Dietary iodine, seaweed consumption, and incidence risk of metabolic syndrome among postmenopausal women: a prospective analysis of the Korean Multi-Rural Communities Cohort Study (MRCohort)

Association between seaweed intake and risk of type 2 diabetes mellitus: a prospective cohort study

This study aimed to identify the longitudinal association between seaweed and type 2 diabetes mellitus (T2DM) in the Korean population. Data from 148 404 Korean adults aged 40 years and older without a history of T2DM, cardiovascular disease or cancer at baseline were obtained from the Korean Genome and Epidemiology Study data. The participants' seaweed intake was obtained using a validated semi-quantitative food frequency questionnaire, and the diagnosis of T2DM was surveyed through a self-reported questionnaire during follow-up. The hazard ratio (HR) and 95 % confidence interval (CI) for T2DM were calculated using the Cox proportional hazard regression, and the dose-response relationship was analysed using a restricted cubic spline regression. Participants had a mean follow-up period of 5 years. Participants with the highest seaweed intake had a 7 % lower risk of T2DM compared with the group with the lowest intake (95 % CI (0·87, 0·99)). Interestingly, this association was stronger in those with normal weight (HR: 0·88, 95 % CI (0·81, 0·95)), while no association was observed in participants with obesity. Spline regression revealed an inverse linear relationship between seaweed intake and T2DM risk in participants with normal weight, showing a trend where increased seaweed intake is related to lower instances of T2DM (Pfor nonlinearity = 0·48). Seaweed intake is inversely associated with the onset of T2DM in Korean adults with normal weight.

The correlation between iodine and metabolism: a review

Iodine is involved in the synthesis of thyroid hormones and plays a crucial role in human life. Both iodine deficiency and excess are common issues in certain populations. Iodine also has extrathyroidal effects on organs that can uptake it independently of thyroid hormones. Recently, multiple clinical studies have shown a connection between iodine intake and metabolic disorders, such as metabolic syndrome, obesity, diabetes, hypertension, and dyslipidemia. However, the results of these studies have been inconsistent, and the mechanisms behind these associations are still not well understood. Therefore, in this review, we aim to examine the recent research progress regarding the relationship between iodine and metabolic disorders, along with the relevant mechanisms.

Seaweed intake modulates the association between VIPR2 variants and the incidence of metabolic syndrome in middle-aged Koreans

Vasoactive intrinsic peptide receptor (VIPR2), a circadian gene, is involved in metabolic homeostasis and metabolic syndrome (MetS). Seaweeds contain polysaccharides that regulate metabolic homeostasis, possibly by altering the effects of VIPR2 variants. We examined the relationship between VIPR2 expression and the incidence of MetS based on seaweed consumption. This study included 4979 Koreans aged ≥40 years using data from the Ansan-Ansung cohort of the Korean Genome and Epidemiology Study. The total seaweeds included were laver, kelp, and sea mustard. A multivariable Cox proportional hazards model was used to analyze the interactions between the VIPR2 rs6950857 genotype associated with MetS incidence and seaweed intake after adjusting for covariates such as region. A total of 2134 patients with MetS were followed for an average of 8.9 years. In men with the GG genotype of rs6950857, the highest quintile of seaweed consumption was associated with a decreased incidence of MetS compared with that of the lowest quintile (hazard ratio, 0.78; 95% confidence interval, 0.62-0.98). We identified a unique association between the rs6950857 genotype, seaweed intake, and MetS. These findings highlight the importance of VIPR2 and the regulatory role of seaweed consumption in MetS incidence.

Effect of the Interaction between Seaweed Intake and LPL Polymorphisms on Metabolic Syndrome in Middle-Aged Korean Adults

This study aimed to examine the effect of the interaction between seaweed (laver, kelp, and sea mustard) intake and lipoprotein lipase gene (LPL) rs17482735 genotypes on the incidence of metabolic syndrome (MetS). The Korean Genome and Epidemiology Study (KoGES) data of Korean adults aged 40-69 years were used in this study. Information on seaweed intake was obtained from the food frequency questionnaire. To investigate the interaction between seaweed intake and LPL rs17482735 genotypes on the incidence of MetS, multivariable Cox proportional hazard models were used after adjusting for confounding variables. There was no significant association in women, but men with TG and TT genotypes of rs17482753 had lower incidence of MetS (HR 0.83, 95% CI 0.71-0.95, p-value = 0.01), low HDL-cholesterol levels (HR 0.81, 95% CI 0.69-0.95, p-value = 0.01), high triglyceride levels (HR 0.83, 95% CI 0.70-0.99, p-value = 0.0471), and high blood pressure (HR 0.79, 95% CI 0.67-0.93, p-value = 0.004). Furthermore, the incidence of MetS was lower in men with the highest laver and total seaweed intake and TG and TT genotypes of rs17482735 (HR 0.60, 95% CI 0.43-0.84; HR 0.57, 95% CI 0.41-0.79, respectively). High seaweed intake was negatively associated with MetS, suggesting that LPL genetic variations, particularly in men, may be helpful in preventing MetS. These results demonstrate that seaweed intake considering LPL genotypes may be beneficial for preventing and treating MetS.

How Do Brown Seaweeds Work on Biomarkers of Dyslipidemia? A Systematic Review with Meta-Analysis and Meta-Regression

Dyslipidemia is a common chronic disease that increases the risk of cardiovascular disease. Diet plays an important role in the development of dyslipidemia. As people pay increased attention to healthy eating habits, brown seaweed consumption is increasing, particularly in East Asian countries. The association between dyslipidemia and brown seaweed consumption has been previously demonstrated. We searched for keywords associated with brown seaweed and dyslipidemia in electronic databases such as PubMed, Embase, and Cochrane. Heterogeneity was estimated using the I2 statistic. The 95% confidence interval (CI) of the forest plot and heterogeneity were confirmed using meta-ANOVA and meta-regression. Funnel plots and publication bias statistical tests were used to determine publication bias. Statistical significance was set at p < 0.05. In this meta-analysis, we found that brown seaweed intake significantly decreased the levels of total cholesterol (mean difference (MD): −3.001; 95% CI: −5.770, −0.232) and low-density lipoprotein (LDL) cholesterol (MD: −6.519; 95% CI: −12.884, −0.154); nevertheless, the statistically significant association of brown seaweed intake with high-density lipoprotein (HDL) cholesterol and triglycerides were not observed in our study (MD: 0.889; 95% CI: −0.558, 2.335 and MD: 8.515; 95% CI: −19.354, 36.383). Our study demonstrated that brown seaweed and its extracts decreased total cholesterol and LDL cholesterol levels. The use of brown seaweeds may be a promising strategy to reduce the risk of dyslipidemia. Future studies involving a larger population are warranted to investigate the dose–response association of brown seaweed consumption with dyslipidemia.

Iodine Bioavailability and Accumulation of Arsenic and Cadmium in Rats Fed Sugar Kelp (Saccharina latissima)

Suboptimal iodine status is a prominent public health issue in several European coun-tries. Brown algae have a high iodine content that, upon intake, may exceed the recommended dietary intake level, but iodine bioavailability has been reported to be lower than from potassium iodide (KI) and highly depends on algae species. Further, potential negative effects from other components in algae, such as cadmium (Cd) and arsenic (As), have also been addressed. In this study, we observed a lower bioavailability of iodine from farmed sugar kelp (Saccharina latissima) than from KI in female Wistar IGS rats. Urinary iodine excretion was 94-95% in rats fed KI and 73-81% in rats fed sugar kelp, followed by increased faecal iodine levels in rats fed sugar kelp. No effects on body weight, feed efficiency, or plasma markers for liver or kidney damage were detected. The highest dose of iodine reduced plasma free thyroxine (fT4) and total T4 levels, but no significant effects on circulating levels of thyroid-stimulating hormone (TSH) and free triiodo-thyronine (fT3) were detected. Faeces and urine measurements indicate that 60-80% of total As and 93% of Cd ingested were excreted in rats fed 0.5 and 5% kelp. Liver metabolomic profiling demonstrates that a high inclusion of sugar kelp in the diet for 13 weeks of feeding modulates metabolites with potential antioxidant activity and phytosterols.

Nutrition-wide association study of microbiome diversity and composition in colorectal cancer patients

BACKGROUND

The effects of diet on the interaction between microbes and host health have been widely studied. However, its effects on the gut microbiota of patients with colorectal cancer (CRC) have not been elucidated. This study aimed to investigate the association between diet and the overall diversity and different taxa levels of the gut microbiota in CRC patients via the nutrition-wide association approach.

METHODS

This hospital-based study utilized data of 115 CRC patients who underwent CRC surgery in Department of Surgery, Seoul National University Hospital. Spearman correlation analyses were conducted for 216 dietary features and three alpha-diversity indices, Firmicutes/Bacteroidetes ratio, and relative abundance of 439 gut microbial taxonomy. To identify main enterotypes of the gut microbiota, we performed the principal coordinate analysis based on the β-diversity index. Finally, we performed linear regression to examine the association between dietary intake and main microbiome features, and linear discriminant analysis effect size (LEfSe) to identify bacterial taxa phylogenetically enriched in the low and high diet consumption groups.

RESULTS

Several bacteria were enriched in patients with higher consumption of mature pumpkin/pumpkin juice (ρ, 0.31 to 0.41) but lower intake of eggs (ρ, -0.32 to -0.26). We observed negative correlations between Bacteroides fragilis abundance and intake of pork (belly), beef soup with vegetables, animal fat, and fatty acids (ρ, -0.34 to -0.27); an inverse correlation was also observed between Clostridium symbiosum abundance and intake of some fatty acids, amines, and amino acids (ρ, -0.30 to -0.24). Furthermore, high intake of seaweed was associated with a 6% (95% CI, 2% to 11%) and 7% (95% CI, 2% to 11%) lower abundance of Rikenellaceae and Alistipes, respectively, whereas overall beverage consumption was associated with an 10% (95% CI, 2% to 18%) higher abundance of Bacteroidetes, Bacteroidia, and Bacteroidales, compared to that in the low intake group. LEfSe analysis identified phylogenetically enriched taxa associated with the intake of sugars and sweets, legumes, mushrooms, eggs, oils and fats, plant fat, carbohydrates, and monounsaturated fatty acids.

CONCLUSIONS

Our data elucidates the diet-microbe interactions in CRC patients. Additional research is needed to understand the significance of these results in CRC prognosis.

Association of Seaweed Consumption with Metabolic Syndrome and Its Components: Findings from the Korean Genome and Epidemiology Study

This study aimed to investigate the association between seaweed consumption and the odds of developing metabolic syndrome in middle-aged and elderly Koreans. The study included 5777 adults aged 40-69 years from 2001 to 2002 in the Ansan and Ansung cohorts of the Korean Genome and Epidemiology Study. Data on the consumption of seaweed, including laver and kelp/sea mustard, were obtained using a semiquantitative food frequency questionnaire. Multivariable logistic regression models were used to assess the association between seaweed consumption and the odds of developing metabolic syndrome and its components. Women in the highest tertile of laver consumption had lower odds of developing metabolic syndrome than those in the lowest tertile (adjusted odds ratio [AOR]: 0.70; 95% confidence interval [CI]: 0.54-0.92). Both men and women in the highest tertile of laver consumption had lower odds of abdominal obesity than those in the lowest tertile (AOR: 0.64, 95% CI: 0.42-0.98 for men; AOR: 0.53, 95% CI: 0.39-0.72 for women). These findings suggest that laver consumption is inversely associated with the odds of developing metabolic syndrome and abdominal obesity in Korean adults.

Seaweed and Iodine Intakes and SLC5A5 rs77277498 in Relation to Thyroid Cancer

BACKGRUOUND

This study aims to elucidate the associations among dietary seaweed (gim and miyeok/dashima) and iodine intakes, the rs77277498 polymorphism of the SLC5A5 gene codifying the sodium/iodine symporter, and thyroid cancer risk in a Korean population.

METHODS

We conducted a case-control study of 117 thyroid cancer cases and 173 controls who participated in the Cancer Screenee Cohort between 2002 and 2014 at the National Cancer Center, Korea. The amount of seaweed and iodine consumption (g/day) was estimated using the residual energy adjustment method. We calculated odds ratios (ORs) and their 95% confidence intervals (CIs) using a multivariable logistic regression model for the separate and combined effect of dietary iodine-based intake and SLC5A5 polymorphism (rs77277498, C>G) on thyroid cancer.

RESULTS

Dietary gim and iodine intakes were inversely associated with thyroid cancer, with ORs of 0.50 (95% CI, 0.30 to 0.83) and 0.57 (95% CI, 0.35 to 0.95), respectively, whereas the associations for dietary miyeok/dashima and total seaweed intakes were not significant. However, compared with individuals carrying the C/C genotype of the rs77277498 polymorphism with a low intake of all dietary factors, those carrying the G allele with a high intake had a lower risk of thyroid cancer, with ORs of 0.25 (95% CI, 0.10 to 0.56), 0.31 (95% CI, 0.12 to 0.77), 0.26 (95% CI, 0.10 to 0.62), and 0.30 (95% CI, 0.12 to 0.73) for the consumption of gim, miyeok/dashima, total seaweed, and iodine, respectively.

CONCLUSION

In summary, our results supported the evidence of the protective effects of dietary gim and iodine intake against thyroid cancer risk, and this association can be strengthened by SLC5A5 rs77277498 genotypes.

Seaweed Exhibits Therapeutic Properties against Chronic Diseases: An Overview

Seaweeds or marine macroalgae are known for producing potentially bioactive substances that exhibit a wide range of nutritional, therapeutic, and nutraceutical properties. These compounds can be applied to treat chronic diseases, such as cancer, cardiovascular disease, osteoporosis, neurodegenerative diseases, and diabetes mellitus. Several studies have shown that consumption of seaweeds in Asian countries, such as Japan and Korea, has been correlated with a lower incidence of chronic diseases. In this study, we conducted a review of published papers on seaweed consumption and chronic diseases. We used the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) method for this study. We identified and screened research articles published between 2000 and 2021. We used PubMed and ScienceDirect databases and identified 107 articles. This systematic review discusses the potential use of bioactive compounds of seaweed to treat chronic diseases and identifies gaps where further research in this field is needed. In this review, the therapeutic and nutraceutical properties of seaweed for the treatment of chronic diseases such as neurodegenerative diseases, obesity, diabetes, cancer, liver disease, cardiovascular disease, osteoporosis, and arthritis were discussed. We concluded that further study on the identification of bioactive compounds of seaweed, and further study at a clinical level, are needed.

Inverse Association Between Iodine Status and Prevalence of Metabolic Syndrome: A Cross-Sectional Population-Based Study in a Chinese Moderate Iodine Intake Area

PURPOSE

To investigate the relationship between iodine intake status and the prevalence of metabolic syndrome (MetS) through a population-based survey.

PATIENTS AND METHODS

In total, 2691 Chinese adults participated in this cross-sectional study, and they were stratified by urinary iodine concentration (UIC) and sex. Fasting blood samples were used to assess biochemical parameters, including thyroid function and antibodies. Urine samples were collected in the morning to measure UIC. Multivariate regression logistic analysis was performed for the overall population and sex subgroups.

RESULTS

An inverse association was observed between iodine intake status and MetS prevalence in Chinese adults. Compared with individuals with adequate iodine status, those with high-iodine status had significantly low MetS risks, and the adjusted odds ratios (95% confidence interval) were 0.70 (0.57-0.86, P <0.01) and 0.75 (0.6-0.95, P <0.05). A high MetS risk was observed in the iodine-deficient group, which did not reach statistical significance. There was a significant inverse linear trend between the risk of MetS and UIC in the total population and male subgroup (P for trend <0.05), which was not observed in the female subgroup (P for trend >0.05).

CONCLUSION

An inverse association was observed between iodine intake status and the risk of developing MetS in Chinese adults. Sufficient iodine status is a potential protective factor for MetS development. Males may benefit from increased iodine intake, while females would need to achieve a more-than-adequate iodine status to gain metabolic benefits.

Bioactive Properties of Marine Phenolics

Phenolic compounds from marine organisms are far less studied than those from terrestrial sources since their structural diversity and variability require powerful analytical tools. However, both their biological relevance and potential properties make them an attractive group deserving increasing scientific interest. The use of efficient extraction and, in some cases, purification techniques can provide novel bioactives useful for food, nutraceutical, cosmeceutical and pharmaceutical applications. The bioactivity of marine phenolics is the consequence of their enzyme inhibitory effect and antimicrobial, antiviral, anticancer, antidiabetic, antioxidant, or anti-inflammatory activities. This review presents a survey of the major types of phenolic compounds found in marine sources, as well as their reputed effect in relation to the occurrence of dietary and lifestyle-related diseases, notably type 2 diabetes mellitus, obesity, metabolic syndrome, cancer and Alzheimer's disease. In addition, the influence of marine phenolics on gut microbiota and other pathologies is also addressed.