A very-low carbohydrate content in a high-fat diet modifies the plasma metabolome and impacts systemic inflammation and experimental atherosclerosis

Ketogenic diets (KDs) are very high-fat low-carbohydrate diets that promote nutritional ketosis and are widely used for weight loss, although concerns about potential adverse cardiovascular effects remain. We investigated a very high-fat KD's vascular impact and plasma metabolic signature compared to a non-ketogenic high-fat diet (HFD). Apolipoprotein E deficient (ApoE -/-) mice were fed a KD (%kcal:81:1:18, fat/carbohydrate/protein), a non-ketogenic high-fat diet with half of the fat content (HFD) (%kcal:40:42:18, fat/carbohydrate/protein) for 12 weeks. Plasma samples were used to quantify the major ketone body beta-hydroxybutyrate (BHB) and several pro-inflammatory cytokines (IL-6, MCP-1, MIP-1alpha, and TNF alpha), and to targeted metabolomic profiling by mass spectrometry. In addition, aortic atherosclerotic lesions were quantified ex-vivo by magnetic resonance imaging (MRI) on a 14-tesla system. KD was atherogenic when compared to the control diet, but KD mice, when compared to the HFD group (1) had markedly higher levels of BHB and lower levels of cytokines, confirming the presence of ketosis that alleviated the well-established fat-induced systemic inflammation; (2) displayed significant changes in the plasma metabolome that included a decrease in lipophilic metabolites and an increase in hydrophilic metabolites; (3) had significantly lower levels of several atherogenic lipid metabolites, including phosphatidylcholines, cholesterol esters, sphingomyelins, and ceramides; and (4) presented significantly lower aortic plaque burden. KD was atherogenic and was associated with specific metabolic changes but alleviated the fat-induced inflammation and lessened the progression of atherosclerosis when compared to the HFD.

Supplementation with medium-chain fatty acids increases body weight loss during very low-calorie ketogenic diet: a retrospective analysis in a real-life setting

BACKGROUND

Very low-calorie ketogenic diet (VLCKD) has shown to significantly reduce body weight and fat mass, as well as inflammation. These effects are supported by nutritional ketosis, which triggers the utilization of the ketone body as an energy source. Medium-chain fatty acids (MCTs) might serve as potential enhancers of ketone bodies production with a greater effect on weight loss. Nevertheless, no clinical studies have evaluated the effect of MCTs supplementation in addition to VLCKD. Therefore, the present study aimed to evaluate whether the supplementation with MCTs can induce a greater weight reduction during the ketogenic phase of VLCKD.

METHODS

In this retrospective study, 263 women with overweight/obesity (body mass index, BMI: 35.7 ± 5.3 kg/m²) aged 37.5 ± 14.2 years followed one of these dietary protocols for 45 days: (a) Control group, 83 participants (31.6%) (VLCKD without MCTs), (b) VLCKD + MCTs group, 86 participants (32.7%) (MCTs supplementation - 20 g/day- during VLCKD starting from the first day of the active phase), (c) VLCKD + earlyMCTs, 94 participants (35.7%) (MCTs supplementation - 20 g/day-starting from 5 days before the beginning of the VLCKD active phase. Anthropometric measures, body composition, and c-reactive protein (CRP) concentrations were collected at the beginning and at the end (45 days) of the VLCKD intervention.

RESULTS

MCTs supplementation significantly decreased body weight, BMI, and waist circumference as compared to the control group, with a greater effect in the VLCKD + earlyMCTs group. A two-fold decrease in fat mass and an increase in muscle mass were observed in the VLCKD + earlyMCTs group as compared to the control group. As for inflammation, hs-CRP concentrations (assessed as absolute percent change) were significantly lower in the VLCKD + MCTs group (p = 0.009) and the VLCKD + earlyMCTs group (p = 0.011) than in the control group. A logistic regression model showed that VLCKD + earlyMCTs increase the likelihood of improvement of BMI classes (OR: 1.85, 95% CI 1.02-3.36) also after adjusting for the potential confounding factors.

CONCLUSION

MCTs supplementation (20 g/day) may be a useful tool to enhance the beneficial effect of VLCKD on the reduction of body weight and fat mass. In particular, MCTs supplementation before the beginning of the VLCKD active phase might facilitate ketosis thus contributing to the effectiveness of the nutritional intervention.

Medium-chain triglycerides may improve memory in non-demented older adults: a systematic review of randomized controlled trials

BACKGROUND

Ketosis has been exploited for its neuroprotective impact and treatment of neurological conditions via ketone production. Exogenous medium-chain triglyceride (MCT) supplementation may induce nutritional ketosis. The aim of this systematic review is to explore the effects of MCTs on memory function in older adults without cognitive impairment.

METHODS

A systematic literature search of PubMed, Cochrane Library, Scopus, and Web of Science was employed from inception until April 2022 for randomized controlled trials (RCTs) in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, investigating the impact of MCT oils on components of memory. Risk of bias (RoB2) tool was utilized for quality assessment.

RESULTS

Six trials were included for qualitative synthesis, in which two studies examined the effect of MCTs through a ketogenic meal. MCT supplementation compared to controls was associated with improved indices of memory function in 4 out of 6 studies, particularly working memory. A meta-analysis was not employed due to the low number of studies, therefore, a true effect measure of MCT supplementation was not explored.

CONCLUSIONS

MCT supplementation may enhance working memory in non-demented older adults. These effects may be more prominent in individuals with lower baseline scores, from short and long-term supplementation. Further studies are warranted to confirm these findings in terms of optimal dose and MCTs composition, which may protect from memory decline during aging.

Type 2 Myocardial Infarction Related to Very Low Carbohydrate Ketogenic Diet

A 38-year-old male with no history of cardiac disease presented with chest pain typical of acute coronary syndrome. He assumed very-low-carbohydrate ketogenic diet (VLC-KD) 4 weeks prior to admission but no other lifestyle change. Workup showed dynamic ST-T changes on electrocardiogram, significantly elevated troponins, ketonuria, and mild rhabdomyolysis. Transthoracic echocardiogram revealed mild inferior wall hypokinesia and cardiac catheterization showed normal coronaries; hence, the diagnosis of type II myocardial infarction (MI) was established. Although the pathogenesis remains unclear, this temporal association between VLC-KD and type 2 MI raised some concerns about VLC-KD’s cardiovascular safety profile.

Depressive symptoms improve over 2 years of type 2 diabetes treatment via a digital continuous remote care intervention focused on carbohydrate restriction

Depressive symptoms are prevalent among people with type 2 diabetes (T2D) and, even at low severity levels, are associated with worse diabetes outcomes. Carbohydrate restriction is an effective treatment for T2D but its long-term impacts on depressive symptoms are unclear. In the current study we explored changes in depressive symptoms over 2 years among 262 primarily non-depressed T2D patients participating in a continuous remote care intervention emphasizing carbohydrate restriction. Subclinical depressive symptoms decreased over the first 10 weeks and reductions were maintained out to 2 years. Increased frequency of blood ketone levels indicative of adherence to low carbohydrate eating predicted decreases in depressive symptoms. Concerns have been raised with recommending restrictive diets due to potential negative impacts on quality-of-life factors such as mood; however, results of the current study support positive rather than negative long-term impacts of closely monitored carbohydrate restriction on depressive symptoms.

Nutritional Ketosis in Parkinson's Disease - a Review of Remaining Questions and Insights

Nutritional ketosis has promise for treating Parkinson's disease. Three previous studies explored the use of a ketogenic diet in cohorts with Parkinson's disease, and, while not conclusive, the data suggest non-motor symptom benefit. Before the ketogenic diet can be considered as a therapeutic option, it is important to establish with greater certainty that there is a reliable symptomatic benefit: which symptoms or groups of symptoms are impacted (if non-motor symptoms, which ones, and by which mechanism), what timescale is needed to obtain benefit, and how large an effect size can be achieved? To accomplish this, further investigation into the disease mechanisms based on pre-clinical data and hints from the clinical outcomes to date is useful to understand target engagement and gauge which mechanism could lead to a testable hypothesis. We review research pertaining to ketogenic diet, exogenous ketones, fasting, clinical studies, and theoretical review papers regarding therapeutic mechanisms from direct ketone body signaling and indirect metabolic effects. Through discussion of these findings and consideration of whether the ketogenic diet can be regarded as therapeutically useful for adjunctive therapy for Parkinson's disease, we identify remaining questions for the clinician to consider prior to recommending this diet.

Impact of a 2-year trial of nutritional ketosis on indices of cardiovascular disease risk in patients with type 2 diabetes

BACKGROUND

We have previously reported that in patients with type 2 diabetes (T2D) consumption of a very low carbohydrate diet capable of inducing nutritional ketosis over 2 years (continuous care intervention, CCI) resulted in improved body weight, glycemic control, and multiple risk factors for cardiovascular disease (CVD) with the exception of an increase in low density lipoprotein cholesterol (LDL-C). In the present study, we report the impact of this intervention on markers of risk for atherosclerotic cardiovascular disease (CVD), with a focus on lipoprotein subfraction particle concentrations as well as carotid-artery intima-media thickness (CIMT).

METHODS

Analyses were performed in patients with T2D who completed 2 years of this study (CCI; n = 194; usual care (UC): n = 68). Lipoprotein subfraction particle concentrations were measured by ion mobility at baseline, 1, and 2 years and CIMT was measured at baseline and 2 years. Principal component analysis (PCA) was used to assess changes in independent clusters of lipoprotein particles.

RESULTS

At 2 years, CCI resulted in a 23% decrease of small LDL IIIb and a 29% increase of large LDL I with no change in total LDL particle concentration or ApoB. The change in proportion of smaller and larger LDL was reflected by reversal of the small LDL subclass phenotype B in a high proportion of CCI participants (48.1%) and a shift in the principal component (PC) representing the atherogenic lipoprotein phenotype characteristic of T2D from a major to a secondary component of the total variance. The increase in LDL-C in the CCI group was mainly attributed to larger cholesterol-enriched LDL particles. CIMT showed no change in either the CCI or UC group.

CONCLUSION

Consumption of a very low carbohydrate diet with nutritional ketosis for 2 years in patients with type 2 diabetes lowered levels of small LDL particles that are commonly increased in diabetic dyslipidemia and are a marker for heightened CVD risk. A corresponding increase in concentrations of larger LDL particles was responsible for higher levels of plasma LDL-C. The lack of increase in total LDL particles, ApoB, and in progression of CIMT, provide supporting evidence that this dietary intervention did not adversely affect risk of CVD.

Acute hyperketonaemia alters T-cell-related cytokine gene expression within stimulated peripheral blood mononuclear cells following prolonged exercise

PURPOSE

We investigated the effect of the racemic β-hydroxybutyrate precursor, R,S-1,3-butanediol (BD), on T-cell-related cytokine gene expression within stimulated peripheral blood mononuclear cells (PBMC) following prolonged, strenuous exercise.

METHODS

A repeated-measures, randomised, crossover study was conducted in nine healthy, trained male cyclists (age, 26.7 ± 5.2 years; VO_2peak, 63.9 ± 2.5 mL kg^-1 min^-1). Participants ingested 0.35 g kg^-1 of BD or placebo 30 min before and 60 min during 85 min of steady-state (SS) exercise, which preceded a ~ 30 min time-trial (TT) (7 kJ kg^-1). Blood samples were collected at pre-supplement, pre-exercise, post-SS, post-TT and 1-h post-TT. Whole blood cultures were stimulated with Staphylococcal enterotoxin B (SEB) for 24 h to determine T-cell-related interleukin (IL)-4, IL-10 and interferon (IFN)-γ mRNA expression within isolated PBMCs in vitro.

RESULTS

Serum cortisol, total circulating leukocyte and lymphocyte, and T-cell subset concentrations were similar between trials during exercise and recovery (all p > 0.05). BD ingestion increased T-cell-related IFN-γ mRNA expression compared with placebo throughout exercise and recovery (p = 0.011); however, IL-4 and IL-10 mRNA expression and the IFN-γ/IL-4 mRNA expression ratio were unaltered (all p > 0.05).

CONCLUSION

Acute hyperketonaemia appears to transiently amplify the initiation of the pro-inflammatory T-cell-related IFN-γ response to an immune challenge in vitro during and following prolonged, strenuous exercise; suggesting enhanced type-1 T-cell immunity at the gene level.

Nutritional ketosis for mild cognitive impairment in Parkinson's disease: A controlled pilot trial

INTRODUCTION

Glucose hypometabolism and insulin resistance increase risk for and accelerate progression in Parkinson's disease and neurocognitive disorders. We conducted a proof of concept trial to determine whether ketogenesis, a metabolic adaptation induced by dietary carbohydrate restriction, can improve cognitive performance in Parkinson's disease patients with mild cognitive impairment.

METHODS

We enrolled patients with mild cognitive impairment associated with Parkinson's disease in an eight-week nutritional intervention with random assignment to either high-carbohydrate consumption typical of the Western dietary pattern (n = 7) or to a low-carbohydrate, ketogenic regimen (n = 7). We assessed changes in cognitive performance as well as motor function, anthropometrics, and metabolic parameters.

RESULTS

Relative to the high-carbohydrate group, the low-carbohydrate group demonstrated improvements in lexical access (p = 0.02, Cohen's f effect size = 0.76) and memory (p = 0.01, f = 0.87) and as well as a trend for reduced interference in memory (p = 0.06, f = 0.60). The low-carbohydrate group also exhibited reduced body weight (p < 0.0001, f = 1.89) and increased circulation of beta-hydroxybutyrate (p = 0.01, f = 0.90). Change in body weight was strongly associated with memory performance (p = 0.001). Motor function was not affected by the intervention.

CONCLUSION

Nutritional ketosis enhanced cognitive performance in Parkinson's disease-associated mild cognitive impairment in this pilot study. This metabolic intervention and its mechanisms deserve further investigation in the context of neurodegeneration.

Nutritional Ketosis for Weight Management and Reversal of Metabolic Syndrome

PURPOSE OF REVIEW

The goal of this paper is to review current literature on nutritional ketosis within the context of weight management and metabolic syndrome, namely, insulin resistance, lipid profile, cardiovascular disease risk, and development of non-alcoholic fatty liver disease. We provide background on the mechanism of ketogenesis and describe nutritional ketosis.

RECENT FINDINGS

Nutritional ketosis has been found to improve metabolic and inflammatory markers, including lipids, HbA1c, high-sensitivity CRP, fasting insulin and glucose levels, and aid in weight management. We discuss these findings and elaborate on potential mechanisms of ketones for promoting weight loss, decreasing hunger, and increasing satiety. Humans have evolved with the capacity for metabolic flexibility and the ability to use ketones for fuel. During states of low dietary carbohydrate intake, insulin levels remain low and ketogenesis takes place. These conditions promote breakdown of excess fat stores, sparing of lean muscle, and improvement in insulin sensitivity.

Improvement in patient-reported sleep in type 2 diabetes and prediabetes participants receiving a continuous care intervention with nutritional ketosis

OBJECTIVE

Sleep disruption is frequently associated with type 2 diabetes (T2D) and hyperglycemia. We recently reported the effectiveness of a continuous care intervention (CCI) emphasizing nutritional ketosis for improving HbA1c, body weight and cardiovascular risk factors in T2D patients. The present study assessed the effect of this CCI approach on sleep quality using a subjective patient-reported sleep questionnaire.

METHODS

A non-randomized, controlled longitudinal study; 262 T2D and 116 prediabetes patients enrolled in the CCI and 87 separately recruited T2D patients continued usual care (UC) treatment. Patients completed the Pittsburgh Sleep Quality Index (PSQI) questionnaire. A PSQI score of >5 (scale 0 to 21) was used to identify poor sleepers.

RESULTS

Global sleep quality improved in the CCI T2D (p < 0.001) and prediabetes (p < 0.001) patients after one year of intervention. Subjective sleep quality (component 1), sleep disturbance (component 5) and daytime dysfunction (component 7), also showed improvements in the CCI T2D (p < 0.01 for sleep quality and sleep disturbance; and p < 0.001 for daytime dysfunction) and prediabetes patients (p < 0.001 for all three components); compared to the UC T2D group after one year. The proportion of patients with poor sleep quality was significantly reduced after one year of CCI (T2D; from 68.3% at baseline to 56.5% at one year, p = 0.001 and prediabetes; from 77.9% at baseline to 48.7% at one year, p < 0.001).

CONCLUSION

This study demonstrates improved sleep quality as assessed by PSQI in patients with T2D and prediabetes undergoing CCI including nutritional ketosis but not in T2D patients receiving UC. The dietary intervention benefited both sleep quality and the severity of T2D symptoms suggesting that nutritional ketosis improves overall health via multiple mechanisms.

Effects of differing levels of carbohydrate restriction on mood achievement of nutritional ketosis, and symptoms of carbohydrate withdrawal in healthy adults: A randomized clinical trial

OBJECTIVES

To our knowledge, minimal research exists on the effects of diets differing in carbohydrate restriction on symptoms of carbohydrate withdrawal and mood, and the achievement of nutritional ketosis (NK). The aim of this study was to compare ketonaemia, symptoms of carbohydrate withdrawal, and mood. We hypothesized that a moderate carbohydrate restriction would result in fewer symptoms and a reduced effect on mood.

METHODS

Seventy-seven healthy participants (25 men and 52 women; mean age: 39 y, range: 25-49; mean body mass index 27 kg/m², range: 20-39) were randomized to receive either a very-low-carbohydrate ketogenic diet (VLCKD), low-carbohydrate diet (LCD), or moderately low-carbohydrate diet (MCD), containing 5%, 15%, and 25% total energy (TE) from carbohydrate, respectively, for 3 wk. Fasting blood ketone measures were recorded daily upon waking along with a data from symptom questionnaire and a 5-point mood-state scale. Using analysis of variance and a 5% two-sided α level to determine statistical significance, between-group outcomes were analyzed. Additional association and analyses were conducted by multiple linear regression.

RESULTS

In 75 of 77 initial participants included for analysis, mean serum levels of β-hydroxybutyrate (βOHB) were increased by 0.27 ± 0.32, 0.41 ± 0.38, and 0.62 ± 0.49 mmol/L for MCD, LCD, and VLCKD, respectively (P = 0.013). The achievement of NK was consistent for both VLCKD and LCD groups and sporadic for the MCD group. Only the VLCKD group exhibited 95% confidence interval levels that were consistently ≥0.5 mmol/L. The overall mean change in sum of symptoms scores (SOSS) from baseline was 0.81 ± 2.84 (P < 0.001). Changes in SOSS were highest in the VLCKD group (1.49 ± 2.47), followed by LCD (0.65 ± 2.70) and MCD (0.18 ± 3.3; P = 0.264). Small, statistically significant increases were seen for headache severity, constipation, diarrhea, halitosis, muscle cramps and muscle weakness, and light-headedness, whereas intestinal bloating and craving for sugar and starch improved from baseline. Only halitosis (P = 0.039) and muscle weakness (P = 0.005) differed significantly between the groups. Mood improved significantly from baseline overall, but there was no significant difference between groups (P = 0.181) CONCLUSIONS: Diets containing 5% TE from carbohydrates are ketogenic, but diets containing between 15% and 25% TE from carbohydrates can also result in mean βOHB ≥0.5 mmol/L. There was no meaningful difference in symptoms of carbohydrate withdrawal between diets that contain 5% to 25% TE from carbohydrate, and mood was improved overall, with no significant difference between interventions. Our conclusion, therefore, is that reduced carbohydrate diets should be prescribed by need rather than the desire to mitigate symptoms of carbohydrate withdrawal.