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Biomedical subjects

A M Stephen

Publications and source records attributed to A M Stephen.

At least 19 recordsLinked to original sources
PubMed2000

Use of food labels and beliefs about diet-disease relationships among university students.

OBJECTIVE: The purpose of this study was to measure the reported use of nutrition information on food labels by a population of university students and to determine if label users differed from non-users in terms of gender and specific beliefs related to label information and diet-disease relationships, specifically fat and heart disease and fibre and cancer. DESIGN: A single-stage cluster sampling technique was used. Data was obtained using a self-administered, validated questionnaire. SETTING: The present investigation took place at the University of Saskatchewan, Canada in the autumn of 1997. SUBJECTS: : A total of 553 students in randomly selected classes in the College of Arts and Science took part in the survey (92% response rate). The sample consisted of roughly equal numbers of males and females, most between the ages of 18 and 24. RESULTS: There were approximately equal numbers of label users and non-users among males, while label users outnumbered non-users by almost four to one among females. The importance of nutrition information on food labels was the only belief that differed significantly between label users and non-users for both sexes. For females, no other beliefs distinguished label users from non-users. However, for males, significant differences were found between label users and non-users on the beliefs that nutrition information is truthful and that a relationship between fibre and cancer exists. CONCLUSIONS: Females appear to use food labels more often than do males. The only consistently observed difference between label users and non-users (male and female) was that users believed in the importance of nutrition information on food labels while non-users did not.

Adolescent↗
PubMed1997

Association between dietary fiber intake and the folate status of a group of female adolescents.

The main objective of this study was to assess the association between dietary fiber intake and the folate status of Canadian female adolescents. We also assessed dietary folate intakes and evaluated the prevalence of biochemical folate deficiency in these subjects. Female adolescents aged 14-19 y (n = 224) were recruited and fasting blood samples were collected. Dietary intakes (3-d food record) were recorded and participants were classified as lactoovovegetarians, semivegetarians, or omnivores on the basis of food-consumption patterns assessed with food-frequency questionnaires. Fourteen percent, 17%, and 26% of lactoovovegetarians, semivegetarians, and omnivores, respectively, had dietary folate intakes below their predicted requirements; 1%, 4%, and 23%, respectively, had serum folate concentrations indicative of deficiency. Despite low dietary folate intakes and serum folate concentrations, few subjects had homocysteine concentrations indicative of deficiency, suggesting that the degree of folate depletion had not yet produced functional consequences. Most important, results suggest that the consumption of nonstarch polysaccharide is significantly associated with serum folate concentrations (P < 0.001). For each 1-g increase in nonstarch polysaccharide intake, a 1.8% increase in serum folate concentration is expected. In summary, we propose that an increase in nonstarch polysaccharide intake may promote the intestinal biosynthesis of folate, providing a complementary strategy to enhance the folate nutriture of humans.

Adolescent↗
PubMed1995

Intake of carbohydrate and its components--international comparisons, trends over time, and effects of changing to low-fat diets.

Carbohydrate constitutes the major source of dietary energy for all peoples of the world. However, it has been difficult to make accurate determinations of intakes of carbohydrate and its constituents because of lack of individual assessments in which carbohydrate components are included. For many countries, only food balance information is available and values for total carbohydrate are often derived by difference. Available information indicates that carbohydrate consumption decreased in many industrialized nations as prosperity led to an increased consumption of fat. Fat intakes have fallen over the past two decades and carbohydrate intakes have increased, but still do not approach the 60-70%contribution of carbohydrate to total energy in developing countries. A negative image for carbohydrate has led to a reluctance to accept it as a legitimate dietary component, particularly in North America. New evidence of the beneficial effects of starch in the diet indicates that increased consumption of carbohydrate, especially in the form of starch, should be promoted in Western countries.

Adult↗
PubMed1995

Effect of green lentils on colonic function, nitrogen balance, and serum lipids in healthy human subjects.

Green lentils are an increasingly popular food, but their effects on human colonic function and serum lipids have been studied little. Nine healthy males aged 19-38 y consumed for 3-wk periods a controlled Western diet and the same diet supplemented with 130 g dry lentils/d [which contained 11.8 g non-starch polysaccharide (NSP)] incorporated into loaves, cakes, and soups. Protein was equilibrated with soy protein isolate and carbohydrate with soft drinks. Radioopaque markers were used to calculate mean transit time (MTT) and to correct fecal weight for infrequency of bowel movements. Feces were collected throughout the study and blood was taken on 2 d at the end of each period. Lentils increased fecal weight from 131 +/- 12 g/d (means +/- SEM) to 189 +/- 17.4 g/d (44.9%) (P < 0.005). MTT was unchanged: 46 +/- 6 h for the control diet and 43 +/- 4 h for the lentils (NS). Fecal nitrogen was increased to 2.49 +/- 0.08 g/d for lentils compared with 1.74 +/- 0.09 g/d for the control diet (P < 0.001) and urine nitrogen decreased to 15.31 +/- 0.52 g/d with the lentils compared with 15.90 +/- 0.51 g/d for the control diet (P < 0.05); nitrogen balance was unaffected. Serum lipids were unchanged by addition of lentils to the diet. Green lentils were effective in increasing fecal weight and can therefore make a valuable contribution to a healthy diet.

Adult↗
PubMed1995

The tar reduction study: randomised trial of the effect of cigarette tar yield reduction on compensatory smoking.

BACKGROUND: Observational and short term intervention studies have reported that smokers of low tar cigarettes inhale more deeply (that is, compensate) than those who smoke high tar cigarettes. To quantify this effect a long term randomised trial was conducted on the effects of switching to low tar cigarettes. METHODS: The trial was carried out between April 1985 and March 1988 among cigarette smokers in the British Civil Service, measuring blood carboxyhaemoglobin (COHb) levels and serum cotinine levels as markers of tobacco smoke intake. Volunteers first switched to a cigarette brand yielding around 10% less tar than their usual brand to identify smokers able to change brand. The 434 subjects who successfully switched were then randomly allocated to one of three groups: (a) "fast reduction" group which changed to a brand of cigarettes with a tar yield of about half that of their usual brand; (b) "slow reduction" group which reduced to the same level in steps over several months; and (c) a control group which continued smoking cigarettes with a tar yield 10% lower than their usual brand. RESULTS: Over the course of the trial cigarette consumption declined slightly in all three groups. In both the "fast reduction" and the "slow reduction" groups, intake of COHb and cotinine was reduced, though not to the same extent as the yield reduction. Comparison of the results before randomisation with those at the end of the trial showed that a reduction in carbon monoxide yield of 45% was associated with a decrease in carbon monoxide intake of 19% (95% confidence interval 14% to 24%) and that a reduction in nicotine yield of 40% was associated with an 11% (6% to 16%) reduction in nicotine intake, reflecting relative intakes of about 1.5 for both carbon monoxide and nicotine in the "fast reduction" group. Results were similar in the "slow reduction" group with a 42% reduction in carbon monoxide yield, a 16% (11% to 22%) reduction in carbon monoxide intake, a 37% reduction in nicotine yield, and a 6% (0% to 13%) reduction in nicotine intake. Estimates of compensation derived from these results were 65% for carbon monoxide, 79% for nicotine, and 62% for tar. CONCLUSIONS: Compensation, demonstrated when switching from a high tar cigarette to a low tar one, was incomplete. Advising people who have failed to give up smoking to switch to low tar cigarettes will reduce the intake of smoke constituents to a small extent. This would be expected to decrease their risk of smoking-related diseases, although by a smaller amount than would be achieved by giving up smoking altogether.

Adaptation, Psychological↗
PubMed1994

Trends in individual fat consumption in the UK 1900-1985.

Mortality from coronary heart disease is decreasing in a number of Western countries, although the pattern of the decrease differs from country to country. In the UK the mortality rate from coronary heart disease has declined since 1979, whereas in the USA mortality from this disease began to fall in 1968 and has continued since that time. Of many factors suggested as reasons for the decline, diet has been implicated, particularly dietary fat intake. However, food balance information suggests little change in fat intake. A recent examination of all published studies from the USA where individual fat intake has been reported indicated that fat intake in that country has fallen steadily since the mid 1960s. The present study describes a similar compilation of all published studies from the UK giving individual fat intakes. Ninety-seven studies, representing information for 24,045 individuals, were used. Studies ranged in size from two to 3581 individuals and were drawn from all regions of the UK. Most studies used 7 d weighed intakes as the method of dietary assessment. Quadratic regression equations were applied to the fat intakes from all studies over time, with each study weighted by the number of individuals surveyed. Data were also divided into 10-year periods and weighted fat intakes for each decade were calculated. Data were expressed for all studies, then subdivided into males, females, children and the elderly. Comparisons between Scotland and the South-East of England were made. Results indicate that fat represented 30% or less of dietary energy in the UK until the 1930s, when it began to rise. This rise was curtailed by rationing during and after the Second World War, after which the rise continued, reaching a plateau of about 40% energy in the late 1950s, with little change until the late 1970s. Trends were similar in all age-groups, but less change has occurred recently in Scotland compared with South-East England. These results differ from the pattern in the USA and suggest that if greater changes in mortality from coronary heart disease are to be seen in the UK a greater reduction in dietary fat intake will have to occur.

Adolescent↗
PubMed1994

Whole grains--impact of consuming whole grains on physiological effects of dietary fiber and starch.

Much of the present research on the physiological effects of dietary fiber and starch has been done on sources isolated from the parent material, and it is not clear whether they have the same effects if fed in the intact or whole grain. For dietary fiber, physiological effect depends on extent of fermentation in the large intestine, and this is influenced by chemical composition, solubility, physical form, and presence of lignin or other compounds. All of these factors are altered by isolation of a fiber source from the whole grain, and hence effects of eating fiber vary. Similarly, physical form and presence in the whole grain will affect digestibility of starch in the small intestine, which in turn influences the glycemic response and colonic effects determined by the extent of malabsorption and entry into the colon. Starch that enters the colon is fermented and produces short-chain fatty acids, particularly butyrate, which is necessary to maintain a healthy mucosa. Hence, their presence within the whole grain may have important implications for health for both dietary fiber and starch. Evidence indicates that such effects are beneficial and that whole-grain consumption should be encouraged.

Dietary Carbohydrates↗
PubMed1993

The gum exudate of Encephalartos friderici-guilielmi.

Studies of the structure of the polysaccharide gum exudate from Encephalartos friderici-guilielmi (a Cycad) confirmed its resemblance to those from other species of the same genus. Partial acid hydrolysis gave numerous products which showed a strong correlation with those from E. longifolius gum. The course of sequential Smith degradations was monitored by analysis of the molecular weights and composition of the products. The mild acid-hydrolysis step of the Smith degradation proceeded in two stages, the second being very slow but yielding a (1-->3)-D-galactan with < 20% of other residues (D-mannose, and some L-arabinose and L-rhamnose). A tentative formulation of the gum shows L-rhamnose and D-glucuronic acid residues exterior to a branched D-galactan framework; these structures are 3-linked to D-mannose, through D-galactopyranosyl or possibly L-arabinopyranosyl residues, within mannoglucuronoglycan chains. Other units occupy O-4 of D-mannose.

Arabinose↗
PubMed1993

The gum exudate of Encephalartos longifolius Lehm. (female): further hydrolytic studies.

Sequential, acid hydrolysis of the gum exudate from Encephalartos longifolius cones gave the neutral disaccharides beta-Gal-(1-->3)-Ara (1), beta-Gal-(1-->3)-Gal, and beta-Gal-(1-->6)-Gal; the triouronic acid beta-GlcA-(1-->6)-beta-Gal-(1-->3)-Ara (2); and the biouronic acids described earlier, namely, beta-GlcA-(1-->6)-Gal (3), beta-4-O-MeGlcA-(1-->6)-Gal, and beta-GlcA-(1-->2)-Man (4). Oligomers up to the tetramer of beta-GlcA-(1-->2)-Man alpha-linked through O-4 of GlcA characterised the inner, core region of the complex acidic polysaccharide. Alternating GlcA and Man residues were indicated by FABMS of methylated, acid-degraded gum. The presence of the constituent sugar units was confirmed by methylation of the gum and partition chromatography of the products of acid hydrolysis. Partial hydrolysis gave fractions containing terminal and in-chain GlcA attached to Gal and Man. Base-catalysed degradation of the methylated products showed Rha to be exterior to GlcA in the periphery.

Arabinose↗
PubMed1993

Molecular structures of gum exudates from Hakea species.

Partial acid-hydrolysis of the gum exudates from Hakea sericea and H. gibbosa yields L-arabinose, D-galactose, D-xylose, D-mannose, D-glucuronic acid, the aldobiouronic acid GlcA (beta 1,2)Man, and a dimer of this acid alpha-linked from D-Man to O-4 of GlcA. Methylation analysis showed the modes of linkage of the sugar units to be typical of those present in plant polysaccharide exudates of the arabinogalactan type, while partial acid hydrolysis and Smith degradations established the position of linkage of the peripheral sugar assemblies at O-3 of D-Man in the interior core. Some minor differences were noted between the molecular structures of the gums from these two species of Hakea, the Gal:Ara ratio being higher for H. sericea gum.

Carbohydrate Sequence↗
PubMed1993

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.

Adult↗
PubMed1991

Starch and dietary fibre: their physiological and epidemiological interrelationships.

Until the 1980s, starch in the human diet was assumed to be totally degraded and absorbed in the small intestine. Several lines of evidence since then have indicated that this is not the case, including studies of factors controlling stool output, stool bulk on elemental diets, epidemiological studies of starch intakes in developed versus developing nations, and indications using breath hydrogen that fermentation takes place in the large intestine when starch is fed. Of the few direct estimations of starch escaping absorption in the small intestine that have been carried out, one has been conducted using intubation of healthy volunteers, where two different starch meals were fed and samples aspirated from the terminal ileum. This study demonstrated that 8-10% starch escaped absorption on average, with subjects varying from 2 to 20%. Hence a sizeable proportion of starch consumed daily may reach the large intestine, with important physiological consequences. Neither small intestinal transit time nor volume of flow were related to the extent of starch malabsorption in this study. However, many factors may play a role in the extent of malabsorption, and research is continuing to investigate physiological and food characteristics that may influence the digestion and absorption of starch.

Diet↗
PubMed1990

The use of bacteriophage-mediated depolymerisation in investigations of the structure of the capsular polysaccharide from Klebsiella serotype K71.

The structure (1) of the heptasaccharide repeating-unit of the capsular polysaccharide from Klebsiella serotype K71 follows from methylation analysis and n.m.r. and mass-spectrometric studies of the oligosaccharides obtained on depolymerisation of the polysaccharide with a bacteriophage-borne endo-rhamnosidase. [formula; see text].

Bacteriophages↗
PubMed1990

Trends in individual consumption of dietary fat in the United States, 1920-1984.

Coronary heart disease mortality has declined in the United States since 1968. Because diet has been implicated, a search was conducted of published individual assessments of food intake since 1920. One hundred seventy-one studies, ranging from 8 to 20,000 subjects and covering all ages, all ethnic groups, and both sexes, were analyzed by regression, with values weighted by number of subjects in each study. Results show fat intakes rising from approximately 34% energy in the 1930s to 40-42% in the late 1950s to mid 1960s then falling steadily to approximately 36% energy in 1984. This trend was seen for all age and sex groups. Saturated and monounsaturated fatty acid intakes fell from 18-20% energy in the early 1950s to 12-13% energy in 1984 whereas polyunsaturated fatty acid intakes rose from 2-4% energy to 7.5%. These results differ markedly from food supply trends and indicate a fall in US fat intake, which preceded the decline in heart disease mortality.

Age Factors↗
PubMed1987

Bacteriophage-associated lyase activity against Klebsiella serotype K64 capsular polysaccharide.

Bacteriophage phi 64 possesses a lyase that depolymerises the capsular polysaccharide of Klebsiella K64 into a hexasaccharide having an unsaturated derivative of glucuronic acid at the non-reducing end (1). The unsaturated hex-4-enuronic acid residue generated was characterised spectroscopically (u.v. and n.m.r.) and by g.l.c.-m.s. after hydrogenation of the double bond. Partial hydrolysis, Smith degradation, methylation analysis, and n.m.r. spectroscopy have been used to establish the structures of oligosaccharides produced from the polysaccharide. Evidence from 1H-n.m.r. spectroscopy indicates that the D-Man rho residue that undergoes fission is beta. (Formula: see text).

Bacteriophages↗
PubMed1987

Effect of changing transit time on colonic microbial metabolism in man.

An investigation was made of the effect of changing mean transit time (MTT) by administration of drugs which affect colonic motility on faecal microbial mass in man. Senokot was used to accelerate and codeine and/or loperamide to prolong transit in subjects maintained on a constant high fibre diet. Doses of Senokot or codeine/loperamide were adjusted to halve or double transit time measured during a three week control period on diet alone. Stools were collected throughout and analysed for bacterial mass by a gravimetric procedure. Transit was measured by a continuous marker method. Senokot decreased mean transit time from 63.9 to 25.0 hours (n = 6), with increased stool weight from 148 to 285 g/day. Bacterial mass increased in all subjects from a mean of 16.5 to 20.3 g/day (dry weight) (p less than 0.025). Codeine/loperamide increased mean transit time from 47.1 to 87.6 hours (n = 5), with decreased stool weight from 182 to 119 g/day. Bacterial mass decreased in all but one subject from a mean of 18.9 to 16.1 g/day (NS). There was a significant correlation between transit time and bacterial mass in all three periods (r = 0.77, p less than 0.001). Changes in transit time are shown to alter microbial growth in the human colon and result in altered stool output, on a constant diet. Factors which affect transit may be as important as diet in determining large bowel function and hence susceptibility to disease.

Adult↗