Selected health and behavioral effects related to the use of caffeine

Consumption of organic and functional food. A matter of well-being and health?

Health is an important motivation for the consumption of both organic and functional foods. The aim of this study was to clarify to what extent the consumption of organic and functional foods are characterized by a healthier lifestyle and a higher level of well-being. Moreover, the influence of social desirability on the respondents' response behavior was of interest and was also analyzed. Well-being and health was measured in a sample of 555 German consumers at two levels: the cognitive-emotional and the behavioral level. The results show that although health is an important aspect for both functional food and organic food consumption, these two forms of consumption were influenced by different understandings of health: organic food consumption is influenced by an overall holistic healthy lifestyle including a healthy diet and sport, while functional food consumption is characterized by small "adjustments" to lifestyle to enhance health and to increase psychological well-being. An overlap between the consumption of organic and functional food was also observed. This study provides information which enables a better characterization of the consumption of functional food and organic food in terms of well-being and health.

A linkage analysis of cigarette and alcohol consumption in an unselected Mexican American population

The use of alcohol and tobacco is highly prevalent. Studying the rate of consumption in a non-selected population could contribute to the elucidation of pathways involved in addiction or to the development of prevention programs. The San Antonio Family Heart Study has approximately 1,400 members with longitudinal data and did not select the proband with regard to exposure status. The goal of this study was to perform genome-wide linkage analysis of the rate of alcohol and cigarette consumption in a "normal" population. We used SOLAR to perform variance-components based analysis of the transformed maximal rate of consumption. Despite estimated heritabilities of 0.52 (P < 0.001) for cigarette and 0.39 (P < 0.001) for alcohol consumption, univariate linkage analyses produced only suggestive LOD scores, however the second suggestive linkage peak for the alcohol phenotype was present at 148 cM on chromosome 10, in the exact vicinity of the peak for the cigarette phenotype. In a bivariate analyses, the environmental correlation between alcohol and cigarette consumption was not significantly different from zero (rho(e) = -0.15, P = 0.18) and the overall genetic correlation was not different from zero (rho(g) = 0.16, P = 0.34). The results from the bivariate linkage analysis found a maximum LOD score of 3.82 (genome-wide P = 0.0054) at 151 cM on chromosome 10, at the location of the overlapping peaks from the univariate analyses.

Early renal injury induced by caffeine consumption in obese, diabetic ZSF1 rats

Our previous studies indicate that prolonged caffeine consumption exacerbates renal failure in nephropathy associated with the metabolic syndrome. Reduced activity of the antioxidant defense system and beneficial effects of antioxidant therapy have been reported in diabetic rats and humans. The purpose of this study was to examine the early renal effects of caffeine consumption and the effects of concomitant antioxidant therapy in young obese, diabetic ZSF1 rats. Eleven-week-old male ZSF1 rats were randomized to drink tap water, caffeine (0.1%), tempol (1 mmol/L), or a solution containing caffeine and tempol for nine weeks. Caffeine significantly reduced body weight and glycosuria (weeks 2-9), improved glucose tolerance (week 9), had no effect on elevated plasma triglycerides, plasma cholesterol (week 9) and blood pressure (week 9), and significantly increased plasma cholesterol level (weeks 5 and 9). Yet, as early as after two weeks, caffeine greatly augmented proteinuria and increased renal vascular resistance (RVR) and heart rate (HR: week 9). Tempol had no effects on metabolic status and development of proteinuria, did not alter caffeine-induced metabolic changes and early proteinuria, and attenuated caffeine-induced increase in HR and RVR. Immunohistochemical analysis revealed significant glomerular and interstitial inflammation, proliferation, and fibrosis in control animals. Caffeine augmented the influx of glomerular and interstitial macrophages (ED1+ cells) influx, glomerular and tubular proliferative response, and glomerular collagen IV content. Tempol abolished the exacerbation of renal inflammation, proliferation, and fibrosis induced by caffeine. In conclusion, in nephropathy associated with the metabolic syndrome, caffeine--most likely through the interaction with adenosine receptors and interference with anti-inflammatory and/or glomerular hemodynamic effects of adenosine--augments proteinuria and stimulates some of the key proliferative mechanisms involved in glomerular remodeling and sclerosis. Tempol does not prevent early renal injury (i.e., proteinuria) induced by caffeine, yet abolishes late renal inflammatory, proliferative, and fibrotic change induced by chronic caffeine consumption in obese ZSF1 rats.

High caffeine intake in adolescents: associations with difficulty sleeping and feeling tired in the morning

The objective of this study was to examine the association between caffeine usage in U.S. adolescents and the frequency that feeling tired in the morning and having difficulty sleeping is reported. In this study we found that feeling tired in the morning and having difficulty sleeping was experienced more commonly in those adolescents that have a high intake of caffeine.

Long-term caffeine consumption exacerbates renal failure in obese, diabetic, ZSF1 (fa-fa(cp)) rats

BACKGROUND

Our preliminary studies indicate that chronic caffeine consumption has adverse renal effects in nephropathy associated with high blood pressure and insulin resistance. The purpose of this study was to investigate the effects of early (beginning at 8 weeks of age) and long-term (30 weeks) caffeine treatment (0.1% solution) on renal function and structure in obese, diabetic ZSF1 rats.

METHODS

Metabolic and renal function measurements were performed at six-week intervals and in a subset of animals (N = 6 per group) heart rate (HR) and mean arterial blood pressure (MABP) were monitored by a radiotelemetric technique. At the end of the study acute, measurements of renal hemodynamics and excretory function were conducted in anesthetized animals.

RESULTS

Caffeine produced a very mild increase (4 to 5%) of MABP and HR, but greatly augmented proteinuria (P < 0.001), reduced creatinine clearance (P < 0.05) and had a mixed effect on metabolic status in obese ZSF1 rats. Caffeine significantly reduced body weight, glycosuria, fasting glucose and insulin levels and improved glucose tolerance, had no effect on elevated plasma triglycerides levels and significantly increased plasma cholesterol level (P < 0.001). Acute measurements of renal function revealed increased renal vascular resistance (95.1 +/- 11 vs. 50.7 +/- 2.4 mm Hg/mL/min/g kidney, P < 0.01) and decreased inulin clearance (0.37 +/- 0.11 vs. 0.97 +/- 0.13 mL/min/g kidney, P < 0.002) in caffeine-treated versus control animals, respectively. Caffeine potentiated the development of more severe tubulointerstitial changes (P < 0.05) and increased focal glomerulosclerosis (14.7 +/- 1.7 vs. 6.5 +/- 0.9%, caffeine vs. control, P < 0.002).

CONCLUSION

The present study provides the first evidence that caffeine (despite improving insulin sensitivity) exacerbates renal failure in obese, diabetic ZSF1 rats. Further mechanistic studies of adverse renal effects of caffeine in chronic renal failure associated with metabolic syndrome are warranted.

Effects of caffeine and high ambient temperature on haemodynamic and body temperature responses to dynamic exercise

Caffeine can enhance mean arterial blood pressure (MAP) and attenuate forearm blood flow (FBF) and forearm vascular conductance (FVC) during exercise in thermal neutral conditions without altering body temperature. During exercise at higher ambient temperatures, where a greater transfer of heat from the body core to skin would be expected, caffeine-induced attenuation of FBF (i.e. cutaneous blood flow) could attenuate heat dissipation and increase body temperature (T(re)). We hypothesized that during exercise at an ambient temperature of 38 degrees C, caffeine increases MAP, and attenuates FBF and FVC such that T(re) is increased. Eleven caffeine-naive, active men, were studied at rest and during exercise after ingestion of a placebo or 6 mg kg(-1) of caffeine. MAP, heart rate (HR), FBF, FVC, T(re) skin temperature (T(sk)) and venous lactate concentrations (lactate) were assessed sequentially during rest at room temperature, after 45 min of exposure to an ambient temperature of 38 degrees C, and during 35 min of submaximal cycling. Heat exposure caused increases in MAP, FBF, FVC and T(sk) that were not altered by caffeine. HR, T(re), and lactate were unaffected. During exercise, only MAP (95 +/- 2 vs. 102 +/- 2 mmHg), HR (155 +/- 10 vs. 165 +/- 10 beats min(-1)), and lactate (2.0 +/- 0.4 vs. 2.3 +/- 0.4 mmol l(-1)) were increased by caffeine. These data indicate that increases in cutaneous blood flow during exercise in the heat are not reduced by caffeine. This may be because of activation of thermal reflexes that cause cutaneous vasodilation capable of offsetting caffeine-induced reductions in blood flow. Caffeine-induced increases in lactate, MAP and HR during exercise suggest that this drug and high ambient temperatures increase production of muscle metabolites that cause reflex cardiovascular responses.

Phytochemicals for the prevention of breast and endometrial cancer

Although there is evidence that phytochemicals decrease the incidence of breast and endometrial cancer, many observations are only phenomenologic, and much work needs to be done to explore basic mechanisms and the strategic exploitation of their interactions. The multiplicity of phytochemical actions at different sites in the process of tumorigenesis may eventually lead to the development of a multiagent strategy designed to maximize the complementary effects of different agents. A number of effects with possible relevance to cancer chemoprevention have been excluded from this review, including effects of phytochemicals on the immune response; the question of dietary restriction, which has a profound effect on tumorigenesis; the relatively low methionine levels in some phytochemicals such as soy, which may limit the synthesis of polyamines necessary for tumor growth [151]; and the fact that diets higher in plant products are usually lower in fat and result in leaner individuals with less potential for the synthesis of estradiol in adipose tissue. Also, many studies dealing solely with in vitro mutagenesis were excluded.

Renal and metabolic effects of caffeine in obese (fa/fa(cp)), diabetic, hypertensive ZSF1 rats

In Western society, the triad of hypertension, metabolic syndrome and obesity (which caries a high risk for renal disease) is increasing, as is the intake of caffeine. However, no information is available regarding the metabolic or renal consequences of caffeine consumption in this complex disease entity. The purpose of this study was to investigate the effects of chronic caffeine consumption on renal function and metabolic status in obese ZSF1 rats, an animal model of obesity, hypertension and the metabolic syndrome. Fifteen, 18-week-old male, obese ZSF1 rats were randomized to drink tap water (Cont, n = 8) or 0.1% solution of caffeine (Caff, n = 7) for 8 weeks. Metabolic and renal function measurements were performed at baseline and after 4 and 8 weeks of treatment. Caffeine treatment significantly (p < 0.05) reduced body weight, food, and fluid consumption and improved insulin sensitivity (fasting insulin 129.6+/-8.1 vs 97.5+/-3.6 microIU/mL; fed insulin 146.3+/-8.5 vs 110.6+/-3.4 microIU/mL; fasting glucose 138.7+/-13.4 vs 145+/-8.0 mg/dL; fed glucose 373+/-19.4 vs 283.3+/-19.6 mg/dL, Cont vs Caff, respectively). After 8 weeks of caffeine treatment, animals were less glycosuric as compared with control group. Area under glucose curves (AUC-glucose) in oral glucose tolerance test did not differ between the two groups (AUC- glucose: 592.5+/-42.7 vs 589.5+/-20.5 mg/dL x h, Cont vs Caff), whereas caffeine treatment significantly decreased AUC of insulin (AUC-insulin: 257.77+/-12.9 vs 198.0+/-5.9 microIU/mL x h, Cont vs. Caff, p<0.05). No differences were found with regard to plasma triglycerides and glycerol levels; however, caffeine significantly increased cholesterol levels after 4 and 8 weeks (2F-Anova, p<0.001). Moreover, caffeine significantly decreased creatinine clearance after 4 and 8 weeks (CrCl, Cont: 3.5+/-0.4, Caff: 2.2+/-0.2 L/kg/day, p<0.05) and increased protein/CrCl ratio (Cont: 323+/-30, Caff: 527+/-33 mg/L/day). Caffeine treatment for 8 weeks tended to increase plasma norepinephrine levels (p<0.06), but the two groups did not differ with regard to plasma renin activity, blood pressure, renal blood flow or and renal vascular resistance. The study indicates that caffeine improves insulin sensitivity but increases plasma cholesterol levels and impairs renal function in obesity with the metabolic syndrome and hypertension. Our results imply that the health consequences of chronic caffeine consumption may depend heavily on underlying pathophysiology process.

Effects of caffeine on blood pressure, heart rate, and forearm blood flow during dynamic leg exercise

This study examined the acute effects of caffeine on the cardiovascular system during dynamic leg exercise. Ten trained, caffeine-naive cyclists (7 women and 3 men) were studied at rest and during bicycle ergometry before and after the ingestion of 6 mg/kg caffeine or 6 mg/kg fructose (placebo) with 250 ml of water. After consumption of caffeine or placebo, subjects either rested for 100 min (rest protocol) or rested for 45 min followed by 55 min of cycle ergometry at 65% of maximal oxygen consumption (exercise protocol). Measurement of mean arterial pressure (MAP), forearm blood flow (FBF), heart rate, skin temperature, and rectal temperature and calculation of forearm vascular conductance (FVC) were made at baseline and at 20-min intervals. Plasma ANG II was measured at baseline and at 60 min postingestion in the two exercise protocols. Before exercise, caffeine increased both systolic blood pressure (17%) and MAP (11%) without affecting FBF or FVC. During dynamic exercise, caffeine attenuated the increase in FBF (53%) and FVC (50%) and accentuated exercise-induced increases in ANG II (44%). Systolic blood pressure and MAP were also higher during exercise plus caffeine; however, these increases were secondary to the effects of caffeine on resting blood pressure. No significant differences were observed in heart rate, skin temperature, or rectal temperature. These findings indicate that caffeine can alter the cardiovascular response to dynamic exercise in a manner that may modify regional blood flow and conductance.