To decide which foods are most beneficial to eat raw, one must keep in mind which nutrients are lost through heat and then make their choice based on these criteria. Cooking, as opposed to sprouting or lacto-fermentation, leads to a loss of heat-sensitive vitamins, enzymes, phytonutrients, prebiotics, and probiotics that are altered or destroyed by heat.
Here are some foods that should be eaten raw:
Bell Peppers: Raw bell peppers contain more vitamin C than cooked bell peppers because vitamin C is a heat-sensitive vitamin. Bell peppers also contain capsaicin, a compound that gives peppers their spiciness and is associated with various health benefits, including reducing pain and inflammation. Capsaicin is more concentrated in raw bell peppers.
Broccoli should be eaten raw, for example in a broccoli tabbouleh, a classic of raw food nutrition, or as broccoli sprouts. Broccoli contains a compound called glucoraphanin, which can be converted into sulforaphane, a compound with anti-cancer properties. Broccoli needs to be chopped and/or chewed for this conversion to take place, and heat inactivates the enzyme that catalyzes the conversion of glucoraphanin to sulforaphane. Read our article on this topic here.
Garlic: Raw garlic has shown antibacterial and antifungal effects. Allicin is a sulfur-containing compound that forms when garlic is chopped, crushed, or chewed. Allicin gives garlic its characteristic smell and taste and is also associated with many of garlic's health benefits, including antimicrobial and cardiovascular effects. Allicin is quite unstable and heat-sensitive. Cooking can break down allicin. One study found that roasting or steaming garlic for 6-10 minutes reduced the allicin content by more than 90%.
Nuts and Seeds: In general, nuts and seeds are rich in vitamins that are lost during cooking. To optimize the nutrient content of seeds, it is better to sprout them rather than consume them unsprouted or as flour.
Red Onions: Raw red onions contain compounds that have anti-inflammatory effects and may protect against cancer. Cooking reduces the content of these compounds.
Fruits and Vegetables Rich in Vitamin C: In general, all foods like citrus fruits, berries, kiwi, melon, bell peppers, and broccoli are rich in vitamin C, which is heat-sensitive. Consuming these foods raw can help maximize their vitamin C content.
Sources:
Akter S. et al. (2016). Is raw better? A systematic review and meta-analysis of clinical trials of raw (uncooked) food diets. Journal of the Academy of Nutrition and Dietetics, 116(12), 1978-1988.
Bongoni, R., et al. (2014). Red onions: thermal effects on pungency, sugars, and antioxidant activity. Food Science and Nutrition, 2(3), 213-219.
Nutrient loss during cooking. (n.d.). Retrieved from Harvard Health Publishing: www.health.harvard.edu/staying-healthy/nutrient-loss-during-cooking
Vallejo, F., Tomás-Barberán, F. A., & García-Viguera, C. (2002). Glucosinolates and vitamin C content in edible parts of broccoli florets after domestic cooking. European Food Research and Technology, 215(4), 310-316.
Verkerk, R., Schreiner, M., Krumbein, A., Ciska, E., Holst, B., Rowland, I., ... & Dekker, M. (2009). Glucosinolates in Brassica vegetables: the influence of the food supply chain on intake, bioavailability and human health. Molecular nutrition & food research, 53(S1), S219-S265.
Song, K., & Milner, J. A. (2001). The influence of heating on the anticancer properties of garlic. The Journal of nutrition, 131(3), 1054S-1057S.
Lawson, L. D., & Gardner, C. D. (2005). Composition, stability, and bioavailability of garlic products used in a clinical trial. Journal of agricultural and food chemistry, 53(16), 6254-6261.