Dietary Glycemic Index and Load and the Risk of Type 2 Diabetes: Assessment of Causal Relations.
Plain language summary
It is generally accepted that certain diet and lifestyle choices contribute to a person’s risk of developing type 2 diabetes (T2D). In this meta-analysis, researchers set out to review previous studies and assess whether there is any evidence that the amount and type of carbohydrate (measured by Glycaemic Index (GI) and Glycaemic Load (GL)) in a person’s diet has a direct influence on their risk of developing T2D. The authors concluded with a high level of confidence that eating high GI and GL foods can lead to a higher risk of developing T2D. They suggest that nutrition advice that favours low GI and GL foods could produce significant cost savings for public healthcare.
While dietary factors are important modifiable risk factors for type 2 diabetes (T2D), the causal role of carbohydrate quality in nutrition remains controversial. Dietary glycemic index (GI) and glycemic load (GL) have been examined in relation to the risk of T2D in multiple prospective cohort studies. Previous meta-analyses indicate significant relations but consideration of causality has been minimal. Here, the results of our recent meta-analyses of prospective cohort studies of 4 to 26-y follow-up are interpreted in the context of the nine Bradford-Hill criteria for causality, that is: (1) Strength of Association, (2) Consistency, (3) Specificity, (4) Temporality, (5) Biological Gradient, (6) Plausibility, (7) Experimental evidence, (8) Analogy, and (9) Coherence. These criteria necessitated referral to a body of literature wider than prospective cohort studies alone, especially in criteria 6 to 9. In this analysis, all nine of the Hill's criteria were met for GI and GL indicating that we can be confident of a role for GI and GL as causal factors contributing to incident T2D. In addition, neither dietary fiber nor cereal fiber nor wholegrain were found to be reliable or effective surrogate measures of GI or GL. Finally, our cost-benefit analysis suggests food and nutrition advice favors lower GI or GL and would produce significant potential cost savings in national healthcare budgets. The high confidence in causal associations for incident T2D is sufficient to consider inclusion of GI and GL in food and nutrient-based recommendations.
Psychological mechanisms in a digital intervention to improve physical activity: A multicentre randomized controlled trial.
British journal of health psychology. 2018;(2):296-310
OBJECTIVES The randomized controlled trial examined factors that might be responsible for individual differences in physical activity change among men and women who participated in a lifestyle intervention. The main purpose of the analyses regarded the role of psychological mechanisms involving motivation, planning, self-monitoring, and habit strength. DESIGN A two-arm digital intervention was conducted in Italy, Spain, and Greece to improve physical activity levels, with follow-ups at 3 and 6 months after baseline assessment. METHODS Participants were 1,564 adults at baseline, n = 638 at 6-month follow-up. Linear mixed models examined the intervention effects, and a two-group longitudinal structural equation model explored which psychological constructs (motivation, planning, self-monitoring, habit strength) were associated with changes in physical activity. RESULTS In addition to an overall increase in self-reported activity, there were interactions between time and sex and between time and experimental groups, and a triple interaction between time, sex, and experimental groups, indicating that men reported an increase in activity independent of groups, whereas women in the active control group did not benefit from the intervention. Planning, self-monitoring, and habit strength mediated sequentially between initial motivation and follow-up physical activity. CONCLUSIONS Although the intervention produced overall improvements in physical activity, the time-by-treatment interaction emerged only for women. The mechanism included a sequence leading from motivation via planning, self-monitoring, and habit strength towards physical activity. Statement of contribution What is already known on this subject? Digital lifestyle interventions can be effective in terms of physical activity performance gains. Men are on average more physically active than women. Long-term adherence rates to digital interventions are usually low. What does this study add? Giving users of an online platform more interactive options did not make a difference. Women gained more than men from adaptive, dynamic online platform content. Individual characteristics (motivation, planning, self-monitoring, habit) were more important than online treatment features.
Coffee, tea and decaffeinated coffee in relation to hepatocellular carcinoma in a European population: multicentre, prospective cohort study.
International journal of cancer. 2015;136(8):1899-908
Plain language summary
The most investigated risk factors for Hepatocellular carcinoma (HCC) (Liver cancer) are alcohol, diet and obesity. This cohort study looks at tea and coffee (caffeinated and decaffeinated) consumption with HCC risk using data from the European Prospective Investigation into Cancer and nutrition study (EPIC). The EPIC study recruited 521,000 apparently healthy participants, aged 25-70 years, from 10 European countries between 1992 and 2000. Their diets were assessed by questionnaire alongside biometric data and other lifestyle factors. The researchers were able to identify 201 HCC cases among 486,799 men/women, after a median follow-up of 11 years. Some data had to be excluded based on cultural tea and coffee drinking habits (particularly lack of data from certain nationalities). There was coffee data from 163,672 participants drinking an overall median of 354 ml/d among men and 290 ml/d among women. The results found that increased coffee intake in participants in the highest compared to the lowest quintile had a lower HCC risk by 72%. There was no significant data for decaffeinated coffee. Tea drinkers represented just 66% of the total cohort and median intakes were 107 ml/d for men and 190 ml/d for women. Tea intake was also inversely associated with HCC incidence with 60% lower HCC risk. The study concludes that intakes of coffee and, to a lesser extent, tea are associated with lower HCC incidence. The incidence of HCC in participants was low so further studies are necessary.
Inverse associations of coffee and/or tea in relation to hepatocellular carcinoma (HCC) risk have been consistently identified in studies conducted mostly in Asia where consumption patterns of such beverages differ from Europe. In the European Prospective Investigation into Cancer and nutrition (EPIC), we identified 201 HCC cases among 486,799 men/women, after a median follow-up of 11 years. We calculated adjusted hazard ratios (HRs) for HCC incidence in relation to quintiles/categories of coffee/tea intakes. We found that increased coffee and tea intakes were consistently associated with lower HCC risk. The inverse associations were substantial, monotonic and statistically significant. Coffee consumers in the highest compared to the lowest quintile had lower HCC risk by 72% [HR: 0.28; 95% confidence intervals (CIs): 0.16-0.50, p-trend < 0.001]. The corresponding association of tea with HCC risk was 0.41 (95% CI: 0.22-0.78, p-trend = 0.003). There was no compelling evidence of heterogeneity of these associations across strata of important HCC risk factors, including hepatitis B or hepatitis C status (available in a nested case-control study). The inverse, monotonic associations of coffee intake with HCC were apparent for caffeinated (p-trend = 0.009), but not decaffeinated (p-trend = 0.45) coffee for which, however, data were available for a fraction of subjects. Results from this multicentre, European cohort study strengthen the existing evidence regarding the inverse association between coffee/tea and HCC risk. Given the apparent lack of heterogeneity of these associations by HCC risk factors and that coffee/tea are universal exposures, our results could have important implications for high HCC risk subjects.
Healthy lifestyle and risk of breast cancer among postmenopausal women in the European Prospective Investigation into Cancer and Nutrition cohort study.
International journal of cancer. 2015;136(11):2640-8
Plain language summary
Breast cancer is the most common cancer among women. A number of modiﬁable lifestyle factors have been shown to be associated with breast cancer risk including diet, physical activity, smoking, alcohol consumption and body fat. A health index combining these five risk factors was created and used to establish an association between lifestyle and breast cancer risk amongst participants of the European Prospective Investigation into Cancer and Nutrition (EPIC) study, a large prospective epidemiological study which recruited 521,330 healthy men and women, including 242,918 postmenopausal women, across Europe. The diet score was based on intakes of seven dietary factors: cereal ﬁbre, folate, the ratio of polyunsaturated to saturated fat, fatty ﬁsh (as a marker for omega-3 fatty acids), margarine (as a marker for industrially produced trans-fats), glycaemic load and fruits and vegetables. There was a lower risk of breast cancer in postmenopausal women with healthier lifestyles. All individual components of the healthy lifestyle index were signiﬁcantly associated with breast cancer risk, except smoking. The combined healthy lifestyle index was overall more strongly associated with breast cancer risk compared to the individual factors. The authors conclude that breast cancer prevention policies should include strategies to engage all women in lasting healthy diet and lifestyle habits.
Breast cancer is the most common cancer among women and prevention strategies are needed to reduce incidence worldwide. A healthy lifestyle index score (HLIS) was generated to investigate the joint effect of modifiable lifestyle factors on postmenopausal breast cancer risk. The study included 242,918 postmenopausal women from the multinational European Prospective Investigation into Cancer and Nutrition (EPIC) cohort, with detailed information on diet and lifestyle assessed at baseline. The HLIS was constructed from five factors (diet, physical activity, smoking, alcohol consumption and anthropometry) by assigning scores of 0-4 to categories of each component, for which higher values indicate healthier behaviours. Hazard ratios (HR) were estimated by Cox proportional regression models. During 10.9 years of median follow-up, 7,756 incident breast cancer cases were identified. There was a 3% lower risk of breast cancer per point increase of the HLIS. Breast cancer risk was inversely associated with a high HLIS when fourth versus second (reference) categories were compared [adjusted HR = 0.74; 95% confidence interval (CI): 0.66-0.83]. The fourth versus the second category of the HLIS was associated with a lower risk for hormone receptor double positive (adjusted HR = 0.81, 95% CI: 0.67-0.98) and hormone receptor double negative breast cancer (adjusted HR = 0.60, 95% CI: 0.40-0.90). Findings suggest having a high score on an index of combined healthy behaviours reduces the risk of developing breast cancer among postmenopausal women. Programmes which engage women in long term health behaviours should be supported.
Combined impact of lifestyle factors on prospective change in body weight and waist circumference in participants of the EPIC-PANACEA study.
PloS one. 2012;(11):e50712
BACKGROUND The evidence that individual dietary and lifestyle factors influence a person's weight and waist circumference is well established; however their combined impact is less well documented. Therefore, we investigated the combined effect of physical activity, nutrition and smoking status on prospective gain in body weight and waist circumference. METHODS We used data of the prospective EPIC-PANACEA study. Between 1992 and 2000, 325,537 participants (94,445 men and 231,092 women, aged between 25-70) were recruited from nine European countries. Participants were categorised into two groups (positive or negative health behaviours) for each of the following being physically active, adherent to a healthy (Mediterranean not including alcohol) diet, and never-smoking for a total score ranging from zero to three. Anthropometric measures were taken at baseline and were mainly self-reported after a medium follow-up time of 5 years. RESULTS Mixed-effects linear regression models adjusted for age, educational level, alcohol consumption, baseline body mass index and follow-up time showed that men and women who reported to be physically active, never-smoking and adherent to the Mediterranean diet gained over a 5-year period 537 (95% CI -706, -368) and 200 (-478, -87) gram less weight and 0.95 (-1.27, -0.639) and 0.99 (-1.29, -0.69) cm less waist circumference, respectively, compared to participants with zero healthy behaviours. CONCLUSION The combination of positive health behaviours was associated with significantly lower weight and waist circumference gain.
Social inequalities and mortality in Europe--results from a large multi-national cohort.
PloS one. 2012;(7):e39013
BACKGROUND Socio-economic inequalities in mortality are observed at the country level in both North America and Europe. The purpose of this work is to investigate the contribution of specific risk factors to social inequalities in cause-specific mortality using a large multi-country cohort of Europeans. METHODS A total of 3,456,689 person/years follow-up of the European Prospective Investigation into Cancer and Nutrition (EPIC) was analysed. Educational level of subjects coming from 9 European countries was recorded as proxy for socio-economic status (SES). Cox proportional hazard model's with a step-wise inclusion of explanatory variables were used to explore the association between SES and mortality; a Relative Index of Inequality (RII) was calculated as measure of relative inequality. RESULTS Total mortality among men with the highest education level is reduced by 43% compared to men with the lowest (HR 0.57, 95% C.I. 0.52-0.61); among women by 29% (HR 0.71, 95% C.I. 0.64-0.78). The risk reduction was attenuated by 7% in men and 3% in women by the introduction of smoking and to a lesser extent (2% in men and 3% in women) by introducing body mass index and additional explanatory variables (alcohol consumption, leisure physical activity, fruit and vegetable intake) (3% in men and 5% in women). Social inequalities were highly statistically significant for all causes of death examined in men. In women, social inequalities were less strong, but statistically significant for all causes of death except for cancer-related mortality and injuries. DISCUSSION In this European study, substantial social inequalities in mortality among European men and women which cannot be fully explained away by accounting for known common risk factors for chronic diseases are reported.
Serum levels of IGF-I, IGFBP-3 and colorectal cancer risk: results from the EPIC cohort, plus a meta-analysis of prospective studies.
International journal of cancer. 2010;126(7):1702-15
Plain language summary
Insulin-like growth factor-I (IGF-1) plays an important role in growth and development as a function of available energy and essential nutrients from body reserves and diet. The aim of the study was to examine the relationships of colorectal cancers with serum levels of IGF-I, and with 2 measures of IGF-binding protein (IGFBP)-3. The study also examined whether relative risks associated to IGF-I levels were modiﬁed by anthropometric and dietary factors. A meta-analysis was performed where the study results were combined with the results from previously published prospective studies. For the study, 1,121 case sets with IGF-1 and total IGFBP-3 measurements were observed. For each case participant with colon or rectum cancer, 1 control participant was selected randomly. Control were matched to cases depending on a set criteria. The study found no association between colorectal cancer risk and serum levels of IGF-1 or IGFBP-3. However, the results from the meta-analysis showed only a very mild signiﬁcant positive association. Overall, ﬁndings from the study together with those from the prospective cohort studies indicate a modest role for elevated circulating IGF-I levels in the development of colorectal cancer.
Several prospective studies have shown a moderate positive association between increasing circulating insulin-like growth factor-I (IGF-I) levels and colorectal cancer risk. However, the associations were often statistically nonsignificant, and the relationship of cancer risk with IGF-I's major binding protein, IGFBP-3, showed major discrepancies between studies. We investigated the association of colorectal cancer risk with serum IGF-I, total and intact IGFBP-3, in a case-control study nested within the EPIC cohort (1,121 cases of colorectal cancer and 1,121 matched controls). Conditional logistic regression was used to adjust for possible confounders. Our present study results were combined in a meta-analysis with those from 9 previous prospective studies to examine the overall evidence for a relationship of prediagnostic serum IGF-I with colorectal cancer risk. In the EPIC study, serum concentrations of IGF-I and IGFBP-3 showed no associations with risk of colorectal cancer overall. Only in subgroup analyses did our study show moderate positive associations of IGF-I levels with risk, either among younger participants only (and only for colon cancer) or among participants whose milk intakes were in the lowest tertile of the population distribution (RR for an increase of 100 ng/ml = 1.43 [95% CI = 1.13-1.93]). Nevertheless, in the meta-analysis a modest positive association remained between serum IGF-I and colorectal cancer risk overall (RR = 1.07 [1.01-1.14] for 1 standard deviation increase in IGF-I). Overall, data from our present study and previous prospective studies combined indicate a relatively modest association of colorectal cancer risk with serum IGF-I.
Dietary and lifestyle factors in relation to plasma insulin-like growth factor I in a general population sample.
European journal of cancer prevention : the official journal of the European Cancer Prevention Organisation (ECP). 2003;(3):229-34
There is evidence that the insulin-like growth factor system (IGF), particularly IGF-I, is important in human carcinogenesis. We studied in a general, though not strictly random population sample of 620 adults, the relationship of IGF-I to demographic, lifestyle and dietary factors, the latter ascertained through an extensive validated questionnaire. Plasma IGF-I levels declined significantly with age and the decline was more evident among women than among men. Tobacco smoking, body mass index and regular physical activity were unrelated to this hormone and a positive association with height was not statistically significant. Neither protein nor carbohydrate intake was related to plasma IGF-I levels but there was inconsistent evidence that ethanol intake may be inversely associated with plasma IGF-I and saturated and polyunsaturated lipids may be positively associated with it. The findings are evaluated in conjunction with evidence indicating that the incidence of cancer is lower among women than among men, height is a risk factor for several forms of cancer, and saturated and polyunsaturated lipids have been more closely linked to human and animal carcinogenesis than monounsaturated lipids.