Given that the main argument for a raw food diet is that this is "the 'natural' way for humans to eat", we can't discuss a raw food diet without at the very least considering the two leading theories of how man climbed down from the trees, stood erect on two legs and developed a bigger brain.
Richard Wrangham, in Catching Fire, holds the view that it was the discovery of fire, thereby allowing food to be cooked, that enabled greater and easier access to nutrient density. In turn, this facilitated the evolution from a larger to smaller gut and from a smaller to bigger brain. Others share the belief it was access to nutrient-dense animal foods - notably the softer and nutrient-dense bone marrow and brain - that did the trick.
I believe it is an overly simplistic view to say that cooked food (anything over 47C) is dead food, with diminished life force and nutrient value, when it has, in the successful evolution and survival of man, been quite spectacularly successful.
While we might share a large amount of DNA with the chimpanzee (around 94%), we are yet, quite obviously, not the same. At the very least, chimps and orang utans have a larger colon to gut ratio, strong jaws and large teeth - perfect to chew and digest the large quantity of fibrous fruits and tough leaves (high in fibre) which, along with fermentation in the colon, provides enough calories to support the animal.
Humans have the opposite - a smaller colon to gut ratio, with a weaker jaw and smaller teeth - perfect for cooked foods, which require less energy to digest and soften the strong cellulose fibre.
While certainly heat in fermentation or cooking does destroy enzymes, de-natures protein and can destroy Vitamin C and some heat-sensitive minerals such as thiamine, it remains that cooking food provides incredible nutrient density and energy that is easily accessible. Lightly cooking meat, for example, makes it more easily digestible - it starts breaking down the protein molecules.
But heat can also make some big differences to vegetables - it can soften and break down the fibrous cellulose (that's why a lot of raw kale, even when blended, will give you tummy problems), it helps to improve the digestibility of complex carbohydrate (especially the starch/cellulose so that cooked potato or sweet potato is more digestible cooked than raw) and it can break down some problematic aspects of raw foods, such as oxalic acid and goitrogens. This article does not allow the space to go into these two aspects more deeply, but it is simply incorrect to say they have no impact.
In the end, very little in life is ever black and white, and I believe it is the same with raw and cooked foods. All healthy human groups include raw food (where appropriate to the food) and understand the value of that life force. However, no healthy human groups eat solely raw food. This view is supported by many, including the same Richard Wrangham, who, as a biological anthropologist, found no human group eats all their food raw, as did Weston Price many years before.
I have always (as my parents' generation before me) consumed raw foods, including cabbage in my mum's favourite coleslaw and we called it a salad. We ate raw, fresh seasonal fruit and called it an apple or pear, not a 'raw food', but we also ate those foods cooked. We also consumed raw animal products meats (steak tartare), raw milk, raw eggs in raw milk (mum's egg flip) but, equally if not more importantly, this was all in the context of the nourishing foundations that my work is based upon - good soil, in season, as close to harvest as possible, prepared so that it is optimal for the human body (soaking, sprouting, cooking etc), good fats, good gut ecology, as close as possible to its natural state, delicious and within the context of a less stressed life.
We must also remember that those foods that may be considered to offer a higher proportion of nutrients when raw are useless if they cannot be digested, absorbed and utilised. Raw Cacao, for example, might have lots of magnesium, but it's also extremely high in phytic acid which binds the magnesium - you won't be able to access it. Fermentation, where high temperatures are reached, can break this and other anti-nutrients (such as the oxalates that are highly prevalent in cacao) down, and indeed this traditional nourishing wisdom of fermenting, roasting and grinding the cacao bean has been known for some 3000 years. Cacao was never consumed raw or unroasted. Yes, some things might be lost when heating food, but some things will be gained. More of the antioxidant lycopene in tomatoes is just one example, for there are indeed many.
When choosing vegetables to eat raw, it pays to bear in mind that nature tends to provide season-appropriate foods. In summer, it provides lighter, less carbohydrate- dense and higher water content vegetables and fruits. These all require less cooking and are easy to eat raw.
Yet it gives us the almost opposite in the cooler months - these denser carbohydrate root vegetables, and thicker and more cellulose-dense leaves (cabbage, kale, collards) and fruits provide us with more fuel to keep us warm, but will need cooking to make that goodness accessible.
Yes, you could also blend those leaves up and break down the cellulose (the infamous green smoothie) but that is often not enough for some. I simply and absolutely do not agree, because this is what I have seen, that it offers better nutrition than when cooked.
With regard to seeds - grains, legumes, nuts and other seeds - yes, they can be sprouted and you will end up with a highly nutrient-dense food, without heat. But on a cold day, you might be better off cooking them and eating a lovely bowl of warm grainy, beany goodness and then adding some lovely kale in the last 10 minutes to soften its sturdy fibers. It's never just about the food, but the many contexts of that food, including its thermal properties.
Just because it is now cooked does not diminish the exceptional capacity of real food to heal, nourish and delight - that is simply a highly fractionalised and shallow approach to the subject of wholesome eating. All those same foods, even some of the lighter, easier to digest summer vegetables, can still be cooked and offer exceptional nourishment such as the classic and delicious lettuce and pea soup.
Jude Blereau is a wholefood cook and writer based on Perth. www.wholefoodcooking.com.au