1.
Comparing Acute, High Dietary Protein and Carbohydrate Intake on Transcriptional Biomarkers, Fuel Utilisation and Exercise Performance in Trained Male Runners.
Furber, M, Pyle, S, Roberts, M, Roberts, J
Nutrients. 2021;13(12)
-
-
-
Free full text
Plain language summary
Dietary modification to improve exercise endurance has become a popular strategy. The reduction of carbohydrates to enhance adaptations due to training has been shown on a cellular level. In low carbohydrate diets, fat is the usual substitute, however long-term adherence to this is often difficult. Using protein instead of fat may be an alternative, but there is little research on this. This study aimed to investigate the impact of a short-term high-protein, reduced carbohydrate diet compared to a high-carbohydrate diet in combination with endurance running on exercise performance and cellular adaptations. The results showed that any cellular adaptations were due to fuel availability, rather than the fuel type and that a high protein diet compromised high intensity exercise performance. It was concluded that a high-protein, low-carbohydrate diet in combination with endurance training is of no benefit to endurance running performance. This study could be used by healthcare professionals to recommend that athletes and especially runners who wish to improve endurance do not switch to a high-protein, low carbohydrate diet and that other dietary modifications are investigated.
Abstract
Manipulating dietary macronutrient intake may modulate adaptive responses to exercise, and improve endurance performance. However, there is controversy as to the impact of short-term dietary modification on athletic performance. In a parallel-groups, repeated measures study, 16 trained endurance runners (maximal oxygen uptake (V˙O2max): 64.2 ± 5.6 mL·kg-1·min-1) were randomly assigned to, and provided with, either a high-protein, reduced-carbohydrate (PRO) or a high-carbohydrate (CHO) isocaloric-matched diet. Participants maintained their training load over 21-consecutive days with dietary intake consisting of 7-days habitual intake (T1), 7-days intervention diet (T2) and 7-days return to habitual intake (T3). Following each 7-day dietary period (T1-T3), a micro-muscle biopsy was taken for assessment of gene expression, before participants underwent laboratory assessment of a 10 km treadmill run at 75% V˙O2max, followed by a 95% V˙O2max time to exhaustion (TTE) trial. The PRO diet resulted in a modest change (1.37-fold increase, p = 0.016) in AMPK expression, coupled with a significant increase in fat oxidation (0.29 ± 0.05 to 0.59 ± 0.05 g·min-1, p < 0.0001). However, a significant reduction of 23.3% (p = 0.0003) in TTE post intervention was observed; this reverted back to pre levels following a return to the habitual diet. In the CHO group, whilst no change in sub-maximal fuel utilisation occurred at T2, a significant 6.5% increase in TTE performance (p = 0.05), and a modest, but significant, increase in AMPK (p = 0.042) and PPAR (p = 0.029) mRNA expression compared to T1 were observed; with AMPK (p = 0.011) and PPAR (p = 0.044) remaining significantly elevated at T3. In conclusion, a 7-day isocaloric high protein diet significantly compromised high intensity exercise performance in trained runners with no real benefit on gene markers of training adaptation. A significant increase in fat oxidation during submaximal exercise was observed post PRO intervention, but this returned to pre levels once the habitual diet was re-introduced, suggesting that the response was driven via fuel availability rather than cellular adaptation. A short-term high protein, low carbohydrate diet in combination with endurance training is not preferential for endurance running performance.
2.
Hypothesis and data-driven dietary patterns and colorectal Cancer survival: findings from Newfoundland and Labrador colorectal Cancer cohort.
Sharma, I, Roebothan, B, Zhu, Y, Woodrow, J, Parfrey, PS, Mclaughlin, JR, Wang, PP
Nutrition journal. 2018;17(1):55
-
-
-
Free full text
Plain language summary
Diet and lifestyle play a role in the risk and outcome of chronic diseases including colorectal cancer (CRC). This prospective follow-up study looked at the association between different dietary patterns and the risk of death and cancer recurrence in people with CRC. Over 500 CRC patients diagnosed between 1999 and 2003 were followed-up until 2010. Participants completed a food frequency questionnaire based on their diet a year prior to diagnosis, and this was used to identify several dietary patterns. Diets that were high in processed meats (HR 1.82), meat and dairy products (HR 2.19), and total grains, sugar and soft drinks (HR 1.95) were associated with a higher risk of mortality, cancer recurrence or metastasis. Poor adherence to a Mediterranean-style diet increased the risk of overall mortality (HR 1.62). Prudent vegetable, high sugar pattern, Recommended Food Scores and Dietary Inflammatory Index had no significant association with either mortality or combined mortality, recurrence or metastasis. The authors concluded that the risk of mortality, recurrence and metastasis in patients with colorectal cancer varies with different dietary patterns.
Abstract
BACKGROUND Dietary patterns are commonly used in epidemiological research, yet there have been few studies assessing if and how research results may vary across dietary patterns. This study aimed to estimate the risk of mortality/recurrence/metastasis using different dietary patterns and comparison amongst the patterns. METHODS Dietary patterns were identified by Cluster Analysis (CA), Principal Component Analysis (PCA), Alternate Mediterranean Diet score (altMED), Recommended Food Score (RFS) and Dietary Inflammatory Index (DII) scores using a 169-item food frequency questionnaire. Five hundred thirty-two colorectal cancer patients diagnosed between 1999 and 2003 in Newfoundland were followed-up until 2010. Overall Mortality (OM) and combined Mortality, Recurrence or Metastasis (cMRM) were identified. Comparisons were made with adjusted Cox proportional Hazards Ratios (HRs), correlation coefficients and the distributions of individuals in defined clusters by quartiles of factor and index scores. RESULTS One hundred and seventy cases died from all causes and 29 had a cancer recurrence/metastasis during follow-up. Processed meats as classified by PCA (HR 1.82; 95% confidence interval (CI) 1.07-3.09), clusters characterized by meat and dairy products (HR 2.19; 95% CI 1.03-4.67) and total grains, sugar, soft drinks (HR 1.95; 95% CI 1.13-3.37) were associated with a higher risk of cMRM. Poor adherence to AltMED increased the risk of all-cause OM (HR 1.62; 95% CI 1.04-2.56). Prudent vegetable, high sugar pattern, RFS and DII had no significant association with both OM and cMRM. CONCLUSION Estimation of OM and cMRM varied across dietary patterns which is attributed to the differences in the foundation of each pattern.
3.
A controlled trial of gluten-free diet in patients with irritable bowel syndrome-diarrhea: effects on bowel frequency and intestinal function.
Vazquez-Roque, MI, Camilleri, M, Smyrk, T, Murray, JA, Marietta, E, O'Neill, J, Carlson, P, Lamsam, J, Janzow, D, Eckert, D, et al
Gastroenterology. 2013;144(5):903-911.e3
-
-
-
Free full text
-
Plain language summary
The relationship between gluten exposure and diarrhoea-predominant irritable bowel syndrome (IBS-D) is not well understood. Non-celiac IBS-D patients who are positive for HLA-DQ2/8 genes associated with CD can show symptom improvement on a gluten-free diet (GFD). The aim of this 4-week parallel randomized controlled clinical trial in HLA-DQ2/8 positive and negative patients with IBS-D was to assess the effects of a gluten-containing diet (GCD) compared to a GFD on bowel function, gut transit, small bowel (SB) and colonic barrier functions as measured by two-sugar excretion permeability test and mRNA expression of TJ proteins in mucosa of the small bowel (SB) and rectosigmoid (RS) derived by biopsy. Immune response to diets was also measured as cytokine production from peripheral blood mononuclear cells (PBMCs). Patient were recruited from the Mayo clinic’s database of IBS suffers, and invited to participate. Patients with diagnosed CD were excluded. Genotype analysis was performed for HLA-DQ2 and HLA-DQ8. 22 patients were placed on the GCD (11 HLA-DQ2/8–negative and 11 HLA-DQ2/8–positive) and 23 on the GFD (12 HLA-DQ2/8−negative and 11 HLA-DQ2/8–positive. All meals and snacks were ingested or prepared in the Mayo Clinic. Patients were advised to eat only the foods provided by the study dieticians. Gluten-free and gluten-containing meals were prepared using the same macronutrient content (20% protein, 30% fat, 50% carb). Compliance to the diet was assessed by direct questioning by the dietitians and reported to be excellent. All patients were ingesting gluten in their diet prior to starting the study. At 4-weeks, a statistically significant decrease in stool frequency of subjects on GFD compared to subjects on GCD (p=0.04) was seen. This effect was more pronounced in subjects who were HLA-DQ2 or 8 positive (p=0.019) There was no significant diet effect (GFD vs. GCD) on, daily stool form, ease of passage or gastric emptying. The GCD was associated with higher small bowel (SB) permeability (based on 0–2 hr levels of mannitol (p=0.028) and lactulose:mannitol ratio (P=0.0012)). SB permeability was greater in HLA-DQ2/8–positive than −negative patients (P=.018). No significant differences in colonic permeability were observed. Significant diet-associated changes in occludin expression in SB mucosa in the HLA-DQ2 or 8 positive group were seen (p=0.017). Expressions of tight junction proteins (zonulin (ZO-1), occludin, and claudin-1 mRNA) in colonic mucosa were significantly lower in GCD relative to GFD in the overall groups, particularly in subjects with HLA-DQ2 or 8 positive status. Cytokine response was higher (interleukin-10) in response to GCD than GFD (unrelated to HLA genotype). A limitation in the quantification of TJ protein expression is that it was solely based on PCR (mRNA expression). In future, other methods should be included to directly identify these proteins and their distribution. The inability to document alterations in colonic permeability using the 2-sugar excretion profile from 8 to 24 hours is a limitation. This may be due to lack of sensitivity of the lactulose and mannitol excretion test, for example, due to the metabolism of both sugars by colonic bacteria. Another limitation is that the mechanism for improvement in stool frequency on a GFD in the absence of changes in colonic transit was not elucidated by our studies. This study does not specifically address the effects of gluten protein per se, and it is possible that other proteins in wheat flour may be responsible for the changes observed. The author concludes that this study provide mechanistic explanations for the observation that gluten withdrawal may improve patient symptoms in IBS. The data also partially explains that the biological effects of gluten were associated with HLA-DQ2 or 8 genotype. The relationship of dietary factors, innate and adaptive immune responses and mucosal interactions in IBS-D deserve further study. Further clinical studies evaluating the effects of gluten withdrawal in patients with IBS-D are needed.
Abstract
BACKGROUND & AIMS Patients with diarrhea-predominant irritable bowel syndrome (IBS-D) could benefit from a gluten-free diet (GFD). METHODS We performed a randomized controlled 4-week trial of a gluten-containing diet (GCD) or GFD in 45 patients with IBS-D; genotype analysis was performed for HLA-DQ2 and HLA-DQ8. Twenty-two patients were placed on the GCD (11 HLA-DQ2/8 negative and 11 HLA-DQ2/8 positive) and 23 patients were placed on the GFD (12 HLA-DQ2/8 negative and 11 HLA-DQ2/8 positive). We measured bowel function daily, small-bowel (SB) and colonic transit, mucosal permeability (by lactulose and mannitol excretion), and cytokine production by peripheral blood mononuclear cells after exposure to gluten and rice. We collected rectosigmoid biopsy specimens from 28 patients, analyzed levels of messenger RNAs encoding tight junction proteins, and performed H&E staining and immunohistochemical analyses. Analysis of covariance models was used to compare data from the GCD and GFD groups. RESULTS Subjects on the GCD had more bowel movements per day (P = .04); the GCD had a greater effect on bowel movements per day of HLA-DQ2/8-positive than HLA-DQ2/8-negative patients (P = .019). The GCD was associated with higher SB permeability (based on 0-2 h levels of mannitol and the lactulose:mannitol ratio); SB permeability was greater in HLA-DQ2/8-positive than HLA-DQ2/8-negative patients (P = .018). No significant differences in colonic permeability were observed. Patients on the GCD had a small decrease in expression of zonula occludens 1 in SB mucosa and significant decreases in expression of zonula occludens 1, claudin-1, and occludin in rectosigmoid mucosa; the effects of the GCD on expression were significantly greater in HLA-DQ2/8-positive patients. The GCD vs the GFD had no significant effects on transit or histology. Peripheral blood mononuclear cells produced higher levels of interleukin-10, granulocyte colony-stimulating factor, and transforming growth factor-α in response to gluten than rice (unrelated to HLA genotype). CONCLUSIONS Gluten alters bowel barrier functions in patients with IBS-D, particularly in HLA-DQ2/8-positive patients. These findings reveal a reversible mechanism for the disorder. Clinical trials.govNCT01094041.