Chapter 11 Notes PDF

Minerals are inorganic elements representing ~4% of total body weight and are involved in osmotic properties of body fluids, bone and teeth structure, regulation of body processes, and serving as cofactors for metalloenzymes. - Minerals are classified based on magnitude of need into major minerals...

Minerals are inorganic elements representing ~4% of total body weight and are involved in osmotic properties of body fluids, bone and teeth structure, regulation of body processes, and serving as cofactors for metalloenzymes. - Minerals are classified based on magnitude of need into major minerals (macrominerals) like Ca, P, Mg, Na, K, Cl, and S, microminerals like Fe, Cu, Zn, Mn, and ultra-trace minerals like Se, I, Mo, Cr. - Major minerals like calcium, phosphorus, and magnesium have various functions in the body such as bone mineralization, nerve transmission, muscle contraction, blood clotting, enzyme regulation, and membrane permeability. - Good food sources of calcium include milk, cheese, yogurt, canned salmon with bones, fortified cereals, juices, and plant-based milks. - Calcium absorption mechanisms involve transport systems regulated by calcitriol, passive paracellular transport, calbindin D9k shuttling Ca across cells, and Ca-ATPase pump and Na+/Ca2+ exchanger on the basolateral side. - Factors like oxalate, phytic acid, and certain nutrients/substances can either enhance or inhibit calcium absorption, affecting its bioavailability. - Hormones involved in calcium homeostasis include Vitamin D, Parathyroid Hormone (PTH), and Calcitonin, which regulate serum calcium levels, bone calcium, renal calcium reabsorption, and intestinal calcium absorption. - Recommended daily intake for calcium is 1,000-1,200 mg for adults, with an upper limit of 2,000-2,500 mg to prevent toxicity. - Deficiency of calcium can lead to muscle tetany, osteopenia, osteoporosis, and other health issues, especially in at-risk populations. - Assessment of calcium status is challenging, with bone densitometry like DEXA scans being the most reliable method to evaluate bone mineral content. - Phosphorus is the second most abundant inorganic element in the body and is usually combined with other elements forming compounds like PO42-. - Phosphorus sources include meat, fish, dairy products, nuts, legumes, cereals, and processed foods containing phosphoric acid.- NPT2a is mainly expressed in the kidney - NPT2b is primarily found in the small intestine and is regulated by calcitriol - NPT2c is located in the kidney and is associated with growth - Key homeostatic hormones related to phosphorus metabolism include PTH, FGF23, and calcitriol - Phospholipase C releases phosphorus from phospholipids during digestion - Phosphorus bound to organic molecules must be hydrolyzed by alkaline phosphatase in the brush border - Intestinal absorption of phosphorus occurs mainly through passive diffusion throughout the small intestine, with smaller amounts absorbed via NPT2b, particularly in the ileum - Most dietary phosphorus is absorbed in the small intestine through passive diffusion - Intestinal absorption of phosphorus is highest in infants and children, ranging from 65% to 90%, while adults absorb around 55% to 80% - Phosphorus is quickly absorbed into the blood, with around 55% existing as HPO42-, 35% as complexed with Ca, Mg, Na, and 10-20% bound to proteins - Approximately 85% of phosphorus in the body is stored in the skeleton - Most phosphorus is excreted in urine, with a small amount excreted in feces - Regulation of serum phosphorus levels involves mechanisms in the kidney that parallel intestinal absorption - The bulk of filtered phosphate is reabsorbed in the renal proximal tubule by NPT2a and NPT2c - Regulation of serum phosphorus levels is negatively influenced by PTH and FGF23, and possibly positively by calcitriol - Circulating phosphorus is freely filtered by the glomerulus, with 85%-90% reabsorbed daily - High phosphorus diets in renally compromised individuals can lead to increased phosphorus excretion - Urinary phosphorus levels roughly equal absorbed phosphorus under normal phosphorus status - Functions of phosphorus include being a main anion in cells, contributing to the skeleton, energy metabolism, second messenger signaling, phosphorylation of substrates, and maintaining acid-base balance- Restoring calcium levels - Administration of magnesium produces an immediate rise in serum PTH - Severe magnesium deficiency - Includes hypomagnesemia along with - Hypocalcemia and hypokalemia - Increased potassium excretion - Retention of sodium - Low PTH levels - Neurological and muscular symptoms such as tremor, muscle spasms, and tetany - Loss of appetite, nausea, vomiting, and personality changes - Magnesium disease - Hypertension - Foods high in magnesium (fruits, vegetables, whole grains) are frequently high in potassium and dietary fiber - It is difficult to evaluate the independent effects of magnesium on blood pressure - Low blood magnesium may play a modest role in the development of hypertension - Very high doses of magnesium seem to work in individuals with low magnesium levels - Cardiovascular disease - Some studies have found decreased mortality in cardiovascular disease populations that routinely consume "hard" water - The relationship between dietary magnesium and the risk of cardiovascular disease remains unclear, but recent meta-analyses suggest an inverse association with circulating magnesium levels and the incidence of coronary heart disease, hypertension, and type 2 diabetes - Magnesium therapy may benefit in improving endothelial function in individuals with cardiovascular disease - Preeclampsia-eclampsia - A disease unique to pregnancy that may occur anytime between 20 weeks of pregnancy and 6 weeks after birth - Affects approximately 7% of pregnant women in the US - Preeclampsia is characterized by elevated blood pressure, proteinuria, and severe edema - Eclampsia occurs in addition to seizures as part of a triad of symptoms - Approximately 5% of women with preeclampsia progress to eclampsia, which is a significant cause of maternal death - High-dose IV magnesium sulfate (MgSO4) is a common treatment choice for preventing eclamptic convulsions that may occur in association with preeclampsia-eclampsia in late pregnancy or during labor - MgSO4 is believed to relieve cerebral blood vessel spasm and act as a vasodilator in both peripheral and cerebral vasculature - Additionally, it may protect the blood-brain barrier and limit cerebral edema formation - Vascular effects of magnesium - Other disorders - Osteoporosis - Epidemiological studies suggest that magnesium deficiency is one of the risk factors for osteoporosis, but there is no clear relationship between magnesium intake and bone mineral density - Some studies suggest an interaction between magnesium and vitamin D in bone health in older adults - Migraine headaches - Mixed results show that magnesium may be beneficial for some types of migraines - Asthma - IV infusions of magnesium may be beneficial for acute asthma, but there is limited data on chronic asthma or oral supplements