Alexandra L. Jenkins

The glycaemic index of foods tested in diabetic patients: a new basis for carbohydrate exchange favouring the use of legumes.

SummaryRecently diabetic patients have been encouraged to increase their carbohydrate intake, but exact details of which foods to use are lacking. To determine whether sufficiently large differences existed to justify more specific dietary advice, we compared the glycaemic responses to 50 g carbohydrate portions of different foods, taken as breakfast test meals by groups of five to seven diabetic patients. Two-to threefold differences were seen amongst the 15 foods tested. The glycaemic responses for spaghetti, ‘All-bran’, rice and beans were significantly below those for bread, while ‘Cornflakes’ were above. Factors predicted to influence this were without effect, including: substituting wholemeal for white bread, increasing substantially the simple sugars (using ‘All-bran’ or bananas instead of wholemeal bread) and doubling meal protein by adding cottage cheese to bread. Paired comparisons of the glycaemic response to the five legumes with those of the seven other starchy foods (breads, spaghetti, rice, Cornflakes, oatmeal porridge and potatoes) showed that the mean peak rise in blood glucose concentration and mean area under the glucose curve after beans were 23 and 28% lower, respectively, than the mean for the other foods (p < 0.001). Such results suggest a potentially valuable role for dried leguminous seeds in carbohydrate exchanges for individuals with impaired carbohydrate tolerance. These large differences in the blood glucose response to different food cannot at present be predicted directly from tables of chemical composition. Nevertheless, physiological testing may both aid in understanding the factors responsible and help selection of the appropriate carbohydrate foods for the diabetic diet.

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 I−1 using a randomized, crossover design. Patients were given pre‐weighed diets (59% energy as carbohydrate, 21% fat, and 24g 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 I−1; p < 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 I−1 p < 0.05, and 5.5 ± 0.4 vs 5.9 ± 0.5 mmol I−1, p < 0.02, respectively. Urinary C‐peptide excretion, as an index of insulin secretion, was 30% lower on the low than the high glycaemic index diet (2.05 ± 0.30 vs 2.93 ± 0.49 nmol mmol‐creatinine−1; p < 0.02), urinary urea was reduced by 19% (347 ± 27 vs 402 ± 39 mmol 24‐h−1; p < 0.025), consistent with enhanced colonic fermentation. These results suggest that low glycaemic index starchy foods may be beneficial in the treatment of Type 2 diabetes.

Reduction in postprandial glucose excursion and prolongation of satiety: possible explanation of the long-term effects of whole grain Salba (Salvia Hispanica L.).

Despite strong correlations linking whole-grain consumption to reductions in heart disease, the physiological mechanisms involved remain ambiguous. We assessed whether Salba (Salvia Hispanica L.) whole grain reduces postprandial glycemia in healthy subjects, as a possible explanation for its cardioprotective effects observed in individuals with diabetes. The study used acute, randomized, double-blind, controlled design in which 11 healthy individuals (6 males and 5 females; body mass index 22.3±2.8 kg/m2) received 0, 7, 15 or 24 g of Salba baked into white bread. Capillary samples and appetite ratings were collected over 2 h after consumption. A dose-response reduction in postprandial glycemia (P=0.002, r2=0.203) was observed with all three doses of Salba, significantly decreasing incremental areas under the curve (iAUCs) and time point-specific blood glucose (P<0.05). Appetite ratings were decreased at 60 min after high, 90 min after high and intermediate and at 120 min after all treatments (P<0.05). Decrease in postprandial glycemia provides a potential explanation for improvements in blood pressure, coagulation and inflammatory markers previously observed after 12-week Salba supplementation in type II diabetes.

Comparison of regular and parboiled rices: explanation of discrepancies between reported glycemic responses to rice

Abstract The glycemic responses of rice processed in different ways and cooked for different lengths of time have been studied in diabetic subjects. The mean glycemic index (GI) of regular long grain white rice (83±5) in 5 IDDM and 13 NIDDM patients was significantly below that of white bread (100, p

The glycaemic index values of foods containing fructose are affected by metabolic differences between subjects.

Background/Objectives:Glycaemic responses are influenced by carbohydrate absorption rate, type of monosaccharide absorbed and the presence of fat; the effect of some of these factors may be modulated by metabolic differences between subjects. We hypothesized that glycaemic index (GI) values are affected by the metabolic differences between subjects for foods containing fructose or fat, but not for starchy foods.Subjects/Methods:The GI values of white bread (WB), fruit leather (FL) and chocolate-chip cookies (CCC) (representing starch, fructose and fat, respectively) were determined in subjects (n=77) recruited to represent all 16 possible combinations of age (⩽40, >40 years), sex (male, female), ethnicity (Caucasian, non-Caucasian) and body mass index (BMI) (⩽25, >25 kg/m2) using glucose as the reference. At screening, fasting insulin, lipids, c-reactive protein (CRP), aspartate transaminase (AST) and waist circumference (WC) were measured.Results:There were no significant main effects of age, sex, BMI or ethnicity on GI, but there were several food × subject-factor interactions. Different factors affected each foods area under the curve (AUC) and GI. The AUC after oral glucose was related to ethnicity, age and triglycerides (r 2=0.27); after WB to ethnicity, age, triglycerides, sex and CRP (r 2=0.43); after CCC to age and weight (r 2=0.18); and after FL to age and CRP (r 2=0.12). GI of WB was related to ethnicity (r 2=0.12) and of FL to AST, insulin and WC (r 2=0.23); but there were no significant correlations for CCC.Conclusions:The GI values of foods containing fructose might be influenced by metabolic differences between –subjects, whereas the GI of starchy foods might be affected by ethnicity. However, the proportion of variation explained by subject factors is small.

Effect of whole and ground Salba seeds (Salvia Hispanica L.) on postprandial glycemia in healthy volunteers: a randomized controlled, dose-response trial

Objective:Incorporation of seeds into food products may attenuate postprandial glycemia. Whether these should be consumed as whole or in ground form is not known.Subjects/Methods:Using an acute, randomized controlled crossover design, the glycemic response of 13 healthy participants (6M:7F; 25.4±2.6 kg/m2) was studied on nine separate occasions. Test meals consisted of 7, 15 or 24 g of whole or ground Salba baked into white bread, and three control breads matched for energy, and macronutrient profile. Capillary blood samples were collected at fasting and over 2 h post consumption.Results:A significant effect of dose (P=0.04), but no effect of form (P=0.74) or dose-form interaction (P=0.98) was found. No adverse events were reported.Conclusion:This study demonstrates that both ground and whole Salba are equally effective in attenuating blood glucose levels in a dose-dependent manner when incorporated into bread. Flexibility in the use of either the ground or whole seed may increase the ease of incorporation and acceptability as a dietary supplement.

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.

Fiber and Physiological and Potentially Therapeutic Effects of Slowing Carbohydrate Absorption

The dietary recommendations of diabetes associations, heart foundations, and cancer agencies encourage the use of higher carbohydrate intakes derived from minimally processed or high fiber foods (1–5). A characteristic of such foods is often that they are more slowly absorbed than many refined and highly processed foods. The assumption that slow absorption of nutrients is of benefit is central to the original fiber hypothesis (6) and has been described as a new therapeutic principle (7). Fibers that have proved especially useful include the soluble fibers. Early on purified soluble fibers such as guar and pectin were found to be particularly useful in lowering cholesterol in patients at high risk of heart disease (8,9). This paved the way for current interest in high soluble fiber foods such as beans, oats (e.g. oat bran), barley, etc., all of which have been shown to have these effects (10). Our own current interest has been in the use of traditional starchy foods, e.g. beans, dried peas, lentils, barley, etc., or starchy foods processed in traditional ways, e.g. pumpernickel bread (whole kernel rye), bulgur (cracked parboiled wheat), pasta, etc. These foods reduce serum cholesterol in patients at risk of heart disease and also provide better blood glucose control in patients with diabetes. There is also evidence that they may be of benefit in liver disease and in kidney disease because of their effects on amino acid and nitrogen metabolism. A growing body of evidence suggests that many traditionally processed foods, especially those still eaten in parts of the world where heart disease, diabetes and colonic diseases are rare, may owe much to the fact that their carbohydrate, possibly due to fiber content, is more slowly absorbed. Other means by which these same effects can be produced include the use of specific digestive enzyme inhibitors and increased feeding frequency.

Comparison of flax ( Linum usitatissimum ) and Salba-chia ( Salvia hispanica L.) seeds on postprandial glycemia and satiety in healthy individuals: a randomized, controlled, crossover study

Background/Objectives:Flax and Salba-chia seeds have risen in popularity owing to their favorable nutrient composition, including a high fiber content. Despite having comparable nutritional profiles, preliminary observations suggest differences in gelling properties, an attribute that may alter the kinetics of food digestion. Thus, we compared the effect of two seeds on postprandial glycemia and satiety scores.Subjects/Methods:Fifteen healthy participants (M/F: 5/10; age: 23.9±3 years; BMI: 22.2±0.8 kg/m2) were randomized to receive a 50 g glucose challenge, alone or supplemented with either 25 g ground Salba-chia or 31.5 g flax, on three separate occasions. Blood glucose samples and satiety ratings were collected at fasting and over 2-h postprandially. In addition, in vitro viscosity of the beverages was assessed utilizing standard rheological methodology.Results:Both Salba-chia and flax reduced blood glucose area under the curve over 120 min by 82.5±19.7 mmol/l (P<0.001) and 60.0±19.7 mmol/l (P=0.014), respectively, relative to a glucose control. Salba-chia reduced peak glucose (−0.64±0.24 mmol/l; P=0.030) and increased time to peak (11.3±3.8 min; P=0.015) compared with flax. Salba-chia significantly reduced the mean ratings of desire to eat (−7±2 mm; P=0.005), prospective consumption (−7±2 mm; P=0.010) and overall appetite score (−6±2 mm; P=0.012), when compared with flax. The viscosity of Salba-chia, flax and control was 49.9, 2.5, and 0.002 Pa·s, respectively.Conclusions:Despite the similarities in nutritional composition, Salba-chia appears to have the ability to convert glucose into a slow-release carbohydrate and affect satiety to a greater extent than flax, possibly due to the higher fiber viscosity. Incorporation of either flax or Salba-chia into the diet may be beneficial, although use of Salba-chia may confer additional benefit.

Grains, Legumes, Fruits, and Vegetables: Lente Carbohydrate Sources in the Mediterranean Diet

Foods of plant origin have always played a central role in the nutrition of Mediterranean peoples. The Roman conquest of Egypt was to secure a grain supply: Britain was valued by Rome as the granary of the North. Legumes also were highly prized in biblical times. Esau gave away his inheritance for a “mess of Pottage,” a bowl of lentil soup. Cicero, the great republican Roman orator and statesman, derived his name from the chick-pea (Cicer arietanum) due to the pealike lesion on the nose of one of his ancestors. Cereals and legumes, therefore, represent foods that have been respected for their essential functions in the human diet since antiquity. We suggest that one of the reasons why many of these traditional foods have special health attributes, in addition to being low in saturated fat, is that they are also slowly absorbed.