Sodium dietary requirement

Sodium chloride [7647-14-5] is an essential dietary component. It is necessary for proper acid—base balance and for electrolyte transfer between the iatra-and extracellular spaces. The adult human requirement for NaCl probably ranges between 5—8 g/d. The normal diet provides something ia excess of 10 g/d NaCl, and adding salt duting cooking or at the table iacreases this iatake. 

All patients with ascites require counseling on dietary sodium restriction. Salt intake should be limited to less than 800 mg sodium (2 g sodium chloride) per day. More stringent restriction may cause faster mobilization of ascitic fluid, but adherence to such strict limits is very difficult. Patients usually respond well to sodium restriction accompanied by diuretic therapy.14,22,31,32 The goal of therapy is to achieve urinary sodium excretion of at least 78 mEq (78 mmol) per day.22 While a 24-hour urine collection provides this information, a spot urine sodium/ potassium ratio greater than 1.0 provides the same information and is much less cumbersome to perform. 

B. Selenium in the form of selenocysteine is required for three enzymes that remove iodide from thyroid hormones. There are no signihcant areas in which dietary intake of sodium or potassium are problems. Fluorine deficiency is not associated with thyroid hormone metabolism. 

In terms of mineral content, potato is best known as an important source of dietary potassium, which plays a fundamental role in acid-base regulation and fluid balance and is required for optimal functioning of the heart, kidneys, muscles, nerves, and digestive systems. Health benefits of sufficient potassium intake include reduced risk of hypokalemia, osteoporosis, high blood pressure, stroke, inflammatory bowel disease (IBD), kidney stones, and asthma. A high intake of potassium and low intake of sodium have been hypothesized to reduce the risk of stroke (Larsson et al., 2008 Swain et al., 2008). However, most American women 31-50 years old consume no more than half of the recommended amoimt of potassium and men s intake is only moderately higher (lOM, 2004). 

Sodium removal is the next important step—by dietary salt restriction or a diuretic—especially if edema is present. In mild failure, it is reasonable to start with a thiazide diuretic, switching to more powerful agents as required. Sodium loss causes secondary loss of potassium, which is particularly hazardous if the patient is to be given digitalis. Hypokalemia can be treated with potassium supplementation or through the addition of a potassium-sparing diuretic such as spironolactone. As noted above, spironolactone should probably be considered in all patients with moderate or severe heart failure since it appears to reduce both morbidity and mortality. 

Almost all the evidence showing that phytate decreases zinc absorption in man and animals is based on pure phytate added to the diet. The effect of natural phytate is variable (18). It has, however, been reported that phytate in bran affected zinc bioavailability in the same way as sodium phytate (19). Dietary fibre in the rural Iranian diet was considered to be the main cause of zinc deficiency in Iran (20). However, the addition of 26 g of fibre from various sources to the American diet did not have any significant effect on the zinc requirements of male adults (21). Similarly, Indian men consuming a diet containing only 10.8 mg of zinc were reported to be in balance in spite of a dietary fibre intake of 50 g per day (22). Moreover, the presence of fibre and phytate in soy flour did not affect the bioavailability of zinc added as zinc carbonate, to the diet of rats (17), although others (23) have reported that the bioavailability of zinc in breakfast cereals depends mainly on their phytate-zinc molar ratio. Our results indicate that there is some, as yet, undetermined difference in the phytate or the fibre of cereals which affects the bioavailability of zinc. It may be some component of dietary fibre (24) or the intrinsic differences in the protein-phytate-mineral complex (10). 

Amounts of dietary sodium in excess of the kidney s ability to dilute and to excrete it in the urine leads directly to hypertension and indirectly to coronary heart disease and stroke. Although sodium chloride is required at about 1 g day, a typical Western diet, in fact, may contain from 8 to 12 g day. If renal transport is impaired, sodium ion accumulates and the osmotic pressure of the blood rises. Dietary reduction of salt can ameliorate some but not all of the problems. A wide variety of low-salt food products is now available. 

Whether dietary fiber is required for the health of the colonocylcs has not been proven, although evidence suggests such a requirement Absorption of salts and water is a major function of the large intestine. Short-chain fatly adds stimulate the absorption of sodium, chloride, and water in the colon (Hoverstad, 1986). in the absence of short-chain fatty acids, the mucosa of the colon may become inflamed or atrophied. 

Acquit coagulation defects are more common, and may be due to liver disease (since bile is required for absorption of vitamin K), dietary deficiency of vitamin K, or ingesUon of oral anticoagulant agents. Most of these can be treated by giving vitamin K and its congeners, menadiol sodium phosphate or phytomenadione. 

Absorption of vitamin C from the small intestine is a carrier-mediated process that requires sodium at the luminal surface. Transport is most rapid in the ileum and resembles the sodium-dependent transport of sugars and amino acids, but the carrier is distinct for each class of compound. Some ascorbate may also enter by simple diffusion. With dietary intake less than 100 mg/d, efficiency of absorption is 80-90%. With intake equal to the RDA, plasma ascorbate is 0.7-1.2 mg/dL, and the ascorbate pool size is 1500 mg. Scurvy becomes evident when the pool is less than 300 mg, at which point plasma ascorbate is 0.13-0.24 mg/dL. Highest tissue concentrations of ascorbate are in the adrenal gland (cortex > medulla). 

These results are consistent with an aberration in central osmoreceptor or sodium sensor or ANG Il-sensitive mechanisms that influence body fluid and sodium homeostasis. The results of this study suggest a potential requirement for n-3 PUFAs, early in life, for normal development and neural function. Evidence that early dietary n-3 PUFA... 

The metabolic acidosis associated with hyperkalemic distal (type IV) RTA with hyporeninemic-hypoaldosteronemia that is often seen in patients with diabetes meUitus may be corrected by the treatment of hyperkalemia alone (see Chap. 50). The use of supplemental alkali (1 to 2 mEq/kg per day) to increase sodium intake and stimulate distal tubular potassium secretion may be beneficial. A minority of patients require the administration of pharmacologic amounts of fludrocortisone." Type TV RTA resulting from a generalized distal tubular disorder often responds to low doses of alkali (1.5 to 2.0 mEq/kg per day). ° Corrections of the acidosis along with modest dietary potassium restriction (to 1 mEq/kg per day) wfll often result in the maintenance of serum potassium levels of 5 mEq/L or less. 

The Food and Nutrition Board has removed the three electrolytes from its table of estimated safe and adequate daily dietary intake because sufficient information is not available to establish a recommended amount. The major dietary source of sodium and chloride is table salt (40% sodium and 60% chloride). Physicians still recommend that the intake of sodium be restricted to 1-2 g daily. The recommended intake of chloride is approximately 1.7-5.1 g daily. However, getting enough sodium and chloride is not a problem. In fact, sodium intake in the United States is about 5-7 g/day, far in excess of the 1-2 g/day required by a normal adult. 

Water and sodium intake should be carefully matched to the losses. Dietary sodium restriction and diuretics may be required to prevent sodium overload. 

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