White Vegetables : A Forgotten Source of Nutrients In Nutrition , Can We “ See ” What Is Good for Us ? 1 – 3

The selection of foods to eat is a complex interplay of vision, taste, smell, and texture. In addition to microand macronutrients, plant-based foods also contain several classes of phytochemicals. In many cases, the phytochemicals account for the various colors of foods. Although aesthetically pleasing, the color of foods may mislead consumers as to their phytochemical content, which is particularly true with regard to polyphenols. Polyphenols are a broad class of compounds with antioxidant and other health benefits. Human vision is limited to a small window (390–765 nm) of the electromagnetic spectrum. Many important phytochemicals (e.g., vitamin C) have no absorbance in this range. Therefore, the human eye cannot directly judge the vitamin C content of foods. Being able to see in the ultraviolet range allows bees to locate the pollen-rich region of flowers, whereas pit vipers locate their prey by being able to “see” them in the infrared range. Assessing the impact of phytochemicals on human health depends on several factors. Colorless phytochemicals in unprocessed foods may be lost during the cooking process because no visual guide exists to ensure their retention. The molecular structures of phytochemicals influence the extent to which they are altered by cooking processes and the methods by which they are absorbed from the gastrointestinal tract. Extensive metabolism by phase I/II enzymes and by the gut microbiome may also create compounds that the eye is never allowed to appreciate. Adv. Nutr. 4: 327S–334S, 2013. Introduction Knowledge concerning which foods are suitable for eating was gained by trial and error over tens of thousands of years. With the introduction of agricultural practices, food availability became more certain. Before the arrival of national and international travel, food choices were determined by the plants and animals that could be domesticated within the region, local environmental conditions that affect crop growth (altitude, latitude, temperature, and available water supply), seasonal changes, food storage capabilities between seasons (and sometimes years), and the nature of the foods themselves (i.e., taste, texture, and smell). Through modern interstate and international travel, a wide variety of foods is now available to almost all societies, providing a far greater choice of foods than ever before. In addition tomacronutrients (carbohydrates, fats, proteins, and fiber) and micronutrients (vitamins and minerals), all plant-based foods contain phytochemicals that form the nonnutritive part of the diet. These secondary metabolites are produced for the benefit of the plant rather than for the consumer. However, these phytochemicals may also affect the health of the consumer. Beneficial effects may be derived from carotenoids, flavonoids, and other phytochemicals. Consuming whole foods with their associated phytochemicals may provide greater health benefits due to synergistic effects between the phytochemicals (1). However, phytochemicals also include alkaloids and polyketides with undefined or even toxic effects, and this factor must be considered when making food choices. Role of color in foods Some researchers have emphasized the role of color in the optimal selection of foods (2). Color can improve the aesthetics of foods, and consuming colorful foods is considered 1 Published in a supplement to Advances in Nutrition. Presented at the Purdue University Roundtable on “White Vegetables: A Forgotten Source of Nutrients” held June 18–19, 2012 in Chicago, IL. The roundtable was sponsored by Purdue University. The roundtable and supplement publication were supported by an unrestricted grant from the Alliance for Potato Research and Education. All roundtable speakers received travel funding and an honorarium for participation in the meeting and manuscript preparation. The views expressed are those of the authors. The supplement coordinator was Catherine Nnoka, a paid consultant to the Alliance for Potato Research and Education. Guest editor Connie Weaver received compensation from the Alliance for Potato Research and Education for travel expenses, manuscript preparation, and editorial services for the supplement publication. Guest editor Cheryl Anderson received compensation from the Alliance for Potato Research and Education for editorial services. 2 Operation of the UAB Targeted Metabolomics and Proteomics Laboratory is supported in part by grants from the UAB Skin Disease Research Center (C. Elmets, PI–P30AR50948) and the UAB-UCSD O’Brien Center for Acute Kidney Injury (A. Agarwal, PI P30 DK079337). 3 Author disclosures: S. Barnes, J. Prasain, and H. Kim, no conflicts of interest. * To whom correspondence should be addressed. E-mail: sbarnes@uab.edu. ã2013 American Society for Nutrition. Adv. Nutr. 4: 327S–334S, 2013; doi:10.3945/an.112. 003558. 327S at N O R T H D A K O T A S T A T E U N IV E R S IT Y on M ay 0, 2015 advannutrition.org D ow nladed fom