Association of Habitual Green Tea Consumption with Sarcopenia Assessed Using SARC-F in Community-Dwelling Japanese Older People: A Cross-Sectional Study

To ascertain whether habitual green tea consumption is associated with sarcopenia among Japanese older adults, using the screening tool for sarcopenia (SARC-F). This cross-sectional study in Mukawa, Hokkaido, Japan, was conducted between June and September 2022 and included 364 Japanese participants older than 65 y. Habitual green tea consumption and energy intake were ascertained using a validated self-administered food frequency questionnaire. Sarcopenia was evaluated using the SARC-F. Multivariable logistic regression analysis was used to estimate the odds ratio (OR) and 95% confidence interval (CI) of sarcopenia risk across participant tertiles of green tea consumption, with adjustments for age, sex, body mass index, living alone, habitual exercise, walking hours, current smoking status, current alcohol consumption status, energy intake, protein intake, vegetable intake, and fruit intake. In this study of 364 participants (154 men and 210 women), the prevalence of sarcopenia risk was 9.3%. The multivariable-adjusted OR [95% CI] of green tea consumption for ≥1 cup/d compared with that of <1 cup/wk of sarcopenia was 0.312 [0.129-0.752]. Higher habitual green tea consumption was inversely associated with sarcopenia among Japanese older adults. Further longitudinal studies are required to confirm these findings.

Are popular books about diet and health written based on scientific evidence? A comparison of citations between the USA and Japan

OBJECTIVES

To describe and compare the references cited in popular books about diet and health between the USA and Japan.

DESIGN

Books were selected based on their best-seller rankings in the diet and health category of online bookstores. We identified references throughout all pages of the books and examined the number of references, reference format (identifiable or not) and presence of specific types of references, such as systematic reviews of human research. We compared the characteristics of references between the two countries and examined related factors to citation.

SETTING

Cross-sectional study.

PARTICIPANTS

Books (n 100 in each country).

RESULTS

Among 100 books from each country, sixty-five US and sixty-six Japanese books had references. Forty-five US books cited more than 100 references, against only five Japanese books. The number of books that cited systematic reviews of human research differed between the USA (n 49) and Japan (n 9). Additionally, the number of books that provided identifiable information for all references was significantly higher in the USA (n 63) than in Japan (n 42). Books whose first authors have licences of medical doctors were more likely to cite references than those without in both countries.

CONCLUSIONS

Two-thirds of books about diet and health cited references in both the USA and Japan, but Japanese books cited fewer references and were less likely to cite systematic reviews and provide identifiable references than US books. Further research into the scientific reliability of information in books about diet and health is warranted.

Association between total fat and fatty acid intake and the risk of type 2 diabetes mellitus among Japanese adults: Analysis based on the JACC study

BACKGROUND

We prospectively examined the association between total fat and fatty acid intake and type 2 diabetes (T2D) among Japanese adults.

METHODS

This study was conducted using data from the Japan Collaborative Cohort Study for Evaluation of Cancer Risk (JACC). A validated food frequency questionnaire evaluated the intake of total fat and fatty acids. Diabetes was assessed using self-reported data. Multivariable logistic regression analysis was performed to calculate the odds ratios (ORs) and 95% confidence intervals (CIs) of incident T2D across quintiles of total fat and fatty acid intake after adjusting for potential confounders.

RESULTS

A total of 19,088 non-diabetic participants (age range, 40-79 years) enrolled in the JACC between 1988 and 1990 were included in this study. During the five-year study period, 494 the participants developed T2D. The OR of T2D for the highest versus lowest quintiles was 0.58 (95% CI, 0.37-0.90) for total fat, 0.78 (95% CI, 0.51-1.20) for saturated fatty acid (SFA), 0.55 (95% CI, 0.35-0.86) for monounsaturated fatty acids (MUFA), 0.61 (95% CI, 0.39-0.96) for polyunsaturated fatty acids (PUFA), 0.64 (95% CI, 0.42-0.99) for n-3 PUFA, and 0.70 (95% CI, 0.45-1.09) for n-6 PUFA. Total fat and fatty acid (except SFA and n-6 PUFA) intake were inversely associated with T2D in men. Total fat and fatty acid intake were not associated with T2D in women.

CONCLUSION

Higher intakes of total fats, MUFA, PUFA, and n-3 PUFA were inversely associated with T2D among Japanese men.

Association between dietary carbohydrate intake and risk of type 2 diabetes: a systematic review and meta-analysis of cohort studies

Background

Previous meta-analyses have assessed the relationship between carbohydrate intake and type 2 diabetes (T2D) risk; however, they included few studies of Asian populations who have a higher carbohydrate intake and lower insulin secretory capacity than non-Asians. Since the publication of the previous meta-analyses, three further studies of Asian populations have been conducted. Based on this background, the present study aimed to perform an updated systematically examine observational studies concerning the link between dietary carbohydrate intake and T2D risk.

Methods

We conducted a systematic search for cohort studies that investigated the target association. For each analyzed study, parameter-adjusted risk ratios were used to compare the lowest and highest carbohydrate-intake groups in terms of their risk of incident T2D. The risk ratios were calculated using a random-effects model.

Results

Ten publications were analyzed. Overall, carbohydrate intake was found not to be associated with increased risk ratios of incident T2D (risk ratio [RR] = 1.07; 95% confidence interval [95% CI] = 0.94, 1.21; P < 0.01, I2 = 61.9%). However, studies of Asian populations reported that high carbohydrate intake is significantly associated with this risk (RR = 1.29; 95% CI 1.15, 1.45; P = 0.59, I2 = 0.0%).

Conclusions

This updated meta-analysis showed that, overall, carbohydrate intake is not associated with the risk of T2D; nevertheless, a significant association exists among Asian populations. To confirm the association between dietary carbohydrate intake and T2D risk observed in this study, further evidence from long-term observational studies of Asian populations is required.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13340-023-00642-0.

Association between low-carbohydrate diet score and incidence of type 2 diabetes among Japanese adults: the JACC Study

We prospectively examined the association between low-carbohydrate diet (LCD) score and incidence of type 2 diabetes (T2D) in Japanese adults using Japan Collaborative Cohort Study for Evaluation of Cancer Risk (JACC Study) data. A total of 19 084 (7052 men and 12 032 women) Japanese non-diabetic participants aged 40-79 years, who enrolled in the JACC study between 1988 and 1990, were included in our analysis. Dietary intake was evaluated using a validated food-frequency questionnaire. The overall, animal and vegetable LCD scores were calculated by dividing the study participants into eleven categories based on the percentages of energy from carbohydrates, protein and fat. The incidence of T2D was assessed using a self-administered questionnaire. We used multivariable logistic regression analysis to estimate the odds ratios (ORs) and 95 % confidence intervals (CIs) of incident T2D across the quintile of each LCD score, with adjustment for potential confounders. During the 5-year study period, 490 adults (247 men and 243 women) developed T2D. The multivariable-adjusted OR of incident T2D for the highest v. lowest quintiles of overall and animal LCD scores, respectively, were 0·64 (95 % CI 0·42, 0·99) and 0·83 (95 % CI 0·55, 1·27) for men, 0·78 (95 % CI 0·51, 1·18) and 0·84 (95 % CI 0·57, 1·24) for women. The vegetable LCD score was associated with a lower risk of T2D in men (OR 0·51; 95 % CI 0·33, 0·77). Our results suggest that diets lower in carbohydrates and higher in fat and protein are unlikely to higher the T2D risk among Japanese individuals.

Green Tea Consumption and Risk of Depression Symptoms: A Systematic Review and Meta-Analysis of Observational Studies

This systematic review and meta-analysis aimed to investigate the association between green tea consumption and depression symptom risk, using subgroup analyses concerning study design, geographical region of study, adjustment factors, age, cut-off for the highest consumption category, and depression assessment methods applied. We used PubMed to search for relevant literature. The inclusion criteria were studies that (a) investigated this association as a primary or secondary outcome; (b) published in English; (c) assessed and reported hazard ratios or odds ratios (ORs) and the corresponding 95% confidence intervals (CIs) for depression symptoms, or included sufficient information to allow their calculation; (d) included at least two groups differentiated based on green tea consumption (e.g., high and low); (e) reported the prevalence of depression symptoms in each group; and (f) reported the sample size for each group. Eight articles were found to meet all criteria. The results indicated that high green tea consumption is inversely associated with depression symptoms. The pooled OR was 0.66 (95% CI 0.58-0.74), and significant heterogeneity was not observed. Subgroup analysis showed that study design impacted results (cohort study [one study]: OR=0.29, 95% CI=0.04-2.14; cross-sectional study [seven studies]: OR=0.66, 95% CI=0.59-0.75). These findings suggest that green tea consumption reduces the risk of depression symptoms. This association was also observed in the cohort study included, but the results in which did not reach the significant level. Therefore, further cohort studies are needed to confirm the potential causal relationship in this regard.

Effects and contents of nutrition education relating to sarcopenia and frailty for Japanese older adults: A systematic review

This systematic review aimed to clarify whether nutrition education relating to sarcopenia and frailty for Japanese older adults has been effective and to identify the content of nutrition education that is provided to participants. We examined relevant studies published before January 2021. The inclusion criteria were as follows: (i) studies on nutrition education provided by experts; (ii) studies on Japanese participants aged 60 years or older; (iii) full papers published in English or Japanese; and (iv) studies with outcomes that include measurement items related to sarcopenia and frailty. A search strategy was designed using keywords such as "Japan" or "Japanese" and "nutrition education." In total, 798 titles and 179 abstracts were examined, and 63 full texts were selected for reading. Ten articles met all the inclusion criteria. Only two studies aimed to determine the effectiveness of nutrition education. We could not clarify whether nutrition education relating to sarcopenia and frailty for Japanese older adults was effective. However, we did identify various nutrition education contents on sarcopenia and frailty for Japanese older adults. Further studies are needed as follows: (i) studies designs that can determine whether nutrition education is effective; (ii) studies in which the content of the cooking training can be reproduced; (iii) studies in which the intervention group and the control group have the same educational content with different duration and frequency; (iv) studies that are written in English; and (v) studies that are conducted on men. Geriatr Gerontol Int 2021; 21: 1084-1092.

Association of dietary protein intake with skeletal muscle mass in older adults: A systematic review

Protein supplementation has been shown to be effective in attenuating the loss of lean body mass and muscle mass in older adults; however, its benefits as dietary protein remain unclear. This systematic review of observational studies aimed to investigate the association of dietary protein intake with skeletal muscle mass (SM). Observational studies that investigated the association of dietary protein intake with SM in older adults were retrieved from MEDLINE, Web of Science and Cochrane-CENTRAL databases. Of the 26 analyses in the 17 studies, 18 showed a significant positive association. In cohort studies, 55.6% (five of nine analyses) showed a significant positive association. Of these, four analyses were adjusted for well-known confounding factors, used energy-adjusted protein intake, and used the amount of change of SM between baseline and follow-up as the outcome, with two of them showing a significant positive association. Although 69.2% (18 of 26 analyses) of the 17 studies showed a significant positive association between dietary protein intake and SM in older adults, most studies were cross-sectional and had at least one important methodological limitation. Therefore, we could not draw any conclusions. Thus, well-designed cohort studies are needed in future to identify the association between dietary protein intake and SM in older adults. Geriatr Gerontol Int 2021; 21: 1077-1083.

Association between Protein Intake and Skeletal Muscle Mass among Community-Dwelling Older Japanese: Results from the DOSANCO Health Study: A Cross-Sectional Study

Whether the source of dietary protein intake is related to appendicular skeletal muscle mass (AMM) and muscle mass (MM) remains unclear. We conducted this cross-sectional study of 277 residents (115 men, 162 women) aged ≥65 years in Japan to examine the association of the amount of dietary protein intake with AMM and MM. We measured dietary protein intake using a brief self-administered diet history questionnaire. AMM and MM were assessed based on bioelectrical impedance. Multivariable linear regression analyses were used to estimate β coefficients that were adjusted for potential confounders. Among Japanese women aged ≥75 years, but not among women aged 65-74 years, dietary animal protein intake was significantly associated with AMM (β (95% confidence interval (CI)): 0.25 (0.10, 0.40)) and MM (β (95% CI): 0.40 (0.16, 0.64)). However, dietary vegetable protein intake was not associated with AMM (β (95% CI): -0.17 (-0.74, 0.41)) and MM (β (95% CI): -0.30 (-1.23, 0.63)). Furthermore, in men aged ≥65 years, dietary protein intake was not associated with AMM or MM. In conclusion, dietary animal protein intake, but not vegetable protein intake, were positively associated with AMM and MM among this population of Japanese women aged ≥75 years.

Effects of Evening-Only Low-Carbohydrate Meal on Healthy Volunteers

We performed a pre/post-interventional study with participants as self-controls to evaluate the effects of consuming an evening-only low-carbohydrate meal (LCM) at 1800 h on biochemical measures of glucose and lipid metabolism. Study participants comprised 14 healthy men (age range, 20-29 y) who, consumed standard test meals (STMs) or LCM at 1800 h. Blood samples were collected at fasting, and at 60-, 120-, and 240 min after the start of the meals. The 60-min postprandial levels and the area under the curve (AUC) 0-120 min for plasma glucose were significantly lower after the LCM than after the STMs. The 60- and 120-min postprandial levels and the AUC _{0-240 min} for plasma insulin were significantly lower after the LCM than after the STMs (p<0.01). Postprandial triglyceride (TG) levels at 120- and 240 min and the AUC _{0-240 min} were significantly higher after the LCM than after the STMs (p<0.05, p<0.01, and p<0.05, respectively). The interleukin-6 levels were significantly higher 240 min after the STMs than before the meals (p<0.05), but not after the LCM. In these healthy volunteers, consuming an LCM at 1800 h suppressed postprandial hyperglycemia and insulin secretion; however, postprandial TG increased. Consuming an LCM at 1800 h was beneficial as it inhibited elevation of blood glucose; however, it may also increase the risk of arteriosclerosis through increasing TG levels.