It was said in the previous article that we would save our discussion about phosphorous (P) for later and well later is now so let us begin. As an electrolyte, phosphorous normally exists as phosphate (PO43-) in the blood which makes it a so-called polyatomic ion (a molecule with a positive or negative charge) in the fact that it is bound to four oxygen (O) atoms. It also pairs up with hydrogen (H) to make dihydrogen phosphate or H2PO4– (a weak acid; pH less than 7) and hydrogen phosphate HPO42- (the conjugate [paired] base; pH greater than 7). These two polyatomic ions are very important as buffering agents in our cells meaning that, when in balance with each other, they help to maintain a desirable pH (one that is resistant to change to maintain homeostasis).
- Although this picture is truly lame to look at, just know there is constant conversion between H2PO4– and HPO42- to adjust for pH fluctuation
Phosphate is also involved in a process called phosphorylation (not as complicated as it sounds) and simply describes the addition of a phosphate group to another molecule in the body. Well now we have no choice but to talk about our high energy friend adenosine tri-phosphate (ATP). Without phosphorylation there could be no ATP and without ATP there could be no life (at least for us mammals and reptiles). All comedy aside, ATP is an energized molecule useful in mechanisms of active transport. It is “deactivated” when it gives up one of its three phosphates thus becoming ADP or adenosine diphosphate. So phosphorylation of these ADP molecules is very important to regenerate or re-energize these molecules as ATP.
In the previous article, phosphorus was hinted at being a vital component in the health of our bones and this was revealed in the chemical name of hydroxyapatite which is (Ca10(PO4)6(OH)2). Hydroxyapatite is the inorganic compound responsible for the hardness of our bones and teeth of which 85% of all phosphorus resides. Matter of fact, our enamel is further strengthened when the teeth are exposed to the fluoride in our toothpaste and/or drinking water (or maybe it’s just a ploy to make us all retarded). A modest amount of fluoridation at 0.7 to 1.2 parts per million (4 ppm is the maximum upper limit in city water) is enough to change hydroxyapatite into fluoroapatite to increase resistance to tooth decay. Like calcium, the mineral phosphorus is also helped by vitamin D in regards to increased intestinal absorption (but then too much phosphate in the blood deactivates vitamin D). Excess phosphorus is fortunately filtered out of the blood by the kidneys and is excreted in the urine.
Amongst those of us who drink colas (and I’m not pointing fingers…you know who you are), the phosphoric acid in these beverages can corrode teeth enamel, lead to lower bone density, and increase the risk for chronic kidney disease when consumption is at two drinks or more per day (especially in combination with a diet that is low in calcium). This just goes to show that not all forms of phosphorus are going be good for us and we should probably steer clear of white phosphorus by the way unless we want to experience incendiary burns and scorched lungs (red phosphorus is okay though as it helps us light our matches). Dietary deficiency of phosphorus is extremely uncommon and is usually the result of prolonged starvation but symptoms such as bone pain, osteomalacia (bone softening), muscle weakness, and increased risk for infection would manifest if this was the case. Toxicity can occur in those with impaired renal function, excessive dietary consumption and supplement abuse (Upper Tolerable Intake Level [UL] is 4,000 mg daily), and symptoms include increased urinary calcium loss, tetany (involuntary muscular contraction), hypotension, tachycardia (heart beats faster than it should), and cardiovascular calcification (atherosclerosis). The Recommended Dietary Allowance (RDA) for adults aged 19 years or older is 700 milligrams per day with cow dairy (247 -385 mg per 8 ounces [oz]) and meat (104 – 252 mg per 3 oz) being our best sources followed by lentils (178 mg in 1/2 cup) and nuts (107 to 134 mg per 1 oz).
For those of us who were looking forward to being able to play with white phosphorus (so sorry to disappoint you), there is a suitable substitution if fireworks were on the mind and that is magnesium. In its form as an alkaline-earth metal, university lab personnel (and students should they be so lucky) often use small strips of magnesium to test a captivating reaction that takes place when carefully exposed to the flame of a Bunsen burner. When the magnesium ignites upon heat of combustion it produces an extremely bright white light that is difficult to look at and it burns HOT (insert “don’t try this at home” disclaimer). We’ve got to see it to believe it now don’t we?
As the cation Mg2+, magnesium has many roles in the body such as acting as a co-factor in enzymatic reactions responsible for blood pressure regulation, blood glucose control, protein synthesis, and nerve and muscle function. It is also involved in the body’s energy pathways much like phosphate and it has a place in oxidative phosphorylation matter of fact in addition to glycolysis (the breakdown of glucose for energy). Curiously, magnesium helps contribute to the development of bone structure and 50 – 60% is present in the bones but it is actually an antagonist to calcium (also an alkaline-earth metal) which means that these two nutrients compete against each other for absorption (the same goes for calcium versus iron…can’t they just get along?). Although, magnesium is willing to help out calcium in addition to potassium in times of need when it comes to the active transport of these two ions across cell membranes for maintenance of normal heart rhythm, muscular contraction, and nerve impulse transmission (magnesium is also involved in DNA and RNA synthesis and is necessary in the production of the antioxidant glutathione). Like some of the other electrolytes already mentioned, magnesium will be excreted in the urine when there is too much of it in the body or it will be reabsorbed by the kidneys if there is a deficiency (more or less will be absorbed in the small intestine depending on intracellular concentration).
We should be pleased to know that it is magnesium to the rescue whenever we are suffering from moderate constipation because supplemental magnesium induces a laxative effect. It is actually the primary ingredient in Phillips’ Milk of Magnesia at 500 mg elemental magnesium in the form of magnesium hydroxide. Some medicines such as Extra-strength Rolaids for heartburn and upset stomach include magnesium hydroxide to help relieve symptoms.
Along with potentially potassium and calcium, magnesium is another electrolyte where dietary deficiency can be a problem but a true pathological deficiency is rare because the body will make adjustments by excreting less of it in the urine and will maximize absorption from foods. In addition to starvation, individuals who have malabsorptive disorders (such as Crohn’s disease or Ulcerative Colitis) can suffer from true electrolyte related deficits as well as individuals affected by acute but severe illness, chronic alcohol abuse, and certain medications. In those afflicted, symptoms of magnesium deficiency could include nausea and vomiting, fatigue, numbness and tingling, muscle cramps, abnormal heart beat, and seizures. Toxicity often stems again from supplement abuse and the overuse of laxatives or antacids with magnesium hydroxide (UL is 350 mg daily for supplements only) and symptoms could include diarrhea, hypotension (low blood pressure), confusion, abnormal heart beat, and deterioration of kidney function. The RDA for dietary magnesium is 400 mg per day and 310 mg per day in men and women aged 19 to 30 years, respectively, (increases to 420 mg and 320 mg post 30 years old) and our best sources include oat bran (96 mg in 1/2 cup), wheat bran (93.1 mg in 1/2 cup), brown rice (86 mg in 1 cup), almonds (78 mg in 1 oz), spinach (78 mg in 1/2 cup cooked), and Swiss chard (75 mg in 1/2 cup cooked).