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Thursday, September 23, 2010

2.12d Magnesium/Phosphorus/Selenium/Zinc

Physician's Notebooks 2  - http://physiciansnotebook.blogspot.com - See Homepage

Minerals: scroll down for  Magnesium, Phosphorus, Selenium & Zinc
2.12d: Magnesium Mg -Update 06 Dec. 2017
Magnesium (Mg) in food becomes the 2+ cation (Mg2+) in our bodies after its neutral atom's losing 2 outer electrons. Abundant in seawater, it is part of a number of enzymes in nerves; it is important in body fluids and neuron transmission, especially in blocking transmission. So Mg2+ injection (as Magnesium Sulfate) blocks norepinephrine's hypertensive effect of small arteries and is used in emergency lowering of very high blood pressure.   
Mg2+ is easily tested in blood. I have interest because my blood test showed repeatedly borderline low Mg (hypomagnesemia) 1.6 to 1.9 mg per dL. I did not see or feel any bad sign or symptom but had it gone just a little lower it could have caused muscle weakness or heart arrhythmia. Why was I getting such a low Mg2+? Recently I got a most likely answer. For years I have followed a regimen of daily wine drinking, and daily low cholesterol Statin, ACE inhibitor and beta blocker pills any of which may cause the slightly low Mg2+. Last year because of surgery I stopped the regimen except for the daily beta blocker pill and, after the month off, my blood test still showed the low Mg2+. So I guess it was due to the daily beta blocker. I did not stop the beta blocker: My lowest Mg2+ on it had not been below 1.6 and no bad effect, and the beta blocker is doing a good job. Instead, I decided to try to increase my Mg2+ by eating. The best Mg-rich food is almond nuts. And since the best daily food magnesium for an adult is c.400 mg, and a reasonable number of almonds a day will supply it, I started to eat almonds, and, after several months, now my blood test shows normal Mg2+. And even though I do not see or feel a difference, I think I have done a good thing for my healthy longevity by normalizing my blood Mg2+. This also shows the benefit of using blood tests.
Phosphorus P
Phosphorus: (P5+ or 3+) is a non-metal of in Periodic Table Group 15 with nitrogen, arsenic, antimony and bismuth. In nutrition, P occurs as phosphate PO43-, hypophosphate HPO42-, and di-hydrogen phosphate H2PO4-. Chemical reactions involving tacking PO43-,(phosphorylation) and removing them (dephosphorylation) onto so-called "second messengers" by kinases or posphatases are keys to understanding intracellular signaling down to the nuclear gene level.
In bone, the phosphate PO43- is combined with Ca2+ as Ca3(PO4)2.
In food, P is in the protein and also in cereal grain. Milk and its products are the best source of P with Ca2+. Pure phosphorus deficiency from lack in diet is rare; it occurs in the starving person who suddenly gets food and overeats. Then it is rapidly fatal from heart arrhythmia. If you have been starving (or even fasting for up to 48 hours), be careful not to overeat but rather to limit the first day to snacks containing phosphorus (milk feeding).
    Inorganic phosphate is the form of P tested in blood, its value moves in opposite direction from blood plasma Ca++, both being under control of parathyroid hormone and vitamin D through kidney excretion and intestinal absorption.
   Phosphorus absorption from food occurs in the small intestine and is enhanced by vitamin D, so vitamin D deficiency causes low plasma phosphorus. Taking too much vitamin D causes high blood-test Phosphorus and when we see it in a teen age boy it usually means a soccer mom (in the U.S., an over protective, good-health seeking mother) feeding her son overdoses of vitamin D. 
Selenium Se
was discovered in 1823, its name derives from Greek selene, “Moon”, it is a reddish non-metal in the oxygen-sulfur group and so closely related to sulfur it can replace it in the amino acids cysteine and methionine.
Selenium attracted attention after a Chinese scientist in 1979 reported that Se food supplementation prevented a heart disease called Keshan from the part of China where Se in soil is low. But it was not until 1989 that the U.S. Food and Nutrition Board issued an RDA for it.
Selenium is important in the conversion of the thyroid hormone T4 to the most active form T3 so a Selenium deficiency could lead to low thyroid function even with normal thyroid gland and function
   Selenium is anti-oxidant. It can prevent vitamin E deficiency in animal on deficient vitamin E diet. Most foods contain it.
   Cancer: Selenium at 200 microgram (0.2 mg) a day daily dose may be preventive against colon, prostate and lung cancers. Research on selenium’s other anti-cancer effects is ongoing.
   Selenium's toxicity in adults who ate from 27 mg (500 X RDA) to 2400 mg a day has ranged from nausea at lower dose to near delirium at highest dose.
Zinc Zn
Its outermost orbital has 2 electrons, making Zn an electron-donor, reducing agent, with combining valence +2. After donating 2 electrons it is Zn2+. As found pure in soil it is bluish white brittle metal. For thousands of years its alloy with copper has been used as brass and when Zn is coated over iron to prevent corrosion it makes galvanized iron.   
Shellfish and red meat are a Zn source. Whole grain cereal is rich in Zn, mostly in the bran and wheat germ parts; Zn in cereal is not as efficiently absorbed as meat Zn. Some breakfast cereals add Zn.
   Severe Zn Deficiency shows a characteristic dermatitis surrounding body orifice (mouth, anus, vulva): acrodermatitis. It is treated by high Zn supplements. It has been noted in experimental Zn deficiency in volunteers.
Purely breastfed infant of mom with low or borderline Zn intake is at risk because breast milk has almost no Zn and such an infant should get Zn supplements. The semi-starved person (homeless derelict, anorexia) is also at risk. 
Acrodermatitis enteropathica is a genetic disease from a blockage in the intestinal absorption of Zn due to enzyme defect. Babies born with it have typical acrodermatitis. It is overcome by 45 mg of Zn in pill a day compared to usual 5 mg Zn requirement. 
Evaluation of Zn Status: In Zn deficiency, the blood serum Zn concentration will be less than 40 mg/dL.
   World Health Org advice of Zn daily intake was set for first time in late 1980s. Zn should be part of prenatal vitamin and mineral pill. 
There has been speculation that Zn deficiency is part of HIV/ AIDS illness, and many AIDS sufferers buy Zn supplements, but no evidence of benefit. Also diabetics have been reported to have low Zn in blood but study of supplementation suggests taking Zn may worsen diabetes.
   Toxicity: Outbreak of acute Zn toxicity occurred due to drinking beverage or eating food out of galvanized iron containers and also it is a cause of metal fume fever in galvanized iron workers. Chronic Zn toxicity occurs from dose of Zn as low as 50 mg a day for over 1 year. It induces copper deficiency whose sign is low HDL cholesterol (increased heart attack and stroke), depressed immunity (increased infection), anemia and various symptoms of brain and spinal cord dysfunction. Upper Limit for Zn intake is 40 mg a day. 
   Chapter Continues w. Minor Minerals next. Click 2.12e The Minor Metals in Nutrition and Toxicity


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