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Chapter 10. Nutritional Diseases

Essential Nutrients

An adequate diet must provide sufficient total proteins, sufficient total calories, essential amino acids, essential fatty acids, vitamins, and minerals. A deficiency of any of these dietary factors leads to disordered cellular metabolism and cellular injury with recognizable symptoms and signs of nutritional deficiency. Nutritional diseases arising from total protein-energy deficiency and various vitamin and mineral deficiencies are well-recognized (Table 10-1).

Table 10–1. Principal Human Nutrients and Disorders Resulting from Nutritional Deficiency or Excess.
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Table 10–1. Principal Human Nutrients and Disorders Resulting from Nutritional Deficiency or Excess.
Nutrient Physiologic Importance Deficiency Excess
Protein Numerous. Marasmus; kwashiorkor; growth retardation. None.
Calories Numerous. Marasmus; kwashiorkor; growth retardation. Obesity.
Fat-soluble vitamins 1
Vitamin A Retinol is constituent of retinal rod pigment rhodopsin. Maintain epithelia. Loss of night vision; increased thickness of squamous epithelia; Bitot's spots; xerophthalmia, keratomalacia (eyes); follicular hyperkeratosis (skin). Bleeding; hepatosplenomegaly 2 (rare).
Vitamin D (cholecalciferol) 1,25-Dihydroxycholecalciferol activates calcium absorption in intestine and causes bone mineralization. Rickets (children); osteomalacia (adults). Hypercalcemia leading to metastatic calcification and renal damage 2 (rare).
Vitamin K Required for synthesis of prothrombin and clotting factors, VII, IX, and X. Hypoprothrombinemia resulting in bleeding tendency. Hemolytic anemia 2 (rare).
Water-soluble vitamins 1
Vitamin C (ascorbic acid) Required for synthesis of collagen and osteoid. Scurvy; impaired wound healing. Minimal—possibly urinary calculi.
Thiamine (vitamin B 1 ) Coenzyme in decarboxylase systems; required for synthesis of acetylcholine. Beriberi (wet and dry); Wernicke's encephalopathy; Korsakoff's syndrome. Transient flushing, dizziness.
Riboflavin (vitamin B 2 ) Constituent of flavoproteins. Cheilosis, glossitis, angular stomatitis; corneal vascularization. None.
Niacin Constituent of NAD and NADP. Pellagra. Flushing due to vasodilation occurs with intravenous injection (rare).
Pyridoxine (vitamin B 6 ) Coenzyme for decarboxylase and transaminase systems. Glossitis; blepharitis; dermatitis; cheilosis; peripheral neuropathy; sideroblastic anemia. Transient paresthesias.
Folic acid Required for nucleic acid synthesis. Megaloblastic anemia. None.
Vitamin B 12 Required for nucleic acid synthesis. Megaloblastic anemia; subacute combined degeneration of spinal cord; peripheral neuropathy. None.
Minerals
Iron Constituent of hemoglobin and myoglobin. Hypochromic anemia; loss of mucosal integrity. Hemochromatosis.

1 The fat-soluble vitamins are present especially in fatty foods (milk, butter, etc) and may be deficient when there is fat malabsorption for any reason. Water-soluble vitamins are widely distributed in fruits, vegetables, and animal products, with the exception of vitamin B 12 , which is found almost exclusively in meat. Water-soluble vitamins are less affected by generalized malabsorption states; specific malabsorption of vitamin B 12 occurs in pernicious anemia.

2 Note that excess amounts of fat-soluble vitamins accumulate in body fat stores and may lead to toxicity; toxicity of water-soluble vitamins is much rarer, probably because of rapid excretion of any excess in the urine.

Nutritional Deficiency

Deficiency of an essential nutrient may arise in a variety of ways.

Primary Nutritional Deficiency

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