The researchers did not look at beta-carotene or carotenoid intake specifically. The one third of subjects with the highest intake of carrots had an odds ratio of 0.4 for developing coronary heart disease compared to the third with the lowest intake. If you control for all the foods the study measured, this risk reduction is somewhat attenuated but still significant. Looking at green vegetables and fresh fruit, there is again a suggestion that something in these foods reduces coronary heart disease. The carotenoids are one of many plausible reasons for these findings, but of course fruits and vegetables also contain many other phytochemicals and other compounds.
Prospective studies are more credible than case-control studies in some ways.
The differences were highly significant. To approach these questions, let us turn to studies that have collected data specifically on carotenoid intake. Rather than using coronary heart disease as the outcome, the investigators measured carotid wall thickness, which has been shown to be correlated with risk of coronary disease. The bottom section of the table gives an estimate of provitamin A based on a food frequency questionnaire. This reflects total carotenoid intake, not only beta-carotene.