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There is a need to increase the options for vitamin D fortification. We have developed a method to fortify hard cheese with vitamin D. Our aim was to characterize the bioavailability of vitamin D from fortified cheeses. Eighty adults were randomized to weekly servings of fortified Cheddar cheese (DC) (34 g; n = 20); fortified low-fat cheese (DLF) (41 g; n = 10); liquid vitamin D supplement (1 mL), taken with food (DS +) (n = 20) or without food (DS-) (n = 10); placebo cheddar cheese (n = 10); or placebo supplement (n = 10). The treatments contained 28,000 IU cholecalciferol (vitamin D3), equivalent to 4000 IU (100 µg/d). The primary outcome was the comparison of vitamin D bioavailability, as measured by the serum 25-hydroxyvitarnm D [25(OH)D] response, between fortified cheeses and supplement. In the placebo groups, initial 25(OH)D, 55.0 ± 25.3 nmol/L, declined over the 8-wk winter protocol, to 50.7 ± 24.2 nmol/L (P = 0.046). In the vitamin D-treated groups, the mean increases in 25(OH)D over 8 wk were: 65.3 ± 24.1 (DC), 69.4 ± 21.7 (DLF), 59.3 ± 23.3 (DS +), and 59.3 ± 19.6 nmol/L (DS-); these changes differed from the placebo groups (P < 0.0001) but not from one another (P = 0.62). Compared with baseline, serum parathyroid hormone decreased with both fortification (P = 0.003) and supplementation (P = 0.012). These data demonstrate that vitamin D is equally bioavailable from fortified hard cheeses and supplements, making cheese suitable for vitamin D fortification.

Discussion

Our results show that vitamin D is bioavailable from fortified cheddar and low-fat cheese. The change in 25(OH)D from baseline to 8 wk was significantly greater in the subjects consuming fortified cheddar or low-fat cheese compared with those consuming the placebo. Furthermore, the fortified cheeses produced a change in 25(OH)D that did not differ from vitamin D supplement, demonstrating that vitamin D is equally bioavailable from fortified cheese and supplement. These findings are similar to those of Natri et al. (52), who showed that bread fortified with cholecalciferol increases serum 25(OH)D as effectively as a supplement.

We also found that differences in the fat content of the fortified cheeses did not affect vitamin D bioavailability. The increases in serum 25(OH)D did not differ between subjects consuming fortified regular-fat cheddar cheese, comprised of -33% fat, or fortified low-fat cheese, comprised of -7% fat. These observations are consistent with those of Tangpricha et al. (53) in which peak serum vitamin D concentrations did not differ significantly after the ingestion of vitamin D in whole milk, skim milk, or corn oil on toast. We also did not observe any significant changes in serum 25(OH)D between subjects consuming vitamin D supplemented with food and those consuming it without food. We conclude that taking a vitamin D supplement together with food also does not alter its bioavailability.

In conclusion, we found that fortified cheese enhances vitamin D status as effectively as a supplement. The extension of vitamin D fortification to cheese and other such foods that are widely distributed, frequently consumed, and exhibit good bioavailability Js an inexpensive and effective approach for increasing the availability of vitamin D in the diet. This will improve vitamin D intakes in the population and could help to bring about the public health benefits that many experts are now proposing may result from a greater consumption of vitamin D.