Processed fruits and vegetables have been long considered to have lower nutritional value than their fresh commodities due to the loss of vitamin C during processing. This research group found vitamin C in apples contributed < 0.4% of total antioxidant activity, indicating most of the activity comes from the natural combination of phytochemicals. This suggests that processed fruits and vegetables may retain their antioxidant activity despite the loss of vitamin C. Here it is shown that thermal processing elevated total antioxidant activity and bioaccessible lycopene content in tomatoes and produced no significant changes in the total phenolics and total flavonoids content, although loss of vitamin C was observed. The raw tomato had 0.76 +/- 0.03 micromol of vitamin C/g of tomato. After 2, 15, and 30 min of heating at 88 degrees C, the vitamin C content significantly dropped to 0.68 +/- 0.02, 0.64 +/- 0.01, and 0.54 +/- 0.02 micromol of vitamin C/g of tomato, respectively (p < 0.01). The raw tomato had 2.01 +/- 0.04 mg of trans-lycopene/g of tomato. After 2, 15, and 30 min of heating at 88 degrees C, the trans-lycopene content had increased to 3.11+/- 0.04, 5.45 +/- 0.02, and 5.32 +/- 0.05 mg of trans-lycopene/g of tomato (p < 0.01). The antioxidant activity of raw tomatoes was 4.13 +/- 0.36 micromol of vitamin C equiv/g of tomato. With heat treatment at 88 degrees C for 2, 15, and 30 min, the total antioxidant activity significantly increased to 5.29 +/- 0.26, 5.53 +/- 0.24, and 6.70 +/- 0.25 micromol of vitamin C equiv/g of tomato, respectively (p < 0.01). There were no significant changes in either total phenolics or total flavonoids. These findings indicate thermal processing enhanced the nutritional value of tomatoes by increasing the bioaccessible lycopene content and total antioxidant activity and are against the notion that processed fruits and vegetables have lower nutritional value than fresh produce. This information may have a significant impact on consumers' food selection by increasing their consumption of fruits and vegetables to reduce the risks of chronic diseases.

Epidemiological studies have consistently shown that regular consumption of fruits and vegetables is strongly associated with reduced risk of developing chronic diseases, such as cancer and cardiovascular disease. It is now widely believed that the actions of the antioxidant nutrients alone do not explain the observed health benefits of diets rich in fruits and vegetables, because taken alone, the individual antioxidants studied in clinical trials do not appear to have consistent preventive effects. Work performed by our group and others has shown that fruits and vegetable phytochemical extracts exhibit strong antioxidant and antiproliferative activities and that the major part of total antioxidant activity is from the combination of phytochemicals. We proposed that the additive and synergistic effects of phytochemicals in fruits and vegetables are responsible for these potent antioxidant and anticancer activities and that the benefit of a diet rich in fruits and vegetables is attributed to the complex mixture of phytochemicals present in whole foods. This explains why no single antioxidant can replace the combination of natural phytochemicals in fruits and vegetables to achieve the health benefits. The evidence suggests that antioxidants or bioactive compounds are best acquired through whole-food consumption, not from expensive dietary supplements. We believe that a recommendation that consumers eat 5 to 10 servings of a wide variety of fruits and vegetables daily is an appropriate strategy for significantly reducing the risk of chronic diseases and to meet their nutrient requirements for optimum health.

Epidemiological studies have shown that consumption of whole grains and grain-based products is associated with reduced risk of chronic diseases. The health benefits of whole grains are attributed in part to their unique phytochemical composition. However, the phytochemical contents in grains have been commonly underestimated in the literature, because bound phytochemicals were not included. This study was designed to investigate the complete phytochemical profiles in free, soluble conjugated, and insoluble bound forms, as well as their antioxidant activities in uncooked whole grains. Corn had the highest total phenolic content (15.55 +/- 0.60 micromol of gallic acid equiv/g of grain) of the grains tested, followed by wheat (7.99 +/- 0.39 micromol of gallic acid equiv/g of grain), oats (6.53 +/- 0.19 micromol of gallic acid equiv/g of grain), and rice (5.56 +/- 0.17 micromol of gallic acid equiv/g of grain). The major portion of phenolics in grains existed in the bound form (85% in corn, 75% in oats and wheat, and 62% in rice), although free phenolics were frequently reported in the literature. Ferulic acid was the major phenolic compound in grains tested, with free, soluble-conjugated, and bound ferulic acids present in the ratio 0.1:1:100. Corn had the highest total antioxidant activity (181.42 +/- 0.86 micromol of vitamin C equiv/g of grain), followed by wheat (76.70 +/- 1.38 micromol of vitamin C equiv/g of grain), oats (74.67 +/- 1.49 micromol of vitamin C equiv/g of grain), and rice (55.77 +/- 1.62 micromol of vitamin C equiv/g of grain). Bound phytochemicals were the major contributors to the total antioxidant activity: 90% in wheat, 87% in corn, 71% in rice, and 58% in oats. Bound phytochemicals could survive stomach and intestinal digestion to reach the colon. This may partly explain the mechanism of grain consumption in the prevention of colon cancer, other digestive cancers, breast cancer, and prostate cancer, which is supported by epidemiological studies.

Cardiovascular disease and cancer are ranked as the first and second leading causes of death in the United States and in most industrialized countries. Regular consumption of fruit and vegetables is associated with reduced risks of cancer, cardiovascular disease, stroke, Alzheimer disease, cataracts, and some of the functional declines associated with aging. Prevention is a more effective strategy than is treatment of chronic diseases. Functional foods that contain significant amounts of bioactive components may provide desirable health benefits beyond basic nutrition and play important roles in the prevention of chronic diseases. The key question is whether a purified phytochemical has the same health benefit as does the whole food or mixture of foods in which the phytochemical is present. Our group found, for example, that the vitamin C in apples with skin accounts for only 0.4% of the total antioxidant activity, suggesting that most of the antioxidant activity of fruit and vegetables may come from phenolics and flavonoids in apples. We propose that the additive and synergistic effects of phytochemicals in fruit and vegetables are responsible for their potent antioxidant and anticancer activities, and that the benefit of a diet rich in fruit and vegetables is attributed to the complex mixture of phytochemicals present in whole foods.

Consumption of fruits and vegetables has been associated with reduced risk of chronic diseases such as cardiovascular disease and cancer. Phytochemicals, especially phenolics, in fruits and vegetables are suggested to be the major bioactive compounds for the health benefits. However, the phenolic contents and their antioxidant activities in fruits and vegetables were underestimated in the literature, because bound phenolics were not included. This study was designed to investigate the profiles of total phenolics, including both soluble free and bound forms in common fruits, by applying solvent extraction, base digestion, and solid-phase extraction methods. Cranberry had the highest total phenolic content, followed by apple, red grape, strawberry, pineapple, banana, peach, lemon, orange, pear, and grapefruit. Total antioxidant activity was measured using the TOSC assay. Cranberry had the highest total antioxidant activity (177.0 +/- 4.3 micromol of vitamin C equiv/g of fruit), followed by apple, red grape, strawberry, peach, lemon, pear, banana, orange, grapefruit, and pineapple. Antiproliferation activities were also studied in vitro using HepG(2) human liver-cancer cells, and cranberry showed the highest inhibitory effect with an EC(50) of 14.5 +/- 0.5 mg/mL, followed by lemon, apple, strawberry, red grape, banana, grapefruit, and peach. A bioactivity index (BI) for dietary cancer prevention is proposed to provide a new alternative biomarker for future epidemiological studies in dietary cancer prevention and health promotion.