Association between dietary caffeine, coffee, and tea consumption and depressive symptoms in adults: A systematic review and dose-response meta-analysis of observational studies

Common questions and misconceptions about caffeine supplementation: what does the scientific evidence really show?

Caffeine is a popular ergogenic aid that has a plethora of evidence highlighting its positive effects. A Google Scholar search using the keywords "caffeine" and "exercise" yields over 200,000 results, emphasizing the extensive research on this topic. However, despite the vast amount of available data, it is intriguing that uncertainties persist regarding the effectiveness and safety of caffeine. These include but are not limited to: 1. Does caffeine dehydrate you at rest? 2. Does caffeine dehydrate you during exercise? 3. Does caffeine promote the loss of body fat? 4. Does habitual caffeine consumption influence the performance response to acute caffeine supplementation? 5. Does caffeine affect upper vs. lower body performance/strength differently? 6. Is there a relationship between caffeine and depression? 7. Can too much caffeine kill you? 8. Are there sex differences regarding caffeine's effects? 9. Does caffeine work for everyone? 10. Does caffeine cause heart problems? 11. Does caffeine promote the loss of bone mineral? 12. Should pregnant women avoid caffeine? 13. Is caffeine addictive? 14. Does waiting 1.5-2.0 hours after waking to consume caffeine help you avoid the afternoon "crash?" To answer these questions, we performed an evidence-based scientific evaluation of the literature regarding caffeine supplementation.

Diet strategies for promoting healthy aging and longevity: An epidemiological perspective

In recent decades, global life expectancies have risen significantly, accompanied by a marked increase in chronic diseases and population aging. This narrative review aims to summarize recent findings on the dietary factors influencing chronic diseases and longevity, primarily from large cohort studies. First, maintaining a healthy weight throughout life is pivotal for healthy aging and longevity, mirroring the benefits of lifelong, moderate calorie restriction in today's obesogenic food environment. Second, the specific types or food sources of dietary fat, protein, and carbohydrates are more important in influencing chronic disease risk and mortality than their quantity. Third, some traditional diets (e.g., the Mediterranean, Nordic, and Okinawa) and contemporary dietary patterns, such as healthy plant-based diet index, the DASH (dietary approaches to stop hypertension) diet, and alternate healthy eating index, have been associated with lower mortality and healthy longevity. These patterns share many common components (e.g., a predominance of nutrient-rich plant foods; limited red and processed meats; culinary herbs and spices prevalent in global cuisines) while embracing distinct elements from different cultures. Fourth, combining a healthy diet with other lifestyle factors could extend disease-free life expectancies by 8-10 years. While adhering to core principles of healthy diets, it is crucial to adapt dietary recommendations to individual preferences and cultures as well as nutritional needs of aging populations. Public health strategies should aim to create a healthier food environment where nutritious options are readily accessible, especially in public institutions and care facilities for the elderly. Although further mechanistic studies and human trials are needed to better understand molecular effects of diet on aging, there is a pressing need to establish and maintain long-term cohorts studying diet and aging in culturally diverse populations.

Caffeine intake and anxiety: a meta-analysis

The results from studies on relationship between caffeine intake and risk of anxiety remains controversial, so we conducted a meta-analysis to summarize the evidence about the association between caffeine intake and risk of anxiety. Relevant articles were identified by researching PubMed, Web of Science, Cochrane library, Embase, CNKI, WANFANG DATA, SinoMed and VIP from the inception to December, 2022. Three investigators independently sifted through the literature, extracted the data, and evaluated the quality of the included studies based on predetermined selection criteria and assessed articles with Risk of bias assessment tool for Cochrane systematic reviews and analytical cross-sectional study quality assessment tool from JBI PACES. After assessing the quality of the literature, meta-analysis was performed using Revman 5.4 and Stata 12.0. Data were obtained from eight articles, and 546 participants from 14 studies in eight articles from healthy populations were included in the caffeine-anxiety analyses. As the scales used to assess anxiety vary in the literature, we chose standardized mean difference as the outcome indicator. In terms of overall effect, the results of the meta-analysis showed that caffeine intake increased the risk of anxiety [SMD = 0.94, 95% Cl = (0.28, 1.60), p < 0.05]. After suspecting that dose size might be responsible for the heterogeneity by sensitivity analysis, we performed subgroup analysis according to dose size and found that low-dose caffeine intake moderately increased the risk of anxiety [SMD = 0.61, 95%Cl = (0.42, 0.79), p < 0.05], whereas high-dose caffeine intake had a highly significant increase in the risk of anxiety [SMD = 2.86, 95%Cl = (2.50, 3.22), p < 0.05]. The results confirm that caffeine intake is associated with an elevated risk of anxiety in healthy individuals without psychiatric disorders, especially when the intake dose is greater than 400 mg.

Variables Affecting the Extraction of Antioxidants in Cold and Hot Brew Coffee: A Review

Coffee beans are a readily available, abundant source of antioxidants used worldwide. With the increasing interest in and consumption of coffee beverages globally, research into the production, preparation, and chemical profile of coffee has also increased in recent years. A wide range of variables such as roasting temperature, coffee grind size, brewing temperature, and brewing duration can have a significant impact on the extractable antioxidant content of coffee products. While there is no single standard method for measuring all of the antioxidants found in coffee, multiple methods which introduce the coffee product to a target molecule or reagent can be used to deduce the overall radical scavenging capacity. In this article, we profile the effect that many of these variables have on the quantifiable concentration of antioxidants found in both cold and hot brew coffee samples. Most protocols for cold brew coffee involve an immersion or steeping method where the coffee grounds are in contact with water at or below room temperature for several hours. Generally, a higher brewing temperature or longer brewing time yielded greater antioxidant activity. Most studies also found that a lower degree of coffee bean roast yielded greater antioxidant activity.

Caffeine intake is associated with less severe depressive symptoms in noncancer populations: an analysis based on NHANES 2007-2016

Depression and cancer are both prevalent diseases worldwide. Numerous cancer patients experience psychological illnesses, especially depression, following a malignancy's dismal prognosis. Although some research has suggested that caffeine may be protective against depressive symptoms, it is still unclear how caffeine and cancer patients are related. Thus, we hypothesized that moderate daily caffeine intake may reduce the risk of depression in both the cancer and noncancer populations. Data were extracted and combined from the National Health and Nutrition Examination Survey from 2007 to 2016. After controlling for potential confounding factors, interaction effects analysis was used to clarify the interaction between caffeine and cancer on depressive symptoms. Linear regression analysis and restricted cubic splines were used to further analyze the relationship between caffeine and depression in cancer and noncancer populations. A total of 24,145 participants were included in the analysis. In the noncancer population, the quartile 3 group of caffeine intake showed a negative association between caffeine intake and Patient Health Questionnaire-9 (PHQ-9) scores (β = -0.23, 95% confidence interval, -0.45 to -0.01; P = .041). No association between caffeine intake and PHQ-9 scores was observed in the cancer population. In both cancer and noncancer populations, restricted cubic splines indicated a nonlinear trend between caffeine and PHQ-9 scores, with the lowest PHQ-9 scores when caffeine intake was 119.52 mg. In the noncancer population, moderate daily caffeine intake (quartile 3 group; range, 119.5-236.5 mg) was associated with reduced depressive symptoms, whereas in the cancer population, no association was found between caffeine intake and depression.

Soft Drinks and Symptoms of Depression and Anxiety in Overweight Subjects: A Longitudinal Analysis of an European Cohort

BACKGROUND

Studies about the association of carbonated/soft drinks, coffee, and tea with depression and anxiety are scarce and inconclusive and little is known about this association in European adults. Our aim was to examine the association between the consumption of these beverages and depressive and anxiety symptom severity.

METHODS

A total of 941 European overweight adults (mean age, 46.8 years) with subsyndromal depression that participated in the MooDFOOD depression prevention randomized controlled trial (Clinical Trials.gov identifier: NCT2529423; date of the study: from 2014 to 2018) were analyzed. Depressive and anxiety symptom severity and beverage consumption were assessed using multilevel mixed-effects ordinal logistic regression models for each beverage consumption (carbonated/soft drink with sugar, carbonated/soft drink with non-nutritive sweeteners, coffee, and tea) with the three repeated measures of follow-up (baseline and 6 and 12 months). A case report form for participants' sociodemographic and clinical characteristics, the Food Frequency Questionnaire, the Patient Health Questionnaire-9, the Generalized Anxiety Disorder 7-Item Scale, the MINI International Neuropsychiatric Interview 5.0, the Short Questionnaire to Assess Health-Enhancing Psychical Activity, and the Alcohol Use Disorders Identification Test were the research tools used.

RESULTS

Daily consumption of carbonated/soft drinks with sugar was associated with a higher level of anxiety. Trends towards significance were found for associations between both daily consumption of carbonated/soft drinks with sugar and non-nutritive sweeteners and a higher level of depression. No relationship was found between coffee and tea consumption and the level of depression and anxiety.

CONCLUSIONS

The high and regular consumption of carbonated/soft drink with sugar (amount of consumption: ≥1 unit (200 mL)/day) tended to be associated with higher level of anxiety in a multicountry sample of overweight subjects with subsyndromal depressive symptoms. It is important to point out that further research in this area is essential to provide valuable information about the intake patterns of non-alcoholic beverages and their relationship with affective disorders in the European adult population.

Appraising the causal relationship between plasma caffeine levels and neuropsychiatric disorders through Mendelian randomization

BACKGROUND

Caffeine exposure modifies the turnover of monoamine neurotransmitters, which play a role in several neuropsychiatric disorders. We conducted a Mendelian randomization study to investigate whether higher plasma caffeine levels are causally associated with the risk of anorexia nervosa, bipolar disorder, major depressive disorder (MDD), and schizophrenia.

METHODS

Summary-level data on the neuropsychiatric disorders were obtained from large-scale genome-wide association studies (GWASs) of European ancestry participants (n = 72,517 to 807,553) and meta-analyzed with the corresponding data from the FinnGen study (n = 356,077). Summary-level data on plasma caffeine were extracted from a GWAS meta-analysis of 9876 European ancestry individuals. The Mendelian randomization analyses estimated the Wald ratio for each genetic variant and meta-analyzed the variant-specific estimates using multiplicative random effects meta-analysis.

RESULTS

After correcting for multiple testing, genetically predicted higher plasma caffeine levels were associated with higher odds of anorexia nervosa (odds ratio [OR] = 1.124; 95% confidence interval [CI] = 1.024-1.238, pFDR = 0.039) and a lower odds of bipolar disorder (OR = 0.905, 95% CI = 0.827-0.929, pFDR = 0.041) and MDD (OR = 0.965, 95% CI = 0.937-0.995, pFDR = 0.039). Instrumented plasma caffeine levels were not associated with schizophrenia (OR = 0.986, 95% CI = 0.929-1.047, pFDR = 0.646).

CONCLUSIONS

These Mendelian randomization findings indicate that long-term higher plasma caffeine levels may lower the risk of bipolar disorder and MDD but increase the risk of anorexia nervosa. These results warrant further research to explore whether caffeine consumption, supplementation, or abstinence could render clinically relevant therapeutic or preventative psychiatric effects.