Sports food

A burst of excitement on the international althletic scene has had the world wondering just how much of the althletic performance is due to nutrition. Some say the secret lies in yam, and yet others think it is in food processing and food quality that makes the difference. But is there really a link between performance and nutrition? If so, what is it?

Sugar and your health

Sugar has been, over the years, important to the Caribbean as it is one of our major exports, made from the sugar cane grown in many countries. In addition to using it in sweetening drinks and in cakes, pudding and pastries, we use sugar in our own confectionary such as peppermint candy, tamarind balls. coconut, peanut or almond drops. among many other uses. In this Issue of Nayam News we look at sugar in the diet and whether indiscriminate consumption of sugar leads directly to persons becoming obese.

Crop improvement for human nutrition: the case of the Mexican yam bean [abstract]

The Mexican yam bean (Pachyrhizus erosus) is a tuberous legume native to Central America. This species shows great potential for development as a food crop, to increase the existing limited base of staples that make up the diet in tropical regions, producing both protein rich grain and starch producing tubers. Starch quality is good due to its high digestibility. The major limitation to its use as a staple crop, however, is the low starch content of the tubers. The low variability of the existing gene pool for the genus limits the use of conventional plant breeding for improvement of the crop. Genetic engineering for crop improvement is, therefore adopted. The molecular genetics of carbohydrate metabolism in tubers of the Mexican yam bean is being studied. The result of such studies will guide the application of genetic engineering technology to improve starch content of the tubers. The work reported here describes the cloning of putative genes for the large subunit of ADP-glucose pyrophosphorylase (Agp2) from yam bean tubers. A cDNA library was constructed from RNA isolated from two-month-old yam bean tubers. A probe for Agp2 was prepared by RTPCR analysis of the tuber RNA preparations, using degenerate primers. Four clones, which hybridized to the probe, were isolated for further characterization. (AU)

The effects of chronic S-nitrosoglutathoine adminstration on glucose tolerance in dog animal model

The nitric oxide donor S-nitrosoglutathione (GSNO) has been used to prevent platelet activation in patients with severe pre-eclampsia. The study assesses the chronic administration of GSNO on glucose metabolism in the dog animal model. GSNO (10 mg/kg) was administered intravenously for 14 days and the blood glucose concentration was determined by the glucose oxidase method. Oral glucose tolerance tests revealed an impaired glucose tolerance in the GSNO-treated dogs as reflected by elevated postprandial blood glucose concentrations at the 1.0 hour to 2.5 hour time interval (p < 0.05). The elevated blood glucose concentration was associated with a statistically significant decrease in plasma insulin concentration. The plasma insulin concentration at 1.0 hour in captopril-treated controls was 41.00 uIU/ml compared with 27.33 uIU/ml in GSNO-treated dogs (p < 0.05). In contrast, the plasma glucagon concentration was enhanced by the chronic adminstration of GSNO, as confirmed by a concentration of 75.00 ñ 6.06 pg/ml in GSNO-treated dogs compared with 49.50 ñ 4.64 pg/ml in captopril-treated controls at the 1.0 hour time interval. Linear regression analysis of the data revealed a highly significant and positive correlation between the blood glucose concentration and the plasma glucagon concentration (r = 0.739, p < 0.01). Similarly, a positive correlation existed between the blood glucose concentration and the plasma insulin concentration (r = 0.513, p = 0.307). We conclude that chronic in vivo adminstration of GSNO impairs the parameters of carbohydrate metabolism. Patients who are on protracted treatment with GSNO could be risk for the development of diabetes mellitus.(Au)

Available carbohydrates of cereal grains as affected by storage and insect infestation

Total soluble sugar, reducing sugar, non-reducing sugar and starch contents of wheat, maize and sorghum grains were affected adversely at 25, 50 and 75 percent insect infestation caused by Trogoderma granarium Everts and Rhizopertha dominica Fabricius, separately and mixed population. R. dominica caused significant (P < 0.05) reduction in available carbohydrates at 50 and 75 percent. Mixture of both insect species caused intermediate losses. Storage of cereal grains up to 4 months resulted in substantial increase in sugars and decrease in starch content, but storage for a shorter period of time did not cause any significant changes in levels of carbohydrates (Summary)

Fibre, lente carbohydrates and diabetes mellitus - abstract

In vitro studies have shown that there are differences in rates at which different starch foods are digested. In general, the rate of release of the products of starch digestion relates well to the glycaemic responses to the same foods tested in normal and diabetic volunteers. The foods that are more slowly digested result in a flatter blood glucose response than those which are rapidly absorbed. These slow-release carbohydrate forms might be termed "lente carbohydrates". Many carbohydrate foods which have been staples in traditional diets posses slow-release carbohydrate properties manifested in relatively flat glycaemic responses on feeding. This paper points out the 'lente carbohydrate' properties of cassava (manihot esculeta) and recommends that it be used in modifying the diet of the diabetic (AU)

Glucose tolerance in pre-eclampsia - abstract

In normal pregnancies (NP), carbohydrate metabolism as assessed by oral glucose tolerance is impaired. This study was aimed at assessing whether a complication of pregnancy, pre-eclampsia (PE), exacerbates this impairment of carbohydrate metabolism. Results showed that the fasting plasma glucose levels were not significantly different between the PE (4.62ñ0.27 mM/1) and the NP (4.12ñ0.08 mM/1). However, the fasting plasma insulin levels were significantly higher in the PE (28.4ñ5.9 uU/m1) than in the NP (9.6ñ2.3 uU/m1) (p<0.01). Analysis of the area under the curve showed that the glucose response curves were not significantly different. The insulin response curves displayed a trend of higher circulating insulin levels in the PE compared to the NP; (p<0.07). The insulin to glucose ratio, an index of insulin sensitivity, in the PE (6.21ñ1.37) was significantly higher than that of the NP (2.26ñ0.54) p<0.05). We suggest that the hypertensive complication of pregnancy, PE, is accompanied by hyperinsulinaemia in the basal or fasting state, with an accompanying insulin insensitivity (AU)

Fasting energy utilization in the smaller of twins with epinephrine-deficient hypoglycemia

The possible role of epinephrine deficiency in abnormal utilization of energy sources during fasting was investigated in three pairs of discordant identical twins with recurrent fasting hypoglycemia. The hypoglycemic twins, ages 2, 8 and 9 years, each had beens smaller at birth. Defective epinephrine responsiveness to hypoglycemia was established by administration of 2-deoxyglucose, 50 mg/kg, i.v. In the control twins, this resulted in a rapid increase of plasma glucose (+39 mg/100 ml), free fatty acids (+0.3 mM), and urinary epinephrine (+224 ng/mg creatine). These changes did not occur in the affected twins. Fasting metabolism in the epinephrine-deficient twins was compared to the unaffected twins as controls. Oxidation of carbohydrate and fat were estimated from hourly measurements of oxygen consumption and carbon dioxide production, and utilization of protein was determined from nitrogen excretion. PLasma glucose decreased more rapidly in the affected twins during the 8 hours prior to appearance of symptoms. During this period, carbohydrate was oxidized more rapidly than in the controls (average: 3.1 versus 1.7 mg/kg/min). Plasma á-hydroxybutyrate and free fatty acids was frequently less in relation to glucose. Symptoms occurred when the sum of both glucose and á-hydroxybutyrate was lower than in the controls. Urinary epinephrine excretion increased from an average baseline of 18 to a maximum of 134 ng/mg creatinine in the control twins. The average maximum urinary epinephrine reached in the deficient twins was only 51 ng/mg creatinine, in spite of lower glucose. Plasma insulin decreased in relation to glucose below 40 mg/100 ml in the control twins (r = 0.65), but this did not occur in the deficient twins (r = -0.38). Cortisol and growth hormone responses were similar in the two groups. THerefore, the consequences of inability to increase epinephrine when availability of glucose became acutely limiting were inappropriate persistent oxidation of carbohydrate, decreased circulating alternate substrates from fat, and lack of suppression of insulin. (AU)

Some effects of metabolic acidosis on carbohydrate metabolism in the rat

Metabolic acidosis was induced by feeding ammonium chloride to rats which were maintained on a carbohydrate diet for 48h. Fasting blood glucose was the same in acidotic and control animals, but there was an increase in liver glycogen in the former. Muscle glucogen was unchanged. In vitro glycogenesis was the same in liver slices from normal rats when incubated at a range of pH from 6.90 to 7.40. The peak blood glucose in response to intraperitoneal injections of glucagon was the same in control and acidotic rats. The rate of disappearence of glucose was slower in acidotic rats both after the glucagon induced hyperglycaemia and after intravenously injected glucose. Liver phosphorylase, total glycogen synthetase and the I form of this enzyme were unchanged in acidosis. The data are compatible with the hypothesis that in the acidotic rat there is a block in glycolysis-possibly at the phosphofructokinase step (Summary)

Sugar absorption and intestinal motility in children when malnourished and after treatment

The ability of malnourished children to absorb lactose, sucrose and glucose was tested by perfusing the jejunum. Intestinal motility was measured simultaneously in a perfused segment by a dye dilution technique. These tests were repeated on the same children after 6-16 weeks of treatment. There was a significant correlation between the rate of hydrolysis of disaccharide perfusing the jejunum and the level of disaccharidase activity within the jejunal mucosa. All ten malnourished children had dimished glucose absorption, eight had reduced lactose and six had impaired sucrose hydrolysis and absorption. Children with the most severe mucosal damage had the lowest rate of sugar absorption. The malabsorption of disaccharide was related to the impairment of hydrolysis and not to the malabsorption of the monosaccharide products. Primary hypermotility of the intestine was not a feature of the malnourished group. Water absorption from all infusions occurred only in the treated group. Water entry into the intestinal lumen in the malnourished group was greatest with the most poorly absorbed sugars. The mean transit time of fluid passing down the intestine was inversely correlated with the sugar remaining unabsorbed within the lumen. Treating the malnourished child in hospital produced an increase in glucose, lactose and sucrose absorption. The generalized nature of the malabsorption and the reversibility of the defects suggests that lactose intolerance in these children is related to the nutritional state and not to a genetic predisposition to lactase deficiency. (Summary)

Alterations in carbohydrate metabolism in Jamaican children with severe malnutrition

Carbohydrate metabolism was studied in Jamaican children who had been admitted to hospital with protein-calorie malnutrition. Analysis of liver biopsies showed that levels of protein and glycogen were low in malnutrition and rose with recovery. Hepatic glucose-6-phosphatase was elevated in malnutrition but phosphorylase levels were normal. In the malnourished child there was normal hepatic glycogenolysis as shown by a normal blood glucose response to intravenous glucagon without any detectable rise in blood pyruvate and lactate. Fasting levels of blood lactate as well as lactate-pyruvate ratios rose with recovery from malnutrition. Galactose tolerance tests showed a delayed disappearance of injected galactose, but the maximum increase in blood glucose after galactose injection was the same in all clinical states. Glucose disappearance was delayed after both glucagon and galactose. Muscle glycogen was initially reduced, but there was a markeed "overshot" to supranormal levels during the recovery phase. (AU)

The xylose excretion test

It is thought that this simple and useful procedure can give valuable information on the state of carbohydrate absorption. Details of the determination are presented and the rationale of the test discussed. Diseases associated with defection absorption, such as celiac disease, Whipple's disease, scleroderma, pernicious anemia and certain post-operative states are illustrated. It is suggested that the presence of ascites may account for the low values encountered in some patients with hepatic cirrhosis (AU)