Immunity-building fruits and vegetables are rich in phytochemicals, helping build body immunity. Antioxidants present in plant-based foods reduce the risk of cell damage. Plant-based phytochemical-rich foods help regulate hormones such as estrogen, slow cancer cell growth, block inflammation, and help in immunity building.
Cruciferous vegetables such as broccoli, cauliflower, cabbage, related vegetables, lycopene found in tomato products, pink grapefruit, watermelon, and apricots protect against several types of cancers.
No single antioxidant molecule has been found to replace the health benefits of a combination of natural phytochemicals in fruits and vegetables. Consumers need to eat 5–10 servings of a wide variety of fruits and vegetables daily to mitigate the risk of chronic diseases and to meet nutrient requirements essential for optimum health (Liu, 2004).
Dietary phytochemicals act as modulators of cellular signals that trigger proteins that will make cells turn cancerous (Lee et al., 2001). In both preclinical animal models and human studies, dietary phytochemicals were cancer-preventive (Lee et al., 2013).
Turmeric (curcumin), red chili (capsaicin), cloves (eugenol), ginger (zerumbone), fennel (anethole), kokum (gambogic acid), fenugreek (diosgenin), black cumin (thymoquinone) contain chemicals—shown in the bracket after each herb—that prevent cancer (Aggarwal et al., 2008).
Broccoli and other cruciferous vegetables too are observed to reduce cancer risk in organs such as the colorectum, lung, prostate, and breast. This protection is attributed to the high glucosinolate molecules in such vegetables (Abdul et al., 2013).
Numerous scientific studies have shown that consuming fruits and vegetables significantly reduces cancer incidence. Other cancer-preventive molecules identified as chemopreventive include isothiocyanate, genistein, epigallocatechin gallate, lycopene, and resveratrol. The molecules are found in select herbs, fruits, and vegetables. Some of these have already been listed earlier (Russo et al., 2010).
While phytochemicals, nonnutritive chemicals found in plants and food, modulate cell signals and cause anticancer effects, the challenge is to develop personalized supplements of specific phytochemicals for each clinical situation (González-Vallinas et al., 2013). It is the emerging frontier of cancer-preventive research. Anticarcinogenic action is caused by phytochemicals impeding intracellular signals that trigger cancer (Surh, 2003).
Some phenolic compounds identified in medicinal herbs and dietary plants are phenolic acids, flavonoids, tannins, stilbenes, curcuminoids, coumarins, lignans, quinones, and others (Huang et al., 2009).
Whether a purified phytochemical has the same health benefit as a whole food or a mixture of foods, each with its unique phytochemicals. Most antioxidant activities of fruits and vegetables come from phenolics and flavonoids found in them. The additive and synergistic effects of phytochemicals in fruit and vegetables are responsible for their potent antioxidant and anticancer activity. The benefit of a diet rich in fruits and vegetables is attributed to the complex mixture of phytochemicals present in these whole foods (Liu, 2003).
Tea (Camellia sinensis) and tea components possess anticancer properties in experiments conducted on animal models (Yang et al., 2000). Flavones and isoflavones found in plants are immunity-building and contribute to cancer prevention (Birt et al., 2001).
Also, berries have been found to counteract, reduce, and repair damage caused by oxidative stress and inflammation. These fruits contain phytochemicals that help in immunity building and helping resist cancer. The polyphenol compounds in these fruits are- flavonoids, proanthocyanidins, ellagitannins, gallotannins, phenolic acids, stilbenoids, lignans, and triterpenoids (Seeram, 2008).