Seasonal variation in the serum 25-hydroxyvitamin D levels of young and elderly active and inactive adults in São Paulo, Brazil: The São PAulo Vitamin D Evaluation Study (SPADES)

OBJECTIVE

To evaluate the 25-hydroxyvitamin D [25(OH)D] concentrations in individuals in the city of São Paulo belonging to different age groups and exhibiting specific behavioral characteristics and to correlate the 25(OH)D concentration with the level of UV radiation (UVR).

PATIENTS AND METHODS

A total of 591 individuals were included, distributed as follows: 177 were living in institutions (NURSING, 76.2 ± 9.0 y old), 243 were part of the community elderly (COMMUNITY, 79.6 ± 5.3 y old), 99 were enrolled in a physical activity program targeting the elderly (ACTIVE, 67.6 ± 5.4 y old) and 72 were young (YOUNG, 23.9 ± 2.8 y old). Blood samples from all individuals were collected throughout the year. UVR measurements were taken by an official meteorology institution.

RESULTS

The UVR values varied throughout the year, following a sinusoidal-like pattern. Because of the Earth's orbit, we hypothesized that there would be cyclic patterns for the 25(OH)D and UVR values that repeat every 12 mo. The general formula is represented by the equation P1+P2⋅sin(-2⋅π12⋅(t-P3)) The mean 25(OH)D concentration and the amplitude of the variation were significantly higher for the YOUNG and ACTIVE groups than for the COMMUNITY and NURSING groups. The nadir for UVR was in June, whereas the nadir for the 25(OH)D concentration was in the spring, corresponding to a delay of one season.

CONCLUSIONS

There was seasonal variation in the 25(OH)D concentration for all the groups studied; however, the amplitude of the variation was higher for the groups of young and physically active people, possibly due to the higher level of sunlight exposure for these groups. The lowest 25(OH)D concentration was detected in the spring.

Ascorbic acid biosynthesis: a precursor study on plants

Since the first isolation of ascorbic acid (AsA) in 1928, few papers have been published regarding the biosynthesis of AsA in plants, especially in fruits. It took as long as 1998, before Wheeler, Jones and Smirnoff, based on a study with Arabidopsis leaves, proposed what can be considered the main pathway of biosynthesis of AsA, in which L-galactose (L-GAL) is a key precursor. This paper reports the effectiveness of some precursors (cold or radiolabeled) in the biosynthesis of AsA in different plants: green sweet pepper, white-pulp guava, red-pulp guava, papaya and strawberry at two ripening stages (mature green and ripe for papaya and mature green and half red for strawberry) and broccoli. The 'Smirnoff-Wheeler' pathway was functioning and active in all sources studied, as demonstrated by the increase in AsA contents and incorporation of labeled precursors into AsA. In papaya, the AsA content in the ripe fruit was higher than in the mature green, indicating the synthesis of AsA during ripening. On the other hand, the AsA content in the mature green strawberry was similar to that of the half red fruits. Our data demonstrate that L-GAL and L-Galactono-1,4-lactone (L-GL) are effective precursors for the biosynthesis of AsA in fruits and also provided additional evidence for the participation of D-mannose (D-MAN) and D-glucose-1P in the biosynthesis of AsA in plants.