Does whey protein supplementation during resistance exercise have additional benefits for decreasing hepatic fat content?

BACKGROUND: Exercise and diet have positive effects on hepatic fat reduction, and protein supplementation is known to lower hepatic fat accumulation. However, the effect of a combination of exercise and whey protein supplementation (WPS) on hepatic fat content (HFC) is unknown. METHODS: We investigated the effect of WPS on HFC during resistance exercise and diet control intervention for four weeks. A total of 34 sedentary males participated and were randomly assigned to two groups: a protein supplement group (PSG, n = 18) and a control group (CG, n = 16). The PSG took 60 g of WPS per day, and the CG took 60 g of an isocaloric placebo per day. All participants were fed a calorie-controlled diet throughout the study period, with their daily caloric intake determined by their resting metabolic rate and physical activity level. Both groups performed resistance exercises supervised by experts at 60-70% of their maximum efforts for 60 min/day, 6 days/week for 4 weeks. HFC was assessed using the controlled attenuation parameter (CAP) after an 8 h fast, at pre-, mid-, and post-intervention. Liver enzymes and lipid profile were also analyzed after an 8 h fast and pre- and post-intervention. RESULTS: The CAP was significantly reduced after 4 weeks of intervention in both groups (PSG, p < .001; CG, p = .002). However, there was no significant interaction between the group and changes in CAP. Interestingly, when comparing the pre- and mid-tests, both groups also had significantly reduced CAP (PSG, p = .027; CG, p = .028), but there was a significant difference in the amount of change in CAP between the two groups (PSG, -47.2 ± 25.4 dB/m; CG, -19.5 ± 15.1 dB/m; p = .042). For liver enzymes, there was a significant interaction between the two groups and a change in aspartate transaminase (AST) (p = .038). However, alanine aminotransferase (ALT) levels were significantly decreased only in the PSG group (p = .002). In lipids, both groups showed significantly decreased total cholesterol (p < .001) and low-density lipoprotein cholesterol (p < .001) after the intervention. CONCLUSION: Our data showed that WPS may not enhance the overall effects of resistance exercise on HFC and lipid profiles. However, in part, WPS may have a beneficial effect on liver enzymatic changes and rapid response to resistance exercise-induced HFC reduction.

Effects of Whey Protein Supplement on 4-Week Resistance Exercise-Induced Improvements in Muscle Mass and Isokinetic Muscular Function under Dietary Control.

(1) The purpose of this study was to investigate the effect of whey protein supplementation under dietary control on improvements in muscle mass and function following resistance exercise training. (2) Thirty-two men were randomly assigned to a whey protein supplementation group taking whey protein isolate (PSG, n = 17) and a placebo group (CON, n = 15). Participants were provided with three meals per day corresponding to the estimated individual daily energy intake. The supervised resistance exercise program was conducted 60 min per day, six days per week, for four weeks. (3) Post-intervention, there was a significant interaction between groups in terms of muscle mass increase (p = 0.033, η2 = 0.14), with a greater increase in the PSG. There were also significant interactions between the groups and increases in peak torque of the dominant knee flexors (p = 0.048, η2 = 0.12), dominant shoulder extensors, and non-dominant shoulder extensors (p = 0.028, η2 = 0.15; p = 0.015, η2 = 0.18), and the total work of the dominant knee and shoulder extensors (p = 0.012, η2 = 0.19; p = 0.013, η2 = 0.19), with greater increases in the PSG. (4) These results suggest that whey protein supplementation enhances resistance exercise-induced increase in muscle mass and overall muscular strength and endurance, independent of dietary influence.

Evidence and suggestions for establishing vitamin D intake standards in Koreans for the prevention of chronic diseases.

BACKGROUND/OBJECTIVES: Vitamin D is produced in the skin during sun exposure and is also ingested from foods. The role of vitamin D needs to be considered in the prevention and management of various diseases. Moreover, since the majority of Koreans spend their days indoors, becoming susceptible to the risk of vitamin D deficiency. The current study aims to prepare a basis for determining dietary reference intake of vitamin D in Korea, by reviewing the evidence against various diseases and risks. MATERIALS/METHODS: Literature published in Korea and other countries between 2014 and 2018 was prioritized based on their study design and other criteria, and evaluated using the RoB 2.0 assessment form and United States Department of Agriculture Nutrition Evidence Library Conclusion Statement Evaluation Criteria. RESULTS: Of the 1,709 studies, 128 studies were included in the final systematic analysis after screening. To set the dietary reference intakes of vitamin D based on the selected articles, blood 25(OH)D levels and indicators of bone health were used collectively. Blood vitamin D levels and ultraviolet (UV) exposure time derived from the Korean National Health and Nutrition Examination Survey were analyzed to establish the dietary reference intakes of vitamin D for each stage of the life cycle. The adequate intake levels of vitamin D, according to age and gender, were determined to be in the range of 5-15 µg/day, and the tolerable upper intake level was established at 25-100 µg/day. CONCLUSIONS: The most important variable for vitamin D nutrition is lifestyle. A balanced diet comprising foods with high contents of vitamin D is important, as is vitamin D synthesis after UV exposure. The adequate intake level of vitamin D mentioned in the 2015 Dietary Reference Intakes for Korean (KDRI) remained unchanged in the 2020 KDRI for the management of vitamin D nutrition in Koreans.

Musculoskeletal Health of the Adults Over 50 Years of Age in Relation to Antioxidant Vitamin Intakes.

As the proportion of the elderly population increases rapidly, interest in musculoskeletal health is also emerging. Here, we investigated how antioxidant vitamin intake and musculoskeletal health are related. Adults aged 50 to 80 years with a body mass index (BMI) of 18.5 to 27.0 kg/m2 were included. Bone mineral density (BMD), lean mass (LM), appendicular skeletal muscle mass index (ASMI) were measured using dual-energy X-ray absorptiometry (DXA), and the grip strength and knee extension using hand dynamometer. Nutrient intakes were measured using a 24-hour recall questionnaire. A total of 153 adults (44 men and 109 women) participated in this study. A partial correlation analysis showed a significant positive relationship between vitamin E and BMD and between vitamin C and LM/Height. Participants were classified into three groups according to whether their vitamin E and C intake met the recommended intake for Dietary Reference Intakes for Koreans (KDRIs). The prevalence of having low T-score (< -1.0) and low ASMI (< 7.0 for men and < 5.4 for women) was 51.3% and 15.4% in the group with vitamins C and E intakes below KDRIs. After adjusting for sex, smoking status and energy, protein, vitamin D, and calcium intake, the group with vitamins C and E both below the KDRIs displayed a significantly lower BMD at all test sites and LM/Height compared with vitamin C and/or E intake above the KDRIs groups. We conclude that sufficient intake of vitamin E and C is important for maintaining BMD and lean mass in Korean adults over 50 years of age.

Study on the Improvement of Health and Nutrition Status After a 12-week Protein-Rich Supplementation Regimen in Children and Adolescents With Brain Lesions Disorder.

Through a survey on dietary intake of children and adolescents with brain lesions, the present study aimed to analyze the current status of nutrient intake and examine the effect of high-protein nutrient drink on their nutritional and muscle statuses. The study participants were 90 juvenile participants aged 8-19 years, with brain lesions. The participants were provided with a protein nutrient drink for 12 weeks and a questionnaire survey on dietary intake was performed to analyze the level of nutrient intake before and after ingestion. The physical measurements were taken to determine the improvements in nutrient and muscle statuses. The results showed that, before the intake of protein nutrient drink as a supplement, the participants exhibited lower height, weight, and body mass index than those of the standard levels of healthy individuals, and the level of nutrient intake through diet was lower than those of the required and recommended levels of nutrient intake for Koreans. Conversely, after the intake of protein nutrient drink for 12 weeks, the level of nutrient intake and physical statuses such as weight showed significant improvements. In addition, the muscle status had undergone approximately 10% of change during the intervention with no significant difference. Thus, to ensure an adequate level of nutrient supply to children and adolescents with brain lesions, there is an urgent need to develop a guideline of nutrient intake. The findings in this study are expected to serve as the basic data for such guidelines.

Association between dietary branched-chain amino acid intake and skeletal muscle mass index among Korean adults: Interaction with obesity.

BACKGROUND/OBJECTIVES: The branched-chain amino acids (BCAA), including isoleucine, leucine, and valine, promote muscle protein synthesis. However, obesity may interfere with protein synthesis by dysregulating mitochondrial function in the muscles. This study aimed to examine the association between dietary intake levels of BCAA and skeletal muscle mass index (SMI) in middle-aged participants, and the effect of obesity/abdominal obesity on this association. SUBJECTS/METHODS: The data of 3,966 men and women aged 50-64 years who participated in the 2008-2011 Korea National Health and Nutrition Examination Survey were analyzed. Intake levels of energy-adjusted dietary amino acids were obtained using a 24-hour dietary recall. SMI was calculated by dividing the appendicular skeletal muscle mass by body weight (kg) and multiplying the result by 100%. Multivariable general linear models were used to analyze the association of dietary BCAA intake levels with SMI. RESULTS: The beneficial effects of energy-adjusted dietary BCAA intakes on SMI were greater in the non-obesity/non-abdominal obesity groups; however, no significant associations were observed in the obesity/abdominal obesity groups (P > 0.05). CONCLUSIONS: Healthy weight and sufficient intake of dietary BCAA are recommended to maintain muscle mass.

Leucine-Enriched Protein Supplementation Increases Lean Body Mass in Healthy Korean Adults Aged 50 Years and Older: A Randomized, Double-Blind, Placebo-Controlled Trial.

Early prevention of sarcopenia could be an important strategy for muscle retention, but most studies have focused on subjects aged 65 or older. Therefore, in this study we investigated the effects of leucine-enriched protein supplementation on muscle condition in a sample including late middle-aged adults. A 12-week intervention was performed for 120 healthy community-dwelling adults by providing either leucine-enriched protein supplement [leucine 3 g, protein mixture (casein 50% + whey 40% + soy 10%) 17 g, vitamin D 800IU (20 µg), calcium 300 mg, fat 1.1 g, carbohydrate 2.5 g] or isocaloric carbohydrate supplement twice per day. Appendicular skeletal muscle mass index (ASMI) and lean body mass (LBM) were measured by dual-energy X-ray absorptiometry. A total of 111 participants completed the study, with a dropout rate of 9.2%. LBM normalized by height and body weight (LBM/Wt) was significantly increased (p < 0.001) in the intervention group (0 wk: 633.9 ± 8.5 vs. 12 wk 636.9 ± 8.4 in the intervention group; 0 wk: 638.6 ± 8.3 vs. 12 wk: 632.9 ± 8.1 in the control group). In subgroup analyses, significant differences remained only in subjects between 50 and 64 years of age. We concluded that leucine-enriched protein supplementation can have beneficial effects by preventing muscle loss, mainly for late middle-aged adults.

Protein Intake Recommendation for Korean Older Adults to Prevent Sarcopenia: Expert Consensus by the Korean Geriatric Society and the Korean Nutrition Society.

Sarcopenia, a common clinical syndrome in older adults, is defined as decreased muscle mass, strength, and physical performance. Since sarcopenia is associated with the incidence of functional decline, falls, and even mortality in older adults, researchers and health care providers have been keen to accumulate clinical evidence to advocate the screening and prevention of sarcopenia progression in older adults. The factors that may accelerate the loss of muscle mass and function include chronic diseases, inactivity, and deficiency in appropriate nutritional support. Among these, nutritional support is considered an initial step to delay the progression of muscle wasting and improve physical performance in community-dwelling older adults. However, a nationwide study suggested that most Korean older adults do not consume sufficient dietary protein to maintain their muscle mass. Furthermore, considering age-associated anabolic resistance to dietary protein, higher protein intake should be emphasized in older adults than in younger people. To develop a dietary protein recommendation for older adults in Korea, we reviewed the relevant literature, including interventional studies from Korea. From these, we recommend that older adults consume at least 1.2 g of protein per kg of body weight per day (g/kg/day) to delay the progression of muscle wasting. The amount we recommend (1.2 g/kg/day) is 31.4% higher than the previously suggested recommended daily allowance (i.e., 0.91 g/kg/day) for the general population of Korea. Also, evidence to date suggests that the combination of exercise and nutritional support may enhance the beneficial effects of protein intake in older adults in Korea. We found that the current studies are insufficient to build population-based guidelines for older adults, and we call for further researches in Korea.

The effect of aging on mastication and swallowing parameters according to the hardness change of solid food.

As part of the aging process, multiple oral physiologic changes occur and these changes may cause individuals to reduce food intake or switch the types of food texture. Thus, the need to develop food products for the elderly has increased. To evaluate the suitability of the food products for the elderly, the evaluation method should be verified and it is important to identify the parameters of mastication and swallowing. Therefore, the purpose of this study was to compare the differences of mastication and swallowing parameters between the young adults and the elderly depending on the varying hardness of rice food product. Subjects included 20 young adults and 40 elderly and bolus transit times of video-fluoroscopic swallowing study (VFSS) were used. Four types of rice products with different hardness were provided including cooked rice, soft-boiled rice, rice gruel and thin rice gruel. In the elderly group, the chewing number, oral processing time, post-faucial aggregation time, valleculae aggregation time (VAT), first subsequence duration and total duration were significantly different according to the changes in food hardness. Of the bolus transit times, the VAT and the second subsequence duration (S-S2) were significantly different between the two groups. These results suggest that VAT and S-S2, key VFSS parameters, as well as the chewing number and total duration are useful tools for evaluating the effect of aging on mastication and swallowing of solid foods. PRACTICAL APPLICATIONS: In Korea, the aging population is rapidly increasing. According to recent surveys, a large number of elderly Koreans have reported chewing difficulties and many of them are in the state of under-nutrition. As aging progresses, multiple physiologic changes occur in mastication and swallowing functions. These changes may cause individuals to reduce their food intake or switch to soft food products. Therefore, the development of texture-modified food products for the elderly is needed and they should be developed based on the understandings of the physiology of mastication and swallowing according to different rheological properties of food products consumed in Korea, which are quite different from those of the western countries. In this study, we compared the differences of mastication and swallowing parameters between the young adults and the elderly depending on the varying hardness of rice food product.

EMG Activity of Masseter Muscles in the Elderly According to Rheological Properties of Solid Food.

OBJECTIVE: To assess the impact of aging on masticatory muscle function according to changes in hardness of solid food. METHODS: Each of fifteen healthy elderly and young people were selected. Subjects were asked to consume cooked rice, which was processed using the guidelines of the Universal Design Foods concept for elderly people (Japan Care Food Conference 2012). The properties of each cooked rice were categorized as grade 1, 2, 3 and 4 (5×10(3), 2×10(4), 5×10(4), and 5×10(5) N/m(2)) respectively. Surface electromyography (sEMG) was used to measure masseter activity from food ingestion to swallowing of test foods. The raw data was normalized by the ratio of sEMG activity to maximal voluntary contraction and compared among subjects. The data was divided according to each sequence of mastication and then calculated within the parameters of EMG activities. RESULTS: Intraoral tongue pressure was significantly higher in the young than in the elderly (p<0.05). Maximal value of average amplitude of the sequence in whole mastication showed significant positive correlation with hardness of food in both young and elderly groups (p<0.05). In a comparisons between groups, the maximal value of average amplitude of the sequence in whole mastication and peak amplitude in whole mastication showed that mastication in the elderly requires a higher percentage of maximal muscle activity than in the young, even with soft foods (p<0.05). CONCLUSION: sEMG data of the masseter can provide valuable information to aid in the selection of foods according to hardness for the elderly. The results also support the necessity of specialized food preparation or products for the elderly.