Introdução: O consumo de alimentos com elevado índice glicêmico e carga glicêmica tem sido associado ao aumento no risco de desenvolvimento de síndrome metabólica, importante precursor da doença cardiovascular e do diabetes mellitus tipo 2. Entretanto, esses achados ainda são inconsistentes e a utilização do índice glicêmico e da carga glicêmica para prevenção ou tratamento da síndrome metabólica e dos fatores de risco que a compõe ainda é controversa. Objetivos: Validar o diabetes mellitus autorreferido e verificar a associação do índice glicêmico e da carga glicêmica com a síndrome metabólica e seus componentes. Métodos: Foram utilizados dados provenientes do Inquérito de Saúde de São Paulo (ISA-Capital 2008) referentes a adultos e idosos de ambos os sexos residentes nessa cidade. Trata-se de estudo transversal, de base populacional, com amostra probabilística de indivíduos residentes em domicílios permanentes localizados na área urbana do município. As informações utilizadas são provenientes de um questionário estruturado, dois recordatórios alimentares de 24 horas, exames bioquímicos, valores aferidos de pressão arterial e medidas antropométricas (peso, estatura e circunferência da cintura). Foram estimadas as prevalências de diabetes mellitus e síndrome metabólica para o município de São Paulo. A validação diabetes mellitus autorreferido foi realizada mediante cálculo da sensibilidade, especificidade e valores preditivos positivo e negativo. O consumo alimentar habitual foi obtido por meio da incorporação dos dados alimentares no software Multiple Source Method. A associação entre índice glicêmico e carga glicêmica da dieta e síndrome metabólica e seus componentes foi verificada por meio de modelos de regressão logística estimados segundo faixa etária. Todas as análises levaram em consideração o desenho amostral do estudo. Resultados: As prevalências de diabetes mellitus e síndrome metabólica no município de São Paulo foram estimadas em 8,0 por cento e 30,2 por cento , respectivamente. A sensibilidade do diabetes mellitus autorreferido foi 63,8 por cento (IC 95 por cento : 49,2-76,3), a especificidade 99,7 por cento (IC 95 por cento : 99,1-99,9), o valor preditivo positivo 95,5 por cento (IC 95 por cento : 84,4-98,8) e o valor preditivo negativo 96,9 por cento (IC 95 por cento : 94,9-98,2). O índice glicêmico associou-se com a lipoproteína de alta densidade (OR: 1,16; IC 95 por cento : 1,02-1,32) em adultos e com a síndrome metabólica (OR: 1,24; IC 95 por cento : 1,1-1,37), a glicemia de jejum (OR: 1,15; IC 95 por cento : 1,01-1,31) e a pressão arterial (OR: 1,26; IC 95 por cento : 1,05-1,51) em idosos. Conclusão: O dado de diabetes mellitus autorreferido é válido, especialmente entre idosos residentes no município de São Paulo. Os resultados evidenciam a necessidade do rastreamento do diabetes mellitus em indivíduos assintomáticos que apresentem um ou mais fatores de risco para essa condição, principalmente na população adulta. No presente estudo, o IG da dieta associou-se à SM, glicemia de jejum e pressão arterial elevadas em idosos e apenas ao HDL-c baixo em adultos. As diferentes respostas entre os adultos e idosos podem sugerir que o índice glicêmico tem ação distinta entre os grupos etários. Ressalta-se que a qualidade do carboidrato parece ser mais importante do que a junção da qualidade-quantidade do carboidrato consumido para os parâmetros metabólicos avaliados na população da cidade São Paulo. / Introduction: High glycemic index and glycemic load intake has been associated with an increased risk for developing metabolic syndrome, an important precursor of cardiovascular disease and type 2 diabetes mellitus. However, these findings are inconsistent and the use of glycemic index and glycemic load for prevention or treatment of metabolic syndrome and the risk factors components is still controversial. Objectives: To validate self-reported diabetes mellitus and evaluate the association between glycemic index, glycemic load and metabolic syndrome and its components. Methods: Data were used from the Health Survey of São Paulo (ISA-Capital 2008) related to adults and elderly of both sexes living in this city. It is cross-sectional population-based study of individuals living in permanent homes located in the urban area of the municipality. Information used came from a structured questionnaire, two 24-hour dietary recalls, biochemical analysis, blood pressure and anthropometric measurements (weight, height and waist circumference). Prevalences of diabetes mellitus and metabolic syndrome were estimated for the city of São Paulo. The validation of self-reported diabetes mellitus was made by calculating the sensitivity, specificity, positive and negative predictive values. Usual food intake was achieved by the incorporation of food data in Multiple Source Method software. The association between glycemic index and glycemic load of the diet and metabolic syndrome and its components was verified by logistic regression models according to age group. All analysis took into account the sampling design of the study. Results: Diabetes mellitus and metabolic syndrome prevalences in São Paulo city were 8.0 per cent and 30.2 per cent , respectively. The sensitivity of self-reported diabetes mellitus was 63.8 per cent (95 per cent CI: 49.2 to 76.3), specificity was 99.7 per cent (95 per cent CI: 99.1 to 99.9), the positive predictive value was 95.5 per cent (95 per cent CI: 84.4 to 98.8) and the negative predictive value was 96.9 per cent (95 per cent CI: 94.9 to 98.2). Glycemic index was associated with high density lipoprotein cholesterol (OR: 1.16; 95 per cent CI: 1.02 to 1.32) in adults and with metabolic syndrome (OR: 1.24; 95 per cent CI: 1.1 to 1, 37), fasting blood glucose (OR: 1.15; 95 per cent CI: 1.01 to 1.31) and blood pressure (OR: 1.26; 95 per cent CI: 1.05 to 1.51) in elderly. Conclusion: Self- report diabetes mellitus data is valid, especially among elderly people living in São Paulo. The results show the need for diabetes mellitus screening in asymptomatic individuals who have one or more risk factors for this condition, especially in adults. Glycemic index was associated with metabolic syndrome and elevated fasting blood glucose and blood pressure in elderly and only with low high density lipoprotein cholesterol in adults. The different responses among adults and elderly may suggest that glycemic index has distinct action between age groups. Carbohydrate quality seems to be more important than the joint quality-quantity of the ingested carbohydrate for metabolic parameters evaluated in the population of São Paulo city.

Glycemic intake influences the rise in blood glucose concentration following consumption of a carbohydrate containing meal, known as the postprandial glycemic response. The glycemic response is a result of both the type and amount of carbohydrate foods consumed and is commonly measured as the glycemic index (GI) or glycemic load (GL), where the GI is a ranking in comparison to glucose and the GL is an absolute value encompassing both the GI and amount of carbohydrate consumed. Evidence from controlled trials in rat models suggests that glycemic intake has a role in development of insulin resistance, however trials and observational studies of humans have produced conflicting results. As insulin resistance is a precursor to type 2 diabetes mellitus, lifestyle factors that could prevent development of this condition have important public health implications. Previous observational studies have used food frequency questionnaires to assess usual diet, which could have resulted in a lack of precision in assessment of individual serve sizes, and have been limited to daily measures of glycemic intake. Daily measures do not take fluctuations in glycemic intake on a per meal basis into account, which may be a more relevant measure for investigation in relation to disease outcomes. This PhD research was conducted in a group of Brisbane women aged 42 to 81 years participating in the multidisciplinary Brisbane Longitudinal Assessment of Ageing in Women (LAW study). Older women may be at particular risk of insulin resistance due to age, hormonal changes, and increases in abdominal obesity associated with menopause, and the LAW study provided an ideal opportunity to study the relationship between diet and insulin resistance. Using the diet history tool, we aimed to assess the glycemic intake of the population and hypothesised that daily GI and daily GL would be significantly positively associated with increased odds of insulin resistant status. We also hypothesised that a new glycemic measure representing peaks in GL at different meals would be a stronger predictor of insulin resistant status than daily measures, and that a specially designed questionnaire would be an accurate and repeatable dietary tool for assessment of glycemic intake. To address these hypotheses, we conducted a series of studies. To assess glycemic intake, information on usual diet was obtained by detailed diet history interview and analysed using Foodworks and the Australian Food and Nutrient (AUSNUT) database, combined with a customised GI database. Mean ± SD intakes were 55.6 ± 4.4% for daily GI and 115 ± 25 for daily GL (n=470), with intake higher amoung younger participants. Bread was the largest contributor to intakes of daily GI and GL (17.1% and 20.8%, respectively), followed by fruit (15.5% and 14.2%, respectively). To determine whether daily GI and GL were significantly associated with insulin resistance, the homeostasis model assessment of insulin resistance (HOMA) was used to assess insulin resistant status. Daily GL was significantly higher in subjects who were insulin resistant compared to those who were not (134 ± 33 versus 114 ± 24 respectively, P<0.001) (n=329); the odds of subjects in the highest tertile of GL intake being insulin resistant were 12.7 times higher when compared with the lowest tertile of GL (95% CI 1.6-100.1, P=0.02). Daily GI was not significantly different in subjects who were insulin resistant compared to those who were not (56.0 ± 3.3% versus 55.7 ± 4.5%, P=0.69). To evaluate whether a new glycemic measure representing fluctuations in daily glycemic intake would be a stronger predictor of insulin resistant status than other glycemic intake measures, the GL peak score was developed to express in a single value the magnitude of GL peaks during an average day. Although a significant relationship was seen between insulin resistant status and GL peak score (Nagelkerke’s R2=0.568, P=0.039), other glycemic intake measures of daily GL (R2=0.671, P<0.001) and daily GL per megajoule (R2=0.674, P<0.001) were stronger predictors of insulin resistant status. To develop an accurate and repeatable self-administered tool for assessment of glycemic intake, two sub-samples of women (n=44 for the validation study and n=52 for the reproducibility study) completed a semi-quantitative questionnaire that contained 23 food groupings selected to include the top 100 carbohydrate foods consumed by the study population. While there were significant correlations between the glycemic intake questionnaire and the diet history for GL (r=0.54, P<0.01), carbohydrate (r=0.57, P<0.01) and GI (r=0.40, P<0.01), Bland-Altman plots showed an unacceptable difference between individual intakes in 34% of subjects for daily GL and carbohydrate, and 41% for daily GI. Reproducibility results showed significant correlations for daily GL (r=0.73, P<0.001), carbohydrate (r=0.76, P<0.001) and daily GI (r=0.64, P<0.001), but an unacceptable difference between individual intakes in 25% of subjects for daily GL and carbohydrate, and 27% for daily GI. In summary, our findings show that a significant association was observed between daily glycemic load and insulin resistant status in a group of older women, using a diet history interview to obtain precise estimation of individual carbohydrate intake. Both the type and quantity of carbohydrate are important to consider when investigating relationships between diet and insulin resistance, although our results suggest the association is more closely related to overall daily glycemic intake than individual meal intake variations. A dietary tool that permits precise estimation of carbohydrate intake is essential when evaluating possible associations between glycemic intake and individual risk of chronic diseases such as insulin resistance. Our results also suggest that studies using questionnaires to estimate glycemic intake should state degree of agreement as well as correlation coefficients when evaluating validity, as imprecise estimates of carbohydrate at an individual level may have contributed to the conflicting findings reported in previous studies.

Background: Puerto Ricans experience high prevalence of type 2 diabetes (diabetes). Stress is a risk factor for diabetes. The allostatic load (AL) model explains how stress influences disease through a chain of physiological changes. Puerto Ricans experience psychological and physiological (obesity and high glycemic load (GL)) stressors linked with diabetes, yet how these stressors impact the AL chain and how their interplay affects glucose metabolism remains unknown. Methods: Using data from the Boston Puerto Rican Health Study, this thesis sought to examine: 1) the relationship between GL and primary AL markers, 2) the interaction between perceived stress and GL on HbA1c, and if primary AL markers mediate this interaction, and 3) the interaction between change in weight and in perceived stress on HbA1c. Results: 1) GL change over 2 years was associated with increases in primary AL markers in women. 2) Women with high perceived stress and high GL had higher HbA1c and primary AL markers did not mediate this interaction. 3) In women, there was an interaction between change in weight and perceived stress on HbA1c over 2 years, with the effect of weight change on HbA1c being greater with increases in perceived stress. None of these associations were observed in men. Conclusion: This study partially confirms the AL model in Puerto Rican women but not in men. It provides data to inform intervention targets to prevent and manage diabetes in Puerto Rican women and identifies women at high risk of diabetes in this minority group.

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