Provitamin A carotenoid intake and carotid artery plaques: the Atherosclerosis Risk in Communities Study

Serum carotenoids and atherosclerosis. The Rotterdam Study

High circulating levels of carotenoids have been thought to exhibit a protective function in the development of atherosclerosis. We investigated whether aortic atherosclerosis was associated with lower levels of the major serum carotenoids in alpha-carotene, beta-carotene, beta-cryptoxanthin, lutein, lycopene, and zeaxanthin-in a subsample of the elderly population of the Rotterdam Study. Aortic atherosclerosis was assessed by presence of calcified plaques of the abdominal aorta. The case-control analysis comprised 108 subjects with aortic atherosclerosis and controls. In an age- and sex-adjusted logistic regression model, serum lycopene was inversely associated with the risk of atherosclerosis. The odds ratio for the highest compared to the lowest quartile of serum lycopene was 0.55 (95% CI 0.25-1.22; p(trend)=0.13). Multivariate adjustment did not appreciably alter these results. Stratification by smoking status indicated that the inverse association between lycopene and aortic calcification was most evident in current and former smokers (OR=0.35; 95% CI 0.13-0.94; p(trend)=0.04). No association with atherosclerosis was observed for quartiles of serum concentrations of alpha-carotene, beta-carotene, lutein, and zeaxanthin. In conclusion, this study provides evidence for a modest inverse association between levels of serum lycopene and presence of atherosclerosis, the association being most pronounced in current and former smokers. Our findings suggest that lycopene may play a protective role in the development of atherosclerosis.

Antioxidants for vascular disease

The epidemiologic data do not support a strong role for vitamin C in reducing risk of coronary disease. The evidence supporting a protective effect for the family of dietary carotenoids is stronger, but any important protective effect attributable to the specific supplementation of beta-carotene can be excluded. Conversely, results from observational and experimental studies consistently support an effect of vitamin E supplementation on reducing risk of coronary heart disease. The evidence suggests that the major effect, if any, is found at supplemental intake levels at or greater than 100 IU/d. If confirmed in further trials, the net benefit of vitamin E supplementation among populations with existing coronary disease may be substantial, although the current available evidence is insufficient to warrant a change in public policy recommendations.

Beta-carotene and risk of coronary heart disease. A review of observational and intervention studies

The production of free radicals may favour the processes of atherosclerosis, and antioxidant vitamins (including beta-carotene), which partly prevent such processes, might favorably influence cardiovascular disease (CVD); thus, their supplementation might be a useful tool in the prevention of coronary heart disease (CHD). The relationship between beta-carotene and CHD has been investigated in several observational studies, including ecological, cohort and case-control studies. Six cohort studies reported relative risks (RR) of CHD between 0.27 and 0.78 for high beta-carotene levels (plasma/serum levels and dietary intake), but four more recent ones reported RR around unity (range 0.84 to 1.19). The evidence from case-control studies supports a role of beta-carotene in the prevention of CHD (odds ratios, OR, between 0.37 and 0.71), with a possible stronger protection for current smokers. The four published randomized clinical trials of beta-carotene supplementation found RR close to unity (range 0.96 to 1.26) for the relation between beta-carotene and CHD. The apparent discrepancy between observational and intervention studies may depend on several factors. The benefit reported in some observational studies may be related to consumption of foods rich in beta-carotene rather than beta-carotene itself, as foods rich in beta-carotene are usually rich also in other antioxidant vitamins and micronutrients, or to time-related factors, i.e., longer supplementation in intervention studies. Thus, a reasonable recommendation for the prevention of CHD for the general population is to consume a balanced diet with emphasis on antioxidant rich fruit and vegetables and whole grains.

Dietary carotenoids and certain cancers, heart disease, and age-related macular degeneration: a review of recent research

Key epidemiologic studies show associations between high dietary intakes of certain carotenoid-containing fruits and vegetables and reduced risk of prostate cancer, breast cancer, head and neck cancers, cardiovascular disease, and age-related macular degeneration, although overall the evidence is inconsistent. Little is known about the potential biochemical mechanisms whereby carotenoids might protect against disease, and human intervention trials are limited to high dose beta-carotene, which is not protective against lung cancer or cardiovascular disease. Authoritative scientific organizations continue to emphasize increased consumption of fruits and vegetables but do not make specific recommendations for carotenoids because of a lack of data that directly link them to disease reduction.

beta-Carotene, carotenoids and the prevention of coronary heart disease

The importance of low density lipoprotein (LDL) oxidation to the atherosclerotic process has led to the examination of beta-carotene as a possible preventive agent. Several epidemiologic studies show an inverse association between serum/adipose beta-carotene levels and coronary heart disease risk. Randomized clinical trials, however, have not shown any benefit, and perhaps even an adverse effect, of beta-carotene supplementation. A number of possible confounding factors may explain the inconsistency between the trials and epidemiologic evidence. Other carotenoids that are correlated with beta-carotene both in the diet and in the blood might be important factors, as might other plant-derived compounds. Alternatively, low serum carotenoid levels may reflect either increased lipoprotein density or the presence of inflammation, both factors emerging as important novel risk factors for coronary heart disease. Whereas the trial results support no preventive role for beta-carotene, the epidemiologic evidence does generally support the idea that a diet rich in high carotenoid foods is associated with a reduced risk of heart disease.