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Unlike the other twelve vitamins, vitamin D is only conditionally essential - in a preindustrial society people had adequate exposure to sunlight and the vitamin was a hormone, as the primary natural source of vitamin D was the synthesis of cholecalciferol in the lower layers of the skin's epidermis, triggered by a photochemical reaction with ...
Absorption of dietary iron in iron salt form (as in most supplements) varies somewhat according to the body's need for iron, and is usually between 10% and 20% of iron intake. Absorption of iron from animal products, and some plant products, is in the form of heme iron, and is more efficient, allowing absorption of from 15% to 35% of intake.
The body regulates iron levels by regulating each of these steps. For instance, enterocytes synthesize more Dcytb, DMT1 and ferroportin in response to iron deficiency anemia. [29] Iron absorption from diet is enhanced in the presence of vitamin C and diminished by excess calcium, zinc, or manganese. [30]
CYP2R1 is cytochrome P450 2R1, an enzyme which is the principal vitamin D 25-hydroxylase. [5] [6] In humans it is encoded by the CYP2R1 gene located on chromosome 11p15.2. [7]It is expressed in the endoplasmic reticulum in liver, where it performs the first step in the activation of vitamin D by catalyzing the formation of 25-hydroxyvitamin D. [8]
A deficiency occurs if a person doesn't get enough vitamin D from sunlight or food, or if their body can't synthesize or absorb vitamin D properly due to an underlying condition or medication.
There is such a thing as vitamin D toxicity that can pose serious health risks. “Overdoing it on vitamin D, usually from high-dose supplements, can lead to elevated calcium levels in the blood ...
The most significant factor regulating iron uptake is the amount of iron present in the body. Iron absorption increases with sufficient iron storage and vice versa. Increased erythrocyte synthesis also stimulates iron absorption in the gut. [15] Therefore, oral bioavailability of iron varies greatly, ranging from less than 1% to greater than 50 ...
Younger vitamin users had the highest risk. Among those who joined one of the studies before their 55th birthday, the mortality rate for those who took the supplements every day was 15% higher ...