Water and Major Minerals PDF

FOOD & HEALTH F24 / FDE428 Water and the Major Minerals Dr. Ipek Bayram  Water and the Body Fluids Water accounts for about 60% of an adult’s body weight. Water makes up about 75% of the weight of lean tissue. ○ Lean tissue is the sum of body wate...

FOOD & HEALTH F24 / FDE428 Water and the Major Minerals Dr. Ipek Bayram  Water and the Body Fluids Water accounts for about 60% of an adult’s body weight. Water makes up about 75% of the weight of lean tissue. ○ Lean tissue is the sum of body water, total body protein, carbohydrates, non-fat lipids and minerals. Females, elderly, and obese people have a smaller proportion of lean tissue; thus, a lower proportion of their body weight is water.  Water and the Body Fluids The water in the body fluids: Carries nutrients and waste products Maintains structure of large molecules, (e.g. proteins, glycogen) Participates in metabolic reactions Serves as a solvent for minerals, vitamins, glucose and amino acids Acts as a lubricant and cushion around joints and inside the eyes Aids in regulation of body temperature (e.g. evaporation through sweat) Maintains blood volume Distribution of Body Fluids Fluid inside cells is called intracellular fluid, whereas fluid outside cells is called extracellular fluid. The extracellular fluid that surrounds each cell is called interstitial fluid, whereas the extracellular fluid in the blood vessels is called intravascular fluid. The compositions of intercellular and extracellular fluids differ from each other. They continuously lose and replace their components, yet remains constant under normal conditions. ○ Since imbalances can be devastating, the body quickly responds by adjusting both water intake and excretion as needed.  Water Intake Thirst and satiety influence water intake in response to changes sensed by the mouth, hypothalamus, and nerves. When water intake is inadequate, the blood becomes concentrated, the mouth becomes dry, and the hypothalamus initiates drinking behavior. When water intake is excessive, the stomach expands and stretch receptors send signals to stop drinking.  Dehydration Dehydration develops when too much water is lost and not replaced. A first sign of dehydration is thirst. If a person is unable to obtain water or fails to perceive the thirst message, the symptoms may progress rapidly: weakness, exhaustion, and delirium. Notice that an early sign of dehydration is fatigue. Dehydration develops with either inadequate water intake or excessive water losses.  Water Intoxication Water intoxication is rare but can occur with excessive water intake and kidney disorders that reduce urine production. The symptoms may include confusion, convulsions, and even death. Excessive water ingestion (10 to 20 liters) within a few hours dilutes the sodium concentration of the blood and contributes to a dangerous condition known as hyponatremia. ○ Guidelines suggest limiting fluid intake during times of heavy sweating to between 1-1.5 liters per hour. Water Intoxication Water Sources The obvious dietary source of water is water itself, which provides about one-third of the total water intake. Other beverages and nearly all foods also contain water. Most fruits and vegetables contain up to 90% water, and many meats and cheeses contain at least 50%. Metabolic water is also generated as an end product during condensation reactions. The water derived daily from these three sources averages about 2.5 liters.  Water Losses The body must excrete enough water to carry away the waste products. This obligatory water excretion is a minimum of about 500 milliliters of water each day. ○ If a person drinks more water, the kidneys excrete more urine, and the urine becomes more dilute. ○ In addition to urine, water is lost from the lungs as vapor and from the skin as sweat; some is also lost in feces. On average, daily losses total about 2.5 liters. Maintaining this balance requires healthy kidneys and an adequate intake of fluids.  Water Recommendations Water needs vary depending on diet, activity, environmental temperature, and humidity; therefore, a general water requirement is difficult to establish. AI for a person who expends 2000 kcalories a day is 2 to 3 liters of water. Total water includes not only drinking water, but water in beverages and in foods as well. Any beverage can readily meet the body’s fluid needs, but those with few or no kcalories do so without contributing to weight gain. Choices include tea, coffee, nonfat and low-fat milk, artificially sweetened beverages, fruit and vegetable juices, and sports drinks.  Health Effects of Water The kind of water a person drinks may also make a difference to health. Hard water has high concentrations of calcium and magnesium; but the principal mineral of soft water is sodium or potassium. In the body, soft water with sodium may aggravate hypertension and heart disease. In contrast, the minerals in hard water may benefit these conditions. Soft water also more easily dissolves certain contaminant minerals, such as cadmium and lead, from old plumbing pipes. These contaminant minerals harm the body. People who live in buildings with old plumbing should run the cold water tap a minute or two to flush out harmful minerals whenever the water faucet has been off for more than 6 hours. Many people select bottled water, believing it to be safer than tap water and therefore worth its substantial cost.  Blood Volume and Blood Pressure The kidneys are central to the regulation of blood volume and blood pressure. The kidneys reabsorb needed substances and water; and excrete wastes in the urine. Instructions on whether to retain or release substances or water come from antidiuretic hormone (ADH), renin, angiotensin, and aldosterone. ADH: Whenever blood volume or blood pressure falls too low, or whenever the extracellular fluid becomes too concentrated, the hypothalamus signals the pituitary gland to release ADH. ADH is a water-conserving hormone that stimulates the kidneys to reabsorb water, which trigger thirst. Drinking water raise the blood volume and dilute the concentrated fluids, thus helping to restore homeostasis. Hormone regulating region on the brain stem  Blood Volume and Blood Pressure Renin: Cells in the kidneys respond to low blood pressure by releasing an enzyme called renin. Through a complex series of events, renin causes the kidneys to reabsorb sodium. Sodium reabsorption is always accompanied by water retention, which helps to raise blood volume and blood pressure. Angiotensin: In addition to its role in sodium retention, renin hydrolyzes a protein from the liver called angiotensinogen to angiotensin I. Angiotensin I is inactive until another enzyme converts it to its active form—angiotensin II. Angiotensin II is a powerful vasoconstrictor that narrows the diameters of blood vessels, thereby raising the blood pressure. Aldosterone: In addition to acting as a vasoconstrictor, angiotensin II stimulates the release of the hormone aldosterone from the adrenal glands. Aldosterone signals the kidneys to excrete potassium and to retain more sodium, and therefore water.  Maintaining a balance of about two- thirds of the body fluids inside the cells and one-third outside is vital to the life of the cells. If too much water were to enter the cells, they might rupture; if too much water were to leave, they would collapse. To control the movement of water, the cells direct the movement of the major minerals—sodium, chloride, potassium, calcium, phosphorus, magnesium, and sulfur.  Dissociation of Salt in Water When a mineral salt such as sodium chloride (NaCl) dissolves in water, it dissociates into ions—positively and negatively charged particles (Na+ and Cl–). Unlike pure water, which conducts electricity poorly, ions dissolved in water carry electrical current. Thus, salts that dissociate into ions are called electrolytes. In all electrolyte solutions, anion and cation concentrations are balanced. If an anion enters the fluid, a cation must accompany it or another anion must leave so that electrical neutrality will be maintained. Thus, whenever sodium (Na+) ions leave a cell, potassium (K+) ions enter. Electrolytes Attract Water Electrolytes attract water. Each water molecule has a net charge of zero, but the oxygen side of the molecule has a slight negative charge, and the hydrogens have a slight positive charge. Both positive and negative ions attract clusters of water molecules around them. This attraction dissolves salts in water and enables the body to move fluids into appropriate compartments.  Water Follows Electrolytes Some electrolytes reside primarily outside the cells, whereas others reside predominantly inside the cells. Whenever electrolytes move across the cell membrane, water follows. The movement of water across a membrane toward the more concentrated solutes is called osmosis. The amount of pressure needed to prevent the movement of water across a membrane is called the osmotic pressure.  Proteins Regulate Flow of Fluids and Ions Proteins also attract water and help to regulate fluid movement. When proteins leak out of the blood vessels into the spaces between the cells, fluids follow and cause the swelling of edema. In addition, transport proteins in the cell membranes regulate the passage of positive ions and other substances from one side of the membrane to the other. Negative ions follow positive ions, and water flows toward the more concentrated solution.  Fluid and Electrolyte Imbalance Some medications, severe, prolonged vomiting and diarrhea, heavy sweating, burns, and traumatic wounds may incur such great fluid and electrolyte losses. If fluid is lost by vomiting or diarrhea, sodium is lost indiscriminately. If the adrenal glands oversecrete aldosterone (due to tumor), the kidneys may excrete too much potassium. People can replace the lost fluids and minerals by drinking plain cool water and eating regular foods. Some cases, however, demand rapid replacement of fluids and electrolytes—for example, when diarrhea threatens the life of a malnourished child. Oral rehydration therapy (ORT)—a simple solution to treat dehydration caused by diarrhea. Sugar (4tsp), salt (1/2 tsp), water (½ liter) to treat dehydration  The body uses its ions not only to help maintain fluid and electrolyte balance, but also to regulate the acidity (pH) of its fluids. The body must maintain the pH within a narrow range to avoid life-threatening consequences. Slight deviations in either direction can denature proteins. Enzymes couldn’t catalyze reactions and hemoglobin couldn’t carry oxygen Three systems defend the body against fluctuations in pH—buffers in the blood, and respiration in the lungs.  Regulation of pH Bicarbonate (a base) and carbonic acid (an acid) protect the body against changes in acidity by acting as buffers—substances that can neutralize acids or bases. Carbon dioxide, which is formed all the time during energy metabolism, dissolves in water to form carbonic acid in the blood. Carbonic acid, in turn, dissociates to form hydrogen ions and bicarbonate ions. The appropriate balance between carbonic acid and bicarbonate is essential to maintaining optimal blood pH. The lungs control the concentration of carbonic acid by raising or slowing the respiration rate. If too much carbonic acid builds up, the respiration rate speeds up. This hyperventilation increases the amount of carbon dioxide exhaled, thereby lowering the carbonic acid concentration. Conversely, if bicarbonate builds up, the respiration rate slows; carbon dioxide is retained and forms more carbonic acid.  The Minerals—An Overview Minerals are inorganic elements that always retain their chemical identity. In contrary to vitamins that are organic and easily destroyed, minerals are not destroyed by heat, air, acid, or mixing. ○ In fact, the ash that remains when a food is burned contains all the minerals that were in the food originally. Some minerals, such as potassium, are easily absorbed into the blood, transported freely, and readily excreted by the kidneys, much like the water- soluble vitamins. Other minerals, such as calcium, are more like fat-soluble vitamins in that they must have carriers to be absorbed and transported.  The Minerals—An Overview Some foods contain binders that impact mineral bioavailability. Two examples are phytates and oxalates that occur in foods of plant origin. Similar to vitamins, an excess of a mineral can create an inadequacy of another, supplements are often to blame. ○ When sodium intake is high, both it and calcium are excreted. This is an example of mineral interactions.  Minerals in a 60-kilogram human body The distinction between the major and trace minerals does not mean that one group is more important than the other—all minerals are vital. The major minerals are so named because they are present, and needed, in larger amounts in the body.  Major Minerals Sodium Sodium is the principal cation of the extracellular fluid. Sodium also helps maintain acid-base balance and is essential to nerve impulse transmission and muscle contraction. Sodium travels freely in the blood until it reaches the kidneys. Then, kidneys return to the blood the exact amount of sodium the body needs. When blood sodium rises, as when a person eats salted food; thirst signals the person to drink until the appropriate sodium-to-water concentration is restored. Then, the kidneys excrete both the excess water and the excess sodium together. Both too much and too little sodium in the diet increase the risk of heart disease.  Sodium Recommendations Sodium deficiency is rare; the body is able to adapt its sodium losses via sweat and urine. High sodium is correlated with high blood pressure. Because of this, the UL is 2300 mg. The average sodium intake in the United States is 3400 mg, which exceeds recommendations—and most adults will develop hypertension at some point in their lives. Most sodium is consumed as salt (sodium chloride). Adults with prehypertension or hypertension are recommended to consume < 1500mg of sodium. The eating plan especially for lowering sodium is called DASH (Dietary Approaches to Stop Hypertension)  Sodium Deficiency In extreme cases, a drop in blood-sodium levels causes hyponatremia. Hyponatremia is caused by excessive sodium losses, not inadequate sodium intake. Symptoms of hyponatremia include headache, confusion, seizures, and coma. ○ Sweating causes loses in sodium and water. If too much water is consumed, hyponatremia develops (marathon runners). Chronic excessive sodium intake damages blood vessels, kidneys, brain, heart, and increases risk of death from heart disease. Acute symptoms of excessive sodium are edema and high blood pressure. Prolonged excessive sodium contributes to hypertension.  Sodium and Hypertension A high sodium intake was considered the primary factor responsible for high blood pressure. Salt has a greater effect on blood pressure than either sodium or chloride alone or in combination with other ions. The elevation of blood pressure in response to a high-salt diet over years might give permanent damage to blood vessels. A high salt intake correlates strongly with heart disease, and salt restriction (to no more than 1500 mg/day) helps to lower blood pressure.  Sodium and Bone Loss (Osteoporosis) High salt intake associated with increased calcium excretion ○ Potassium as protective factor DASH diet recommendation - low in sodium and abundant in potassium-rich fruits and vegetables and calcium-rich low-fat milk. Processed foods have the most sodium ○ Processed foods have reduced potassium ○ Fresh fruits and vegetables have the least sodium Sodium and Potassium Contents of Processed Foods  Potassium In contrast to sodium (outside the cell), potassium is a principal intracellular cation; inside the body cells Roles in the body ○ Helps maintain fluid and electrolyte balance ○ Helps maintain cell integrity ○ Aids in nerve impulse transmission and muscle contraction ○ It affects many aspects of homeostasis, including a steady heartbeat.  Potassium Intakes 1. Potassium is abundant in all cells; however, processing destroys cells. Therefore, fresh foods are the richest sources of potassium. 2. Potassium has a(n) AI of 4700 mg/day. 3. Diets low in potassium raise blood pressure. 4. To meet potassium needs, people are recommended to consume more: fresh fruits and vegetables. Potassium in Selected Foods  Potassium Deficiency and Toxicity Deficiency characterized by: ○ Increase in blood pressure, kidney stones, bone turnover ○ If deficiency progress: irregular heartbeats, muscle weakness, glucose intolerance Toxicity: ○ No UL ○ Might result from overconsumption of supplements or potassium salts or from certain diseases ○ Kidneys accelerate excretion ○ If injected into a vein, heart can stop.  Chloride Essential nutrient Roles in the body ○ Major anion of extracellular fluids Moves passively across membranes Associates with sodium and potassium ○ Helps maintain fluid and electrolyte balance ○ Part of hydrochloric acid in gastric juice Serious consequence of vomiting: loss of HCl from stomach  Chloride Intakes Abundant in processed foods Recommendations slightly higher, but still equivalent to those of sodium Deficiency and toxicity ○ Diets rarely lack chloride ○ Deficiency might develop due to disorders leading deficiency ○ Toxicity might develop due to water deficiency  Calcium Most abundant mineral in the body! Adequate intake ○ Grows a healthy skeleton in early life ○ Helps minimize bone loss in later life Majority of body’s calcium in bones and teeth ○ Part of bone structure ○ Calcium bank  Calcium in Body Fluids Helps to maintain normal blood pressure Extracellular calcium ○ Participates in blood clotting Intracellular calcium ○ Binds proteins in cells and activates them Regulation of muscle contraction Transmission of nerve impulses Secretion of hormones Activation of some enzyme reactions  Calcium Balance 1. Calcitonin is released when blood calcium is high. Calcitonin helps to inhibit activation of vitamin D; prevents calcium reabsorption in the kidneys; inhibit osteoclast cells release calcium into the blood. 2. Parathyroid hormone (PTH) stimulates vitamin D activation. This enhances calcium absorption in the intestines. Osteoclast cells release calcium into the blood. PTH raises blood calcium levels. 3. Blood calcium above normal level results in calcium rigor: the muscles contract and cannot relax. 4. Blood calcium below normal causes calcium tetany—also characterized by uncontrolled muscle contraction.  Calcium Balance These conditions do not reflect a dietary excess or lack of calcium; they are caused by a lack of vitamin D or by abnormal secretion of the regulatory hormones. A chronic dietary deficiency of calcium, or a chronic deficiency due to poor absorption over the years, depletes the bones. Calcium Recommendations Hormones maintain blood concentration regardless of dietary intake ○ When intake is low, bones suffer Recommendations set high: ○ To retain calcium in bones ○ To accommodate 30% average absorption rate 1300 mg/day for adolescents 1000 mg/day for adults up to age 50 1200 mg/day for women >50 and everyone >70 Phases of Bone Development Throughout Life Calcium in Selected Foods  Calcium Deficiency Match these With these 1. Osteoporosis a) Achieved by late 20s Reaching peek bone mass 2. Peek bone mass b) Low bone mass means denser bones protect against inevitable age-related 3. Bone loss c) Begins at ages 30 to 40 bone loss and fractures. 4. Osteopenia d) Porous and fragile Osteoporosis is “silent” because the body shows no bones, called a “silent” symptoms. Osteopenia is less 1–d disease severe than osteoporosis. 2–a 3–c 4–b  Phosphorus Second most abundant mineral in body ○ 85% is found combined with Ca in hydroxyapatite crystals of bone and teeth Roles in body ○ Part of major buffer system ○ Part of DNA and RNA ○ Assists in energy metabolism ○ Helps transport lipids in the blood ○ Structural component of cell membranes  Phosphorus Intakes Deficiencies are unlikely Best sources ○ Protein-rich foods—meat, poultry, fish, milk, cheese UL ○ Toxicity is rare ○ 4000 mg Phosphorus in Selected Foods  Magnesium Body locations ○ More than half is in bones Bone Mg acts as reservoir to ensure normal blood concentrations as with Ca Roles ○ Maintains bone health ○ Energy metabolism and ATP production ○ Inhibits muscle contraction and blood clotting ○ Supports normal function of immune system  Magnesium Intakes Sources ○ Legumes, seeds, nuts, leafy green vegetables ○ Hard water ○ Mineral water: Bioavailability is 50% but improves when water is consumed with meal. Deficiency rarely occurs ○ Impairs central nervous system activity ○ Exacerbate inflammation and chronic diseases Protective against hypertension ○ Hard water contributions ○ Low rates of heart disease UL applies to non-food sources Magnesium in Selected Foods  Sulfate Oxidized form of sulfur Sources ○ Food and beverages ○ Amino acids Methionine Cysteine Skin, hair, nails contain rigid proteins high in sulfur No recommended intake ○ Normal protein intake