It is widely known that eating more fruits and vegetables is better for your overall health and it's not just grandma saying this anymore. The recently published and updated 2010 Dietary Guidelines for Americans stated this and even dedicated two full pages pointing out the benefits of a plant-based diet for one's health . But is eating a raw food diet better than eating a diet with some cooked foods in it?
This claim has been made by many raw-foodists as they say eating a diet devoid of any cooked foods or at least eating only a minimal amount of cooked food is the only way to achieve optimal health. To be considered a raw food diet one must consume 75% or more of their food raw. Some raw-foodists say that eating a 100% raw diet is the only way to achieve perfect health. So what's the right answer?
Unfortunately, this is not an easy topic to paint a clear black and white picture about and no long term studies are available to date to adequately determine whether a raw food diet is superior for one's overall health. If anything there seems to be pros and cons to both sides. Let's take a look at what the scientific world has to say about all of this.
Are cooked foods more toxic?
Many raw food advocates claim that cooked foods are toxic and therefore should not be consumed. While they do have some good points regarding the formation of certain carcinogens and other toxic agents in cooked foods it appears that the method of cooking plays a significant role in all of this.
▸ Heterocyclic Amines (HCAs)
▪ Defined as chemicals that are formed when amino acids (building blocks of
protein), sugar, and creatinine/creatine react with one another at high
temperatures . Creatinine and creatine are found in meat and therefore HCAs
are only formed and eaten when consuming the flesh of an animal or fish.
▪ The higher the temperature and the longer the meat is cooked for play a
significant role in the formation of HCAs. Frying, broiling, baking, and grilling will
all increase the formation of HCAs especially above 300℉ [3,4,5].
▪ HCAs have been shown to be mutagenic which means they can cause mutations
and damage DNA . This may increase one's risk of cancer and numerous
epidemiological studies have linked a high consumption of well-done, fried, or
barbecued meats to an increased risk of colorectal cancer, breast cancer,
prostate cancer, and pancreatic cancer [7,8,9,10,11].
▸ Maillard molecules
▪ Many raw-foodist say that Maillard reactions (reactions between a protein and
carbohydrate) produced by cooking "creates an endless chain of toxic molecules
be able to adapt to because of the unpredictability of the chemicals". This claim is
made, of course, without any long term scientific data providing any proof of this.
▪ Maillard reactions are responsible for a portion of the browning effect and
flavoring of different food products .
▪ Maillard molecules are not just produced in foods but also via non-food pathways
in the human body when collagen and free sugars undergo cross-linking to
produce Advanced Glycation Endproducts (AGE's) which occur at an advanced
stage of a Maillard reaction . In diabetic patients this reaction is accelerated
due to elevated blood sugar and has led to tissue degeneration. Diabetics also
have decreased kidney function which has been shown to reduce the clearance
of AGE's from the body leading to increased renal-vascular injury . However,
these damaging effects don't seem to occur in non-diabetic patients.
▪ Consuming a diet rich in Maillard reaction products has actually been shown to
have antioxidant effects in vitro (in test tube laboratory experiments) and has also
been shown to reduce oxidative damage to LDL (bad cholesterol) but it still
remains to be seen in vivo (in living organisms) .
▸ Polycyclic Aromatic Hydrocarbons (PAHs)
▪ PHAs are carcinogens formed when meats are grilled over an open flame or by
smoking meat products [3,16]. They are also found in car exhaust fumes,
polluted air, and cigarette smoke.
▪ An increase in the incremental lifetime cancer risk of individuals has been shown
in those who have a higher daily dietary exposure to PHAs .
▪ Found in moderate amounts in heated protein-rich foods and in high amounts in
cooked carbohydrate-rich foods such as potatoes, potato chips, beetroot, and
crisp bread . Acrylamides are not found, however, in unheated or boiled
▪ Acrylamides have shown mixed results with being a possible carcinogen in
humans. Epidemiological studies have shown an increased risk of ovarian and
endometrial cancer, renal cell cancer, breast cancer, and oral cavity cancer when
exposed to higher levels of acrylamides but a decreased risk in lung and bladder
cancer in women and prostrate and oro- and hypopharynx cancer in men .
As you can see from above there are many different factors that go into the potential toxicity of foodstuffs. It appears from reviewing the scientific data that cooking foods for longer periods of time at higher temperatures can lead to increased exposure to potential toxins. In contrast, using water based cooking methods such as boiling or steaming reduces or eliminates these risks.
In addition, it is also clear that consuming a plant-based diet and limiting or avoiding meat products all together will dramatically reduce your exposure to potentially harmful carcinogens such as HCAs and PAHs. The benefits of increasing health promoting vegetables in one's diet was shown to be the case in a review of 28 studies on the consumption of raw vs. cooked vegetables and cancer risk. It showed that increasing your consumption of vegetables in general whether raw or cooked led to a decreased risk of several different types of cancer .
Do Cooked Foods Contain Less Nutrition?
Another claim by raw food advocates is that when you cook food you destroy the nutrients and enzymes in food that make them worth eating in the first place. This topic of interest has some valid points to it. As you will see below a portion of vitamins and minerals are lost in cooked foods but this is not always the case. The debate whether an essential role is played by enzymes contained within raw foods will also be discussed.
▸ Vitamin C tends to be one of the vitamins that is most affected by cooking.
Depending on cooking method and cooking ware used a loss of anywhere from
18%-60% can be seen when cooking frozen vegetables .
▸ One study looked at the effects of heating tomatoes and showed an increase in
total antioxidant activity and in lycopene content despite a loss in vitamin C . It
also showed no significant changes in the amount of two powerful antioxidant
classes known as phenolics and flavonoids.
▸ Cooking carrots has been shown to increase the availability of carotenoids .
One study showed an increase from 3% to 27% in beta-carotene content in raw vs.
cooked carrots .
▸ Different cooking methods was shown to make a different in total antioxidant
capacity in cooking the following vegetables - carrots, courgettes (zucchini), and
broccoli. Boiling, steaming, and frying were all tested. Frying showed the least
amount of retained antioxidants while water based methods preserved more
antioxidant compounds particularly the carotenoids .
▸ One review of the vitamin and mineral content of raw vs. cooked foods showed a
10-25% overall loss of vitamins in cooked foods with only a negligible loss of
▸ Many raw-foodists claim that enzymes found in the plant food that you eat is used
to help digest this food thereby preserving your own body's supply of enzymes.
However, it has been shown that 90% of all nutrients are absorbed in the small
intestine and that the majority of the plant enzymes consumed in foods we eat
are destroyed in the stomach before the food gets to the small intestine and this
food is then broken down by the body's own bile and pancreatic enzymes .
It is apparent that eating both raw and cooked foods has it's pros and cons in regards to the nutritional value of the foods being consumed. Again water based cooking methods have been shown to minimize the loss of vitamins and minerals. In some cases steaming or boiling can even lead to an increase in the amount of certain antioxidants in select foods.
Another important point to make here is that you can increase the amount of vegetables that you eat in your diet by simply cooking them. This softens the food and makes it easier to consume. Including steamed veggies or a vegetable based soup in one of your daily meals can easily increase your intake of those all important disease fighting phytochemicals and antioxidants that we never seem to get enough of. Eating a 100% raw diet makes it difficult to eat as much of these bulkier foods and those who do eat this way rely heavily on fruit to make up a majority of their diet. I'm not saying that fruit is a bad thing but rather that it's important to maintain a balanced approach in your dietary habits by consuming a wide variety of plant-based foods to meet your nutritional needs.
Don't get me wrong eating raw foods is important and you should try to get at least 50% of your calories this way if possible. But eating a completely raw diet has not been shown in long term studies to be superior. If I missed this data then by all means please comment and share these findings for the benefit of all who read this. If anything an all raw diet has been shown to increase dental erosions  and decrease overall bone mass  in individuals over the long term. Finally, the most important thing you can do for your overall health is include plenty of nutrient dense, plant based foods and reduce or eliminate animal based foods in your diet. This has been shown in numerous studies to decrease your risk of chronic diseases and give you more health and vitality as you go throughout life. I'll leave you with a link to a well done 3 part review article of raw food diets and two short videos discussing a raw food diet for those who are interested in exploring this topic further.
Dustin Rudolph Pharm.D.
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