
Xanthophyll, dihyroxycarotenoid, nonprovitamin A carotenoid
A natural pigment synthesized by plants and microorganisms, lutein is used primarily as an antioxidant and also to prevent and treat cancer, heart disease, and macular degeneration. Lutein has antioxidant (1) (21) and anti-inflammatory (22) effects. It is classified as a nonprovitamin A carotenoid, which also includes lycopene and zeaxanthin. Alpha-carotene, beta-carotene, and beta-cryptoxanthin are classified as provitamin A carotenoids because they can be converted into retinol.
Epidemiologic studies suggest an inverse relationship between increased lutein consumption and decreased incidence of atherosclerosis (2) and cataracts (3) (4) although the effects of dietary lutein on macular degeneration are inconsistent (5) (6) (7). Conclusions from a systematic review and meta-analysis suggest that the current evidence is insufficient to support use of lutein and other dietary antioxidants to prevent early age-related macular degeneration (7) (8).
Inverse associations have been reported between lutein consumption and risk of colon cancer (9), renal cell carcinoma (19) and nonaggressive urothelial cell carcinoma (20). A recent meta-analysis found a modest association between dietary lutein and colorectal cancer (10). Data on the effects of dietary lutein intake and cervical cancer risk are conflicting, (11) (12) whereas no association was found between lutein and lung cancer risk (13).
Kale, spinach, winter squash, cruciferous vegetables, cabbage, green beans, yellow/orange fruits, mangoes, papayas, peaches, oranges (1)
Lutein is a natural pigment synthesized by plants and microorganisms. Lutein accumulates in the retina and lens, and has been associated with a decreased risk of macular degeneration and cataracts (14). Although the physiologic function of lutein in the macular membranes is not known, it is hypothesized that it may protect the retina from oxidative damage (15) (16). Referred to as a nonprovitamin A carotenoid, it is not known to have any vitamin A activity.
Lutein is associated with reduced risk of atherosclerosis (2).
Carotenoids also have antioxidant, immune enhancing properties, inhibit mutagenesis and transformation, and inhibit premalignant lesions (1). Lutein-mediated AP-1 suppression and anti-inflammatory activity have been shown to be due to its strong antioxidative and p38/c-Jun-N-terminal kinase (JNK) inhibitory activities (22).
Current data suggest an association between lutein and decreased risk of colon cancer (9).
In another study of N-nitrosodiethylamine-induced hepatocellular carcinoma (HCC) in rats, lutein was shown to reduce the activity of γ-glutamyl transpeptidase, a marker of cellular proliferation (21).
Absorption:
Intestinal absorption of carotenoids, including lutein, is facilitated by the formation of bile acid micelles containing carotenoids. The presence of fat in the small intestine stimulates the secretion of bile acids from the gall bladder and improves the absorption of carotenoids by increasing the size and stability of the micelles, thus allowing more carotenoids to be solubilized. Bioavailability of lutein is affected by the dose and presence of other carotenoids such as Beta carotene. The bioavailability of lutein from vegetables is approximately 70% (16).
Distribution:
The concentrations of various carotenoids in human serum and tissues are highly variable and depend on food sources, efficiency of absorption, and amount of fat in the diet. Lutein is transported by high-density lipoprotein (HDL) and, to a lesser extent, by very low-density lipoprotein. The serum concentration of carotenoids after a single dose peaks at 24 to 48 hours post dose. The average lutein concentration in human serum is 280 nM (1). Lutein is primarily stored in adipose and the liver. Of all the carotenoids circulating in the body, only two polar species, lutein and zeaxanthin, are contained in the macula (17).
Metabolism/Excretion:
It is assumed that lutein is excreted through the bile and kidneys (14).
Christen WG, et al. Dietary carotenoids, vitamins C and E, and risk of cataract in women: a prospective study. Arch Ophthalmol. Jan 2008;126(1):102-109.
To determine the effects of dietary carotenoids on cataract formation in women, this prospective observational study was undertaken with 35,551 female participants for 10 years. Cataract formation and visual acuity were the primary outcome measures. Reduced risk of cataract formation (18%) was associated with increased dietary lutein/zeaxanthin intake. Randomized, clinical trials of lutein/zeaxanthin in both men and women are necessary to determine if lutein supplementation may also reduce cataract risk.
Ros MM, Bueno-de-Mesquita HB, Kampman E, et al. Plasma carotenoids and vitamin C concentrations and risk of urothelial cell carcinoma in the European Prospective Investigation into Cancer and Nutrition. Am J Clin Nutr. 2012 Oct;96(4):902-10.
This study invovled 856 patients with newly diagnosed urothelial cell carcinoma (UCC) who were were matched with 856 cohort members by sex, age at baseline, study center, date and time of blood collection, and fasting status. Plasma carotenoids including alpha and beta carotenes, beta-cryptoxanthin, lycopene, lutein, and zeaxanthin were measured by using reverse-phase HPLC. The plasma vitamin C was measured by a colorimetric assay. Incidence rate ratios (IRRs) were estimated by using conditional logistic regression with adjustment for smoking status, duration, and intensity. Researchers report that the risk of UCC decreased with greater concentrations of plasma carotenoids (IRR for the highest compared with the lowest quartile: 0.64; 95% CI: 0.44, 0.93; P-trend = 0.04). Plasma lutein was inversely associated with risk of nonaggressive UCC (IRR: 0.56; 95% CI: 0.32, 0.98; P-trend = 0.05). Plasma beta-carotene was also inversely associated with aggressive UCC (IRR: 0.51; 95% CI: 0.30, 0.88; P-trend = 0.02), but no association was observed between plasma vitamin C and risk of UCC.
Plasma lutein and beta-carotene may reduce the risk of UCC.
Bottom Line: Current evidence is not sufficient to know if lutein is useful in preventing macular degeneration. A diet containing lutein-rich fruits and vegetables may lower the risk of colon cancer.
Lutein is a natural pigment synthesized by plants and microorganisms. Because it is an antioxidant, cancer prevention activity has been proposed, but no studies have proved this. Scientists also think that lutein may stimulate the immune system, inhibit the mutation of DNA, or inhibit the growth of pre-cancerous cells. Lutein has been associated with a decreased risk of macular degeneration and cataracts, although researchers are uncertain how lutein exerts this effect. In addition, studies in animals and human subjects have shown that high lutein intake can prevent the progression of atherosclerosis.
Cataracts:
In this large study, 35,551 female participants were followed for 10 years to compare the intake of dietary lutein and cataract. Women who reported high dietary consumption of lutein were less likely to develop cataract, indicating that eating lutein-rich foods may reduce risk of cataract. Further clinical studies of patients taking lutein supplements or placebo are needed to determine if these protective effects were due to dietary lutein alone.
Cancer Prevention:
This study invovled 856 patients with newly diagnosed urothelial cell carcinoma (UCC) who were were matched with 856 members by sex, age at baseline, study center, date and time of blood collection, and fasting status. Plasma carotenoids that were measured included alpha and beta carotenes, beta-cryptoxanthin, lycopene, lutein, and zeaxanthin. Researchers report that the risk of UCC decreased with greater concentrations of plasma lutein and beta-carotene.