Pre-exercise carbohydrate meals: application of glycemic index.

PURPOSE: The purpose of this study was to compare postprandial glycemic, insulinemic, and physiologic responses to a pre-exercise meal calculated to have a low glycemic index (LGI) with one calculated to have a moderately high glycemic index (HGI); each meal provided three foods totaling 1.5 g carbohydrate/kg body weight. METHODS: After an overnight fast, 10 trained cyclists consumed one of the test meals or water 30 min before cycling 2 h at 70% of maximum oxygen uptake (VO2max), followed by cycling to exhaustion at 100% of VO2max. RESULTS: Plasma insulin levels were significantly lower (P < 0.05) after LGI than after HGI through 20 min of exercise. Significantly higher (P < 0.05) respiratory exchange ratios were observed after HGI than after LGI until 2 h of exercise. At that time plasma glucose levels were significantly higher and ratings of perceived exertion lower (P < 0.05) after LGI compared with after HGI. Time to exhaustion was 59% longer after LGI (206.5+/-43.5 s) than after HGI (129.5+/-22.8 s). CONCLUSIONS: These results suggest a pre-exercise LGI may positively affect maximal performance following sustained exercise. The LGI maintained higher plasma glucose levels at the end of 2 h of strenuous exercise than the HGI, which may have better supported subsequent maximal effort.

The reliability of muscle function analysis using different methods of stimulation.

BACKGROUND: The purpose of our study was to determine the reliability of nonvolitional muscle function analysis (MFA) by determining the day-to-day and within-day reliability of conventional electrical stimulation and a newer, magneto-electrical stimulation method, using standard laboratory methodology. METHODS: Ten healthy, human immunodeficiency virus-negative adult men volunteered as subjects. MFA consisted of measuring the maximal relaxation rate, for magneto-electrical stimulation at 1 Hz and conventional electrical stimulation at 20 Hz, and force-frequency ratios using conventional electrical stimulation at 10 Hz:20 Hz and 10 Hz:50 Hz. Within-day and day-to-day reliability were determined by calculating the coefficient of variation (CV) for all subjects. RESULTS: Maximal relaxation rate using magneto-electrical stimulation had a significantly lower CV compared with the other nonvolitional MFA methods (p = .002). CONCLUSIONS: Maximal relaxation rate using magneto-electrical stimulation was more reliable and technically easier than the other muscle function parameters examined. However, the day-to-day CV of muscle function parameters is larger than traditional nutrition assessment techniques. Development within the field should strive to improve testing techniques so that the reliability of MFA will allow definition of a range of normal values against which an individual's value can be compared. Until this is available, the precision and reliability of MFA restrict its use to research and population studies.

Physicians' perceptions of the role of clinical dietitians are changing.

We surveyed a selected group of physicians to determine their opinions regarding appropriate activities and educational background for hospital dietitians. Questionnaires were mailed to 401 physicians listed in the yellow pages of the 1988 San Jose/Santa Clara, Calif, telephone directory. Physicians were chosen from nutrition-related specialties such as cardiology, endocrinology, and gastroenterology. Questionnaires were returned by 123 (30%) physicians. Most physicians viewed dietitians as contributing members of the health care team. However, they believed that the physician should be responsible for ordering therapeutic diets. Most physicians (98%) agreed that one of the most important duties of the dietitian is to assure patient satisfaction with food served. Physicians (94%) also believed that presenting current nutrition information to hospital personnel is an important activity. Counseling patients was an area most physicians (99%) thought should be included in the educational background of dietitians. Sixty percent of the physicians indicated that it is important for the dietitian to understand blood and urine laboratory values. These results indicate that the perceived status of hospital dietitians by physicians has improved since earlier studies.

Nutritional status of HIV-infected patients during the early disease stages.

Nutritional status was monitored in two groups of patients infected with human immunodeficiency virus (HIV) for up to 16 months. Twenty-six subjects were recruited from patients enrolled in acquired immunodeficiency syndrome treatment protocols in the early stages of the disease. Body weight, percent body fat, serum albumin, total protein concentration, hemoglobin, hematocrit, and total lymphocyte count were monitored monthly. Four-day food intake records were kept every 4 months. In the 19 patients followed for 16 months (Group 1), a significant (p less than .05) decrease was observed in body weight, percent body fat, body mass index (BMI), and total protein concentration. Seven subjects (Group 2), with more advanced disease than Group 1, demonstrated a significant (p less than .05) decrease in total lymphocyte count over a 5-month period. This latter group fell just below the normal range for hemoglobin and hematocrit concentrations during the study period. With the exception of a decrease in vitamin B-6, zinc, and total energy intake, food records closely matched the Recommended Dietary Allowance for the age group. Thus, we conclude that decreases in body weight, percent body fat, and BMI may be the earliest indication of decreased nutritional status in HIV-infected patients.

Diet counseling in a multicultural society.

Successful diet counseling is dependent on culturally sensitive communication strategies. Health care practitioners can improve cross-cultured counseling through a four-step process. First, they must become familiar with their own cultural heritages. Second, they must become acquainted with the cultural background of each client. Third, through an in-depth cross-cultural interview, they must establish the client's cultural background, food habit adaptations made in the United States, and personal preferences. Fourth, they must modify diets based on unbiased analysis of the dietary data. The best chance for compliance occurs when diets are modified with consideration for client's cultural and personal preferences.

Southeast Asian renal exchange list.

More than 340,000 Southeast Asians (SE Asians) have immigrated to the United States since 1971. By 1984, 76,000 SE Asians had settled in California. In areas of the U.S. with large SE Asian populations, many foods specific to those people are readily available. Approximately 5% of the total U.S. population has medical problems that lead to kidney disease. Many SE Asian refugees have prior medical problems, such as hepatitis B, that may make them at significantly higher risk for kidney disease. A modified renal exchange list (excluding milk, carbohydrate supplement, and fat group) was developed. This list, made up of foods readily available and commonly eaten by the largest group of SE Asian immigrants, the Vietnamese, categorizes foods by protein, potassium, and caloric content. A separate list, indicating the phosphorus content of these foods, is also included. Asian grocery stores were visited to identify foods available for purchase by SE Asians. The foods were identified, and nutrient composition was found in food composition tables. Because the Vietnamese diet is high in potassium and sodium, planning renal diets poses problems for both patients and dietitians. Close monitoring of diet can retard the progression of renal disease. An exchange list such as this assists both dietitians and renal patients in this important task.