Raw food diets, or ‘Raw Foodism’ encourage people to eat most of their food in a natural, uncooked state. Raw-ism comes in many forms but essentially the staples are fresh fruit, vegetables, nuts, seeds and cold pressed oils.... which sound pretty good.
A high consumption of unprocessed fruits, nuts, vegetables and oils is probably a good thing. The problems reside in a more extreme approach to raw-foodism
Many raw followers are vegan - some do eat raw meat or seafood- hey I don’t mind a good carpaccio or sashimi!
In the US, some people drink raw (unpasteurized) milk. In Australia health authorities advise against this as it can cause serious illness and death from salmonella. If you have lived through a good dose of salmonella, you would not wish it on your worst enemy. Incidentally, the sale of raw milk in Australia is illegal.
One aspect that does raise an eyebrow is the raw food industry, complete with raw bars, bliss balls, cafés, shakes, cakes and chips. Unlike the term “organic” the term “raw” has no legally binding definition.
Raw food enthusiasts avoid anything that has been cooked or heat processed. The rationale being that the cooking process destroys the life-force of the food and its nutrition such as the enzymes, which help digest the food. I'm sure most health conscious people will admit the less processing in their food choices is probably a good thing, but how far do you go?
In terms of specific health benefits from going totally raw, like most extreme approaches when you start to look into the research, it all starts to unravel.
Cooking is a human universal. No society is without it. The consumption of a cooked meal in the evening, usually in the company of family and friends, is normal in every known society. Moreover, without cooking, the human brain (which consumes 20-25% of the body's energy) could not keep running. 
From a genetic perspective, humans have evolved with cooking. Let's face it, sitting around gnawing on a raw Woolly Mammoth would not have been fun.
Are tomatoes more nutritious when consumed cooked?
Yes. The small loss of vitamin C is far out weighed by the increased bioavaibility of polyphenol compounds such as lycopene.
Are cooked carrots more nutritious than raw?
Ever wondered about those super-convenient steamable bags of frozen vegetables you just throw in the microwave?
At least one research study shows the broccoli steamed in the bag is more nutritious compared to regular steam microwaving.
Is the energy and nutrition more readily absorbed from cooking red meat, legumes, cabbages, grains like barley, oats, rice and quinoa, as well as potatoes and root vegetables? Without question!
Cooking kills nutrition?
A lot of raw-food literature cite cooking studies that examined the effects of boiling various foods for long amounts of time. Nowadays not many people boil the crap out of their veggies. Steaming, stir-frying and microwaving are more the norm and when kept short and to a minimum, these methods are shown in quality research to maximize nutrition from vegetables.
For example, steaming or microwaving for 5 minutes or less (depending on the quantity) will preserve most vitamins and enhance nutrition of broccoli, carrots and greens. However, stir-frying red cabbage might be better for antioxidant availability.
One important fact is where your fresh vegetables come from; how long they took to get to you determines their nutrition quality far more than any cooking method. For example, the longer vegetables sit on the shelf or in transit, the more water soluble vitamins are lost. So if you are going to eat fresh, make sure it’s prepped, cooked and consumed quickly.
The bottom line
When you look to the science, there doesn’t seem to be any clear benefit to exclusively committing to the consumption of raw foods. Knowing how to cook your food correctly will often increase the nutrition.
Any diet movement that promotes a high consumption of fresh fruit, vegetables, nuts, seeds and cold pressed oils can’t be too bad nevertheless, I'll have my steak medium-rare, not moving.
1.Genetic Evidence of Human Adaptation to a Cooked Diet. Carmody RN, Dannemann M, Briggs AW, Nickel B, Groopman EE, Wrangham RW, Kelso J. Genome Biol Evol. 2016 Apr 13;8(4):1091-103.
2. A review of the impact of preparation and cooking on the nutritional quality of vegetables and legumes. A D.T. Fabbri., G A.Crosby. International Journal of Gastronomy and Food Science, Volume 3, p2-11, April 2016.
3.Cooking techniques improve the levels of bioactive compounds and antioxidant activity in kale and red cabbage. Daniella Carisa Murador, Adriana Zerlotti Mercadante, Veridiana Vera de Rosso. Food Chemistry, Volume 196, 1,p 1101-1107, April 2016.
4.Effects of different cooking methods on nutritional and physicochemical characteristics of selected vegetables. Miglio C, Chiavaro E, Visconti A, Fogliano V, Pellegrini N. J Agric Food Chem. 2008 Jan 9;56(1):139-47.
5.Effect of steamable bag microwaving versus traditional cooking methods on nutritional preservation and physical properties of frozen vegetables: A case study on broccoli (Brassica oleracea). Innovative Food Science & Emerging Technologies
Volume 31, p116-122, Oct ,2015.