Saturday, 29 June 2013
The raw food diet as the term implies, is one that involves eating only raw food items that have not had any kind of processing, preservation, additives or cooking. Some follow it completely (therefore their diet is 100% raw food only) and others follow it partially (therefore eat some cooked food as a percentage of their diet). There are also those who consume partially cooked foods in a bid to preserve some of the nutrients but whether they would classify themselves as raw foodists is subject to debate. So why follow a raw food diet?
Well, the premise upon which raw foodists follow this diet is ostensibly because they believe that cooking destroys the important nutrients in food. Converts to raw food has gathered momentum largely due to a dedicated movement by enthusiasts, endorsed by celebrities who promote the notion that cooking destroys about 50% of the nutrients in food. Crucially, cooking is thought to destroy all or most of the critical and essential enzymes rendering cooking a damaging process when it comes to nutrition. Raw food enthusiasts actively promote the idea that 'cooked foods are dead foods'. So let's examine these ideas and claims from a scientific perspective by reviewing the evidence for cooking and whether indeed we should all be bothering with cooking at all.
There is certainly some truth in the statement that cooking can destroy some important nutrients. But much depends on the type of food and the type of cooking process. Frying, barbequeing or overcooking is essentially disastrous for the body because it enables the formation of toxic compounds such as acrylamides from frying and carcinogenic compounds such as heterocyclic amines from charring. Cooking also destroys important nutrients. Equally, many water-soluble vitamins are fragile and heat-sensitive therefore cooking will destroy them; boiling things to an inch of their life is probably best avoided! Some plant enzymes function as phytochemical nutrients in the body and can also be lost through overcooking so there is some argument to the cooking theory. Boiling and steaming are the best methods for preserving most of the nutrients.
Certainly, there are numerous benefits of eating raw food, particularly raw fruits and vegetables. Not least of which many advocates have been cured of lifelong illnesses, remission from cancer and have improved their overall health status. Hard to argue with this! However there are limitations to the this diet, namely that some vegetables are simply indigestible and unpalatable to be eaten raw. The image of someone tucking into an uncooked potato is not something that is likely to catch on! Equally, some grains and pulses cannot be eaten raw, on the contrary, rather they may do more damage than good, leading to all sorts of digestive problems. Fruits are more likely to lend themselves to a raw food diet that vegetables but there are some exceptions: carrots, celery, peppers, tomatoes, beans, peas, nuts, seeds and salad leaves amongst others. However, this is nothing new, health practitioners have been advising of the enormous benefits of fruits and vegetables as part of their professional remit as far as long as I can remember so why is this news? Many who switch to a raw food diet are more likely to be eating fruits and vegetables anyway, therefore the health benefits are plain to see. Some have ditched fast foods, processed foods and fried foods so the initial feel-good factor of raw food is simply one that can be attributed to a better quality diet. But do we really need to cook food?
Contrary to what raw foodists will have you believe, cooking is actually beneficial for the body. Not only does it provide vital nutrients by releasing some of the nutrients contained within cells (particularly from plant cells which have a tough cellulose cell wall that can only be broken down by heat), cooking will also destroy pathogens and toxins that are commonly found in our foods. Some meats can transmit parasites as humans are secondary (or final) hosts to their lifecycle therefore cooking food thoroughly is the only way (outside of relying on the body's natural defences and immune system) in which the parasitic lifecycle can be broken. Additionally, cooking also destroys some of the anti-nutrients that bind minerals in the gut and interfere with the utilisation of nutrients which ultimately increases absorption of these nutrients. The best method of cooking is really steaming and boiling for a number of reasons. Not only does this method prevent the formation of the toxic acrylamides that tend to form with frying and other methods, it will also break the cellulose cells walls of plant cells walls in vegetables and release important nutrients from them. A good way of optimising vegetable nutrients is to steam them first and them make a soup; this will also ensure that fewer of the body's enzymes are needed to break down the cellulose cell wall and increase absorption of compounds such as bioflavonoids, lycopene (a powerful antioxidant notably found in tomatoes) lutein and carotenoids (another antioxidant) compared to the raw version. Also, roasting nuts and baking of cereals does not reduce bioavailability or the absorption of protein, rather it increases it.
The Science and the Evidence
Recent studies provide further confirmation to existing data that cooking increases the absorption of certain nutrients and whilst it is true that water-soluble vitamins such as vitamin C, folate and B vitamins, as well as certain minerals are destroyed by cooking, much of this should be viewed with the nutrient content of the whole diet. For instance, vitamin C contributes less than 1% of the total antioxidant activity of fruits and vegetables so apples for example provide less vitamin C compared to antioxidant capacity that its other ingredients such as phenolic acids and flavonoids provide, both of which are made available through cooking. Direct comparisons of nutrient provision of raw vs cooked carrots reveal that only 3-4% of carotenoids are absorbed compared to 15-20% from cooked or mashed carrots. Crucially, absorption rates are much higher from cooked foods compared to supplements. In another study, comparison of raw broccoli vs steamed or frozen broccoli, it was shown that about 25% of the vitamin C and about 20% of selenium (an important mineral) is lost during cooking. However, the other 20 commonly measured nutrients show only an insignificant change. Therefore the claim by raw foodists that 50% of nutrients are lost through cooking is inaccurate - a closer estimate would be in the region of 10%. Cooking has been shown to significantly boost its antioxidant activity, despite a reduction in vitamin C. In a study which determined the ability of corn to quench free radicals was measured, cooked corn outperformed raw corn by 25-50%. Cooking corn releases compounds called ferulic acid, which provides anti-cancer health benefits. Ferulic acid, a unique phytochemical is found in very low concentrations in fruits and vegetables but is actually in very high concentrations in corn. Its bioavailability from corn can be increased substantially by 500-900% through cooking it.
The claim that important plant enzymes are destroyed by cooking is a myth since our very own stomach acid will denature these more effectively than any form of cooking. Further, our own digestive enzymes are powerful substances and perfectly capable of catalysing digestion, plant enzymes are not designed for this purpose in our bodies and therefore redundant in this regard.
Avoiding Nutritional Deficiencies
The biggest concern that many health practitioners have including me over a raw food diet is in the area of nutritional deficiencies. I am yet to meet someone who follows a 100% raw food diet who is glowing with health. Rather, many have sallow complexions, look undernourished to the point of being emaciated and could be harbouring a number of dietary deficiencies that go unreported for many years in the belief (in almost a cult like manner) that raw is the best. The most committed raw foodists avoid dairy foods and if milk is consumed, it has to be unpasteurised, if eggs are consumed it must be raw. They avoid meat in any form and avoid cooked carbohydrates such as pasta amongst other foods that leave them at high risk of nutritional deficiencies. For instance, eggs are a good source of biotin, a nutrient which contributes to healthy hair, skin and bones (amongst other benefits), however, raw eggs contain a protein called avidin, which binds and inactivates biotin. Cooking denatures avidin which renders it incapable of binding to the nutrient biotin therefore cooked eggs are in fact a good source of bioavailable biotin. Additionally, unpasteurised milk can present significant risk because milk is contaminated with bacteria (from the cows, farmers, farm equipment etc...) and it makes a great growth medium therefore consuming unpasteurised milk (depending how fresh it is) can be like ingesting a dose of potential pathogens and it is incumbent upon the immune system and stomach acid to protect the body from this kind of invasion. There is a very good reason why pasteurisation really took off in the manner that it did!
To juice or not to juice?
Perhaps the debate should focus more about the quality of our food rather than whether a raw food diet is good for you or not. As humans, have a long history of being hunter-gatherers, a diets of seeds, berries, nuts, fruits and leaves should not be an alien concept. However, over time, we have learnt to make fire - and with that, cooking , particularly meat (of which we have a longer history than in growing, cultivating and eating crops such as potatoes). Again, I am of the view that a balance to these things is always the best approach. Therefore a certain % of one's diet should be raw; it's not entirely healthy to consume cooked foods all the time. Therefore a combination of raw and cooked is the way to go with this with a variety of fresh fruits and vegetables, perhaps a juice drink once a day and a cooked meal in the evening being the best balance. This will ensure that there is nutritional balance, a certain bioavailability of important nutrients and optimisation of health due to an avoidance of toxins and pathogens from uncooked sources. Ultimately of course, individual constitutions will dictate progress and popularity of raw food as well as personalising one's dietary regimen which suits health needs, address illness, eliminate food intolerances and allergies as well as optimising health and well-being. Who can argue with that?
For more information about raw food diets please visit http://www.rawfoodrecipes.com/
For juicing and raw food recipes please visit http://www.juicingandrawfoods.com/
For nutritional support and more information about vegan or vegetarian diet please visit the Vegetarian Society at https://www.vegsoc.org/or The Vegan Society at http://www.vegansociety.com/