1.
Glycemic Index, Glycemic Load and Cancer Risk: An Updated Meta-Analysis.
Turati, F, Galeone, C, Augustin, LSA, La Vecchia, C
Nutrients. 2019;11(10)
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This 2019 meta-analysis is an update of an earlier 2015 study on the relationship between high Glycemic Index (GI) and Glycemic load (GL) diets and cancer risk. Twenty new epidemiological reports were added to the original seventy-five studies covering a total of 169,00 cancer cases. The theory is that elevated insulin levels, triggered by a high GI diet, increase bioactive chemicals which promote cancer development by inhibiting cell apoptosis and stimulating cell proliferation. This study collated cancers into 3 subgroups of hormonal cancers (breast, endometrium, ovary and prostate), digestive tract cancers (cancers, stomach, colorectum and pancreas) and other (lung, bladder and kidney). The combined results showed that the risk ratio for hormonal-related cancers and GI/GL were modestly elevated but not significant except for a possible moderate positive association between GL and endometrial cancer (RR1.12). There was a positive significant association between high GI intake and colorectal cancer risk (RR 1.20) but not with the other digestive-tract cancers. A high GI was associated with small increased risks of bladder (RR 1.25) and kidney (RR 1.16) cancers. The researchers conclude that the high number of studies and cancer types included provide high statistical power. Although the results show only moderate association this may be relevant at population level given the high incidence of cancers.
Abstract
Diets high in glycemic index (GI) and glycemic load (GL) have been related to an increased risk of selected cancers, but additional quantification is required. We updated a systematic review and meta-analysis published in 2015 to May 2019 to provide quantitative information on GI/GL and cancer risk. Relative risks (RR) and the corresponding 95 % confidence intervals (CI) for the highest versus the lowest categories of GI and GL were extracted from selected studies and pooled using random-effects models. Twenty reports (>22,000 cancer cases) have become available after January 2015, and 15 were added to the meta-analyses by cancer sites, which considered a total of 88 investigations. The five additional reports were reviewed, but not included in the meta-analyses, since data were inadequate to be pooled. For hormone-related cancers, summary RRs for the highest versus lowest GI and GL intakes were moderately increased. They ranged from 1.04 (breast) to 1.12 (endometrium) for GI and from 1.03 (prostate) to 1.22 (ovary) for GL, of borderline significance. High GI was associated with small increased risks of colorectal (summary RR for GI: 1.20, 95% CI, 1.07-1.34-GL: 1.09, 95% CI, 0.97-1.22, 19 studies), bladder (GI: 1.25, 95% CI, 1.11-1.41-GL: 1.10, 95% CI, 0.85-1.42, four studies) and kidney cancers (GI: 1.16, 95% CI, 1.02-1.32-GL: 1.14, 95% CI, 0.81-1.60, five studies). GL was not significantly related to those cancer sites. Stomach, prostate and lung cancers were not associated with GI and GL. The present analysis, based on an updated comprehensive evaluation of the epidemiological literature, indicates moderate unfavorable effects of high versus low GI on colorectal, and possibly bladder and kidney cancers, and a possible moderate positive association between GL and endometrial cancer.
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Food sources of fructose-containing sugars and glycaemic control: systematic review and meta-analysis of controlled intervention studies.
Choo, VL, Viguiliouk, E, Blanco Mejia, S, Cozma, AI, Khan, TA, Ha, V, Wolever, TMS, Leiter, LA, Vuksan, V, Kendall, CWC, et al
BMJ (Clinical research ed.). 2018;363:k4644
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With increasing evidence linking fructose to metabolic disease, current dietary guidelines recommend a reduction of added free sugars, especially fructose-containing sugars from sugars-sweetened beverages (SSBs). However, it is currently unclear whether the negative impact of fructose on metabolic health is as implicative in the context of an overall dietary consumption pattern. The aim of this study was to assess the effect of different sources of fructose-containing sugars on glycaemic control in people with and without diabetes. This review analysed 155 controlled intervention studies and found that fructose-containing sugars in the form of fruit do not have a harmful effect on glycaemic control when compared to energy-matched macronutrient substitutions. Further, harmful effects on glycaemic control were found when excess energy in the form of fructose-containing sugars from SSBs were added to the diet. The authors conclude the food source of fructose-containing sugars on glycemic control is important in the conversation of metabolic health and glycaemic control. While further research is needed to assess a wider variety of food sources, public health professionals should consider the influence of food sources when developing dietary recommendations for the prevention and management of diabetes and other metabolic conditions.
Abstract
OBJECTIVE To assess the effect of different food sources of fructose-containing sugars on glycaemic control at different levels of energy control. DESIGN Systematic review and meta-analysis of controlled intervention studies. DATA SOURCES Medine, Embase, and the Cochrane Library up to 25 April 2018. ELIGIBILITY CRITERIA FOR SELECTING STUDIES Controlled intervention studies of at least seven days' duration and assessing the effect of different food sources of fructose-containing sugars on glycaemic control in people with and without diabetes were included. Four study designs were prespecified on the basis of energy control: substitution studies (sugars in energy matched comparisons with other macronutrients), addition studies (excess energy from sugars added to diets), subtraction studies (energy from sugars subtracted from diets), and ad libitum studies (sugars freely replaced by other macronutrients without control for energy). Outcomes were glycated haemoglobin (HbA1c), fasting blood glucose, and fasting blood glucose insulin. DATA EXTRACTION AND SYNTHESIS Four independent reviewers extracted relevant data and assessed risk of bias. Data were pooled by random effects models and overall certainty of the evidence assessed by the GRADE approach (grading of recommendations assessment, development, and evaluation). RESULTS 155 study comparisons (n=5086) were included. Total fructose-containing sugars had no harmful effect on any outcome in substitution or subtraction studies, with a decrease seen in HbA1c in substitution studies (mean difference -0.22% (95% confidence interval to -0.35% to -0.08%), -25.9 mmol/mol (-27.3 to -24.4)), but a harmful effect was seen on fasting insulin in addition studies (4.68 pmol/L (1.40 to 7.96)) and ad libitum studies (7.24 pmol/L (0.47 to 14.00)). There was interaction by food source, with specific food sources showing beneficial effects (fruit and fruit juice) or harmful effects (sweetened milk and mixed sources) in substitution studies and harmful effects (sugars-sweetened beverages and fruit juice) in addition studies on at least one outcome. Most of the evidence was low quality. CONCLUSIONS Energy control and food source appear to mediate the effect of fructose-containing sugars on glycaemic control. Although most food sources of these sugars (especially fruit) do not have a harmful effect in energy matched substitutions with other macronutrients, several food sources of fructose-containing sugars (especially sugars-sweetened beverages) adding excess energy to diets have harmful effects. However, certainty in these estimates is low, and more high quality randomised controlled trials are needed. STUDY REGISTRATION Clinicaltrials.gov (NCT02716870).