Overall, plant-based, or animal-based low carbohydrate diets and all-cause and cause-specific mortality: A systematic review and dose-response meta-analysis of prospective cohort studies

Dietary factors and cancer outcomes in individuals with type 2 diabetes: A systematic review and meta-analysis of prospective observational studies

INTRODUCTION

Cancer is a major health concern in persons with type 2 diabetes (T2D). Diet plays an important role in progression of diabetes and cancer. We aimed to systematically summarize the evidence on diet and cancer in individuals with T2D.

METHODS

PubMed and Web of Science were searched until August 2023 and followed up via PubMed alert until December 2024. Prospective studies investigating any dietary factor in association with cancer in individuals with T2D were eligible.

RESULTS

We identified 68 studies and conducted 20 meta-analyses. A general low-carbohydrate diet was not associated with cancer outcomes, whereas an inverse association was found for vegetable-based low-carbohydrate diet (HR per 5 points [95 % CI]: 0.90 [0.84, 0.97]; n = 2). We found indications of lower cancer incidence for higher adherence to Dietary Approaches to Stop Hypertension diet, (Alternate) Healthy Eating Index, higher intakes of n-3 fatty acids (0.73 [0.55, 0.98]; n = 2) and higher serum vitamin D (0.95 [0.93, 0.97]; n = 2), as well as a positive association for serum manganese concentrations (1.44 [1.11, 1.87]; n = 2), rated with low to very low certainty of evidence.

CONCLUSION

So far, the certainty of evidence is very limited due to the small numbers of primary studies. There is an indication of a possible association between diet and cancer risk among persons with T2D, but further well-designed prospective cohort studies are warranted.

Associations between carbohydrate quality and the survival of, and life expectancy with lung cancer patient: A prospective cohort study

BACKGROUND

Evidence now suggests that carbohydrate intake quality rather than quantity contributes to improved cancer survival benefits.

METHOD

An adjusted Cox proportional hazard model was used to investigate associations between carbohydrate quality index (CQI) and LC survival. We evaluated whether carbohydrate quantity modified associations between CQI and LC survival. We also assessed the association between life expectancy and CQI in people with LC.

RESULT

Totally, 316 deaths occurred during a mean follow-up period of 30.02 months (standard deviation (SD) = 18.76). A higher CQI score was associated with significantly improved survival among patients with LC (hazard ratio [HR] = 0.60, 95 % confidence interval [CI]: 0.44-0.81). Non-linear dose-response associations between CQI and LC survival were observed (P = 0.005). For CQI sub-indices, the higher solid/total carbohydrate ratio (HR = 0.68, 95 % CI: 0.48-0.96) was associated with better LC survival. Reversely, liquid carbohydrate intake (HR = 1.44, 95 % CI: 1.02-2.04) was associated with increased LC mortality. No significant interactions were observed between the CQI and carbohydrate quantity in terms of LC patient survival. At age 45 years, patients with LC who were in the highest tertile of CQI had an increase of life expectancy of 3.36 years (95 % CI: 0.57-6.16) compared with those in the lowest tertile.

CONCLUSION

High-quality carbohydrate intake was associated with improved LC patient survival. The protective CQI association with LC survival was mostly driven by the whole grain/total grain ratio.

The effect of low-carbohydrate diets, based on changes in intake of dietary saturated fats on circulating TNF-α and interleukin- 6 levels in adults: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Low-carbohydrate diets (LCDs) have been associated with inflammation while there is still conflicting evidence regarding the effects of this type of diet on inflammatory markers and the clinical benefit of them remains uncertain. So, we aimed to ascertain the effects of LCDs on serum concentrations of tumor necrosis factor alpha (TNF-α) and interleukin- 6 (IL- 6) by performing a systematic review and meta-analysis of randomized clinical trials (RCTs).

METHODS

The online databases PubMed, Cochrane Central Register of Controlled Trials (CENTRAL), EMBASE, Web of Science, and Scopus were comprehensively searched up to February 2024, to find pertinent RCTs. Pooled weighted mean difference (WMD) with 95% confidence intervals (CIs) were calculated using the random-effects model.

RESULTS

This meta-analysis of 33 studies assessed a total of 2106 adults irrespective of their health status. Compared with control group, participants on LCDs experienced a decline in IL- 6 levels (WMD: - 0.31 pg/mL; 95% CI: - 0.49 to - 0.12; P = 0.001). However, no significant effect was revealed for TNF-α (WMD: - 0.02 pg/mL; 95% CI: - 0.08 to - 0.03; P = 0.449). Stratification analyses indicated that beneficial effects of LCDs on inflammatory cytokines (WMD: - 0.28 pg/mL; 95% CI: - 0.47 to - 0.10; P = 0.003, WMD: - 0.26 pg/mL; 95% CI: - 0.48 to - 0.03; P = 0.027, for TNF-α and IL- 6, respectively) were stronger when carbohydrate intake was < 10%. The results of Meta-regression analyses suggested that baseline level of both markers remained as a strong predictor of the effect size (P = 0.038 and P = 0.001 for TNF-α and IL- 6, respectively).

CONCLUSION

Adherence to LCDs appeared to be effective at improving inflammatory cytokines particularly, when carbohydrate intake was restricted to less than 10% of total energy. Nevertheless, further rigorously designed clinical trials considering factors such as race and genetic, the sources and quality of dietary carbohydrates, protein, and fat are required to gain a deeper understanding of the impact of LCDs on inflammatory markers.

TRIAL REGISTRATION

PROSPERO, registration no: CRD42023387452.

Evaluating the differential benefits of varying carbohydrate-restricted diets on lipid profiles and cardiovascular risks in dyslipidemia: a meta-analysis and systematic review

Background: carbohydrate-restricted diets (CRDs) have gained attention to address metabolic dysregulation commonly observed in dyslipidemia, a condition posing significant risks to cardiovascular health. However, the effectiveness of CRDs in improving cardiovascular health remains contentious. This meta-analysis comprehensively evaluated the long-term effects of CRDs on glucolipid metabolism and weight loss in individuals with dyslipidemia. Methods: extensive searches were conducted in PubMed, Web of Science, Scopus, the Cochrane Library, and EMBASE. Randomized controlled trials examining the effects of CRDs on glucolipid metabolism and weight loss in adults with dyslipidemia over a minimum of three weeks were included. This analysis compared the differential effects between moderate-low carbohydrate diets (MLCDs) and low carbohydrate diets (LCDs), including a targeted evaluation of animal-based CRDs and dyslipidemic individuals based on the BMI status, thereby addressing gaps in current knowledge. Results: Our findings indicated that CRDs significantly enhanced lipid profiles, including total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), and apolipoprotein B (ApoB), and contributed to weight management in individuals with dyslipidemia. MLCDs were more effective than LCDs in improving all lipid profiles except for TG, which was more effectively managed by LCDs. Animal-based CRDs did not significantly impact lipid profiles. Dyslipidemic individuals with overweight and obesity showed significant changes in TG and ApoB. A noteworthy negative correlation was also observed between TC, TG, and low-density lipoprotein cholesterol levels with higher dietary fiber intake, supporting the beneficial impact of fiber on cardiovascular health. Conclusions: These results for the first time highlighted the potential of adopting MLCDs, particularly those with sufficient fiber content, as a powerful strategy for reducing the risk of cardiovascular diseases in patients suffering from dyslipidemia.

Impact of the ketogenic diet as a dietary approach on cardiovascular disease risk factors: a meta-analysis of randomized clinical trials

BACKGROUND

Cardiovascular diseases (CVD) remain the leading cause of mortality globally, and the scarcity of scientific evidence regarding the impact of ketogenic diets on CVD risk factors necessitates urgent attention and redress.

OBJECTIVES

This meta-analysis evaluates the impact of the ketogenic diet on CVD risk factors compared with control diets through randomized controlled trials (RCTs).

METHODS

The study was registered in advance in the PROSPERO database (CRD42023491853). A systematic search was conducted across PubMed, Web of Science, EMBASE, and Cochrane Library to identify relevant RCTs. Fixed and random effects were employed to calculate the mean differences and 95% confidence intervals (CIs) for changes in CVD risk factors pre- and postketogenic diet intervention.

RESULTS

A total of 27 RCTs with 1278 participants were analyzed. The ketogenic diet intervention presented increase in total cholesterol (mean differences: 0.36 mmol/L; 95% CI: 0.15, 0.57; I2: 85.1%), low-density lipoprotein cholesterol (mean differences: 0.35 mmol/L; 95% CI: 0.20, 0.50; I2: 73.9%) and high-density lipoprotein cholesterol (mean differences: 0.16 mmol/L; 95% CI: 0.09, 0.23; I2: 86.7%) concentrations. Reductions were observed in the triglyceride (mean differences: -0.20 mmol/L; 95% CI: -0.29, -0.11; I2: 72.2%), blood glucose (mean differences: -0.18 mmol/L; 95% CI: -0.33, -0.02; I2: 76.4%), blood insulin (mean differences: -8.32 pmol/L; 95% CI: -14.52, -2.12; I2: 81.5%), diastolic blood pressure (mean differences: -1.41 mmHg; 95% CI: -2.57, -0.26; I2: 49.1%), weight (mean differences: -2.59 kg; 95% CI: -3.90, -1.28; I2: 87.4%), and body mass index (mean differences: -1.59 kg/m2; 95% CI: -2.32, -0.86; I2: 84.5%) concentrations after implementing ketogenic diets.

CONCLUSIONS

Although the ketogenic diet demonstrates benefits in terms of triglyceride, blood pressure, weight, and glycemic control, its impact on CVD risk factors, especially the elevated total cholesterol and low-density lipoprotein cholesterol concentrations, warrants a cautious approach.

Dietary insulin indices and low-carbohydrate diet and the odds of colorectal cancer: a case-control study

BACKGROUND

Regarding the role of insulin and insulin-inducing dietary factors in some cancers' etiology, we hypothesized that the risk of colorectal cancer may be lessened by following a lower carbohydrate and insulinogenic diet. Therefore, we performed this study to explore the association between a low-carbohydrate diet and insulin indices and the odds of colorectal cancer.

METHOD

This hospital-based case-control study was conducted on 150 newly diagnosed colorectal cancer patients and 300 healthy age- and sex-matched hospitalized controls. A valid and reliable food frequency questionnaire was used to calculate the insulin indices and low-carbohydrate diet score. Multivariate logistic regression was used to estimate the association between insulin indices and low-carbohydrate diet and the odds of colorectal cancer.

RESULT

After adjusting for potential confounders, individuals in the highest tertile of insulin indices had a higher risk of colorectal cancer (OR insulin index  = 3.46; 95% CI, 2.00-5.96; OR insulin load  = 2; 95% CI, 1.17-3.41). No association was found between a low-carbohydrate diet and colorectal cancer (OR = 1.55; 95% CI, 0.85-2.84).

CONCLUSION

Current results demonstrated that a high insulinemic diet was associated with a higher risk of colorectal cancer.

Low-carbohydrate dietary score and the incidence of metabolically unhealthy phenotype based on BMI status: a cohort study

There is scarce research focusing on the relationship between the low-carbohydrate dietary score and the development of a metabolically unhealthy phenotype. Therefore, this cohort study was designed to assess the association between the low-carbohydrate dietary score and the risk of metabolically unhealthy phenotypes (MUP). This study included 1299 adults with healthy metabolic profiles who were followed for 5.9 years. Results indicated an inverse association between the second tertile of the low-carbohydrate dietary score and the risk of developing metabolically unhealthy obesity (MUO) (HR: 0.76, 95% CI: 0.59-0.98). In addition, we found an inverse association between the healthy low-carbohydrate dietary score and the risk of MUO (HR: 0.77, 95% CI: 0.60-0.99). Our results revealed a nonlinear inverse association between the low-carbohydrate dietary score and the risk of MUP only in subjects with overweight or obesity. This relationship was independent of animal protein and fat intake. Also, we found that a lower intake of unhealthy carbohydrates was associated with a lower risk of MUP only in subjects with overweight or obesity.

Ketogenic diet and cardiovascular risk - state of the art review

The ketogenic diet is based on extreme carbohydrate intake reduction and replacing the remaining with fat and has become a popular dietary pattern used for weight loss. The relationship between the ketogenic diet and cardiovascular risk is a controversial topic. This publication aimed to present evidence on the ketogenic diet and cardiovascular risk factors and mortality. The ketogenic diet does not fulfill the criteria of a healthy diet. It presents the potential for rapid short-term reduction of body mass, triglycerides level, Hb1Ac, and blood pressure. Its efficacy for weight loss and the above-mentioned metabolic changes is not significant in long-term observations. In terms of cardiovascular mortality, the low-carb pattern is more beneficial than very low-carbohydrate (including the ketogenic diet). There is still scarce evidence comparing ketogenic to the Mediterranean diet. Other safety concerns in cardiovascular patients such as adverse events related to ketosis, fat-free mass loss, or potential pharmacological interactions should be also taken into consideration in future research.

Associations between the New DNA-Methylation-Based Telomere Length Estimator, the Mediterranean Diet and Genetics in a Spanish Population at High Cardiovascular Risk

Biological aging is a relevant risk factor for chronic diseases, and several indicators for measuring this factor have been proposed, with telomere length (TL) among the most studied. Oxidative stress may regulate telomere shortening, which is implicated in the increased risk. Using a novel estimator for TL, we examined whether adherence to the Mediterranean diet (MedDiet), a highly antioxidant-rich dietary pattern, is associated with longer TL. We determined TL using DNA methylation algorithms (DNAmTL) in 414 subjects at high cardiovascular risk from Spain. Adherence to the MedDiet was assessed by a validated score, and genetic variants in candidate genes and at the genome-wide level were analyzed. We observed several significant associations (p < 0.05) between DNAmTL and candidate genes (TERT, TERF2, RTEL1, and DCAF4), contributing to the validity of DNAmTL as a biomarker in this population. Higher adherence to the MedDiet was associated with lower odds of having a shorter TL in the whole sample (OR = 0.93; 95% CI: 0.85-0.99; p = 0.049 after fully multivariate adjustment). Nevertheless, this association was stronger in women than in men. Likewise, in women, we observed a direct association between adherence to the MedDiet score and DNAmTL as a continuous variable (beta = 0.015; SE: 0.005; p = 0.003), indicating that a one-point increase in adherence was related to an average increase of 0.015 ± 0.005 kb in TL. Upon examination of specific dietary items within the global score, we found that fruits, fish, "sofrito", and whole grains exhibited the strongest associations in women. The novel score combining these items was significantly associated in the whole population. In the genome-wide association study (GWAS), we identified ten polymorphisms at the suggestive level of significance (p < 1 × 10-5) for DNAmTL (intergenics, in the IQSEC1, NCAPG2, and ABI3BP genes) and detected some gene-MedDiet modulations on DNAmTL. As this is the first study analyzing the DNAmTL estimator, genetics, and modulation by the MedDiet, more studies are needed to confirm these findings.

Low-carbohydrate diet and risk of cardiovascular disease, cardiovascular and all-cause mortality: a systematic review and meta-analysis of cohort studies

Background: Evidence for the long-term health effect of low-carbohydrate diets (LCDs) is inconsistent. Herein, we aimed to examine the associations of LCDs with cardiovascular disease (CVD) and all-cause and cause-specific mortality. Methods: We searched PubMed, EMBASE, and the Web of Science up to 26 July 2023 for eligible publications. Random-effect models were used to pool the summary relative risks (RRs) and 95% confidence intervals (CIs). Results: A total of 44 studies (17 articles) were included in the systematic review and 38 in the meta-analysis, including 223 657 all-cause deaths (771 609 participants), 14 046 cardiovascular deaths (274 807 participants), 18 264 CVD cases (405 631 participants), and 3634 coronary heart disease (CHD) cases (151 023 participants). Subsequently, the highest LCD score was compared with the lowest one and the pooled RRs (95% CIs) were 1.05 (0.96, 1.14; I2 = 65.1%; n = 13) for CVD, 1.43 (1.18, 1.72; I2 = 25.4%; n = 3) for CHD, 0.93 (0.81, 1.06; I2 = 0.0%; n = 2) for stroke, 1.03 (0.96, 1.10; I2 = 86.6%; n = 13) for all-cause mortality and 1.09 (0.99, 1.19; I2 = 65.1%; n = 10) for cardiovascular mortality. Conclusion: Our analysis showed positive associations of LCDs with CHD. Thus, vigilance is recommended for long-term adherence to this dietary pattern.