Tea intake or consumption and the risk of dementia: a meta-analysis of prospective cohort studies

Green Tea Mitigates the Hallmarks of Aging and Age-Related Multisystem Deterioration

Aging is characterized by progressive multisystem deterioration driven by molecular and cellular mechanisms encapsulated in the twelve hallmarks of aging. Green tea (GT), derived from Camellia sinensis, has garnered significant scientific interest due to its rich polyphenolic composition, particularly epigallocatechin-3-gallate, and its pleiotropic health benefits. In this narrative review, we explored the multifaceted mechanisms through which GT may mitigate the aging hallmarks. Evidence from in vitro, animal, and human studies has shown that GT polyphenols can enhance DNA repair pathways, preserve telomere length, modulate epigenetic aging markers, improve proteostasis and autophagic flux, regulate nutrient-sensing networks, and rejuvenate mitochondrial function. Additionally, GT exhibits anti-inflammatory properties and may restore a physiological gut microbiota composition. Beyond molecular and cellular effects, GT consumption in humans has been associated with improved cognitive function, cardiovascular health, muscle preservation, and metabolic regulation in aging populations. Collectively, these findings highlight GT's potential as a naturally occurring geroscience intervention capable of addressing the interconnected network of aging processes more comprehensively than single-target pharmaceuticals. Future research should focus on optimizing dosing regimens, exploring synergies with other anti-aging strategies, and investigating personalized responses to GT interventions.

Sulforaphane suppresses Aβ accumulation and tau hyperphosphorylation in vascular cognitive impairment(VCI)

Sulforaphane (Sfn) is a compound naturally found in cruciferous vegetables such as broccoli, Brussels sprouts, cabbage, and kale. It is well-known for its antioxidative and anti-inflammatory effects. Sfn has attracted attention for its potential health benefits, particularly its role in brain health and the potential prevention of dementia and neurodegeneration. Alzheimer's disease (AD) and vascular cognitive impairment (VCI) are the top two causes of dementia. Cerebral vascular lesions give rise to VCI and predispose neurons to degeneration and Alzheimer's disease (AD) by Aβ accumulation and tau hyperphosphorylation. In a rat model of VCI by permanent bilateral common carotid artery occlusion (2VO), we tested the protective effect of the phase II enzyme inducer sulforaphane (Sfn). Sfn ameliorates vascular cognitive deficits by reducing the typical white matter injury and neural atrophy pathological changes in VCI. Moreover, for the first time, we demonstrated that it effectively reduced Aβ and toxic p-tau accumulation in VCI. The protective mechanisms of Sfn involve the induction of HO-1 expression, activation of the Akt/GSK3β pathway, and modulation of amyloid precursor protein (APP) expression levels. Our data suggest that Sfn is a promising therapeutic compound to treat VCI and AD. It inhibits short-term neuron and white matter injuries as well as long-term Aβ and p-tau accumulation caused by cerebral vascular lesions.

Tea, coffee, and caffeine intake and risk of dementia and Alzheimer's disease: a systematic review and meta-analysis of cohort studies

Background: Limited and conflicting evidence exists for the associations between tea, coffee, and caffeine intake and risk of dementia and Alzheimer's disease (AD). This meta-analysis aimed to elucidate these associations and quantify potential dose-response relationships. Methods: PubMed, EMBASE, and Web of Science were searched up to 11 June 2024 for cohort studies. Random effects models were used to calculate pooled relative risks (RRs) and 95% confidence intervals (CIs), with the dose-response relationship assessed using restricted cubic splines. The Grading of Recommendations Assessment Development and Evaluation (GRADE) tool was used to assess the risk of bias. Results: Our analysis encompassed 38 cohorts, totalling 751 824 participants and 13 017 dementia and 17 341 AD cases. For dementia, compared with the lowest category, the pooled RRs (95% CI) in the highest category of tea, coffee, and caffeine were 0.84 (0.74-0.96, n = 6), 0.95 (0.87-1.02, n = 9), and 0.94 (0.70-1.25, n = 5), with all rated as low certainty in GRADE. For AD, the pooled RRs (95% CI) in the highest category of tea, coffee, and caffeine compared to the lowest category were 0.93 (0.87-1.00, n = 6), 1.01 (0.90-1.12, n = 10), and 1.34 (1.04-1.74, n = 2), with certainty ratings of low, low, and very low, respectively. Dose-response analysis indicated a non-linear relationship between coffee intake (Poverall = 0.04 and Pnonlinear = 0.01) and dementia risk, showing the protective association of risk of dementia with 1 to 3 cups per day of coffee intake. There is a linear association between tea intake and risk of dementia, with a significantly decreased risk of dementia for each 1 cup per day increase in tea consumption (0.96, 95% CI 0.94-0.99, Poverall = 0.01 and Pnonlinear = 0.68). Conclusion: Increased tea consumption was associated with a decreased risk of dementia and AD, and a non-linear relationship was found between coffee and dementia, supporting public health recommendations for dementia prevention.