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Biomedical subjects

Jim Mann

Publications and source records attributed to Jim Mann.

At least 19 recordsLinked to original sources
PubMed2007

Carbohydrates: is the advice to eat less justified for diabetes and cardiovascular health?

PURPOSE OF REVIEW: Recent randomized controlled trials examining diets of varying carbohydrate composition recommended for people with diabetes and cardiovascular disease and those at risk are summarized. RECENT FINDINGS: Severe carbohydrate restriction results in appreciable initial weight loss and improvement in risk factors. After a year, however, the beneficial effects are equal to or less than those achieved on conventional alternatives. Some people develop elevations of LDL cholesterol. Modest carbohydrate restriction with relatively high intakes of cis-unsaturated fatty acids and protein is acceptable to many people and is more likely to produce sustained benefit in terms of weight loss and cardiovascular risk indicators. SUMMARY: Diets involving moderate carbohydrate restriction are suitable alternatives to high-carbohydrate, high-fibre diets for weight loss and reduction of cardiovascular disease and diabetes risk, as well as to treat individuals with the conditions. As such diets are generally high in protein and unsaturated fatty acids, they are not recommended for those with established or incipient nephropathy. High-carbohydrate, high-fibre diets remain appropriate for use in all those situations, provided carbohydrate is derived principally from minimally processed wholegrain breads and cereals and intact vegetables and fruit. Lower carbohydrate options may be preferable for markedly insulin-resistant individuals.

Cerebrovascular Disorders↗
PubMed2006

Thematic review series: patient-oriented research. Nutritional determinants of insulin resistance.

Interpreting the literature relating to the nutritional determinants of insulin resistance is complicated by the wide range of methods used to determine insulin sensitivity. Excess adiposity is unquestionably the most important determinant of insulin resistance, although the effect may be tempered by a relatively high proportion of lean body mass. Weight loss is associated with improved insulin sensitivity. Thus, diet-related factors that promote excessive energy intake may be regarded as promoters of insulin resistance. In the context of energy balance, diets characterized by high intakes of saturated fat and low intakes of dietary fiber are associated with reduced insulin sensitivity. Total fat intakes greater than the usually consumed range appear to promote insulin resistance, although the relative proportions of total fat and carbohydrate within the usual range appear unimportant. Monounsaturated fatty acids with a cis configuration and fiber-rich carbohydrate foods appear to be appropriate substitutes for saturated fatty acids and rapidly digested glycemic carbohydrates. In animal studies, n-3 unsaturated fatty acids have been shown to enhance insulin sensitivity and fructose and sucrose to increase insulin resistance. However, human data are limited. Large prospective studies currently being conducted should confirm the most appropriate macronutrient composition of diets for preventing and treating insulin resistance as well as establishing whether a range of candidate genes explains the variation in response to dietary change.

Adiposity↗
PubMed2005

Evaluation of diabetes care in the Otago region using a diabetes register, 1998-2003.

AIM: To assess changes in diabetes care between 1998 and 2003 using data from the Otago Diabetes Register. METHODS: A regional diabetes register was established in 1998 to monitor diabetes care in the Otago region, New Zealand. Cross-sectional data relating to process and outcome measures were collected annually from participating general practices, 93% of general practitioners in the region. Generalised estimating equations with robust standard errors were used to test for trends in clinical measures across the study period. RESULTS: Process measures improved dramatically over the 6-year period. The proportion of patients prescribed ACE inhibitors and other antihypertensives increased markedly (32.3-52.4% and 13.2-27.1%, respectively) and both mean systolic and diastolic blood pressure decreased significantly (140.6-137.0 mmHg, p < 0.001 and 78.6-77.0 mmHg, p < 0.001, respectively). The proportion prescribed lipid lowering medication more than trebled (12.4-40.0%), while mean lipid levels improved significantly (total cholesterol: 5.94-5.21 mmol/l, p < 0.001, HDL-cholesterol: 1.23-1.28 mmol/l, p < 0.001 and triglycerides: 2.17-1.94 mmol/l, p < 0.001). Mean weight increased significantly, as did HbA1c in all treatment groups except type 2 diabetic patients treated with combined insulin and oral hypoglycaemic agents. CONCLUSIONS: At a population level appreciable improvements in blood pressure and lipid control were observed, but not glycaemic control, probably due to insufficient attention to necessary lifestyle changes.

Aged↗
PubMed2005

Isocaloric substitution of plant sterol-enriched fat spread for carbohydrate-rich foods in a low-fat, fibre-rich diet decreases plasma low-density lipoprotein cholesterol and increases high-density lipoprotein concentrations.

BACKGROUND AND AIM: The aim of the study was to determine the effects on plasma cholesterol of replacing a plant sterol-enriched fat spread with carbohydrate-rich foods relative to a diet high in saturated fat. METHODS AND RESULTS: Twenty-nine men and women, from the general community, with mean age (SD) 48 (14)y, body mass index 29.0 (6.2)kg/m(2), and plasma total cholesterol concentration 6.48 (0.97)mmol/L completed the randomised, crossover dietary intervention. There were three diets: New Zealand diet (NZ diet) high in total (34%kJ) and saturated (15%kJ) fat, a cholesterol-lowering fibre-rich diet reduced in total (30%kJ) and saturated fat (8%kJ) but including a plant sterol spread (PS diet), and the same cholesterol-lowering diet with the plant sterol spread isocalorically replaced with carbohydrate (CHO diet); total fat, 26%kJ; saturated fat 7%kJ. All foods were provided and each diet was followed for four weeks. Mean (SD) plasma low-density lipoprotein cholesterol concentration declined from 4.68 (0.91)mmol/L on the high saturated fat diet to 4.12 (0.83)mmol/L (P<0.001) on the carbohydrate diet and 3.76 (0.84)mmol/L (P<0.001) on the plant sterol diet. The 20% decrease on the plant sterol diet was significantly greater (P<0.001) than the 12% decrease on the carbohydrate diet. Relative to the NZ diet, mean (95% CI) plasma high-density lipoprotein cholesterol concentration changed by -0.11 (-0.16, -0.06)mmol/L on the CHO diet but was not different at the end of the PS diet, -0.03 (-0.09, 0.02). CONCLUSION: Including a plant sterol-enriched fat spread in a cholesterol-lowering diet produces a more favourable plasma lipid profile than the same diet made lower in total and saturated fat by replacing the spread with carbohydrate-rich foods.

Adult↗
PubMed2004

Insulin resistance in a rural Maori community.

AIM: To determine the prevalence of insulin resistance, impaired fasting glycaemia, impaired glucose tolerance, and diabetes mellitus in a rural Maori community, and to compare different methods for identifying individuals with insulin resistance. METHODS: 589 randomly selected individuals from the Ngati Porou Hauora Register aged 25 years and over and resident on New Zealand's East Coast north of Gisborne were invited to participate in the study. A questionnaire was administered, anthropometric measures made, and blood samples taken for an oral glucose tolerance test and biochemical analysis. Impaired fasting glycaemia, impaired glucose tolerance, and diabetes mellitus were defined according to World Health Organization (WHO) diagnostic criteria, and among those persons with normal glucose tolerance, insulin resistance was calculated according to the McAuley formula and three other recognised methods for calculating insulin sensitivity. RESULTS: The overall age-standardised prevalence of diabetes (both known and newly diagnosed) was 10.6% and the age-standardised prevalence of insulin resistance was 37.0%. Age-specific diabetes rates were high among the older age groups, peaking at 34.1% for 60-69 year olds, whereas age-specific insulin resistance rates were high among the young age groups with the highest rate (44.3%) occurring among 30-39 year olds. Persons identifying as insulin-resistant reported higher rates of gout and family history of diabetes--and were found to have a higher waist circumference, blood pressure, and lower high-density lipoprotein (HDL) cholesterol than those without a glucose metabolism disorder. CONCLUSION: Diabetes is a common disorder among this population, but insulin resistance is even more prevalent, especially among young age groups. This is considerable cause for concern given that insulin resistance is believed to be the underlying cause of most cases of type 2 diabetes mellitus, and is confirmed by these data to be associated with a high degree of cardiovascular risk.

Adult↗
PubMed2004

The hypertriglyceridaemic waist in New Zealand Maori.

The objective of this study was to find a simple practical method of predicting insulin resistance in New Zealand Maori. Thirty-six Maori participants had insulin sensitivity measured using a euglycaemic insulin clamp. Several clinical and easily measured laboratory variables were compared, singly and in combination, with this measure of insulin sensitivity usually regarded as the gold standard. The combination of either fasting insulin and triglycerides or waist circumference and triglycerides, were the best simple methods for predicting insulin resistance in Maori. As insulin assays are not always available and are often not standardised, measurement of waist circumference and triglycerides provides a practical method for predicting insulin sensitivity in New Zealand Maori.

Adult↗
PubMed2002

Determinants of major non-communicable diseases in the elderly: the pilot Freemasons health study.

AIM: To present preliminary results of the pilot phase of the Freemasons Health Study. METHODS: A prospective cohort study, in which determinants of occurrence of stroke and dementia in the elderly will be investigated. RESULTS: The pilot study (n = 507) showed substantial heterogeneity in risk factor levels among participants and suggested outcome rates that would allow a study of 6000 individuals aged 65 years and over to produce statistically reliable results within a few years of follow up. Preliminary results of the pilot study suggest that the demographic (age, sex) and risk factor (namely blood pressure levels and ranges of body mass index) profile of the projected sample of the Freemasons population is similar to that of the general elderly New Zealand population. CONCLUSIONS: The pilot study confirmed that the collection of baseline data from the New Zealand Freemasons population and their spouses is feasible, and that the prevalence of major vascular risk factors in the elderly Freemasons population is similar to that of the general New Zealand population of comparable age. In addition to contributing to our understanding of the aetiology of major non-communicable diseases in the elderly, the proposed major study provides a unique opportunity to investigate the determinants of health and requirements for care in an elderly New Zealand population.

Aged↗
PubMed2002

Discrepancies in nutritional recommendations: the need for evidence based nutrition.

The widespread acceptance that 'evidence-based medicine' should determine all aspects of clinical practice leads to a consideration as to whether 'evidence-based nutrition' should be based on similar principles. Randomised controlled trials (RCT) are universally regarded as the gold standard by which to determine whether a drug is appropriate in a particular clinical situation. The evidence for some nutritional recommendations is indeed substantiated by RCT but in the case of some chronic diseases, notably cancers, where nutritional factors may operate as promoters or protectors many years before the onset of clinical disease, RCT may not be particularly appropriate. A range of experimental studies and descriptive epidemiological approaches may be regarded as sufficient to justify nutritional recommendations or dietary guidelines. Recommendations for the prevention and treatment of selected diseases will be considered in the context of their evidence-base.

Chronic Disease↗
PubMed2002

Mortality in British vegetarians.

OBJECTIVE: To compare the mortality of British vegetarians and non-vegetarians. DESIGN: Analysis of original data from two prospective studies each including a large proportion of vegetarians--the Oxford Vegetarian Study and the Health Food Shoppers Study. Standardised mortality ratios (SMRs) compared with the population of England and Wales were calculated from deaths before age 90 for vegetarians and non-vegetarians in each study. Death rate ratios (DRRs) for vegetarians compared with non-vegetarians within each study were calculated for each of 14 major causes of death. SETTING: UK. SUBJECTS: Twenty-one thousand men and women aged 16-89 years at recruitment, including more than 8,000 vegetarians. RESULTS: SMRs for all causes of death were significantly below the reference level of 100 in both studies: 52 (95% confidence interval (CI) 49-56) based on 1,131 deaths in the Oxford Vegetarian Study and 59 (57-61) based on 2,346 deaths in the Health Food Shoppers Study. For all causes of death, the DRR for vegetarians compared with non-vegetarians was close to one in both studies: 1.01 (95% CI 0.89-1.14) in the Oxford Vegetarian Study, 1.03 (0.95-1.13) in the Health Food Shoppers Study. CONCLUSIONS: British vegetarians have low mortality compared with the general population. Their death rates are similar to those of comparable non-vegetarians, suggesting that much of this benefit may be attributed to non-dietary lifestyle factors such as a low prevalence of smoking and a generally high socio-economic status, or to aspects of the diet other than the avoidance of meat and fish.

Adolescent↗