beta-carotene and Heart-Diseases

Experimental evidence indicates a strong connection between oxidative damage, cancer, and aging. Epidemiological observations suggest that a diet rich in fruits and vegetables is associated with lower incidence of some cancers and longer life expectancy; since fruits and vegetables contain natural antioxidants, a considerable effort has been dedicated to understanding their effects in experimental studies and in human trials.. A: Effects of antioxidant-containing food and supplements on oxidation damage in humans. Intervention trials employing a variety of biomarkers have shown either a slight decrease in oxidation damage or no effect. B: Effects of selected antioxidants on mortality and cancer incidence. β-carotene and α-tocopherol, alone or in combination, increase cardiovascular and all-cause mortality or have no effect. In some studies, β-carotene and retinyl palmitate significantly increase the progression of lung cancer and aggressive prostate cancer. Protection against cardiovascular mortality or no effect of vitamin E has been reported, with an increase of all-cause mortality at dosages greater than 150 IU/day. Selenium showed beneficial effects on gastrointestinal cancer and reduced the risk of lung cancer in populations with lower selenium status. For multivitamin and mineral supplementation, no significant reduction of mortality or cancer incidence was observed, but some reports indicate a possible preventive effect in cervical cancer.. The majority of supplementation studies indicate no variation of general mortality and of cancer incidence or a detrimental effect on both. Antioxidant supplements so far tested seem to offer no improvement over a well-balanced diet, possibly because of the choice of the substances tested or of an excessive dosage. However, new natural or synthetic compounds effective in vitro and in experimental studies might still be worth investigating in human trials.

Topics: Aging; alpha-Tocopherol; Antioxidants; Ascorbic Acid; beta Carotene; Biomarkers; Dietary Supplements; Diterpenes; Heart Diseases; Humans; Incidence; Life Expectancy; Neoplasms; Randomized Controlled Trials as Topic; Retinyl Esters; Selenium; Trace Elements; Vitamin A; Vitamin E; Vitamins

Recent evidence introduces the possibility that lutein and zeaxanthin may protect against the development of the two common eye diseases of aging, cataract and macular degeneration. This potential and the lack of other effective means to slow the progression of macular degeneration have fueled high public interest in the health benefits of lutein and zeaxanthin and the proliferation of supplements containing them on pharmacy shelves. An understanding of the biologic consequences of limiting or supplementing with these carotenoids is only beginning to emerge. Some epidemiologic evidence supports a role in eye disease and, to a lesser extent, cancer and cardiovascular disease. However, the overall body of evidence is insufficient to conclude that increasing levels of lutein and zeaxanthin, specifically, will confer an important health benefit. Future advances in scientific research are required to gain a better understanding of the biologic mechanisms of their possible role in preventing disease. Additional research is also required to understand the effect of their consumption, independent of other nutrients in fruits and vegetables, on human health. The newly advanced ability to measure levels of lutein and zeaxanthin in the retina in vivo creates a unique opportunity to contribute some of this needed evidence.

Topics: Aging; beta Carotene; Cataract; Chronic Disease; Fruit; Heart Diseases; Humans; Lutein; Macular Degeneration; Neoplasms; Stroke; Tissue Distribution; Vegetables; Xanthophylls; Zeaxanthins

Antioxidants in foods and supplements are being widely promoted for their health benefits. Protection from heart disease is one claim that seems compelling in light of scientific evidence and large-scale observational studies. But will antioxidant supplements help your patients? To examine this question, Dr Tran reviews numerous clinical studies and evaluates the discrepancies between observational and clinical results.

Topics: Antioxidants; Ascorbic Acid; beta Carotene; Dietary Supplements; Heart Diseases; Humans; Vitamin E

Carotenoids are natural pigments which are synthesized by plants and are responsible for the bright colors of various fruits and vegetables. There are several dozen carotenoids in the foods that we eat, and most of these carotenoids have antioxidant activity. Beta-carotene has been best studied since, in most countries it is the most common carotenoid in fruits and vegetables. However, in the U.S., lycopene from tomatoes now is consumed in approximately the same amount as beta-carotene. Antioxidants (including carotenoids) have been studied for their ability to prevent chronic disease. Beta-carotene and others carotenoids have antioxidant properties in vitro and in animal models. Mixtures of carotenoids or associations with others antioxidants (e.g. vitamin E) can increase their activity against free radicals. The use of animals models for studying carotenoids is limited since most of the animals do not absorb or metabolize carotenoids similarly to humans. Epidemiologic studies have shown an inverse relationship between presence of various cancers and dietary carotenoids or blood carotenoid levels. However, three out of four intervention trials using high dose beta-carotene supplements did not show protective effects against cancer or cardiovascular disease. Rather, the high risk population (smokers and asbestos workers) in these intervention trials showed an increase in cancer and angina cases. It appears that carotenoids (including beta-carotene) can promote health when taken at dietary levels, but may have adverse effects when taken in high dose by subjects who smoke or who have been exposed to asbestos. It will be the task of ongoing and future studies to define the populations that can benefit from carotenoids and to define the proper doses, lengths of treatment, and whether mixtures, rather than single carotenoids (e.g. beta-carotene) are more advantageous.

Topics: Animals; Antioxidants; beta Carotene; Biological Availability; Carotenoids; Clinical Trials as Topic; Fruit; Heart Diseases; Humans; Neoplasms; Vegetables

Topics: Antioxidants; Ascorbic Acid; beta Carotene; Fruit; Heart Diseases; Humans; Neoplasms; Nutritional Requirements; Vegetables; Vitamin E; Vitamins

Topics: beta Carotene; Female; Fruit; Heart Diseases; Humans; Male; Neoplasms; Nutrition Policy; United States; Vegetables

5alpha-Reductase type 2, the predominant prostatic isozyme of this protein, converts testosterone to dihydrotestosterone. It has been hypothesized that individuals with greater 5alpha-reductase activity are at increased risk for prostate cancer (CaP). A single nucleotide polymorphism of the 5alpha-reductase type 2 gene (SRD5A2) gives rise to a substitution of leucine (leu) for valine (val) at codon 89 (V89L), the presence of which may affect serum androstanediol glucuronide (AAG) levels. We studied the effect of this polymorphism on the risk of prostate cancer in a prospective, nested, case-control design within the Physicians' Health Study. In all controls (n = 799), the leu allele frequency was 0.30. Among the 386 controls with plasma AAG levels available, there was no significant association between AAG levels and V89L genotype. We also detected no significant association between risk for CaP and genotype [odds ratio: val/val = 1.0 (reference), leu/val = 0.96 (95% confidence interval, 0.76-1.20), and leu/ leu = 0.84 (95% confidence interval, 0.57-1.24)]. These data do not support a moderate to large effect of the SRD5A2 V89L polymorphism on plasma AAG levels or CaP risk in this predominantly Caucasian cohort, although a small effect cannot be completely excluded.

Topics: 3-Oxo-5-alpha-Steroid 4-Dehydrogenase; Adult; Aged; Aged, 80 and over; Amino Acid Substitution; Anticarcinogenic Agents; Aspirin; beta Carotene; Boston; Double-Blind Method; Heart Diseases; Humans; Isoenzymes; Leucine; Male; Middle Aged; Neoplasms; Polymorphism, Genetic; Prostatic Neoplasms; Risk Factors; Valine; White People

Among apparently healthy men, elevated levels of C-reactive protein (CRP), a marker for systemic inflammation, predict risk of myocardial infarction and thromboembolic stroke. Whether increased levels of CRP are also associated with the development of symptomatic peripheral arterial disease (PAD) is unknown.. Using a prospective, nested, case-control design, we measured baseline levels of CRP in 144 apparently healthy men participating in the Physicians' Health Study who subsequently developed symptomatic PAD (intermittent claudication or need for revascularization) and in an equal number of control subjects matched on the basis of age and smoking habit who remained free of vascular disease during a follow-up period of 60 months. Median CRP levels at baseline were significantly higher among those who subsequently developed PAD (1.34 versus 0.99 mg/L; P=.04). Furthermore, the risks of developing PAD increased significantly with each increasing quartile of baseline CRP concentration such that relative risks of PAD from lowest (referent) to highest quartile of CRP were 1.0, 1.3, 2.0, and 2.1 (Ptrend=.02). Compared with those with no clinical evidence of disease, the subgroup of case patients who required revascularization had the highest baseline CRP levels (median= 1.75 mg/L; P= .04); relative risks from lowest to highest quartile of CRP for this end point were 1.0, 1.8, 3.8, and 4.1 (Ptrend=.02). Risk estimates were similar after additional control for body mass index, hypercholesterolemia, hypertension, diabetes, and a family history of premature atherosclerosis.. These prospective data indicate that among apparently healthy men, baseline levels of CRP predict future risk of developing symptomatic PAD and thus provide further support for the hypothesis that chronic inflammation is important in the pathogenesis of atherothrombosis.

Topics: Adult; Aged; Aged, 80 and over; Antioxidants; Arteriosclerosis; Aspirin; beta Carotene; Body Mass Index; C-Reactive Protein; Cyclooxygenase Inhibitors; Diabetes Mellitus; Double-Blind Method; Heart Diseases; Humans; Hypercholesterolemia; Intermittent Claudication; Male; Middle Aged; Myocardial Revascularization; Peripheral Vascular Diseases; Prospective Studies; Reference Values; Risk Factors

How retinol as a clinical indicator of vitamin A status is related to long-term mortality is unknown. Here we report the results of a prospective analysis examining associations between serum retinol and risk of overall and cause-specific mortality. During a 30-year cohort follow-up, 23,797 deaths were identified among 29,104 men. Participants with higher serum retinol experienced significantly lower overall, CVD, heart disease, and respiratory disease mortality compared to men with the lowest retinol concentrations, reflecting 17-32% lower mortality risk (P

Topics: Alcohol Drinking; alpha-Tocopherol; beta Carotene; Body Mass Index; Cause of Death; Heart Diseases; Humans; Prospective Studies; Vitamin A

Topics: Antioxidants; Arteriosclerosis; beta Carotene; Cholesterol, LDL; Dietary Supplements; Drug Therapy, Combination; Female; Free Radicals; Heart Diseases; Humans; Macular Degeneration; Male; Randomized Controlled Trials as Topic

Topics: Anticarcinogenic Agents; Asbestos; beta Carotene; Carotenoids; Controlled Clinical Trials as Topic; Heart Diseases; Humans; Lung Neoplasms; Neoplasms; Smoking

Topics: Animal Nutritional Physiological Phenomena; Animals; beta Carotene; Clinical Trials as Topic; Disease Models, Animal; Heart Diseases; Humans; Lung Neoplasms; Nutritional Physiological Phenomena; Research Design; Vitamin A

Topics: Ascorbic Acid; beta Carotene; Carotenoids; Heart Diseases; Humans; Male; Neoplasms