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Biomedical subjects

D J Jenkins

Publications and source records attributed to D J Jenkins.

At least 91 records · Page 5Linked to original sources
PubMed1995

Effect of nibbling versus gorging on cardiovascular risk factors: serum uric acid and blood lipids.

Nibbling has been reported to decrease serum cholesterol under fasting conditions, as well as the incidence of cardiovascular disease. It has been suggested that these effects are partly attributable to reduced concentrations of serum insulin, which are also observed. However, data on the effects of nibbling on serum lipids throughout the day are not available, nor is it known how nibbling affects serum uric acid as a further insulin-related risk factor for cardiovascular disease. We have attempted to address these issues. Seven healthy men consumed identical diets in a randomized crossover design either as three meals daily (control) or as 17 meals daily (nibbling) for 2 weeks. On day 13, serum lipid levels were measured over the course of the day (12 hours) together with the 24-hour urinary excretion of mevalonic acid as an indicator of hepatic cholesterol synthesis. Concentrations of uric acid in serum and 24-hour urinary excretion of uric acid were also determined. Mean (+/- SE) percent treatment differences in day-long total, low-density lipoprotein (LDL), and non-high-density lipoprotein (HDL) cholesterol, and apolipoprotein (apo) B were significant, with lower values on the nibbling diet as compared with the control diet (8.1% +/- 1.6%, P = .002; 12.2% +/- 2.6%, P = .005; 10.1% +/- 1.6%, P < .001; and 9.9% +/- 2.6%, P = .008, respectively). No significant difference was seen in the total to HDL cholesterol ratio or in urinary mevalonic acid excretion.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

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.

Adipose Tissue↗
PubMed1995

Nutrition principles and diabetes. A role for "lente carbohydrate"?

The current nutrition recommendations of the American Diabetes Association (ADA) represent a thoughtful synthesis of much current data. They depart from tradition by not advocating specific figures for total fat and carbohydrate intake. Rather, since many issues are still topics of scientific debate, they endorse the principle of individualization and set guidelines accordingly. One topic that may be worthy of further debate is the principle of "spreading the nutrient load," or lengthening the absorption time. This principle covers the effects of altered meal frequency, viscous dietary fibers, low-glycemic index foods, and inhibitors of carbohydrate absorption. In its simplest form it is illustrated by studies of altered meal frequency ("nibbling versus gorging"). Reducing the size and increasing the frequency of meals has been shown acutely to result in lower mean blood glucose and insulin levels over the day in type II diabetes and to result in reduced 24-h urinary C-peptide losses. In the longer term in nondiabetic subjects, total and low-density lipoprotein cholesterol levels are reduced, together with fasting apolipoprotein B and serum uric acid levels, as additional risk factors for coronary heart disease. These and other physiological effects make slowing carbohydrate absorption ("lente carbohydrate") a potentially useful therapeutic modality. However, of the possible ways of slowing absorption, only alteration in meal frequency was of general interest in the current ADA nutrition recommendations. Nevertheless, the effects of slowing carbohydrate absorption by various means may have beneficial metabolic effects in diabetes and may support the use of ethnic foods in diets compatible with further modifications identified more favorably in the current nutrition recommendations (e.g., increased use of monounsaturated fat).

Blood Glucose↗
PubMed1995

Physiological modulation of plasma free fatty acid concentrations by diet. Metabolic implications in nondiabetic subjects.

OBJECTIVE: To determine the effect of varying the amount of carbohydrate and glycemic index (GI) of breakfast test meals on plasma free fatty acid (FFA) responses of nondiabetic subjects and to see whether the glycemic response at lunch was related to the plasma FFA response to breakfast. RESEARCH DESIGN AND METHODS: We studied eight subjects over a 6-h period on four separate occasions using a randomized Latin-square design. They received isocaloric breakfast test meals that were either high (84 g) or low (41 g) in carbohydrate and had either a high (approximately 100) or a low (approximately 70) GI, followed by a standard lunch 4 h later. RESULTS: The initial fall in plasma FFAs after breakfast was similar for all four test meals, but the extent of rebound differed significantly. The mean plasma FFA concentration just before the start of lunch (4 h) was highest after the low-GI, low-carbohydrate breakfast (418 +/- 42 mumol/l), followed by high-GI, low-carbohydrate (277 +/- 48 mumol/l), high-GI, high carbohydrate (227 +/- 32 mumol/l), and low-GI, high-carbohydrate (149 +/- 23 mumol/l) (P < 0.01). The concentration of plasma FFAs at 4 h was directly related to the total area under the glycemic response curve to lunch (r = 0.691, n = 32, P < 0.0001). CONCLUSIONS: In nondiabetic subjects, the type and amount of carbohydrate eaten at breakfast influences the plasma glucose, insulin, and FFA responses to breakfast and also affects the glucose, insulin, and FFA responses to a subsequent standard lunch. The glycemic responses after lunch were closely related to the plasma FFA concentration 4 h after breakfast, which we speculate is due to the inhibitory effect of FFAs on insulin action.

Adult↗
PubMed1995

Optimal diet for reducing the risk of arteriosclerosis.

The primary objectives of current dietary advice for those at risk from coronary artery disease (CAD) focus on progressive restriction of dietary saturated (and trans) fatty acids and cholesterol intake, combined with exercise and achievement of ideal body weight. These principles are endorsed by the official bodies of most western nations concerned with reducing CAD mortality and have recently been reaffirmed by the Adult Treatment Panel of the National Cholesterol Education Program. There has been concern, however, in view of the increasing use of drug therapy, that additional strategies should supplement the primary goals to increase the palatability and effectiveness of the diet. These additional strategies include increased intake of foods high in soluble viscous fibres, vegetable proteins, possibly antioxidants such as vitamin E and the isoflavonoids, increased intake of alpha-linolenic acid and, for those with low high density lipoprotein cholesterol levels, increased monounsaturated fat intake. These strategies translate into advice to significantly increase consumption of specific plant foods such as green leafy vegetables, nuts and seeds, and dried legumes, all of which improve the overall nutritional quality of the diet and contain specific active ingredients. These changes represent a regression to a more primitive diet on the evolutionary scale.

Adult↗
PubMed1995

Implications of altering the rate of carbohydrate absorption from the gastrointestinal tract.

The rate of absorption of carbohydrate from the small intestine plays a major role in determining the metabolic effects of dietary carbohydrate. Factors which reduce the rate of absorption include the nature of the starch and sugars, and the presence of vegetable proteins, fats, viscous fibre, and antinutrients, including lectins and phytates. The rate of absorption can also be manipulated by the use of specific enzyme inhibitors and by increasing the number and frequency of meals while holding caloric intake constant. All these factors contribute to the creation of what may be termed slow release or "lente carbohydrate". The slowing of small intestinal absorption, as exemplified by increased meal frequency ("nibbling"), results in reduced postprandial insulin secretion and lower low-density lipoprotein (LDL) cholesterol and apolipoprotein B concentrations. A further effect of some manipulations which reduce the rate of absorption is increased delivery of carbohydrate to the colon and its absorption after bacterial fermentation to short-chain fatty acids (SCFA). These SCFA may have beneficial effects on colonic health(butyrate) or further inhibit cholesterol synthesis in the liver (propionate). Thus the absorption of "lente carbohydrate" takes place along the full length of the gastrointestinal tract with a wide variety of physiological consequences.

Carbohydrates↗
PubMed1994

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.

Blood Glucose↗
PubMed1994

Method of administration influences the serum cholesterol-lowering effect of psyllium.

To determine whether psyllium must be mixed with food to lower serum cholesterol, 18 modestly hypercholesterolemic subjects were studied for three 2-wk periods, in random order, separated by a 2-wk return to a National Cholesterol Education Program Step 2 diet. Compared with values for subjects consuming control wheat-bran cereal (63 g/d), after 2 wk of 54 g psyllium-enriched cereal/d containing 7.3 g psyllium, serum total, LDL, and HDL cholesterol, respectively, were reduced by 8% (6.15 +/- 0.15 vs 6.71 +/- 0.19 mmol/L, P < 0.01), 11% (4.24 +/- 0.15 vs 4.78 +/- 0.19 mmol/L, P < 0.02), and 7% (0.99 +/- 0.05 vs 1.07 +/- 0.05 mmol/L, P < 0.01). When 7.6 g of the same type of psyllium as in the test cereal was taken between meals, serum total (6.50 +/- 0.19 mmol/L), LDL (4.50 +/- 0.21 mmol/L), and HDL (1.06 +/- 0.06 mmol/L) cholesterol were no different from control values, and total cholesterol was greater than after psyllium cereal (P < 0.05). We conclude that psyllium must be mixed with foods to have the maximum effect on serum cholesterol.

Cholesterol↗
PubMed1994

Psyllium reduces blood lipids in men and women with hyperlipidemia.

To see if a modest amount of soluble fiber reduced blood lipids in subjects with hyperlipidemia who were on a low-fat diet, 42 subjects (21 men, 21 women) consuming an American Heart Association step 2 diet took two servings of breakfast cereal daily for two 2-week periods in a randomized crossover trial. There were two types of test cereals, each providing 6.7 g psyllium fiber daily, and two types of wheat bran control cereals, matched for available carbohydrate and total fiber. Half the subjects tested each type of cereal, and the results were pooled because the psyllium cereals had similar effects on serum cholesterol levels. Comparing values at the end of 2 weeks, psyllium reduced serum total (6.33 +/- 0.12 mmol/L versus 6.76 +/- 0.12 mmol/L, p < 0.001), low-density lipoprotein (LDL; 4.36 +/- 0.11 mmol/L versus 4.73 +/- 0.12 mmol/L, p < 0.001) and high-density lipoprotein cholesterol levels (HDL; 1.10 +/- 0.05 mmol/L versus 1.14 +/- 0.05 mmol/L, p < 0.05) and the LDL/HDL cholesterol ratio (4.27 +/- 0.20 versus 4.48 +/- 0.22, p < 0.02) with no effect on triglycerides. There was no significant interaction between the effects of treatment and sex for any of the blood lipid variables. Women tended to have greater decreases in total, LDL, and HDL cholesterol levels than men, but the percent decrease in LDL/HDL ratio on psyllium was similar in men, 4.9%, and women, 4.7%. It is concluded that 6.7 g of psyllium fiber daily, with a low-fat diet, reduces serum cholesterol levels in both men and women with hyperlipidemia.

American Heart Association↗
PubMed1994

Effect of acute lactulose administration on serum acetate levels in cirrhosis.

Lactulose has been used successfully in the treatment of portal-systemic encephalopathy but its exact mechanism of action is not known. The aim of this study was to observe the systemic effects of the colonic fermentation of an acute lactulose dose in cirrhotics and normal subjects. Six cirrhotic patients and 6 normal subjects were placed on 2 identical 2-d metabolic diets, 1 of which was supplemented with lactulose (1 g/100 kcals to a maximum of 28 g/d). Lactulose increased colonic fermentation in cirrhotic and normal subjects as evidenced by higher breath hydrogen and serum acetate levels. The increase in serum acetate levels after lactulose compared to control was similar in cirrhotic compared to normal subjects. However, the mean serum acetate concentration in the cirrhotics was significantly greater than that in the control subjects (p = 0.039), indicating increased endogenous production, or decreased peripheral utilization of acetate by the cirrhotic liver, or both. No change was observed in blood ammonia, glucose, insulin, or free fatty acid levels with lactulose.

Acetates↗
PubMed1993

Effect on blood lipids of very high intakes of fiber in diets low in saturated fat and cholesterol.

BACKGROUND: It is known that soluble fiber in the diet can lower blood lipid levels. It is less certain, however, that eating foods with soluble fiber will further lower blood lipids when the intake of saturated fat and cholesterol has already been reduced to very low levels. Furthermore, the mechanism of the lipid-lowering effect of fiber has not been elucidated. METHODS: To address these questions, we studied 43 volunteers with hyperlipidemia in a crossover study involving two four-month dietary periods. The two metabolic diets contained foods high in either soluble or insoluble fiber and were separated by a two-month National Cholesterol Education Program Step 2 diet. The metabolic diets were low in saturated fat (< 4 percent of total calories) and cholesterol (< 25 mg per 1000 kcal), high in carbohydrate (> or = 60 percent of total calories), and very high in fiber (> 24 g per 1000 kcal). RESULTS: Blood lipids fell to their lowest levels by week 4 of both study diets. When the soluble-fiber period was compared with the insoluble-fiber period, the subjects' total, low-density lipoprotein (LDL), and high-density lipoprotein (HDL) cholesterol levels were found to be lower by a mean (+/- SE) of 4.9 +/- 0.9 percent (P < 0.001), 4.8 +/- 1.3 percent (P < 0.001), and 3.4 +/- 1.3 percent (P = 0.014), respectively. In contrast, the ratio of total to HDL cholesterol was not significantly different during the two dietary periods. The loss of fecal bile acids was 83 +/- 14 percent greater during the soluble-fiber period than during the insoluble-fiber period (P < 0.001) and was related to the differences in total and LDL cholesterol and apolipoprotein B levels (r = 0.42, P = 0.005; r = 0.49, P < 0.001; and r = 0.33, P = 0.035, respectively). The difference in serum cholesterol levels between the two dietary periods was greater among the men (7.5 +/- 1.2 percent, P < 0.001) than among the women (3.4 +/- 1.2 percent, P = 0.008). CONCLUSIONS: Very high intakes of foods rich in soluble fiber lower blood cholesterol levels even when the main dietary modifiers of blood lipids--namely, saturated fat and cholesterol--are greatly reduced.

Adult↗
PubMed1993

Serum antibodies in canine echinococcosis.

Specific IgG, IgA and IgE antibodies against E. granulosus protoscolex antigen were detected by enzyme-linked immunosorbent assay (ELISA) in sera from dogs experimentally or naturally infected with E. granulosus. The specificities of the IgG, IgA and IgE ELISAs were 100, 100 and 97.3%, respectively. Sera from 626 dogs of different categories and geographic regions in Australia, Uruguay and Kenya were tested. There were distinct differences in antibody responses in experimentally infected canids and in the number of naturally infected dogs found seropositive, depending on geographic region. The overall sensitivities of the ELISA (IgG, IgA and IgE) ranged between 73 and 84%, except for one geographic region where it was 54%. Genetic differences of the dogs and/or antigenic variations of the parasite appear to be responsible for the variations in specific antibody levels in infected dogs. In average, approximately one third of dogs from hyperendemic hydatid regions, without E. granulosus worms at autopsy or negative for E. granulosus infection by arecoline testing, were seropositive for anti-E. granulosus antibodies, suggesting previous infection with or exposure to the parasite. The results of this study demonstrate that, although the diagnosis of current intestinal E. granulosus infection on an individual dog basis is not always reliable by serology, serum antibody ELISA is useful as an epidemiological/educational tool for seroprevalence studies on canine echinococcosis.

Animals↗
PubMed1993

The apolipoprotein E gene and the serum low-density lipoprotein cholesterol response to dietary fiber.

Our goal was to determine whether differences in apolipoprotein E (apo E) influenced the response to dietary changes aimed at reducing serum cholesterol levels, especially increases in fiber. Apo E phenotype and genotype were determined in 43 men and 24 women who had previously taken part in parallel 2-week metabolic dietary studies involving either wheat bran or oat bran supplementation at a level of 6.8 g fiber/1,000 kcal. Fasting blood lipid measurements had been made at the beginning and end of the 2-week metabolic period. Reductions in low-density lipoprotein (LDL) cholesterol levels across both oat and wheat bran diets were significantly different depending on the E allele (P = .048). The LDL cholesterol level reduction for E2 carriers (0.60 +/- 0.14 mmol/L, n = 13) was greater than that for E3 homozygotes (0.21 +/- 0.07 mmol/L, n = 38; P = .014) and E4 carriers (0.28 +/- 0.12 mmol/L, n = 16; P = .09). Only the change in dietary fiber on the oat bran diet was related significantly to the decrease in LDL cholesterol levels (r = -.47, P = .007; n = 32). No such relationship was seen on the wheat bran diet (r = -.010, P = .59; n = 33). Carriers of the E2 allele appear to be more responsive than noncarriers to a dietary change involving increased fiber intake. The data also support a lipid-lowering advantage of oat bran over wheat bran. Current dietary recommendations to reduce serum lipid levels may vary in effectiveness depending on distribution of apo E alleles in the different populations studied.

Adult↗
PubMed1993

Genetic variation associated with differences in the response of plasma apolipoprotein B levels to dietary fibre.

1. We hypothesized that differences within genes whose protein products are involved in apolipoprotein B metabolism could influence the response of plasma apolipoprotein B-containing lipoprotein concentrations to increases in dietary fibre. 2. We studied 67 subjects (43 men and 24 women) who had taken part in parallel 2 week metabolic dietary studies involving either wheat bran or oat bran supplementation. Fasting blood lipid, lipoprotein and apolipoprotein concentrations were measured at the start and end of the 2 week metabolic period. Genotypes were determined using DNA markers for the low-density lipoprotein receptor, apolipoprotein B, apolipoprotein CIII and hepatic lipase gene loci. 3. Reductions in plasma concentrations of apolipoprotein B were significantly different depending on genotype determined with a low-density lipoprotein receptor DNA marker (P = 0.03). There was no significant variation in the reduction of plasma total cholesterol, low-density lipoprotein cholesterol or apolipoprotein B concentrations for alleles of other genes tested. 4. Thus, genetic variability is associated with interindividual differences in the fibre-related reduction in plasma apolipoprotein B and apolipoprotein B-containing lipoprotein concentrations. Implementation of current dietary recommendations to reduce plasma lipoprotein levels with fibre may have variable effects in different individuals in part because of structural differences in candidate genes whose products are involved in lipoprotein metabolism.

Apolipoproteins B↗
PubMed1993

High alpha-linolenic acid flaxseed (Linum usitatissimum): some nutritional properties in humans.

Although high alpha-linolenic acid flaxseed (Linum usitatissimum) is one of the richest dietary sources of alpha-linolenic acid and is also a good source of soluble fibre mucilage, it is relatively unstudied in human nutrition. Healthy female volunteers consumed 50 g ground, raw flaxseed/d for 4 weeks which provided 12-13% of energy intake (24-25 g/100 g total fat). Flaxseed raised alpha-linolenic acid and long-chain n-3 fatty acids in both plasma and erythrocyte lipids, as well as raising urinary thiocyanate excretion 2.2-fold. Flaxseed also lowered serum total cholesterol by 9% and low-density-lipoprotein-cholesterol by 18%. Changes in plasma alpha-linolenic acid were equivalent when 12 g alpha-linolenic acid/d was provided as raw flaxseed flour (50 g/d) or flaxseed oil (20 g/d) suggesting high bioavailability of alpha-linolenic acid from ground flaxseed. Test meals containing 50 g carbohydrate from flaxseed or 25 g flaxseed mucilage each significantly decreased postprandial blood glucose responses by 27%. Malondialdehyde levels in muffins containing 15 g flaxseed oil or flour/kg were similar to those in wheat-flour muffins. Cyanogenic glycosides (linamarin, linustatin, neolinustatin) were highest in extracted flaxseed mucilage but were not detected in baked muffins containing 150 g flaxseed/kg. We conclude that up to 50 g high-alpha-linolenic acid flaxseed/d is palatable, safe and may be nutritionally beneficial in humans by raising n-3 fatty acids in plasma and erythrocytes and by decreasing postprandial glucose responses.

Blood Glucose↗