Nutrient regulation of chemical metabolism in humans

Dietary protein, carbohydrate, cruciferous vegetables, and charcoal-broiled beef can markedly alter the patterns of chemical biotransformations in normal subjects. The specific nutritional factors capable of altering the metabolism of drugs and the range of chemicals, including hormones, whose metabolism can be altered by diet in humans merit further study because they have the potential to influence the biological impact of these substances in humans.

Metabolic mechanisms of drug-nutrient interactions

Metabolic mechanisms of nutrition and drug interactions include 1) the effects of diet on drug metabolism and action and 2) the effects of drugs on nutritional processes. The type, amount, and timing of foods consumed influence drug dissolution, absorption, distribution, metabolism, and excretion. High-fat meals enhance the absorption of griseofulvin and some other drugs. Milk and other sources of calcium inhibit absorption of tetracycline. High-fat meals increase plasma concentrations of free fatty acids and thereby displace many drugs from binding sites on plasma albumin. High-protein diets increase the activity of the mixed-function oxidase system and enhance the metabolism of numerous drugs. High-electrolyte intakes increase excretion of lithium and also diminish the action of diuretic agents. Bile acid sequestrants and some laxatives decrease lipid digestion and absorption, as well as absorption of the fat-soluble vitamins. Numerous drugs, including tetracycline and cholestyramine, bind iron and decrease its absorption. Coumarins inhibit the function of vitamin K. Phenobarbital and other anticonvulsants are inducers of cytochrome P-450 and the mixed-function oxidase system. Long-term treatment with these inducers can cause excessive metabolism and deficiency of vitamin D. Prooxidant drugs such as chloroquine, drugs detoxified by conjugation with glutathione, and alcohol can deplete reduced glutathione with consequent effects on amino acid transport and the redox status of cells. Acid-forming foods acidify the urine and increase the loss of alkaline drugs such as the amphetamines. Base-forming drugs increase the loss of acidic drugs such as barbiturates. The range of metabolic interactions of drugs and nutrients includes the full scope of physiological processes to which drugs and nutrients are subject.

Trophic response of hamster brown adipose tissue: roles of norepinephrine and pineal gland

The objective was to find out whether the reduced amount of brown adipose tissue in myopathic hamsters [Am. J. Physiol. 239 (Cell Physiol. 8): C18-C22, 1980] was secondary to a refractoriness to the trophic influence of norepinephrine. However, no evidence for any trophic influence of norepinephrine on brown adipose tissue of either normal or myopathic hamsters could be detected under experimental conditions that have demonstrated such an influence in rats. A mediator other than norepinephrine, melatonin, secreted by the pineal gland, is known to mediate the control of brown adipose tissue growth induced in hamsters by short photoperiod. Further studies of intact or pinealectomized hamsters showed that the pineal gland was not required for either cold- or diet-induced growth of brown adipose tissue. It is concluded that the defect in control of brown adipose tissue size in the hamster with muscular dystrophy is not due either to abnormal control by norepinephrine or to the pineal gland since neither of these appears to participate in the normal regulation of brown adipose tissue size in relation to environmental temperature or to diet.

Dietary concerns associated with the use of medications

Medications can affect, and be affected by, nutrition. The interactions between drugs and various components in the diet are in part responsible for the erratic drug responses observed in patients. Because of the diversity of food consumption patterns among individuals and the widespread use of drugs, an array of varied and complicated side effects can occur. When vitamins, minerals, or other food components alter drug utilization or when drugs induce nutritional deficiencies, the effect poses a risk to the patient. Drugs can also affect many nutrition-related factors, such as appetite, taste acuity, and gastrointestinal function. Dietary habits or metabolic changes should be examined carefully and evaluated in any patient who unexpectedly gains or loses weight while taking drugs. Medicated patients need to be aware of good nutrition practices and to understand the importance of dietary modifications associated with certain diseases. A nutritious diet not only makes an important contribution to the health of those individuals but also reduces the risk of nutrition disorders or altered drug efficacy. Nutrition counseling should be considered for medicated patients to help them make rational decisions about their food choices.

Implications of nutritional status on human biochemistry, physiology, and health

Optimum nutrition is the level of intake that should promote the highest level of health. Although excess caloric intake will lead to obesity, a deficit in nutrition may result in a tissue depletion of essential nutrients that can lead to biochemical changes and eventually to clinical signs and symptoms. Nutrition requirements may differ according to sex, age, activity, or physiological state and can be influenced by drugs, smoking, alcohol, and other factors. With ever-increasing sedentary life styles and less physically demanding jobs, the resulting reduced caloric requirements have made it more difficult to make nutritionally sound food choices. Nutrition is the single most important component of preventive health care. Diet has been associated with cancer, heart disease, diabetes, stroke and hypertension, arteriosclerosis, and cirrhosis of the liver. The ability of the human to respond to stresses, such as altitude, heat, trauma, surgery, and infection can be influenced by nutritional status. Nutritional status is reflected in a variety of metabolic processes that provide the basis for a number of methods for its assessment.

[Effects of ornithine alpha-ketoglutarate on the nutritional state of intensive-care patients]

Alpha ketoglutarate d'ornithine effects on the nutritional status of patients in an Intensive Care Unit are studied. The authors have chosen a random sample of 44 patients with diseases of comparable severity for paired comparison. Treatment is applied at a dosage of 25 g per day with intravenous nutrition and/or oral feeding (150 Kcal/g of excreted nitrogen). Statistical analysis shows a significant improvement of nitrogen balance and prealbumine level, non significant changes for the other criteria. Alpha ketoglutarate of ornithine influences favorably nitrogen balance, prealbumine levels and the nutritional status.

[Drugs and nutrition: interactions and incompatibilities]

A absorção de drogas pode, às vezes, ser consideravelmente alterada conforme as condições em que são ingeridas, ou seja, em jejum ou junto com alimentos ou fluidos. Além disso, alguns componentes alimentares não devem ser ingeridos com certas drogas por apresentarem efeitos adversos. O presente trabalho aborda essas interações e incompatibilidades existentes entre as drogas e os alimentos.

[Effect of hypokinesia on human nutritional status]

In three series of experiments of 120, 49 and 180 days in duration 36 test subjects were exposed to clinostatic and antiorthostatic hypokinesia. Human requirements for various nutrients were defined under hypokinetic conditions. It was demonstrated that during bed rest exercises together with adequate nutrition and after bed rest certain nutrients can serve as efficient countermeasures against metabolic changes.

Drug-pyridoxal phosphate interactions

In this review it has been pointed out that vitamin B6 and its vitamers can be involved in many interactions with a number of drugs, as well as with the actions of various endocrines and neurotransmitters. Nutritional deficiencies, especially of vitamins and proteins, can affect the manner in which drugs undergo biotransformation, and thereby may also modify the therapeutic efficacy of certain drugs. The differences between nutritional vitamin B6 deficiency and the hereditary disorder producing pyridoxine dependency are discussed. In addition to a pyridoxine deficiency being able to adversely affect drug actions, the improper supplementation with vitamin B6 can in some instances also adversely affect drug efficacy. A decrease by pyridoxine in the efficacy of levodopa used in the treatment of Parkinsonism is an example. The interrelationships and enzymatic interconversions among pyridoxine vitamers, both phosphorylated and non-phosphorylated, are briefly discussed, particularly regarding their pharmacokinetic properties. The ways in which the normal biochemical functions of vitamin B6 may be interfered with by various drugs are reviewed. (1) The chronic administration of isoniazid for the prevention or treatment of tuberculosis can produce peripheral neuropathy which can be prevented by the concurrent administration of pyridoxine. An acute toxic overdose of isoniazid causes generalized convulsions, and the intravenous administration of pyridoxine hydrochloride will prevent or stop these seizures. (2) The acute ingestion of excessive monosodium glutamate will, in some individuals, cause a group of symptoms including among others headache, weakness, stiffness, and heartburn, collectively known as the 'Chinese Restaurant Syndrome.' These symptoms can be prevented by prior supplementation with vitamin B6. The beneficial effect is ascribed to the correction of a deficiency in the activity of glutamic oxaloacetic transaminase, an enzyme that is dependent on pyridoxal phosphate. Some interesting relationships are pointed out between vitamin B6, picolinic acid, and zinc. It is postulated that the intestinal absorption of zinc is facilitated by picolinic acid, a metabolite of tryptophan. The derivation of picolinic acid from tryptophan depends on the action of the enzyme kynureninase, which is dependent on pyridoxal phosphate; therefore, the adequate absorption of zinc is indirectly dependent on an adequate supply of vitamin B6. The formation of pyridoxal phosphate, on the other hand, appears to be indirectly dependent on Zn2++ which activates pyridoxal kinase.(ABSTRACT TRUNCATED AT 400 WORDS)

Vitamin D supplements enhance weight gain and nutritional status in pregnant Asians

In a double blind trial of supplementary vitamin D (1000 iu daily) administered in the last trimester of pregnancy to Asian women living in London, supplemented mothers gained weight faster (63.3 g/day) than those in the control group (46.4 g/day), and at term had significantly higher plasma levels of retinol binding protein and thyroid binding prealbumin indicating better protein-calorie nutrition. Maternal weight gain correlated with postpartum levels of both retinol binding protein and thyroid binding prealbumin. Almost twice as many infants in the unsupplemented group weighed under 2500 g at birth, and had significantly lower retinol binding protein levels than infants of supplemented mothers. The nutritional benefits of supplementation provide further support for the routine administration of vitamin D to all British Asians during pregnancy.

Nutrition and the adolescent: an update

This article reviews selected nutrition research pertinent to adolescent health care. Protein--calorie malnutrition affects 25% of hospitalized adolescents studied, which correlates, as in adults, with increased morbidity and mortality. Some subgroups of adolescents, notably Asian immigrants, have been shown to be at high risk for developing vitamin D deficient rickets. On the other hand, excessive vitamin D intake has been linked to arteriosclerosis in animal models. Calcium supplementation is not likely to be indicated in U.S. adolescents. Iron deficiency prevalence in adolescence is not well documented, owing to the confusion between anemia and iron deficiency. Serum ferritin and free erythrocyte protoporphyrin measures should help to clarify this issue. Zinc nutrition must be assessed in high-risk groups such as those with short stature or Crohn's disease. Oral contraception effects on vitamin B6 and on serum lipids need to be considered in the risk-benefit equation when prescribing this method of birth control for adolescents.

Nutritional effects of oral contraceptive use: a review

Oral contraceptives agents (OCA) have been in use for more than two decades, and at the present time, 150 to 200 million women are using the preparations. Apart from their gynecologic influence, the hormones have been shown to affect a number of metabolic and nutritional processes, some advantageously and others disadvantageously. Concern over the nutritional status of females consuming OCA prompted this review. Eight vitamins and three minerals were investigated. Contraceptive steroid ingestion was shown to depress the physiologic levels of six nutrients (riboflavin, pyridoxine, folacin, vitamin B12, ascorbic acid and zinc), elevate the levels of three others (vitamin K, iron and copper) and provide little or no change in one (alpha tocopherol) and questionable increases in another (vitamin A). It was concluded that females consuming OCA should pay particular attention to vitamin and mineral intake and, if warranted, consume physiologic supplements of needed nutrients.