Raw food diets are a big hit right now - Instagram is swamped with thousands of pictures of raw meals, and more raw food products keep popping up in our supermarkets and health food shops. Advocates of raw food diets, including celebrities like Gwyneth Paltrow, Sting, and Demi Moore, claim the health benefits range from weight loss to detoxifying our bodies. Many supporters of the diet also claim that raw food is 'alive' and cooked food is 'dead', because cooking food supposedly destroys nutrients and enzymes.
On the other hand, most health care professionals dismiss raw food diets as a fad that puts dieters at risk of developing eating disorders, nutritional deficiencies, and of being stigmatized.
As ever, I want to take a balanced look at both sides of the argument using the best evidence we have, to answer some of the common questions about raw food diets:
What is a raw food diet?
The diet consists of uncooked, unprocessed foods – mainly raw fruits, vegetables, nuts, and seeds.
It’s possible to warm your food a bit – but not above 40C (104F). Some like to sprout grains and beans to make them edible without cooking them. Fermenting foods and the use of dehydrators are also allowed to provide a little more variety into your diet.
Does cooking food destroy nutrients?
Yes and no. Certain nutrients, such as vitamin C and folate, are decreased during cooking, especially when vegetables are boiled rather than steamed or baked (1).
However, other nutrients, such as the carotenoids beta-carotene, lycopene, and lutein, are made much more bioavailable (your body can absorb more of it) when cooked (2). Carotenoids are really important because they've been shown to be associated with decreased risk of cancers, cardiovascular diseases, and obesity (3). Another example is curcumin, the yellow pigment found in turmeric that has antioxidant and anti-inflammatory effects shown to protect against many diseases, including cancers, cardiovascular disease, and even arthritis (4-6). Eaten raw, the health effects are limited because of its extremely limited water solubility. However, when cooked, there can be up to a 12-fold increase in the solubility and therefore the amount we can absorb and benefit from (7). One more example is oxalates, found in some plants, which inhibit the absorption of calcium, iron and zinc. Cooking vegetables significantly reduces oxalate levels (8), so when many plant foods are cooked, absorption of calcium, iron and zinc is actually improved.
There’s loads more examples of how cooking food can decrease levels of some nutrients, but increase the bioavailability of others. So while a raw food diet may help you take in higher levels of certain nutrients, sticking solely to raw foods can actually put you at risk of becoming deficient in several others.
Is a raw food diet nutritionally complete?
Raw food diets naturally encourage the consumption of more fruit and veg, and that’s always a good idea. Fruit and veg are rich in vitamins, minerals, fibre, phytonutrients and antioxidants, and a higher intake of them is associated with reduced risk of cardiovascular disease, cancer, and all-cause mortality (9).
However, while it is possible to eat beans and grains ‘raw’, the process involves soaking and sprouting, which can take days. While sprouted foods can be a great addition to the diet (see my guide to sprouting here), the effort involved means most raw foodies won’t eat them regularly enough. And since whole grains, beans, chickpeas, and lentils are significant sources of protein, iron, and zinc - especially important for vegans - it’s easy to become deficient in many of these essential nutrients on a raw food diet.
And this has been shown in human studies: people on raw food diets have shown to have low plasma lycopene (10), and low intakes of vitamin D, zinc, and calcium (11). In fact, almost a third of women surveyed on a raw food diet had partial or complete amenorrhea (missed periods) possibly due to the lack of certain nutrients and calories in the diet (12).
What about the enzymes?
It’s undeniably true – cooking food denatures enzymes found in plants, which is why raw foodies don’t heat their food over 40C.
But hang on a minute… memories of GCSE biology are kicking in here... doesn’t acid also denature enzymes? The hydrochloric acid released by the parietal cells in our stomachs is strong enough to kill bacteria, convert pepsinogen into pepsin to break down proteins, and it’s certainly strong enough to denature almost all plant enzymes. A few do make it through to the small intestine, for example fermented foods like sauerkraut can carry enzymes through to the gut. But the effect is minimal – digestion in the gut relies almost entirely on human-generated bile and pancreatic enzymes.
So it really seems that labelling raw food ‘alive’ and cooked food as ‘dead’ is a classic marketing tactic, designed to play to people’s emotions and to help sell diets / products.
Does a raw food diet help you lose weight?
Most of the evidence around the weight loss effects of raw food diets is anecdotal, not conducted under controlled conditions, and so should be taken with a pinch of salt (more on what evidence to believe here). That being said, it does make sense that you’d lose weight on the diet, seeing as processed foods like cakes, sweets, cookies, doughnuts, pastries, cheese, processed meats (you get the point, lots of the unhealthy foods) are shunned.
But hold on a minute – in order to cut out these junk foods, do you need to be on a raw food diet? Absolutely not. If weight loss is your goal, why not do it in a healthy way that doesn’t put you at risk of deficiencies and still benefits from all the wonderful foods that are usually cooked? For example, whole grains can help with weight loss and have a long list of other health benefits (as I explained here). Beans and pulses, which aren’t typically eaten often on a raw food diet, can also be really helpful with weight loss because they’re so high in protein and fibre, both of which help to increase satiety. Higher protein diets can help preserve muscle during weight loss (13), which improves metabolism and makes the weight loss more sustainable.
So yes, a raw vegan diet can help with weight loss, but it doesn’t seem to be the most sustainable (or enjoyable!) way to do it.
Can a raw vegan diet help with detoxing?
Hmmm, detoxing… I promised balanced arguments, but when it comes to detox diets, there really isn’t any science at all to back them up, so this point has to be a little one-sided!
What does detoxing mean to you? Flushing our system of an accumulation of toxins that builds up in our bodies over time, leaving our organs squeaky clean and healthy?
Well, firstly, isn’t that what our liver, kidneys, gut, skin, and even lungs are for? Your body is unimaginably expert at getting rid of toxins already, and it does so through thousands of complex chemical reactions to create substances that can then be excreted. In fact there’s no known way to make this incredibly complex system, which already works amazingly well, work any better.
Secondly, what toxins exactly are removed by raw food diets, or any ‘detox’ diet for that matter? If these toxins were named, then we could measure them before and after the ‘detoxes’ to test their effectiveness. They’re never actually named, because detoxes are untested, bogus treatments, that belong firmly in the realm of pseudoscience.
As you can probably tell, I feel quite strongly against detox diets. Unfortunately, the word ‘detox’ has been hijacked by entrepreneurs to sell products, treatments, and programmes in exchange for large sums of money. They also encourage people to believe that they can live unhealthily because they can always just ‘detox’ later on to reverse any damage they’ve done. So overall, people end up less healthy, and so do their bank accounts.
Are there any other drawbacks of raw vegan diets?
There’s no doubt about it: a raw vegan diet is restrictive. There are rarely raw food options at restaurants, so one of life’s greatest pleasures – dining out with family and friends – can be at best awkward, or at worst impossible. Friends may also find it difficult to cater for you at dinner parties and so it can even become socially isolating.
And just imagine all of those amazing cuisines / foods that are off the menu on a raw food diet: freshly baked bread, hearty winter stews, barbecued vegetables, rich pasta dishes, curry… imagine a life without curry!
Having a healthy relationship with food is one of the most important ways we can stay healthy and happy. Allowing yourself to believe that some foods can be ‘dead vs. alive’ or even ‘dirty vs. clean’ creates unhealthy eating habits and can even lead to eating disorders like orthorexia, an obsession with eating healthily that paradoxically often becomes dangerously unhealthy for both the mind and the body.
On a practical level, there’s a high level of effort involved with raw food diets too – if you want any kind of variety in your diet, you’ll need to use food dehydrators, and be constantly fermenting foods or soaking / sprouting grains and pulses. It has also been linked to dental problems – the high intake of acidic and sugary fruit, plus the tendency to ‘graze’ throughout the day on raw snacks and juices, leads to tooth decay as plaque acids form on your teeth and damage the enamel.
So what’s the take-home message?
There are some positive aspects of raw food diets: it cuts out processed junk foods and, as with pretty much any type of diet, it at least gets people conscious about what they eat (so many people just eat unconsciously, which in itself can be a dangerous habit).
However, a raw food diet can leave you at risk of deficiencies and can have many other social and psychological drawbacks. While it can help you to lose weight, there are other healthier, more enjoyable, and more sustainable ways to do it. And it certainly doesn't 'detox' your body. An important drawback for me, and for anyone else who enjoys great food, is that you miss out on so many wonderful and healthy cuisines - a travesty in my opinion!
My advice? Eat lots of fruit and vegetables, that's the most important thing. And just eat them how you like them. A varied, balanced, diet containing lots of raw and cooked vegetables (along with whole grains, beans, pulses, nuts, and seeds) is the best solution - and most importantly remember... enjoy your food!
References:
1. Chai, W., & Liebman, M. (2005). Effect of different cooking methods on vegetable oxalate content. Journal Of Agricultural And Food Chemistry, 53(8), 3027-3030.
2. Livny, O., Reifen, R., Levy, I., Madar, Z., Faulks, R., Southon, S., & Schwartz, B. (2003). β-carotene bioavailability from differently processed carrot meals in human ileostomy volunteers. European Journal of Nutrition, 42(6), 338-345.
3. Perveen, R., Suleria, H., Anjum, F., Butt, M., Pasha, I., & Ahmad, S. (2013). Tomato (Solanum lycopersicum) carotenoids & lycopenes chemistry; Metabolism, absorption, nutrition and allied health claims- A comprehensive review. Critical Reviews in Food Science and Nutrition, Critical Reviews in Food Science and Nutrition, 01 January 2013.
4. Teiten, M., Gaascht, F., Eifes, S., Dicato, M., & Diederich, M. (2010). Chemopreventive potential of curcumin in prostate cancer. Genes & Nutrition, 5(1), 61-74.
5. Wongcharoen, & Phrommintikul. (2009). The protective role of curcumin in cardiovascular diseases. International Journal of Cardiology, 133(2), 145-151.
6. Daily, J., Yang, M., & Park, S. (2016). Efficacy of Turmeric Extracts and Curcumin for Alleviating the Symptoms of Joint Arthritis: A Systematic Review and Meta-Analysis of Randomized Clinical Trials. Journal of Medicinal Food, 19(8), 717-729.
7. Kurien, B., Singh, A., Matsumoto, H., & Scofield, R. (2007). Improving the solubility and pharmacological efficacy of curcumin by heat treatment. Assay and Drug Development Technologies, 5(4), 567-76.
8. Chai, W., & Liebman, M. (2005). Effect of different cooking methods on vegetable oxalate content. Journal of Agricultural and Food Chemistry, 53(8), 3027-30.
9. Aune, D., Giovannucci, E., Boffetta, P., Fadnes, L., Keum, N., Norat, T., . . . Tonstad, S. (2017). Fruit and vegetable intake and the risk of cardiovascular disease, total cancer and all-cause mortality—a systematic review and dose-response meta-analysis of prospective studies. International Journal of Epidemiology, 46(3), 1029-1056.
10. Garcia, A., Koebnick, C., Dagnelie, P., Strassner, C., Elmadfa, I., Katz, N., . . . Hoffmann, I. (2008). Long-term strict raw food diet is associated with favourable plasma beta-carotene and low plasma lycopene concentrations in Germans. The British Journal of Nutrition, 99(6), 1293-300.
11. Strassner, C., Doerries, S., Kwanbunian, K., & Leitzmann, C. (1999). Vegetarian raw food diet: Health habits and nutrient intake. American Journal Of Clinical Nutrition, 70(3), 632S.
12. Koebnick, Strassner, Hoffmann, & Leitzmann. (1999). Consequences of a Long-Term Raw Food Diet on Body Weight and Menstruation: Results of a Questionnaire Survey. Annals of Nutrition & Metabolism, 43(2), 69-79.
13. Soenen, S., Martens, E., Hochstenbach-Waelen, A., Lemmens, S., & Westerterp-Plantenga, M. (2013). Normal protein intake is required for body weight loss and weight maintenance, and elevated protein intake for additional preservation of resting energy expenditure and fat free mass. The Journal of Nutrition, 143(5), 591-6.