PubMed Health⌕ Search

Biomedical subjects

A L Jenkins

Publications and source records attributed to A L Jenkins.

At least 19 recordsLinked to original sources
PubMed1992

Metabolic advantages of spreading the nutrient load: effects of increased meal frequency in non-insulin-dependent diabetes.

The acute effect of increasing meal frequency as a model of slow absorption was studied for 1 d in 11 patients with non-insulin-dependent diabetes. On 1 d they took 13 snacks (the nibbling diet) and on another day the same diet was taken as three meals and one snack (the three-meal diet). The nibbling diet reduced mean blood glucose, serum insulin, and C peptide concentrations over the 9.5 h of observation and 24-h urinary C peptide output by 12.7 +/- 3.7% (mean +/- SE) (P = 0.0062), 20.1 +/- 5.8% (P = 0.0108), 9.2 +/- 2.6% (P = 0.0073), and 20.37 +/- 8.12% (P = 0.039), respectively, compared with the three-meal diet. Serum triglyceride concentrations were lower by 8.5 +/- 3.2% (P = 0.037). Despite lower insulin concentrations on the nibbling diet, the concentrations of free fatty acids, 3-hydroxybutyrate, and the insulin-sensitive branched-chain amino acids responded similarly on both treatments. Metabolic benefits seen with increased meal frequency may explain the success of similar agents that prolong absorption, including fiber and enzyme inhibitors.

Adult↗
PubMed1992

Colonic fermentation and markers of colorectal-cancer risk.

The aim of this study was to determine the effect of soluble fiber on indexes of colon-cancer risk in postpolypectomy and nonpolyp patients. Forty-five postpolypectomy and 49 nonpolyp volunteers completed 2-wk metabolic studies where half of the group received oat-bran supplements and the other half took wheat-brain supplements. Colonic biopsies taken before and after the intervention showed no difference in the index of thymidine colonic-crypt-cell labeling, thymidine-labeling pattern, or nuclear aberrations. Nevertheless, fecal pH was significantly reduced by 0.23 +/- 0.07 pH units (P less than 0.002) as an index of increased colonic fermentation on oat bran. This was not associated with increased basal breath hydrogen concentrations; fecal butyrate concentrations were higher on wheat bran. We conclude that soluble fiber as oat brain appears to have no advantage over wheat bran in modifying putative risk factors for colonic cancer.

Butyrates↗
PubMed1992

Wheat-bran and oat-bran supplements' effects on blood lipids and lipoproteins.

To compare the effects of oat-bran fiber on blood lipids, we studied 84 healthy middle-aged men and women who were placed on metabolic diets, for 2 wk, that were supplemented with either wheat bran (n = 42) or oat bran (n = 42). Fiber supplementation was 1.6 micrograms dietary fiber/J (6.8 g dietary fiber/1000 kcal) to a maximum of 16.4 g fiber/d. Significantly greater decrease with oat than with wheat were seen in total cholesterol (0.56 +/- 0.08 mmol/L and 0.29 +/- 0.08 mmol/L, P = 0.022) and low-density-lipoprotein cholesterol (0.39 +/- 0.07 mmol/L and 0.15 +/- 0.07 mmol/L, P = 0.024). No significant differences were seen in high-density lipoprotein, apolipoproteins A-1 and B, or triglyceride. We conclude that oat bran has an advantage over wheat bran in lowering serum lipids when tested in metabolic diets on large numbers of individuals with an initial mean serum cholesterol concentration above the desirable range, at 5.61 +/- 0.16 mmol/L.

Adult↗
PubMed1992

Beneficial effect of a low glycaemic index diet in type 2 diabetes.

Low glycaemic index foods produce low blood glucose and insulin responses in normal subjects, and improve blood glucose control in Type 1 and well-controlled Type 2 diabetic patients. We studied the effects of a low glycaemic index diet in 15 Type 2 diabetic patients with a mean fasting blood glucose of 9.5 mmol l-1 using a randomized, crossover design. Patients were given pre-weighed diets (59% energy as carbohydrate, 21% fat, and 24 g 1000-kcal-1 dietary fibre) for two 2-week periods, with a diet glycaemic index of 60 during one period and 87 during the other. On the low glycaemic index diet, the blood glucose response after a representative breakfast was 29% less than on the high glycaemic index diet (874 +/- 108 (+/- SE) vs 204 +/- 112 mmol min l-1; p less than 0.001), the percentage reduction being almost identical to the 28% difference predicted from the meal glycaemic index values. After the 2-week low glycaemic index diet, fasting serum fructosamine and cholesterol levels were significantly less than after the high glycaemic index diet (3.17 +/- 0.12 vs 3.28 +/- 0.16 mmol l-1, p less than 0.05, and 5.5 +/- 0.4 vs 5.9 +/- 0.5 mmol l-1, p less than 0.02, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Beneficial effect of low-glycemic index diet in overweight NIDDM subjects.

OBJECTIVE: To determine whether low-glycemic index (GI) diets have clinical utility in overweight patients with non-insulin-dependent diabetes mellitus (NIDDM). RESEARCH DESIGN AND METHODS: Six patients with NIDDM were studied on both high- and low-GI diets of 6-wk duration with metabolic diets with a randomized crossover design. Both diets were of similar composition (57% carbohydrate, 23% fat, and 34 g/day dietary fiber), but the low-GI diet had a GI of 58 compared with 86 for the high-GI diet. RESULTS: Small and similar amounts of weight were lost on both diets: 2.5 kg on high-GI diet and 1.8 kg on low-GI diet. On the low-GI diet, the mean level of serum fructosamine, as an index of overall blood glucose control, was lower than on the high-GI diet by 8% (P less than 0.05), and total serum cholesterol was lower by 7% (P less than 0.01). CONCLUSIONS: In overweight patients with NIDDM, reducing diet GI improves overall blood glucose and lipid control.

Blood Glucose↗
PubMed1991

The glycemic index: methodology and clinical implications.

There is controversy regarding the clinical utility of classifying foods according to their glycemic responses by using the glycemic index (GI). Part of the controversy is due to methodologic variables that can markedly affect the interpretation of glycemic responses and the GI values obtained. Recent studies support the clinical utility of the GI. Within limits determined by the expected GI difference and by the day-to-day variation of glycemic responses, the GI predicts the ranking of the glycemic potential of different meals in individual subjects. In long-term trials, low-GI diets result in modest improvements in overall blood glucose control in patients with insulin-dependent and non-insulin-dependent diabetes. Of perhaps greater therapeutic importance is the ability of low-GI diets to reduce insulin secretion and lower blood lipid concentrations in patients with hypertriglyceridemia.

Blood Glucose↗
PubMed1990

Manipulation of fecal pH by dietary means.

Epidemiological and animal studies suggest that colonic fermentation and fecal pH may be risk factors for colorectal cancer. To modify these factors, we sought to develop a simple instrument for use in intervention studies. Three 14-day studies with 32, 40, and 30 healthy volunteers maintained on their regular diet were carried out to evaluate the effect of various food supplements on fecal pH. The interventions tested included supplementary lactulose, Metamucil, oat bran, wheat bran, or no supplement. The results showed that it is possible to provide a simple intervention to reduce fecal pH by 0.4 unit with oat bran administered at 75-100 g/day over a 14-day period, using a wheat combination, equivalent in macronutrients and fiber, as a control.

Adult↗
PubMed1990

Glycemic index of foods in individual subjects.

We studied 12 subjects with diabetes to determine how well the glycemic index (GI) predicted the ranking of glycemic responses of different foods in individuals. All subjects ate three mixed meals (bread, rice, or spaghetti with GIs of 100, 79, and 61, respectively) four times in a randomized complete block design. The mean glycemic response areas of the different meals ranked according to the predicted GI in every individual. The observed mean +/- SD GI values of the meals were significantly different from each other (bread 100 +/- 7, rice 75 +/- 9, spaghetti 54 +/- 9), with no significant difference in response between subjects. It is concluded that individuals share common mean GI values for different foods. Within confidence limits determined by the variability of glycemic responses, the number of repeated tests conducted, and the expected GI difference, the GI can be used to predict the ranking of the mean glycemic responses of mixed meals taken by individuals.

Adult↗
PubMed1989

Nibbling versus gorging: metabolic advantages of increased meal frequency.

We studied the effect of increasing the frequency of meals on serum lipid concentrations and carbohydrate tolerance in normal subjects. Seven men were assigned in random order to two metabolically identical diets. One diet consisted of 17 snacks per day (the nibbling diet), and the other of three meals per day (the three-meal diet); each diet was followed for two weeks. As compared with the three-meal diet, the nibbling diet reduced fasting serum concentrations of total cholesterol, low-density lipoprotein cholesterol, and apolipoprotein B by a mean (+/- SE) of 8.5 +/- 2.5 percent (P less than 0.02), 13.5 +/- 3.4 percent (P less than 0.01), and 15.1 +/- 5.7 percent (P less than 0.05), respectively. Although the mean blood glucose level and serum concentrations of free fatty acids, 3-hydroxybutyrate, and triglyceride were similar during both diets, during the nibbling diet the mean serum insulin level decreased by 27.9 +/- 6.3 percent (P less than 0.01) and the mean 24-hour urinary C-peptide output decreased by 20.2 +/- 5.6 percent (P less than 0.02). In addition, the mean 24-hour urinary cortisol excretion was lower by 17.3 +/- 5.9 percent (P less than 0.05) at the end of the nibbling diet than at the end of the three-meal diet. The blood glucose, serum insulin, and C-peptide responses to a standardized breakfast and the results of an intravenous glucose-tolerance test conducted at the end of each diet were similar. We conclude that in addition to the amount and type of food eaten, the frequency of meals may be an important determinant of fasting serum lipid levels, possibly in relation to changes in insulin secretion.

3-Hydroxybutyric Acid↗
PubMed1989

Hypocholesterolemic effect of vegetable protein in a hypocaloric diet.

Eleven obese volunteers took part in a 12-week study during 8 weeks of which 2 meals of their control 1000 kcal diets were replaced by a soya based liquid formula (1 month) or a milk based liquid formula (1 month). The mean weight loss per month was 2.5 kg (P less than 0.05). On the soya formula total and LDL cholesterol levels were reduced significantly over the month by 10.0 +/- 2.7% (P less than 0.01) and 17.5 +/- 5.6% (P less than 0.02), respectively. Neither the milk based formula or the control low calorie diet lowered serum cholesterol significantly over the diet period. No change was seen in serum triglycerides on any of the 3 diets. No difference was seen between treatments in 24-h urinary C-peptide excretion. The results indicated that use of a vegetable protein supplement in a weight loss program which induced moderate weight loss was associated with a reduction in blood lipids, whereas moderate weight loss on a control low calorie diet or milk based formula was not.

Adult↗
PubMed1989

Low glycemic index foods and reduced glucose, amino acid, and endocrine responses in cirrhosis.

Carbohydrate intolerance is common in patients with cirrhosis. The aim of the present study was to determine whether the beneficial metabolic effects of low glycemic index diets observed in noncirrhotic diabetics also occurred in patients with cirrhosis. Therefore, for one day, five patients with cirrhosis were fed diets in which low glycemic index foods were substituted, replacing those which produced higher blood glucose rises. Reduction in the estimated glycemic impact of the diet by approximately 30% reduced the mean incremental blood glucose level over the day by 40 +/- 5% (p less than 0.001). Measurement at breakfast of amino acid, insulin, and gastric inhibitory polypeptide profiles confirmed a reduction of similar magnitude. No change was seen in pancreatic glucagon, whereas enteroglucagon levels tended to be higher. In view of these findings and the possible long-term benefits of chronic reduction of hyperinsulinism and alteration in amino acid metabolism, this approach to dietary management of cirrhosis warrants further consideration.

Aged↗
PubMed1989

Effect of rectal infusion of short chain fatty acids in human subjects.

Solutions containing 90 mmol sodium acetate plus 30 mmol sodium propionate (90 mM; isotonic), 180 mmol acetate plus 60 mmol propionate (180 mM; hypertonic) or an equivalent volume of isotonic saline were given over a 30-min period in random order by rectal infusion to six healthy subjects. Peripheral venous blood samples were obtained at 30-min intervals over the next 2 h. After the 90 mM infusion, the serum acetate response reached a peak at 60 min and had fallen to baseline by 120 min. The incremental area under the serum acetate response curve after 180 mM was twice that after 90 mM. Propionate was undetectable in serum at any time. Blood glucose fell after all of the infusions, but there was no significant difference between the saline- and short chain fatty acid (SCFA)-containing infusions. SCFA had no significant effect on serum insulin or c-peptide concentrations. However, compared with the saline control, the 180 mM solution resulted in a significant fall in serum free-fatty acids (FFA) and a significant rise in serum total cholesterol and triglyceride, with no change in beta-hydroxybutyrate levels. The data provide strong evidence that colonic SCFA are absorbed and metabolized in the human subject. The fall in FFA suggests that colonic SCFA have an effect on carbohydrate metabolism. In addition, the data provide indirect evidence for utilization of SCFA for lipid synthesis.

Acetates↗
PubMed1988

Wholemeal versus wholegrain breads: proportion of whole or cracked grain and the glycaemic response.

STUDY OBJECTIVE: To determine the effect on the glycaemic response to bread of the ratio of whole cereal grains to milled flour. DESIGN: Randomised assignment of groups of diabetic volunteers to test and control meals, taken after an overnight fast. Test foods were also analysed for in vitro digestion with human saliva. SETTING: Tertiary care centre. PATIENTS: Groups of six drawn from pool of 16 volunteers with diabetes mellitus (11 men, five women; mean age 64 (SE 3); 10 taking insulin, five taking oral agents, one controlled by diet; other characteristics comparable). INTERVENTIONS: All patients took standard white bread control meals on three occasions spanning the study and on different mornings took test meals containing varying ratios of whole cereal grains (barley or cracked wheat) to milled flour (75:25, 50:50, 0:100). All meals contained 50 g available carbohydrate and were eaten in 15 minutes. Capillary blood samples were taken for determination of glucose concentrations every 30 minutes for three hours. END POINT: Glycaemic index of foods (= increase in area under blood glucose concentration curve for test food divided by increase in area under curve for white bread control X 100). MEASUREMENTS AND MAIN RESULTS: Significant trend to lower glycaemic index with increasing proportion of whole cereal grains in test bread (p less than 0.05) and lower in vitro digestibility (p less than 0.001). Breads containing up to 75% whole grain were considered palatable. CONCLUSIONS: Breads containing a high proportion of whole cereal grains may be useful in reducing the postprandial blood glucose profile in diabetics because they are more slowly digested. These breads should be called "wholegrain" in distinction to "wholemeal" breads made from milled flour.

Blood Glucose↗
PubMed1988

Low-glycemic-index starchy foods in the diabetic diet.

Eight patients with noninsulin-dependent diabetes underwent two 2-wk study periods in random order during which they were provided with carbohydrate foods with either a high or low glycemic index (GI). Over both high-GI and low-GI periods there were significant reductions in body weight, serum fructosamine, and cholesterol. Reductions in fasting blood glucose, HbA1c, and urinary c-peptide-to-creatinine ratio were significant only over the low-GI period despite a smaller mean weight loss. Reductions in triglyceride were significant only over the high-GI diet. Inclusion of low-GI foods into diets of patients with diabetes may be an additional measure that favorably influences carbohydrate metabolism without increasing insulin demand.

Aged↗
PubMed1988

Starchy foods and glycemic index.

Different starchy foods produce different glycemic responses when fed individually, and there is some evidence that this also applies in the context of the mixed meal. A major reason appears to relate to the rate at which the foods are digested and the factors influencing this. A similar ranking in terms of glycemic response to specific foods is seen independent of the carbohydrate tolerance status of the groups tested. Potentially clinically useful starchy foods producing relatively flat glycemic responses have been identified. Many of these are considered ethnic or traditional and include legumes; pasta; grains such as barley, parboiled rice, and bulgur (cracked wheat); and whole-grain breads such as pumpernickel. Specific incorporation of these foods into diets has been associated with reductions in low-density lipoprotein cholesterol and triglyceride levels in hyperlipidemia and with improved blood glucose control in insulin-dependent diabetic patients. To facilitate identification of such foods, it has been suggested that the glycemic response should be indexed to a standard (e.g., white bread) to allow comparisons to be made between the glycemic index of foods tested in different groups of subjects. The scope of application of this principle is subject to further investigation. It may be used to expand the range of possibly useful starchy foods for trial in the diets of diabetic patients.

Blood Glucose↗
PubMed1987

Starchy foods, type of fiber, and cancer risk.

Fibers have been classified broadly as predominantly "soluble" or "insoluble," The soluble fibers have little effect on fecal bulk because they are largely fermented to short-chain fatty acids, so lowering colonic pH, and their influence on cancer risk is in relation to these variables. They are associated with increased fecal bile acid losses. Insoluble fibers are much less fermented and enhance fecal bulk without greatly increasing bile acid losses. Their effect in diluting carcinogens or bile acid promoters relates to their protective role in colon cancer. However, high-fiber foods not only contain combinations of different fiber types but also usually contain starch. Under various conditions, and possibly influenced by fiber, substantial amounts of starch (3-20% of dietary intake) may also enter the colon depending on the nature of the foods eaten. These carbohydrates will contribute to the effective fiber load. In considering the action of fiber in the human gut, fiber type, starch, and other components as well as the nature of foods making up the diet must be assessed. These factors are of importance both in interpreting epidemiological leads and in devising logical trials of fiber in terms of intervention.

Carcinogens↗