids.…”