Lutein in Corn and Sweet Potatoes

Linda F. Benedict, Prinyawiwatkul, Witoon, Losso, Jack N., Godber, J. Samuel, Labonte, Don R., King, Joan M.

Jack N. Losso, Don LaBonte, J. Samuel Godber, Joan M. King and Witoon Prinyawiwatkul

Macular (a region of the retina) degeneration is a physiological process that involves the formation of excessive new blood vessels in the retina and is the leading cause of cataract formation, glaucoma and irreversible blindness in diabetic patients and the elderly. The exact cause of age-related macular degeneration (AMD) is not yet known. There are few effective treatments, little prevention and no real cures for these debilitating conditions. Because potential cures are limited and costly, the role of nutrition in preventing these chronic diseases is receiving significant scientific scrutiny.

Lutein has been identified and recognized as one of the dietary strategies (natural sunglasses) that can delay the onset and progression of macular degeneration. The human body easily absorbs lutein and deposits it in the region of the retina called the macula and in the lens of the eye where lutein is able to filter light and prevent oxidation of proteins or lipids within the lens. Epidemiological evidence that supports the inverse relationship between lutein and AMD is consistent. Studies have shown 20 percent to 50 percent lower risk of cataract extraction in people with lutein intake. Lutein also has been shown to be inversely related to the risk of colon cancer in men and women diagnosed with the disease at a younger age. Epidemiological observations have shown that individuals with high levels of serum lutein had a significantly reduced risk of developing coronary heart disease or ischemic stroke. Lutein also binds to aflatoxin and reduces the toxicity of aflatoxin in grain crops like corn.

Eat Green Vegetables
Lutein is an orange-colored pigment, which is highly concentrated in marigold flowers. High levels of lutein are found in kale and spinach, and low levels are found in many other green vegetables. The human body does not synthesize lutein, so it has to be absorbed from external sources. Ingested lutein deposits in the macular region, where it contributes to the density of macular pigment and may prevent macular degeneration. The denser the pigment, the more protection there is from damage caused by natural light in the blue spectrum. Lutein is more effective than other carotenoids in preventing lipid oxidation, a deteriorative process that occurs in the human serum and in the eye.

Researchers have reported that consuming 6 milligrams of lutein a day was associated with a 43 percent lower risk of macular degeneration and increasing the consumption of foods rich in certain carotenoids, in particular darkgreen, leafy vegetables, may decrease the risk of developing AMD. A concentration of 6 milligrams lutein represents about 30 grams of kale or 60 grams of fresh spinach. Other foods containing smaller amounts of lutein include summer squash, green peas, corn and tomatoes.

Potential Lutein Sources
LSU AgCenter research has focused on commodities grown in Louisiana as potential sources of lutein that could add value to Louisiana crops. Corn is an economically viable source of lutein, because during lutein isolation, other value-added products such as oil, proteins and starch can be extracted. Corn varieties are being screened for lutein content. To date three corn samples from varieties DK 697, DKC 68-70 and AP 9843 have been analyzed. More varieties are being screened.

Grits with Lutein
Adding lutein to food is more appealing than using lutein as pills. AgCenter research has demonstrated that lutein can be added to a food product and remain stable during processing. One study involves adding lutein to corn grits and analyzing lutein content after microwave cooking the grits. Lutein was added to corn grits at concentrations reported to reduce the incidence of macular degeneration (cataract formation) by 43 percent. A lutein concentration equivalent to 6 milligrams per serving size was added to corn grits. Lutein was dissolved in ethanol or corn oil and added to corn grits in water. After microwaving the grits, the lutein remained stable.

AgCenter researchers are trying to formulate minimally processed food products that contain high levels of lutein so consumers can obtain their daily intake of lutein.

Sweet Potatoes
AgCenter scientists in the Food Science and Horticulture departments are examining sweet potato leaves and roots as potential sources of lutein. To date, research shows that sweet potato leaves contain more lutein than sweet potato roots. Sweet potato roots are well known for their high content of betacarotene, and this work shows additional health benefits in sweet potatoes. Bienville, a 2002 LSU AgCenter release, shows particularly high levels of lutein in comparison to other varieties. The high lutein content in sweet potato leaves offers a further possibility of value-added. Additional research is needed to understand the economic feasibility of extracting lutein from sweet potato leaves.

Jack N. Losso, Assistant Professor, Department of Food Science; Don LaBonte, Professor, Department of Horticulture; J. Samuel Godber, Professor; Joan M. King, Assistant Professor; and Witoon Prinyawiwatkul, Associate Professor, Department of Food Science, LSU AgCenter, Baton Rouge, La.

(This article appeared in the fall 2002 issue of Louisiana Agriculture.)

11/1/2012 11:10:37 PM
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