chapter 11

Minerals in the Body

• Minerals represent ~4% of total body weight
• Involved in osmotic properties of body fluids, bone structure, and body processes
• Classified as major (macrominerals) or minor (microminerals)
• Major minerals (Ca, P, Mg, Na, K, Cl, S) crucial for bone mineralization, nerve transmission, muscle contraction, blood clotting, enzyme regulation, and membrane permeability
• Good food sources of calcium include milk, cheese, yogurt, fortified cereals.
• Calcium absorption affected by factors like oxalates, phytic acid, and certain nutrients
• Hormones (vitamin D, PTH, calcitonin) regulate calcium homeostasis (levels) and affect bone calcium, renal reabsorption, and intestinal absorption
• Calcium intake recommendations: 1000-1200 mg/day for adults; upper limit of 2000-2500 mg to prevent toxicity
• Deficiency can lead to muscle tetany, osteopenia, osteoporosis
• Assessing calcium status primarily through bone densitometry (DEXA scans)
• Phosphorus (second most abundant inorganic element) found in meat, fish, dairy, nuts, legumes, cereals
• Combined with other elements to form compounds, like PO42-
• Phosphorous absorption regulated by NPT2a, NPT2b, NPT2c. NPT2b is primarily located in the small intestine. NPT2a and NPT2c are located in the kidneys.
• Absorption controlled by calcitriol and other regulatory hormones
• Phosphorus released from phospholipids through phospholipase C
• Primarily absorbed passively in small intestine; some via NPT2b in the ileum

Phosphorus Absorption and Regulation

• Most dietary phosphorus absorbed passively in the small intestine (65-90% in infants/children; 55-80% in adults)
• Absorbed quickly into the blood;
• Primary form: HPO42-
• Approximately 85% of phosphorus stored in the skeleton
• Most phosphorus excreted in urine, small amount in feces
• Regulation of serum/blood phosphorus influenced by PTH and FGF23.
• Positively influenced by calcitriol
• Kidney plays a significant role in phosphorus homeostasis
• 85-90% of circulating phosphorus reabsorbed daily, under normal conditions, urinary phosphorus equals absorbed phosphorus

Magnesium Function and Deficiency

• Involved in many bodily functions, contributing to cell structures and energy metabolism, second messenger signaling, and maintaining acid-base balance
• Foods high in magnesium include fruits, vegetables, whole grains
• Deficiency may contribute to various issues: low PTH, neurological and muscular problems (like tremors and spasms), loss of appetite, nausea, etc.
• High magnesium doses effective for low magnesium level individuals.

Cardiovascular Disease and Magnesium

• Some studies suggest an inverse relationship between circulating magnesium levels and cardiovascular risk factors like coronary heart disease, hypertension, and type 2 diabetes
• May help in improving endothelial function.

Preeclampsia/Eclampsia and Magnesium

• High-dose IV magnesium sulfate (MgSO4) used as a preventive and treatment measure during/related to preeclampsia-eclampsia.
• believed to relieve cerebral blood vessel spasm and act as a vasodilator
• protects the blood-brain barrier

Other Disorders and Magnesium

• Epidemiological studies have linked magnesium deficiency and osteoporosis, but the specific relationship remains unclear
• Some studies suggest potential interaction between magnesium and vitamin D in bone health in older adults
• May have benefits for certain types of migraines, asthma, but limited data available regarding long-term use for chronic conditions.