Vegan diet is exclusively plant-based. It does not include dairy, fish, meat, fowl or any animal food.
Fruits and vegetables are rich in phytochemicals. These help in building body immunity.
We get exposed to oxidants from external sources too. Smoking, alcohol, certain drugs, deep fried, and fatty foods are other sources. We get exposed to oxidants through radiation, UV light, heat shock, and strong sunlight too. Other oxidant sources are air fresheners as well as vehicular and industrial pollutants. Oxidants interact with antioxidants, destroying these. Diet will need to have enough surplus antioxidants to counterbalance the loss from oxidants.
Oxidants are the most common of the cell damage-causing molecules. Oxidants are produced during healthy cellular metabolism. These normally help modulate inflammation, kill bacteria, detoxify toxins, and maintain good vascular (blood vessel) tone. Excess, unutilized oxidants damage cell membranes, lipids, and DNA. This damage gets repaired by antioxidants obtained from food.
Free oxidants that are not neutralized by antioxidants can cause degenerative disease such as atherosclerotic heart disease, diabetes, skin ailments, arthritis, neurodegenerative disorders, cancers, etc.
Cruciferous vegetables such as broccoli, cauliflower, cabbage, related vegetables, lycopene found in tomato products, pink grapefruit, watermelon, and apricots all provide protection from several types of cancers.
No single antioxidant molecule has been found that can replace the health benefits generated by a combination of natural phytochemicals found 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 observed to be 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 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 colorectum, lung, prostate, and breast. This protection is attributed to the presence of high amount of glucosinolates molecules found in such vegetables (Abdull et al., 2013).
This is just a summary of the cancer protection properties of plant-based diets. The role of dietary fiber in building the microbiome in the gut is another factor.
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