The journal Circulation reports that California researchers have demonstrated both in vivo and in vitro that the carotenoid lutein seems to protect arterial tissue from the oxidative damage that leads to heart disease.

Plant pigment provides buffer

In the first study, the researchers analyzed data collected as part of the Los Angeles Atherosclerosis Study on 462 middle-aged men and women with no history of heart disease. Ultrasound was used to determine the intima-media thickness (IMT) of their carotid arteries at the beginning and end of the 18-month study. Serum lutein was measured at the same time points. They found a strong inverse association between serum lutein status and degree of change in IMT over the course of the study. Considering all participants, those in the highest quintile of serum lutein showed almost no change in IMT over the 18-month period (0.004±0.005 mm), while those in the lowest quintile showed a progression of 0.021±0.005 mm (p= 0.01). This trend held for both non-smokers (p= 0.03) and smokers (p= 0.005).

In a second study, they exposed endothelial and smooth muscle cells from human aortas first to lutein--in increasing concentrations--and then to LDL cholesterol. This produced a strong dose-dependent response, where higher doses of lutein were better able than low doses to retard oxidative damage to the cells.

In the third study, mice deficient in apolipoprotein E (apo E) were fed either standard chow or chow with lutein. In addition, LDL receptor-null mice were fed either a high-cholesterol 'Western' diet or high cholesterol diet plus lutein. In the apo E-deficient mice, lutein supplementation reduced the level of lipid hydroperoxides by 30% (p= 0.05). In the LDL receptor-null mice, lutein supplementation reduced arterial lesions by 43%, relative to the non-supplemented mice.

Translating science to practice

All three experiments showed the apparent ability of lutein to slow the progression of LDL-mediated oxidative damage.

The part of this research most easily translated into diet advice is, of course, the epidemiologic data. But as in any observational studies involving humans, it can be difficult to determine the effect of one nutrient independent of all the other dietary and lifestyle factors that influence health. Participants in the highest quintile for lutein, for instance, likely consumed a higher-than-average amount of antioxidant-rich fruits and vegetables. Such a diet also tends to be lower in fat and higher in fiber than a standard 'Western' diet, all factors that would contribute to heart health.

Lutein has appeared in the news in recent years as an antioxidant that may protect against age-related macular degeneration. As with this current research, the health benefits are associated with lutein from foods rather than from dietary supplements. The most common dietary sources of lutein in the Western diet are spinach and kale, with lesser amounts found in other fruits and vegetables and in egg yolks. Greens are not dietary staples for many consumers, however, so there is the temptation to bypass foods in favor of lutein in pill form. But no research to date warrants the use of supplements in place of foods.

Consumer advice

Individuals who are trying to reduce their risk of heart disease are better served by choosing a more plant-based diet that includes a variety of deep-colored fruits and vegetables. That way, they are consuming not only more lutein, but also more of all the antioxidant nutrients that likely help guard against the progression of heart disease.