Which foods contain more nutrients – raw or cooked? The answer isn’t as clear as you might expect. There are many different food preparation methods, with some involving heat to bake, steam, roast, or fry; we eat other foods raw, and some foods dried or sprouted. Each food preparation method has benefits, and the quest to identify the best way to prepare foods to preserve as many nutrients as possible is still underway.When did we start cooking our food?No one knows exactly when humans started using fire to cook food, but historians believe that fire was first routinely used around 1 million years ago. All known human societies eat cooked foods and many biologists believe that developing fire to cook foods was a key change that allowed humans to develop a larger brain with a direct impact on how we evolved as a species. The brain needs more energy for its size than any other organ in our body, and some scientists theorize that developing a larger brain hinged on ancient humans being able to cook food. Cooking foods like meats, potatoes, and grains makes them much easier to chew and digest, which provides more calories for energy.What is a raw foods diet?The raw food diet has been around since the mid-19th century when Sylvester Graham promoted the idea that people would never become ill if they only consumed uncooked foods. Graham was an early supporter of a vegetarian diet to promote health and prevent disease and several of his theories continue today in recommendations for an eating style that is based on whole plants and high in fiber.A raw foods diet is based on a vegan diet that includes fruits, nuts, seeds, and sprouted grains and beans. The actual amount of raw food consumed ranges from 50% to 100% of total calories. The only “cooking” that is allowed is via a food dehydrator that blows hot air through the food at temperatures no higher than 118°F.Proponents of a raw food diet believe that cooking destroys the enzymes needed to digest food, making cooked food less nutrient-dense.To cook or eat raw?Cooking foods can decrease water-soluble and heat-sensitive nutrients like vitamin C and some types of antioxidants. Different types of cooking methods have varying effects and in general more nutrients are lost with higher cooking temperatures, longer cooking times, and immersing foods in water. For example, water-soluble antioxidants called glucosinolates in cauliflower and broccoli are lost during boiling, but unchanged with steaming.However, cooking some vegetables actually increases the ability of our body to digest some types of nutrients, such as the carotenoids in carrots and lutein in tomatoes. Cooking also kills harmful microbes that can cause food poisoning.The raw foods diet theory that cooking destroys the enzymes in foods necessary for digestion and nutrient absorption is false. Our body produces enzymes to digest food and absorb nutrients, and the enzymes in foods are deactivated by stomach acidity.A meta-analysis of nutrient intakes of people who eat raw food vs cooked food showed that some beneficial nutrients are higher when people eat a raw foods diet: fiber, vitamins A, B6, C and E; folate, copper and potassium. However, some nutrients are lower: protein, vitamin B12, phosphorus, and zinc. People who eat a raw foods diet tend to consume less total fat, saturated fat, and cholesterol primarily because they are not eating animal products or dairy foods that are higher in these nutrients. They also tend to consume less sodium because they are not eating processed foods.There is currently no research on any nutrient differences between people who eat a raw diet and those who eat a cooked vegan diet. In general, people who eat a plant-based diet have lower rates of heart disease, high blood pressure, obesity and diabetes.The bottom line: Numerous research studies show that eating more plant sources of food -- vegetables, fruit, grains, nuts and seeds and legumes -- is a key strategy to improved health and decreased risk of cardiovascular disease, obesity, diabetes and cancer. All nutrients except for vitamin B12 are found in plant foods. People who eat a cooked or raw plant-based diet need a B12 supplement or should choose foods that are fortified with B12. Vitamin D is less prevalent in plants, with the major food sources in fish, liver, and egg yolks. However some mushrooms are high in vitamin D and our skin produces vitamin D from the sun’s ultraviolet light.Because uncooked foods like sprouts, berries and lettuce are often linked to food-borne illness, all produce should be thoroughly washed before eating. Due to the increased risk of food-borne illness from some uncooked foods, pregnant women, young children, senior citizens, people with weak immune systems and anyone with a chronic medical condition should not eat a raw foods diet.Our tips: Eating more thoroughly-washed fruit and vegetables either raw or cooked is a priority health goal. Aim for at least 5 servings per day of a variety of fruits and vegetables and more is always better! Include fresh or frozen fruit with breakfast oatmeal or yogurt, add a salad or vegetable soup to lunch, include two different types of vegetables with dinner, and enjoy fruit for snacks or a healthy dessert. Further, cook vegetables in as little water as possible unless you’re making a sauce from the liquid.ReferencesFood for Thought: Was Cooking a Pivotal Step in Human Evolution? Alexandra Rosati. Scientific American. 2-26-18Cooking Up Bigger Brains. Rachael Moeller Gorman. Scientific American. 1-1-2008. https://www.scientificamerican.com/article/cooking-up-bigger-brains/Chan Q, Stamler J, Brown IJ, et al. Relation of raw and cooked vegetable consumption to blood pressure: the INTERMAP Study. J Hum Hypertens. 2014;28(6):353–359. doi:10.1038/jhh.2013.115Chan Q, Stamler J, Brown IJ, et al. Relation of raw and cooked vegetable consumption to blood pressure: the INTERMAP Study. J Hum Hypertens. 2014;28(6):353–359. doi:10.1038/jhh.2013.115Carmody R, Wrangham R. The energetic significance of cooking. Journal of Human Evolution. 2009;57(4):379-391.Cunningham E. What is a raw foods diet and are there any risks or benefits associated with it? J Am Diet Assoc. 2004 Oct;104(10):1623.Suzzane Havala Hobbs. Raw Food Diets. Review of the literature. The Vegetarian Resource Group. https://www.vrg.org/journal/vj2002issue4/2002_issue4_rawfoodsdiet.php published 2002. Accessed 10-20-19.Link LB, Jacobson JS. Factors affecting adherence to a raw vegan diet. Complement Ther Clin Pract. 2008;14(1):53–59. doi:10.1016/j.ctcp.2006.12.005Tuso PJ, Ismail MH, Ha BP, Bartolotto C. Nutritional update for physicians: plant-based diets. Perm J. 2013;17(2):61–66. doi:10.7812/TPP/12-085Hever J. Plant-Based Diets: A Physician's Guide. Perm J. 2016;20(3):15–082. doi:10.7812/TPP/15-082Kara Meyer Robinson. Raw Foods Diet. Web MD. https://www.webmd.com/diet/a-z/raw-foods-diet accessed 10-21-19Author: Lynn Grieger, RDN, CDE, CPT, CHWC