Glycemic response to pasta: effect of surface area, degree of cooking, and protein enrichment.

To see whether food form, the degree of cooking, or protein enrichment affected the glycemic response to pasta, we gave test-meal breakfasts to 13 diabetic patients. Macaroni had a significantly greater glycemic index (GI) (68 +/- 8) than spaghetti (45 +/- 6, P less than .01); the GI of star pastina was intermediate (54 +/- 6). The GI of spaghetti was not significantly affected by cooking for 5 or 15 min (45 +/- 6 and 46 +/- 5, respectively), or by protein enrichment (38 +/- 4). The GI of spaghetti was similar in 11 non-insulin-dependent and 6 insulin-dependent diabetic patients (49 +/- 7 compared with 57 +/- 8). We conclude that different types of pasta may produce different glycemic responses but that these are not necessarily related to differences in cooking or surface area.

Human metabolism of mammalian lignan precursors in raw and processed flaxseed.

BACKGROUND: The mammalian lignans enterolactone and enterodiol are produced in the colon by the action of bacteria on the plant precursor secoisolariciresinol diglycoside, which is found in high concentrations in flaxseed. OBJECTIVE: Two experiments were conducted to determine 1) whether there is a dose response in urinary lignan excretion with increasing flaxseed intake, 2) whether flaxseed processing affects lignan excretion, 3) peak plasma lignan concentrations, and 4) plasma lignan concentrations after chronic supplementation. DESIGN: Nine healthy young women supplemented their diets with 5, 15, or 25 g raw or 25 g processed (muffin or bread) flaxseed for 7 d during the follicular phase of their menstrual cycles. Twenty-four-hour urine samples were collected at baseline and on the final day of supplementation. As an adjunct to the 25-g-flaxseed arm, subjects consumed the supplement for an additional day and blood and urine samples were collected at specific intervals. All blood and urine samples were analyzed for enterolactone and enterodiol by gas chromatography-mass spectroscopy. RESULTS: A dose-dependent urinary lignan response to raw flaxseed was observed (r = 0.72, P < 0.001). The processing of flaxseed as a muffin or bread did not affect the quantity of lignan excretion. Plasma lignan concentrations were greater (P < or = 0.05) than baseline by 9 h after flaxseed ingestion (29.35+/-3.69 and 51.75+/-7.49 nmol/L, respectively). The total plasma area under the curve was higher on the eighth than on the first day (1840.15+/-343.02 and 1027.15+/-95.71 nmol x h/L, respectively). CONCLUSION: Mammalian lignan production from flaxseed precursors is dependent on time and dose but not on processing.

Phytic acid and calcium affect the in vitro rate of navy bean starch digestion and blood glucose response in humans.

Carbohydrate foods that are slowly digested appear beneficial in the management of diabetes and hyperlipidemia. This study determined the effect of endogenous and added phytic acid as well as Ca on the in vitro rate of starch digestion and in vivo blood glucose response to navy bean flour, prepared as unleavened bread. Removal of phytic acid from and addition of Ca to navy bean flour increased the starch digestion in vitro and raised the glycemic response in vivo while readdition of phytic acid to dephytinized flour produced the opposite effect. Carbohydrate malabsorption assessed by breath H2 measurement related negatively to glycemic response but the changes observed were much lower than the changes in glycemic response. This study confirmed the role of both added and endogenous phytic acid in slowing the in vitro rate of starch digestibility and in vivo glycemic response to legumes and the ability of Ca to modify this effect.

Dietary calcium, phytate, and zinc intakes and the calcium, phytate, and zinc molar ratios of the diets of a selected group of East African children.

Dietary zinc, calcium, and phytate intakes of 66 rural Malawian children aged 4-6 y were determined during three seasons on the basis of weighed food records and analyzed food composition data. Height and weight measurements were also recorded and hair samples were collected for zinc analysis. Seasonal daily zinc, calcium, and phytate intakes of females ranged from 6.2 +/- 1.7 to 6.8 +/- 2.1 mg (mean +/- SD), from 335 +/- 170 to 401 +/- 257 mg, and from 1621 +/- 660 to 1729 +/- 592 mg, respectively and, for males, 7.0 +/- 1.7 to 8.0 +/- 2.3 mg, 342 +/- 164 to 473 +/- 310 mg, and 1857 +/- 530 to 2161 +/- 684 mg, respectively. Cereals provided greater than 42% of dietary zinc. Seasonal mean molar ratios of phytate to Zn and Ca x phytate to Zn [per 1000 kcal (4.2 MJ)] and the median Ca to phytate molar ratio ranged from 24 to 27, 151 to 188 mmol/1000 kcal (4.2 MJ), and 3.1 to 3.4, respectively. Over 78% of the children consumed diets with phytate-to-Zn and Ca x phytate.Zn-1 . 1000 kcal-1 molar ratios above values suggested to jeopardize zinc status. Correlations between hair zinc, phytate-to-Zn, and Ca x phytate.Zn-1 . 1000 kcal-1 molar ratios suggest that high phytic acid intakes may compromise zinc status in these children.

Effect of acetate and propionate on calcium absorption from the rectum and distal colon of humans.

To determine the effects of acetate and propionate on calcium absorption from the human distal colon and rectum, six healthy human subjects were given rectal infusions containing 50 mmol CaCl2/L on four separate occasions. Addition of 56.3 mmol acetate/L, 18.7 mmol propionate/L, or acetate and propionate together increased calcium disappearance (expressed as the change in the ratio of calcium to polyethylene glycol) from -5.5 +/- 1.4 to -22.6 +/- 2.8, -23.2 +/- 3.2, and -19.7 +/- 4.6, respectively; P < 0.05. To determine the effects of different acetate and propionate concentrations, six different subjects were studied further. The effects of 18.7 or 56.3 mmol acetate/L on calcium absorption were the same as those of 18.7 mmol propionate/L (-15.7 +/- 1.4), and less than those of 56.3 mmol propionate/L (-20.3 +/- 2.4, P < 0.05). We conclude that both acetate and propionate enhance calcium absorption from the human distal colon, but that propionate has a greater effect at higher concentrations. Further studies are needed to determine the mechanism of calcium absorption from the colon.

Factors affecting starch digestibility and the glycemic response with special reference to legumes.

Large differences exist in the degree to which different starch containing foods affect the blood glucose levels of both normal volunteers and diabetics. These differences appear to relate to the digestibility of the starch and the factors determining this, including: the interaction of starch with fiber, antinutrients (eg, phytate) and protein in the food, together with the nature of the starch itself and its physical form (eg, raw or cooked, ground or whole). In this respect legumes exemplify a class of foods, high in fiber, protein and antinutrients, with a starch which is digested slowly in vitro. They also produce relatively small blood glucose rises after consumption by both normals and diabetics and in the longterm result in improved diabetic control. Identification of more such foods and further understanding of factors determining starch digestibility will allow greater therapeutic use of diet in the management of diabetics and disorders of carbohydrate metabolism.

The effect of phytic acid on in vitro rate of starch digestibility and blood glucose response.

The effect of phytic acid on starch digestibility was studied in vitro and related to the blood glucose response (glycemic index) in healthy volunteers. The glycemic index was found to correlate negatively with the phytic acid content of the food tested. In vitro digestion studies involving human saliva at physiological pH and temperature showed that in the presence of sodium phytate (equivalent to 2% phytic acid based on the starch portion), the rate of digestion of raw wheat starch was reduced significantly by 50%. This was reversed by the addition of calcium which is known to complex phytic acid. Similarly, when sodium phytate was added to unleavened bread, its digestibility was also decreased and in feeding trials high phytate bread produced a flattened blood glucose response.

Growth in children from the Wosera subdistrict, Papua New Guinea, in relation to energy and protein intakes and zinc status.

In a cross-sectional study of 123 children aged 24-120 mo from the Wosera subdistrict of Papua New Guinea, height, weight, hematocrit, hemoglobin, hair zinc, and presence of malaria were measured. Two 24-h recalls were undertaken in 67 of the children aged 72-120 mo; 52%, 73%, and 76% had energy, protein, and zinc intakes, respectively, less than two-thirds of the FAO/WHO/UNU recommendations. Stunting was prevalent (29%); 16% were moderately wasted. The prevalence of stunting and hair zinc concentrations less than 1.68 mumol/g was gender related; 38% of males vs 20% of females had Z scores for height-for-age (HAZ scores) less than -2 (P = 0.04); 26% of males vs 11% of females had hair zinc less than 1.68 mumol/g (P less than 0.05). Analysis of variance showed that age, sex, hemoglobin, and log hair zinc influenced HAZ scores, depending on the age group; both sex and the log of the hair zinc values were significant factors in the older children. Stunting in Worsera children was related to chronic deficits in energy and protein and was excerbated in the older male children by suboptimal zinc status.

The effect of fermented and unfermented milks on serum cholesterol.

Groups of 10 to 13 healthy volunteers were provided with 11 supplements of 2% butterfat milk (2% milk), whole milk, skim milk, yogurt, buttermilk, and sweet acidophilus milk daily for a 3-wk period. Despite increases in caloric intakes on all supplements, no significant increases were found in total, low-density, and high-density lipoprotein cholesterol. A significant weight gain was seen in subjects taking yogurt and acidophilus groups; these were the only two groups showing significant rises in triglyceride levels. These results in normal volunteers focus attention on the current practice of recommending only skim or 2% milk for hyperlipidemic individuals.

Relationship between polyphenol intake and blood glucose response of normal and diabetic individuals.

Five leguminous and eight nonleguminous foods were analyzed for polyphenol concentration by the Prussian Blue and the Folin Denis methods and correlated with blood glucose response (glycemic index) in normal or diabetic volunteers. Polyphenol concentrations and intakes per 50 g available carbohydrate portions were higher in the leguminous foods than those in the nonleguminous foods. In both normal and diabetic individuals, a negative correlation was observed between glycemic index and the concentration or total intake of polyphenols. Polyphenols, especially the large polymeric type or condensed tannins, appear to be responsible in part for the reduced glycemic response to carbohydrate foods and in part to lower blood glucose response to legumes compared with cereal products.

Low glycemic response to traditionally processed wheat and rye products: bulgur and pumpernickel bread.

To look at the effect of processing wheat and rye on blood glucose responses with special reference to bulgur and pumpernickel bread, groups of 9-12 Noninsulin-dependent (NIDDM) and 5-6 Insulin-dependent diabetic volunteers (IDDM) were fed test meals containing 50 g carbohydrate portions of four wheat and three rye products. Glycemic indices for IDDM and NIDDM combined, calculated as the incremental area under the blood glucose response curve, where white bread = 100, demonstrated values of 96 +/- 5 for wholemeal wheat bread, 89 +/- 6 for wholemeal rye bread, 78 +/- 3 for pumpernickel bread, 65 +/- 4 for bulgur, 63 +/- 6 for whole wheat kernels and 48 +/- 5 for whole rye kernels. Results for IDDM and NIDDM were similar (r = 0.96, p less than 0.01). It is concluded that traditional processing of cereals, such as parboiling (bulgur) or the use of wholegrains in bread (pumpernickel) may result in the low GI value associated with the unmilled cereal. Cereal foods processed in these ways may form a useful part of the diet where a reduction in postprandial glycemia is required.

The effect of starch-protein interaction in wheat on the glycemic response and rate of in vitro digestion.

To determine the effect on blood glucose of removal of protein from wheat products, healthy volunteers took test meals of white bread made from either regular or gluten-free flour. After bread made from gluten-free flour, the blood-glucose rise was significantly greater. This corresponded with a significantly more rapid rate of digestion in vitro and reduced starch malabsorption in vivo as judged by breath-H2 measurements. Addition of gluten to the gluten-free bread mix did not reverse these effects. Factors associated with unprocessed wheat flour, such as the natural starch-protein interaction, may therefore be important in wheat products in reducing both their rate of absorption and glycemic response. They may have implications in the dietary management both of diabetes and of diseases where small intestinal absorptive capacity is impaired.

Metabolic effects of a low-glycemic-index diet.

Six healthy male volunteers underwent 2-wk metabolically controlled high-glycemic-index (GI) and low-GI diets in random order. Over the low-GI diet significant reductions were seen in serum fructosamine (7.0 +/- 1.0%, p less than 0.01), 12-h blood glucose profile (37 +/- 7%, p less than 0.01), and total serum cholesterol (15 +/- 3%, p less than 0.01). As a measure of insulin secretion, 24-h urinary C-peptide levels were 32 +/- 10% lower (p less than 0.05) after the low-GI than after the high-GI diet. Lower C-peptide levels were maintained after a standard carbohydrate challenge after the low-GI diet despite higher blood glucose levels. Differences in blood glucose were not seen after a 5-g intravenous glucose challenge. These results are of interest with respect to the effect that prolonged postprandial reductions in nutrient fluxes and insulin secretion may have on carbohydrate and lipid metabolism and renal function.

Rice varieties with similar amylose content differ in starch digestibility and glycemic response in humans.

Three high-amylose rice varieties, IR42, IR36, and IR62, with similar chemical composition including amylose content (26.7-27.0%), were cooked under the same conditions and tested for in vitro digestibility as well as blood glucose and insulin responses in healthy human volunteers. The starch-digestion rate and the glycemic and insulin responses were the highest in IR42, followed by IR36 and, then IR62. The differences were not due to unabsorbed carbohydrate but were related to their physicochemical properties, such as gelatinization temperature, minimum cooking time, amylograph consistency, and volume expansion upon cooking. When the three varieties were cooked for their minimum cooking time, they had the same degree of gelatinization and their starch-digestion rates and glycemic responses were similar. We conclude that amylose content alone is not a good predictor of starch-digestion rate or glycemic response. Rice varieties with similar high-amylose contents can differ in physicochemical (gelatinization) properties and this, in turn, can influence starch digestibility and blood glucose response.

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.

Low glycemic index: lente carbohydrates and physiological effects of altered food frequency.

Many factors influence carbohydrate absorption. Slower rates of absorption may have advantages in reducing postprandial glycemia and insulinemia and, in time, reduce serum low-density-lipoprotein (LDL) cholesterol and apolipoprotein B concentrations. Foods high in viscous fiber or antinutrients, or foods that are resistant to gelatinization, show slower rates of digestion and absorption and may be called low glycemic index or lente carbohydrate foods. Specific enzyme inhibitors may also cause lente effects. Certain small-intestinal effects of lente carbohydrate may be mimicked by altering feeding frequency (eg, nibbling vs gorging). Increased meal frequency reduces post-prandial insulin and glucose responses in people with non-insulin-dependent diabetes and in nondiabetic volunteers and lowers serum concentrations of LDL cholesterol and apolipoprotein B. Reduced hepatic cholesterol synthesis has been reported. Increased meal frequency may also slow small-intestinal absorption in the treatment of conditions such as diabetes, hyperlipidemia, and possibly obesity.

Nutritional attributes of traditional flaxseed in healthy young adults.

The objective was to determine the influence of consuming 50 g flaxseed/d for 4 wk on several indexes of nutrition in young healthy adults. During flaxseed consumption, alpha-linolenate was increased significantly in adipose tissue, and n-3 polyunsaturates were increased in plasma lipids. Plasma LDL cholesterol was also reduced by up to 8%, and total urinary lignan excretion was increased more than fivefold (P < 0.05). Muffins containing 25 g flaxseed did not differ significantly from control muffins in their content of thiobarbituric acid-reactive substances, and alpha-linolenate in the muffins was not significantly reduced by baking. Antioxidant vitamins and lipid hydroperoxides in plasma were not significantly affected by flaxseed consumption. Bowel movements per week increased by 30% while flaxseed was consumed (P < 0.05). We conclude that traditional flaxseed has modest beneficial effects on several indexes of nutritional status without compromising antioxidant status.

Effect of processing on digestibility and the blood glucose response: a study of lentils.

To test the effect of processing on digestibility and the glycemic response to a leguminous seed, a group of eight healthy volunteers took a series of breakfast test meals containing either lentils which had been processed in four different ways or the same amount of carbohydrate as white bread. Lentils, boiled for 20 min, resulted in a flattened blood glucose response by comparison with bread. This was unaltered by blending the lentils to a paste or boiling them for an additional 40 minutes. However the blood glucose response was significantly enhanced by drying the boiled blended lentils for 12 h at 250 degrees F. In vitro digestion with human saliva showed the rate of sugars released from the food related positively to the blood glucose rise. Breath hydrogen studies indicated that carbohydrate malabsorption was too small to account for differences in the blood glucose response. These results emphasize the importance of processing in determining digestibility and hence the glycemic response to a food.

Glycemic responses to foods: possible differences between insulin-dependent and noninsulin-dependent diabetics.

The effect on the blood glucose response of varying the amount (25 or 50 g) and type (bread or beans) of carbohydrate (CH2O) in test meals and of adding fat and protein was examined in a group of insulin dependent and noninsulin dependent diabetic volunteers. With noninsulin-dependent diabetics, the blood glucose area after a half bread portion was 48% that of the full bread meal (p less than 0.001). White pea beans (50 g CH2O) gave a blood glucose response of 41 +/- 5% (p less than 0.001) that of bread (50 g CH2O). A combined meal of bread (25 g CH2O) and beans (25 g CH2O) gave a blood glucose response of 60 +/- 8% of the full bread meal (p less than 0.005) and similar to that expected. Addition to bread of butter and skim milk cheese either singly or in combination had little effect on the glycemic response although a reduced rise was seen after addition of fat and protein as peanut butter. Insulin-dependent diabetics tended to respond similarly to noninsulin-dependent diabetics but their greater variability indicates that other factors in addition to the nature of the food may also be major determinants of their glycemic responses to foods.

Trace element intakes and dietary phytate/Zn and Ca x phytate/Zn millimolar ratios of periurban Guatemalan women during the third trimester of pregnancy.

Repeated 24-h recalls (9-14/subject) were conducted on 52 periurban Guatemalan pregnant women aged 25 +/- 5 y (means +/- SD). Intakes of energy, protein, calcium, zinc, copper, manganese, nonstarch polysaccharide (NSP), phytate, and millimolar ratios of phytate to zinc and (calcium x phytate) to zinc were calculated from food-composition values on the basis of chemical analysis and the literature. Mean (+/- SD) daily intakes were as follows: energy 8694 +/- 1674 kJ, protein 63.0 +/- 13.3 g, calcium 727 +/- 163, zinc 11.3 +/- 2.7, copper 1.3 +/- 0.3, manganese 2.8 +/- 0.6, phytate 2254 +/- 773 mg/d, NSP 26.6 +/- 6.9 g, phytate/zinc 18.8 +/- 4.2, (calcium x phytate)/zinc 706 +/- 21 mmol/MJ. Ninety-four percent had zinc intakes below the recommendations (15 mg) of WHO and the US recommended dietary allowances, assuming 20% absorption. Tortillas were a major source of zinc (46%), copper (20%), manganese (23%), calcium (39%), phytate (68%), and NSP (50%); 19% zinc from flesh foods. Thirty-eight percent had phytate-zinc ratios > 20; 94% had millimolar ratios of (calcium x phytate) to zinc per MJ > or = 22. The high prevalence of millimolar ratios of phytate to zinc and (calcium x phytate) to zinc per MJ above 20 and 22, respectively, may compromise zinc nutriture.