Plant-based raw food diets have been quite a common topic in the context of vegan and other plant-based diets, and the number of websites, blogs, books, workshops and lectures on the subject has been growing steadily in recent years. Raw food is defined as food that has not been heated above 45°C in order to retain its original properties and avoid chemical changes. Some choose to be 100% raw, but generally speaking, anyone eating at least 80% raw can be considered a raw foodist.
Why do humans cook, anyway?
'Cooking as a Biological Trait' (1) makes a hypothesis that cooking is one of the biological traits of humans, which means that heating food might be inherent to us as a species. In other words, we cook because we are human, and we are human because we cook. The article claims that raw food was not sufficient for hunter-gatherers, but that is not a dominant way of life today. Besides, it would be presumptuous to assume that something is good for us or others just because we have always done it. Veganism is a good example. We may not have always been vegan, and most people are not vegan today, but that does not mean that there is no different, perfectly good or even better approach to life and the creatures around us than the most common one.
But is raw food the same?
It may be. Cooked food is delicious. Humans have always cooked; everybody around us cooks. Are there nutrients in raw food which are destroyed by heating, and does cooking create harmful compounds? Raw foodists would concur and suggest avoiding compounds such as acrylamide, AGEs (advanced glycation end-products), heterocyclic amines and PAHs (polycyclic aromatic hydrocarbons). They would add that we are the only animal who cooks, or even destroys food, and that, if you think about it, it is unusual to eat food which cannot live or grow. Metaphorically speaking, if you drop a cooked potato, it will never sprout.
Cooking is not simply heating – it is chemical processing of food which makes some nutrients more, and some less available, neutralizes some compounds, making them less or not toxic to humans, and creates new compounds whose properties and effect on body are being researched.
There is no biologist who has not heard of acrylamide, because the polymerization of this compound forms a gel used in the analysis of biomolecules. It is also a carcinogen and neurotoxin. Biologists know that they have to be very careful while handling acrylamide and wear protective gear. Very recently it has been discovered that this chemical is also found in cooked food, and that food is the primary source of acrylamide for humans. But there is no reason to panic because not all doses are harmful. Exposure is measured in doses or concentrations and duration, and acrylamide in food and its potential hazard to human body is being researched (2). Present research indicates that concentrations of acrylamide in cooked foods are not sufficient to be a health risk (3), but caution is advisable.
AGEs (advanced glycation end-products)
AGEs are compounds formed in reactions between proteins and carbohydrates. These reactions occur in our bodies, and we also ingest their products in food: they are recognizable, for example, by the golden-brown color of roasted food. The levels of AGEs in food have been widely studied in recent years, and databases of AGE content in food items are now available (4). Their levels are much lower in unprocessed foods. Studies have linked them with the development of diabetes, atherosclerosis and other degenerative diseases. However, a 2013 review of previous trials indicated some connection, but asked for further research (5). People in at-risk groups can decide the level of AGEs they want in their diet. The intake of AGEs is considerably lower on a raw food diet.
HCAs are a diverse group of compounds; relevant in the context of raw foodism are those generated by high temperature cooking, especially of animal flesh (fish included), associated with the increased risk of some cancers. Some of them are essential for healthy functioning, and take part in the composition of our bodies.
Polycyclic aromatic hydrocarbons (PAHs)
These compounds are everywhere around us because they are byproducts of burning fuel, so we are constantly exposed to them, but food is the major source (6). They are carcinogenic, but interesting because they are tracked in Space research as possible traces of extraterrestrial life.
After the potential cons of cooking, here are some pros of eating raw. A study has shown that people on a strict raw food diet have normal vitamin A status and favorable plasma beta-carotene concentrations for the prevention of chronic diseases, but also low lycopene levels (7). Raw food diets are also associated with favorable levels of the bad, LDL cholesterol and triglycerides (8). An older study of a small sample of people on a therapeutic raw food diet indicated improvements in cardiovascular parameters and weight loss. The patients also spontaneously abstained from smoking and drinking alcohol (9).
A review of previous studies associated reduced cancer risk to raw vegetables in higher degree than cooked, and stressed the importance of plant-based diets (10). Nuts and berries were in numerous studies shown to decrease inflammatory processes and contribute to cardiovascular health (11), (12), (13), (14), (15), (16), (17).
However, raw food diets also have some drawbacks. Long-term raw food diets can, for example, lead to a high loss of body weight and amenorrhea (18), and are associated with dental erosion (19), lower levels of good cholesterol, and elevated homocysteine concentrations (both linked with an increased risk of heart disease)(8). Bone mass is lower in long-term raw food dieters, although this does not necessarily indicate pathology if other parameters are acceptable (20).
Raw food diets are often criticized for their high concentrations of phytates (found in nuts and seeds), but studies have shown that phytates are not necessarily bad. Although they were found to interfere with mineral absorption and availability, they also have a protective function; low intake is associated with an increased risk of osteoporosis, and high intake with higher bone density, especially in women. Their potential anticarcinogenic activity and effect on blood glucose and lipids have also been researched (21), (22), (23), (24), (25).
Higher intake of raw food is good for your health. We are surrounded by abundance of plant food, and it is ours to decide the ratio of raw food we want to in our diet. Studies that suggest certain risks associated with raw food do not have to act as a deterrent, but rather as a guideline for a raw food diet.
For more information visit:
(1) 'Cooking as a biological trait'., Wrangham R, Conklin-Brittain N., 2003, http://www.ncbi.nlm.nih.gov/pubmed/14527628
(2) Analysis of acrylamide, a carcinogen formed in heated foodstuffs., Tareke E, Rydberg P, Karlsson P, Eriksson S, Törnqvist M., 2002., http://www.ncbi.nlm.nih.gov/pubmed/12166997
(3) A review of the toxicology of acrylamide., Exon JH., 2006, http://www.ncbi.nlm.nih.gov/pubmed/17492525
(5) Dietary advanced glycation end-product restriction for the attenuation of insulin resistance, oxidative stress and endothelial dysfunction: a systematic review., N J Kellow and G S Savige, 2013, http://www.nature.com/ejcn/journal/v67/n3/full/ejcn2012220a.html
(6) Polycyclic aromatic hydrocarbons in the diet., Phillips DH., 1999, http://www.ncbi.nlm.nih.gov/pubmed/10415437
(7) Long-term strict raw food diet is associated with favourable plasma beta-carotene and low plasma lycopene concentrations in Germans., Garcia AL, Koebnick C, Dagnelie PC, Strassner C, Elmadfa I, Katz N, Leitzmann C, Hoffmann I., 2008, http://www.ncbi.nlm.nih.gov/pubmed/18028575
(8) Long-term consumption of a raw food diet is associated with favorable serum LDL cholesterol and triglycerides but also with elevated plasma homocysteine and low serum HDL cholesterol in humans., Koebnick C, Garcia AL, Dagnelie PC, Strassner C, Lindemans J, Katz N, Leitzmann C, Hoffmann I., 2005, http://www.ncbi.nlm.nih.gov/pubmed/16177198
(9) Effects of a raw food diet on hypertension and obesity., Douglass JM, Rasgon IM, Fleiss PM, Schmidt RD, Peters SN, Abelmann EA., 1985, http://www.ncbi.nlm.nih.gov/pubmed/4012382
(10) Raw versus cooked vegetables and cancer risk., Link LB, Potter JD., 2004, http://www.ncbi.nlm.nih.gov/pubmed/15342442
(11) The effect of nuts on inflammation., Salas-Salvadó J, Casas-Agustench P, Murphy MM, López-Uriarte P, Bulló M., 2008, http://www.ncbi.nlm.nih.gov/pubmed/18296371
(12) Nuts and novel biomarkers of cardiovascular disease., Ros E., 2009, http://www.ncbi.nlm.nih.gov/pubmed/19321561
(13) Health benefits of nut consumption., Ros E., 2010, http://www.ncbi.nlm.nih.gov/pubmed/22254047
(14) The effects of nuts on coronary heart disease risk., Kris-Etherton PM, Zhao G, Binkoski AE, Coval SM, Etherton TD., 2001, http://www.ncbi.nlm.nih.gov/pubmed/11368503
(15) The role of tree nuts and peanuts in the prevention of coronary heart disease: multiple potential mechanisms., Kris-Etherton PM, Hu FB, Ros E, Sabate J., 2008, http://www.ncbi.nlm.nih.gov/pubmed/18716180
(16) Fatty acid composition of nuts--implications for cardiovascular health.
Ros E, Mataix J., 2006, http://www.ncbi.nlm.nih.gov/pubmed/17125530
(17) Nuts and berries for heart health., Ros E, Tapsell LC, Sabate J., 2010, http://www.ncbi.nlm.nih.gov/pubmed/20820955
(18) Consequences of a long-term raw food diet on body weight and menstruation: results of a questionnaire survey, Koebnick C, Strassner C, Hoffmann I, Leitzmann C., 1999, http://www.ncbi.nlm.nih.gov/pubmed/10436305
(19) Dental erosions in subjects living on a raw food diet., Ganss C, Schlechtriemen M, Klimek J., 1999, http://www.ncbi.nlm.nih.gov/pubmed/9831783
(20) Low none mass in subjects on a long-term raw vegetarian diet., Fontana L, Shew JL, Holloszy JO, Villareal DT., 2005, http://www.ncbi.nlm.nih.gov/pubmed/15795346
(21) Phytate (myo-inositol hexaphosphate) and risk factors for osteoporosis., López-González AA, Grases F, Roca P, Mari B, Vicente-Herrero MT, Costa-Bauzá A., 2008, http://www.ncbi.nlm.nih.gov/pubmed/19053869
(22) Protective effect of myo-inositol hexaphosphate (phytate) on bone mass loss in postmenopausal women., López-González AA, Grases F, Monroy N, Marí B, Vicente-Herrero MT, Tur F, Perelló J., 2013, http://www.ncbi.nlm.nih.gov/pubmed/22614760
(23) Phytate in foods and significance for humans: food sources, intake, processing, bioavailability, protective role and analysis., Schlemmer U, Frølich W, Prieto RM, Grases F., 2009., http://www.ncbi.nlm.nih.gov/pubmed/19774556
(24) Phytate levels and bone parameters: a retrospective pilot clinical trial., Lopez-Gonzalez AA, Grases F, Perello J, Tur F, Costa-Bauza A, Monroy N, Mari B, Vicente-Herrero T., 2010, http://www.ncbi.nlm.nih.gov/pubmed/20515779
(25) The influence of consumption of phytate on the bone mass in posmenopausal women of Mallorca., López-González AA, Grases F, Marí B, Vicente-Herrero MT, Costa-Bauzá A, Monroy N., 2011, http://www.ncbi.nlm.nih.gov/pubmed/21794821