Protein supplementation: the double-edged sword

Protein supplements are widely consumed by athletes as well as young adults and teenagers going to the gym and are an excellent source to increase protein intake, build muscle mass, and enhance recovery. They are available in the form of powders, gummies, protein bars, and ready-to-drink shakes and have been shown to have effects on almost every system in the body. Subjects consuming whey protein-based supplements regularly show significantly lower systolic blood pressure, while subjects who consume soy-based protein supplements have been reported to show a significant decrease in their systolic and diastolic blood pressures. Favorable effects of soy protein consumption have been observed on the serum lipid profile, with significant decreases in serum low-density lipoprotein and triglyceride levels. Lower postprandial glucose levels have been observed in diabetic subjects as well, which can be attributed to the lower glycemic index of these supplements. This can lead to an indirect decrease in diabetes-related complications. While these supplements affect the body positively, caution has to be exercised while consuming them in excess, as they have been shown to cause hyperfiltration and increased urinary calcium excretion which can, in turn, lead to chronic kidney disease development. This article focuses on the effects of protein supplementation on the human body, with emphasis on the cardiovascular, endocrine, and renal systems.

Antiapoptotic and chemotaxis-stimulating effects of poly (D, L-lactide-co-glycolide)-chitosan and whey proteins against aflatoxicosis-induced splenic and thymic atrophy

BACKGROUND

Aflatoxin B (AFB) induces toxicological effects on the liver and immune organs. The whey proteins can modulate the immune response during aflatoxicosis. Our work evaluates the novel polylactic acid-glycolic acid-chitosan-encapsulated bovine and camel whey proteins against AFB-induced thymic and splenic atrophy in rats.

METHODS AND RESULTS

Seventy adult male Wister albino rats were divided into a control healthy group (G1) and six AFB1-intoxicated groups (G2-G7). One of the following supplements: distilled water, camel whey proteins (CWP), bovine whey proteins, poly (D, L-lactide-co-glycolide) (PLGA)- chitosan-loaded with camel whey protein microparticles (CMP), PLGA-chitosan loaded with bovine whey protein microparticles (BMP), and PLGA-chitosan nanoparticles were administered as prophylactic supplements to AFB1-intoxicated groups. The AFB-treated group showed significantly higher hepatic levels of oxidative stress and lower levels of antioxidants. In the aflatoxicated group, atrophy of the splenic lymphatic nodules and disfigurement in the organisation with an apparent decrease in the thickness of the cortex in the thymus were observed, as well as a decrease in splenic and thymic CD4+T and CD8+T lymphocytes. Moreover, CXCL12 levels were downregulated, whereas tumour necrosis factor-alpha, nuclear factor kappa B, and cleaved caspase-3 levels were upregulated. CWP, BMP, and CMP supplements markedly decreased oxidative stress, inflammation, and apoptosis, as well as significantly raised CXCL12, CD4+T, and CD8+T cells.

CONCLUSIONS

The CWP, BMP, and CMP supplements rescue the liver and immune tissues from the toxic effects of AFB through their antioxidant, antiapoptotic, anti-inflammatory, and chemotaxis-enhancing roles.

Endothelialization of Whey Protein Isolate-Based Scaffolds for Tissue Regeneration

BACKGROUND

Whey protein isolate (WPI) is a by-product from the dairy industry, whose main component is β-lactoglobulin. Upon heating, WPI forms a hydrogel which can both support controlled drug delivery and enhance the proliferation and osteogenic differentiation of bone-forming cells. This study makes a novel contribution by evaluating the ability of WPI hydrogels to support the growth of endothelial cells, which are essential for vascularization, which in turn is a pre-requisite for bone regeneration.

METHODS

In this study, the proliferation and antioxidant levels in human umbilical vascular endothelial cells (HUVECs) cultured with WPI supplementation were evaluated using real-time cell analysis and flow cytometry. Further, the attachment and growth of HUVECs seeded on WPI-based hydrogels with different concentrations of WPI (15%, 20%, 30%, 40%) were investigated.

RESULTS

Supplementation with WPI did not affect the viability or proliferation of HUVECs monitored with real-time cell analysis. At the highest used concentration of WPI (500 µg/mL), a slight induction of ROS production in HUVECs was detected as compared with control samples, but it was not accompanied by alterations in cellular thiol levels. Regarding WPI-based hydrogels, HUVEC adhered and spread on all samples, showing good metabolic activity. Notably, cell number was highest on samples containing 20% and 30% WPI.

CONCLUSIONS

The demonstration of the good compatibility of WPI hydrogels with endothelial cells in these experiments is an important step towards promoting the vascularization of hydrogels upon implantation in vivo, which is expected to improve implant outcomes in the future.

The Effect of High Pressure Homogenization on the Structure of Dual-Protein and Its Emulsion Functional Properties

It has been proven that high-pressure homogenization (HPH) could improve the functional properties of proteins by modifying their structure. This study researched the effect of HPH on the structural and functional properties of whey-soy dual-protein (Soy Protein Isolation-Whey Protein Isolation, SPI-WPI). Different protein solution samples were treated with HPH at 30, 60, 90, 120 and 150 MPa, and the structure changed under different pressures was analyzed by measuring particle size, zeta potential, Fourier infrared spectrum (FTIR), fluorescence spectrum and scanning electron microscope (SEM). The results showed that HPH significantly reduced the particle size of SPI-WPI, changed the secondary and tertiary structures and improved the hydrophobic interaction between molecules. In addition, HPH significantly improved the solubility and emulsification of all proteins, and the improvement effect on SPI-WPI was significantly better than SPI and WPI. It was found that SPI-WPI treated with 60 MPa had the best physicochemical properties. Secondly, we researched the effect of HPH by 60 MPa on the emulsion properties of SPI-WPI. In this study, the SPI-WPI had the lowest surface tension compared to a single protein after HPH treatment. The emulsion droplet size was obviously decreased, and the elastic properties and physical stability of SPI-WPI emulsion were significantly enhanced. In conclusion, this study will provide a theoretical basis for the application of HPH in modifying the structure of dual-protein to improve its development and utilization in liquid specialty food.

Ocular posterior segment microstructural and microvascular morphological changes in protein supplement-consuming bodybuilders

BACKGROUND

To determine the effects of protein supplement (whey protein powder (PP)) on retinal, choroidal and optic nerve head (ONH) microstructure and microvascular morphology in healthy bodybuilders.

METHODS

This cross-sectional study included 23 male adults (consumers, 23 right eyes) who had been routinely consuming whey PP for bodybuilding purposes for ≥ 3 months, and 21 age- and gender-matched healthy volunteers (non-consumers, 21 right eyes) who also attended the gym but did not consume any nutritional supplements. Participants underwent standard ocular exams, enhanced depth imaging optical coherence tomography (EDI OCT), and optical coherence tomography angiography (OCTA) after ≥ 8 h of rest and fasting.

RESULTS

Whey PP was consumed for a median of 9.5 (6-12) months. Whey PP consumers had a median age of 22 (21-22) years, while non-consumers had 21 (20-22) years (p = 0.067). Whey PP consumers had greater microstructural thickness than non-consumers, with subfoveal choroidal thickness (301.40 ± 38.91 versus 278.12 ± 33.58 µm; p = 0.035) being significantly different but not central macular thickness (270.55 ± 24.60 versus 265.85 ± 12.44 µm; p = 0.402). Despite a non-significant difference in superficial and deep capillary plexus vascular densities (VDs), whey PP consumers had relatively lower VDs than non-consumers in all macular regions (p > 0.05). Despite this, whey PP consumers displayed greater ONH VDs, as well as higher global RNFL thickness (116.75 ± 10.41 versus 114.50 ± 11.70 µm) than non-consumers (p > 0.05).

CONCLUSION

Protein supplements, particularly whey PPs, appear to be associated with different changes in the retina and choroid, as well as ONH microstructural and microvascular morphology, implying that paying attention to these clinical aspects when performing ocular tests in bodybuilders who consume nutritional supplements could be critical.

The effects of whey protein on blood pressure: A systematic review and dose-response meta-analysis of randomized controlled trials

AIMS

This systematic review and dose-response meta-analysis was conducted to summarize data from available clinical trials on the effects of whey protein (WP) supplementation on blood pressure (BP) in adults.

DATA SYNTHESIS

A comprehensive literature search was conducted in the electronic databases PubMed, Web of Science, ProQuest, Embase, and SCOPUS from inception to October 2022. Weighted mean differences (WMD) and 95% confidence intervals (CI) were calculated to assess pooled effect sizes. Heterogeneity between studies was assessed using the Cochran's Q test and I2. Subgroup analysis was performed to assess potential sources of heterogeneity. The dose-response relationship was assessed using fractional polynomial modeling. Of the 2,840 records, 18 studies with 1,177 subjects were included. Pooled analysis showed that whey protein supplementation resulted in a significant reduction in systolic blood pressure (WMD: -1.54 mmHg; 95% CI: -2.85 to -0.23, p = 0.021), with significant heterogeneity between studies (I2 = 64.2%, p < 0.001), but not for diastolic blood pressure (DBP) (WMD: -0.27 mmHg; 95% CI: -1.14, 0.59, p = 0.534) with high heterogeneity between studies (I2 = 64.8%, p < 0.001). However, WP supplementation significantly reduced DBP at a dose of ˃30 g/day, in RCTs that used WP isolate powder for their intervention, in sample sizes ≤100, in studies with an intervention duration of ≤10 weeks, and in those studies that were conducted in patients with hypertension and had participants with a BMI of 25-30 kg/m2.

CONCLUSION

This meta-analysis demonstrated that WP intake significantly reduced SBP levels. Further large-scale studies are needed to specify the exact mechanism, and optimal dosage of WP supplementation to obtain a beneficial effect on BP.

Dairy foods and cardiometabolic diseases: an update and a reassessment of the impact of SFA

Type 2 diabetes (T2D) and CVD are major causes of mortality and chronic morbidity. Whilst mortality from CVD has decreased they remain the largest cause of death in Europe and the prevalence of T2D is increasing rapidly. A consistent component of public health advice is to reduce intake of SFA to reduce CVD in particular, which implies limiting dairy food consumption. The prospective studies and randomised controlled trials included in this review show that for dairy foods at least, SFA are not consistently associated with CVD or T2D risk. For CVD the association with dairy foods is generally neutral despite dairy foods being the major source of SFA in many diets. This creates considerable doubt, at least for dairy foods, concerning the validity of the traditional diet-heart hypothesis which positively relates SFA intake to increased serum LDL-cholesterol and subsequent increased CVD. There is now emerging evidence to explain this which is highly relevant to dairy foods. These include the potentially counterbalancing effect of SFA-stimulated HDL-cholesterol and specific food matrix factors. In addition, SFA are associated with the less atherogenic large buoyant LDL particles and possible counterbalancing hypotensive effects of dairy proteins. Overall, dairy foods have either a neutral or beneficial association with CVD and T2D. Beneficial associations are seen for blood pressure and the reduced T2D risk linked to yoghurt consumption, a subject that needs urgent attention given the sharp rise in T2D prevalence in many countries.

Whey Protein Premeal Lowers Postprandial Glucose Concentrations in Adults Compared with Water-The Effect of Timing, Dose, and Metabolic Status: a Systematic Review and Meta-analysis

BACKGROUND

Serving whey protein before a meal in order to lower postprandial blood glucose concentrations is known as a premeal. The underlying mechanisms are only partly understood but may involve stimulation of glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), and insulin secretion together with a slower gastric emptying rate.

OBJECTIVES

The objective of this systematic review and meta-analysis was to review all randomized clinical trials investigating premeals with whey protein in comparison with a nonactive comparator (control) that evaluated plasma glucose, GLP-1, GIP, insulin, and/or gastric emptying rate. Secondary aims included subgroup analyses on the timing and dose of the premeal together with the metabolic state of the participants [lean, obese, and type 2 diabetes mellitus (T2DM)].

METHODS

We searched EMBASE, CENTRAL, PUBMED, and clinicaltrials.gov and found 16 randomized crossover trials with a total of 244 individuals. The last search was performed on 9 August, 2022.

RESULTS

Whey protein premeals lowered peak glucose concentration by -1.4 mmol/L [-1.9 mmol/L; -0.9 mmol/L], and the area under the curve for glucose was -0.9 standard deviation (SD) [-1.2 SD; -0.6 SD] compared with controls (high certainty). In association with these findings, whey protein premeals elevated GLP-1 (low certainty) and peak insulin (high certainty) concentrations and slowed gastric emptying rate (high certainty) compared with controls. Subgroup analyses showed a more pronounced and prolonged glucose-lowering effect in individuals with T2DM compared with participants without T2DM. The available evidence did not elucidate the role of GIP. The protein dose used varied between 4 and 55 g, and meta-regression analysis showed that the protein dose correlated with the glucose-lowering effects.

CONCLUSIONS

In conclusion, whey protein premeals lower postprandial blood glucose, reduce gastric emptying rate, and increase peak insulin. In addition, whey protein premeals may elevate plasma concentrations of GLP-1. Whey protein premeals may possess clinical potential, but the long-term effects await future clinical trials.

Coproduction of amino acids and biohythane from microalgae via cascaded hydrothermal and anaerobic process

In search of the candidate for animal feed and clean energy, a new vision of algal biorefinery was firstly proposed to coproduce amino acids and biohythane via hydrothermal treatment and two-stage anaerobic fermentation. This study focused on the comprehensive analysis of amino acids recovered from Chlorella sp. and the subsequent biohythane production from microalgal residues. The content and recovery rate of amino acids were in the range of 2.07-27.62 g/100 g and 3.65 %-48.66 % with increasing temperature due to more cell wall disruptions. Furthermore, it was rich in essential amino acids for livestock, including leucine, arginine, isoleucine, valine and phenylalanine. A comparable hydrogen production (9 mL/g volatile solids (VS)) was reached at 70 °C and 90 °C, while it reduced to 5.84 mL/gVS at 150 °C. The group at 70 °C got the maximum methane generation of 311.9 mL/gVS, which was 16.67 %, 24.94 %, 38.38 % and 46.49 % higher than that of other groups. Microalgal residues at lower temperature contained more organics, which was the reason for the better biohythane production. The coproduction of amino acids and biohythane at 130 °C was favorable, which led to 43.71 % amino acids recovery and 93.82 mL biohythane production from per gVS of Chlorella sp. The improved microalgal biorefinery could provide an alternative way to mitigate the crisis of food and energy, but animal experimentations and techno-economic assessments should be considered for further study.

Saturated fats, dairy foods and cardiovascular health: No longer a curious paradox?

Cardiovascular diseases (CVDs) are a major cause of death and morbidity in many parts of the world, and many dietary guidelines limit the intake of saturated fatty acids (SFA) as they are regarded as an important risk factor for CVDs due to their association with increased blood cholesterol. Dairy foods are often a major contributor to dietary intake of SFA, and since many dietary guidelines contain restrictions on SFA intake, this can lead to a moderation of dairy food intake despite meta-analyses generally showing dairy to have a neutral or negative association with CVDs. Many prospective studies and randomised controlled trials do not support a simple positive association between SFA intake and the risk of atherosclerotic CVD and its components although some early studies had a number of methodological weakness. Studies that included blood cholesterol data do broadly support the positive relationship between SFA and blood low-density lipoprotein cholesterol (LDL-C) but without increased CVD risk resulting, despite LDL being a causal factor in atherosclerotic CVD. These data suggest that LDL-C alone is not a consistently good predictor or cause of CVD risk, perhaps particularly in relation to dairy food consumption although some non-dairy food studies have also shown LDL-C reduction was not reflected in reduced CVD risk. This narrative review examines some reasons for these findings. Overall, restrictions on dairy food intake do not seem warranted, although there remains a need to further understand the association of different dairy food types with chronic diseases, perhaps particularly for type 2 diabetes.