Health Articles : Vitamins and Supplements : Vitamin D
Vitamin D : Vitamin D
Vitamin DNecessities for vitamin D cannot be based on intakes to achieve maximal retention as for calcium for numerous reasons. The main source of vitamin D for ..... Necessities for vitamin D cannot be based on intakes to achieve maximal retention as for calcium for numerous reasons. The main source of vitamin D for humans is not diet, but rather is produced through photosynthesis of vitamin D from cutaneous 7-dehydrocholesterol upon sunlight exposure to UV B photons with energies between 290 and 315 nm. Furthermore, vitamin D is converted to several metabolites in the body. The 1997 DRI committee used serum 25 (OH) D as the criterion for determining adequacy, as its production is not regulated; therefore, it reflects that both the absorption from the diet and cutaneous synthesis. Reference varies for serum 25 (OH) D were used, but the lower limit of various populations ranged from 20 to 50 nmol/L, likely reflecting obtainable sunlight of the appropriate energy in their environments. In older individuals, AI for vitamin D was based on observed values to protect seasonal variation in PTH, a marker for bone resorption.
Currently, several researchers have questioned the adequacy of current vitamin D recommendations and suggested that daily inputs from diet and cutaneous origin should be 1000 IU or even 3000–5000 IU (75–125 µg). Healthy adults can achieve this level of input chiefly through cutaneous production. Early humans, evolving at the equator in East Africa, would have had cutaneous vitamin D synthesis enough to produce serum 25-hydroxyvitamin D levels at 150 nmol/L. The elderly who have lessened the sun exposure and efficiency of conversion of 7-dehydrocholesterol to vitamin D-3 cannot. As for calcium, there might be different health end points more relevant to different populations for vitamin D; <50 nmol/L of 25 (OH) D might increase risk of secondary hyperparathyroidism enhancing the risk for osteoporosis, rickets or osteomalacia. Holick proposed that higher levels of serum 25 (OH) D (75 nmol/L) might be necessary to maximize cellular health.
Much research is needed to identify appropriate functional end points for vitamin D. Serum 25 (OH) D is an indicator for status, but we have a poor understanding of the relationship of this marker to ultimate the health outcomes. Only currently have we had good information obtainable on the relationship of vitamin D intake and serum 25 (OH) D. Serum 25 (OH) D levels have been connected to serum PTH. Although PTH does promote bone resorption, serum PTH is only a substitute for bone resorption. Additional studies must be conducted to unswervingly relate vitamin D intake to bone loss. Relating vitamin D intakes to measures of most favorable cellular health is in its infancy.
Vitamin D And SkinAfter conducting various research and experiments with vitamin d, it found that skin has also got the inherent capacity of producing vitamin d. As vitamin d is an .....
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