Young light- and water-stressed lettuce plants are subjects of K-State professor C.B. Rajashekar's research efforts to increase phytochemical content and health benefits of fruits and vegetables.Photo courtesy of Kansas State UniversityMANHATTAN, Kan. – According to the Centers for Disease Control and Prevention (CDC), nearly 70 percent of the U.S. population age 20 and older is overweight, with more than 35 percent of that population considered obese. Many people who are obese suffer from a number of degenerative health issues that need to be addressed and prevented, said C.B. Rajashekar, professor of food crops and phytochemicals in Kansas State University’s Department of Horticulture, Forestry and Recreation Resources.

“The United States, I think, health-wise, is not doing well compared to other developed countries,” he said.

A recent push by government agencies, such as the U.S. Department of Agriculture (USDA) and the CDC, has urged Americans to increase their intake of fruits and vegetables to help them eat healthier and combat obesity.

Finding solutions

Fruits and vegetables produce phytochemicals, a special set of chemicals that include antioxidants and can prevent some major diseases such as heart disease, cancer and obesity. Rajashekar said plants are the only living organisms, along with some microbes, that can produce these phytochemicals.

Rajashekar and his team of researchers, including graduate student Anju Giri, are working to improve the phytochemical content of fruits and vegetables, particularly lettuce and tomatoes.

“The plants accumulate these antioxidants and phytochemicals in response to stress,” Rajashekar said. “What we are trying to do is actually stress the plants, make them produce more of these antioxidants and phytochemicals, and thereby improve the nutritional quality of fruits and vegetables.”

Giri, a graduate research assistant in horticulture, said she has always been fascinated with plant science. She became acquainted with Rajashekar and wanted to be involved in his research.

Today, Giri said people are becoming more aware of the importance of adopting a healthy lifestyle to help prevent chronic and degenerative diseases.

“Improving quality of living by developing more nutritious, better-quality food, and the need and importance of research in this area are enticing factors for me to conduct research in this field,” Giri said.

Regulating stress

To stress the plants, Rajashekar said he utilizes “deficit irrigation,” which means providing just enough water for the plants to survive, decreases quantities of fertilizer, provides different levels and types of lighting that include ultraviolet (UV) light and light-emitting diodes (LED), and maintains low temperatures.

“If you have regulated stress, it is good in terms of quality, and it is good in terms of these health-promoting phytochemicals,” Rajashekar said. He adds that many of the practices can be applied in the field.

Most of Rajashekar’s research takes place in high tunnels at the K-State Olathe campus’ horticultural research station. High tunnels, similar to greenhouses, offer researchers greater control over conditions in which the plants are grown, extended growing seasons and protection from harsh climates. He compares enclosed cropping systems with traditional field cropping systems.

While high tunnel production increases the growing season and crop yields, Rajashekar said it might compromise health-promoting qualities and quantities of phytochemicals. High tunnels use a polyethylene-coated lining that blocks the sun’s UV radiation. That’s why Rajashekar is playing with light and exposing his plants to higher levels of red and UV light.

“So far it’s been really good,” he said. “UV is a very important component in increasing the phytochemical content.”

Healthy habits

Rajashekar said he is also comparing organic and conventional styles of cropping systems to determine if there are improved health benefits from consuming organically grown produce. Rajashekar and Giri’s research aims to increase the quality of fruits and vegetables grown in high tunnels and greenhouses, both organically and traditionally, to encourage Americans to eat healthier.

“Everyone wants to be healthy,” Giri said. “If such simple modifications of growing conditions can yield health-promoting benefits in humans, it can cover large groups of people—growers, scientists, industries, and ultimately consumers and communities. What could be more exciting than working with your own interests while bringing all these people together?”

Rajashekar said an important part of the research is breaking the mold of traditional research and trying new methods.

“For a long time, people in crop science, both in agronomy and in horticulture, have focused on yields, and quality has always been the secondary objective,” Rajashekar said.

Now, he said, people are more health conscious. “I think people are trying to watch what they eat and quality is an important part. That’s where our research comes in.”

More information about this research is available through papers co-authored by Rajashekar, available here, here and here.