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Diet intake and endurance performance in Kenyan runners

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Abstract

Training and competing at elite as well as sub-elite level requires an optimal functioning of the body. This review looks at the case of the Kenyan runners, who consume a relatively high-quality diet based on vegetable sources with maize and kidney beans as the staple foods. The diet is high in carbohydrate and total protein, but low to borderline in a few essential amino acids. The timing of diet intake – immediately after training sessions – is optimal for skeletal muscle glycogen resynthesis that is enhanced without the help of insulin up to 60 min after cessation of exercise. Whether the total energy intake of the Kenyan runners is adequate is debatable. However, chronic undernutrition is not possible for athletes who engage in daily high-quality and -quantity physical exercise throughout most of the year. It is suggested that Kenyan runners participate in well-controlled, laboratory studies to investigate the quality of local foods and performance, as well as possible physiological adaptation mechanisms among athletes with a high habitual energy turnover.

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... It is worth mentioning that a great density of capillaries and increased number of mitochondria in the muscular system were observed in the inhabitants of other highaltitude regions such as Peru, Mexico and Tibet. some researchers pay closer attention to Kenyans' diet [13][14]. The diet is very simple: small portions of fried meat, boiled and raw vegetables, fruit, eggs, milk and their favorite ugali groats. ...
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We recently reported that in light exercise (30% VO2max) the oxidation of [1-13C]leucine was significantly increased but the rate of urea production was unchanged (J. Appl. Physiol: Respirat. Environ. Exercise Physiol. 52: 458-466, 1982). We have therefore tested three possible explanations for this apparent incongruity. 1) We infused NaH13CO3 throughout rest and exercise and found that, although altered bicarbonate kinetics in exercise resulted in greater recovery of 13CO2, the difference between rest and recovery was small compared with the increase in the rate of 13CO2 excretion during exercise when [1-13C]leucine was infused. 2) We infused [15N]leucine and isolated plasma urea N to determine directly the rate of incorporation of the 15N. During exercise there was no increase in the rate of 15N incorporation. Simultaneously, we infused [2,3-13C]alanine and quantified the rate of incorporation of 15N in alanine. We found that [15N]alanine production from [15N] leucine more than doubled in exercise, and by deduction, alanine production from other amino acids also doubled. 3) We tested our previous assumption that [1-13C]leucine metabolism in exercise was representative of the metabolism of other essential amino acids by infusing [1-13C] and [alpha-15N]lysine throughout rest and exercise. We found that the rate of breakdown of lysine during exercise was not increased in a manner comparable to that of leucine. Thus, these data confirm our original findings that leucine decarboxylation is enhanced in light exercise but urea production is unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)
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Dietary guidelines for achieving optimal muscle glycogen storage after prolonged exercise have been given in terms of absolute carbohydrate (CHO) intake (8-10 g.kg-1.day-1). However, it is of further interest to determine whether the addition of fat and protein to carbohydrate feedings affects muscle glycogen storage. Eight well-trained triathletes [23.1 +/- 2.0 (SE) yr; 74.0 +/- 3.4 kg; peak O2 consumption = 4.7 +/- 0.4 l/min] undertook an exercise trial (2 h at 75% peak O2 consumption, followed by four 30-s sprints) on three occasions, each 1 wk apart. For 24 h after each trial, the subjects rested and were assigned to the following diets in randomized order: control (C) diet (high glycemic index CHO foods; CHO = 7 g.kg-1.day-1), added fat and protein (FP) diet (C diet + 1.6 g.kg-1.day-1 fat + 1.2 g.kg-1.day-1 protein), and matched-energy diet [C diet + 4.8 g.kg-1.day-1 additional CHO (Polycose) to match the additional energy in the FP diet]. Meals were eaten at t = 0, 4, 8, and 21 h of recovery. The total postprandial incremental plasma glucose area was significantly reduced after the FP diet (P < 0.05). Serum free fatty acid and plasma triglyceride responses were significantly elevated during the FP trial (P < 0.05). There were no differences between trials in muscle glycogen storage over 24 h (C, 85.8 +/- 2.7 mmol/kg wet wt; FP, 80.5 +/- 8.2 mmol/kg wet wt; matched-energy, 87.9 +/- 7.0 mmol/kg wet wt).(ABSTRACT TRUNCATED AT 250 WORDS)
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To study the effects of glycogen depletion and insulin concentration on glycogen synthesis, gastrocnemius glycogen was measured with 13C-nuclear magnetic resonance at 4.7 T after exercise. Subjects performed single-leg toe raises to deplete gastrocnemius glycogen to 75, 50, or 25% of resting concentration (protocol I). Insulin dependence of glycogen synthesis was assessed after depletion to 25% with (protocol II) and without (protocol III) infusion of somatostatin to inhibit insulin secretion. After depletion to 75 and 50%, glycogen resynthesis rates were similar (2.4 +/- 0.7 and 2.8 +/- 0.6 mM/h, respectively). When glycogen was depleted to 25% (< 30 mM), the resynthesis rate was significantly higher (P < 0.02) at 33 +/- 7 mM/h, and it declined to 3.5 +/- 0.9 mM/h at > 35 mM glycogen. At < 35 mM glycogen, synthesis was not affected by low insulin (24 +/- 4 mM/h, protocol vs. 19 +/- 3 mM/h, protocol III), whereas at > 35 mM glycogen, synthesis ceased without insulin (-0.07 +/- 0.19 mM/h, protocol II). After depletion to 25% (protocol III), plasma lactate transiently increased (0.81 mM at rest, 1.82 mM 0 h after exercise, and 0.76 mM 2 h after exercise), whereas other plasma constituents did not significantly change. We conclude that after depletion to < 30 mM initial glycogen resynthesis is insulin independent and glycogen dependent, which suggests local control.
Article
Fifteen non-insulin dependent diabetic volunteers, aged 51 +/- 3.9 years, were studied over a two month period to determine their glycaemic responses to various local foods. They were all on chlorpropamide and one subject was removed from analysis due to concurrent use of insulin. They received on separate occasions two servings of white bread, one serving of: brown bread, white lice, English potatoes, maize meal, millet and cassava each. Each meal contained 50 g of carbohydrate. A total of 107 glucose tolerance tests (GTTs) were performed and the glycaemic index (GI) for each food calculated. The mean blood sugars at 0,60 and 120 minutes were comparable for each food, and the peak rise occurred at 60 minutes. The highest rise (4.0 mmol/I) was seen with millet porridge. The highest GI was seen with white rice and the lowest with English potatoes (159.9 and 34.3 respectively). Overall, the cereals conferred higher GIs than the root vegetables. The GIs of English potatoes, maize meal, millet and cassava significantly differed from that of white bread. It is concluded that, using GIs, dietary guidelines comprising locally available and affordable foods can be made.
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Prevalence of malnutrition among pre-school children can be used to determine the need for nutrition surveillance, nutritional care, or appropriate nutritional intervention programmes. Such data also indicate the target groups and where interventions are required. To determine the at risk groups, extent and magnitude, and regional distribution of malnutrition. A cross sectional study. The survey was conducted in 14 districts representative of the eight provinces of Kenya. Six thousand, four hundred and nineteen children (3294 males and 3125 females) aged six to 72 months selected using the cluster sampling technique from eight provinces were studied. Anthropometric measures of height/length and weight were used to do the assessment. The prevalence of stunting, wasting and underweight were 37%, 6% and 27% respectively. Stunting was highest among the 12-23 months age group (44.8%). A statistically significant difference (p = < 0.005) was found between boys and girls with regard to stunting. This difference was more remarkable when the two were stratified by age group where 29% of the boys were stunted compared to 20% of the girls. Geographically, it was found that there exists great regional disparities with a low (22.6%) in Kiambu and a high (56.5%) in Kwale districts. These results show that malnutrition is still a serious public health problem in Kenya and requires urgent attention. The problem since the first survey in 1977 shows an upward trend, suggesting deterioration over the years. Well thought out and targeted intervention programmes are long overdue. The results of this survey and others emphasize the importance of having a well established surveillance system which would ensure necessary and timely action.
Energy intake and physical work in Guatemalan farmers
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