The new frontier of today's preventive medicine is in your salad.

Many epidemiological and clinical studies have established the benefits of vegetables and fruits in the human diet in prevention of major diseases, including cancer and heart disease. A UConn plant science doctoral student has found that the ingredients that make vegetables and fruits prevent the occurrence and progression of these major diseases, called phytochemicals, can be enhanced by controlling the growing conditions to provide greater health-promoting and disease-preventing properties.

"Phytochemicals occur naturally in plants. A salad is more appetizing and enjoyable to consume than when swallowed as a pill," said Usha R. Palaniswamy, who earned an award from the American Society of Horticultural Science for a portion of her Ph.D. research. "My studies show that concentrations of these chemicals can be altered by environmental conditions such as plant nutritional balance, temperature and light intensity."

Palaniswamy studied two potential salad crops, purslane and watercress, which could become major sources of preventive medicine in the future.

"Among the 13,000 known edible plants, less than 20 are currently being used to provide most of our food needs," she said. "Perhaps it is time to broaden our food base and look for alternative and better sources of the phytonutrients."

Purslane (Portulaca oleracea) was recently identified as the richest terrestrial source of alpha-linolenic acid (LNA), more commonly known as "fish oil," she said. This omega-3 fatty acid plays an essential role in normal human growth, development and in prevention of diseases such as heart disease, hypertension, cancer and inflammatory and auto-immune disorders such as arthritis, psoriasis, and ulcerative colitis.

Purslane, rated as the eighth most common plant in the world, is a common vegetable in the Middle East and Asia. It has been described as the "power food of the future" because of its high nutritive and anti-oxidant properties, Palaniswamy said. It is an excellent source of vitamin E, beta-carotene, ascorbic acid, glutathione, pectin and the essential amino acids. Also, it is the only one among those studied to have eicosapentenoic acid (EPA), which is found in fish and fish oils.

Watercress, a salad crop commonly used as an herb, contains a chemical called phenethyl isothiocyanate (PEITC) that can prevent the progression of cancer caused by tobacco-specific carcinogens. It is also a rich source of vitamins A and C.

Palaniswamy's research shows that the concentration of LNA in purslane leaves and of PEITC in watercress leaves can be optimized by controlling specific conditions during the growth of the crop.

"Our findings indicate that the environmental conditions that produce the highest yield do not necessarily produce the highest phytochemical concentration," she said. "My objectives now are to identify and characterize the environmental conditions and cultural methods that a greenhouse grower can adopt to enhance the nutriceutical content in these salad greens and thus add value in terms of health benefits to the consumer."

Palaniswamy, a native of Madras, India, earned third place in the graduate student poster competition at the 94th international conference of the American Society of Horticultural Science for her presentation entitled, "Omega-3 fatty acid in Portulaca oleracea L. is altered by the source of nitrogen in hydroponic solution." The presentation, which represented a portion of her Ph.D. research and was co-authored by her academic advisors in the plant science department, Associate Professor Richard McAvoy and Professor Bernard Bible, described the best form and ratio of nitrogen to increase purslane's phytochemical content.

Palaniswamy also has an internship in the Office of University Communications this semester and is writing for the Advance.

Renu Sehgal-Aldrich