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PHOTO: Raw food diet advocates argue that food is more nutritious in its natural, uncooked state.(Getty Images: solrunarnarsdottir)

These days every hipster cafe has a glass cabinet full of "raw food treats" — typically packed with dates, cacao nibs and other mysterious ingredients designed to take the edge off the guilty feelings typically accompanying a coffee and cake combo.

But what exactly is the raw food diet and where did it (and its delicious snacks) spring from?

As the name suggests, raw food enthusiasts espouse a diet comprised completely, or at least substantially, of uncooked foods.

Some raw foodies include uncooked meat, eggs and/or milk in their diet. But for the most part, the raw movement is led by vegans, who eat only raw fruit, vegetables, nuts and seeds.

The history of the movement can be traced back as far as the 1850s, when Presbyterian minister and promoter of dietary reform Sylvester Graham started the American Vegetarian Society. But Sydney nutritionist and blogger Catherine Saxelby said the raw food diet really came to prominence about 30 years ago.

"Eating raw has been a big part of the alternative health movement. It was big in the 1980s with Leslie Kenton, a UK naturopath [who] started this 'raw energy' movement. And it's kind of back in trend again now," she said.

Some nutrients damaged, others enhanced

The thinking behind the diet is that cooking above 40 degrees Celsius (just above the normal temperature of the human body) destroys important nutrients and enzymes in our food, and can also form harmful chemicals.

But Ms Saxelby said that was only true to a certain extent.

Cooking does destroy some heat-sensitive vitamins, such as vitamin C and folate.

There is also evidence that eating excessive amounts of browned or roasted food, which contain high levels of compounds called advanced glycation end products (AGEs), could lead to an increased risk of developing age-related diseases such as cataracts, Alzheimer's Disease, heart disease and stroke.

Similarly, eating too much burnt, barbecued and char-grilled food has been linked to an increased risk of cancer, because of the formation of carcinogenic substances called polycyclic aromatic hydrocarbons (PAHs).

But research has shown that while some nutrients are lost through cooking, most vegetables retain substantial concentrations of their vitamins and minerals, particularly if you use a wide variety of different cooking techniques — including steaming, blanching, simmering and stir frying — and avoid overcooking them in big pots of water.

And in some cases, cooking fruit and vegetables actually makes it easier for the body to absorb the nutrients they contain.

"Cooking doesn't kill all nutrients, and it actually increases bio-availability of others," Ms Saxelby said.
"There's lots of nice studies on lycopene in tomatoes. It's related to vitamin A and it's in red and orange coloured fruit. When it's raw in tomatoes you probably get about 20 per cent absorption into the body, but when you cook tomatoes … the bioavailability goes up to about 100 per cent."

There are also studies that show the beta-carotene in carrots, which the body converts to vitamin A, is absorbed more readily when they are cooked — particularly with the addition of a small amount of olive oil.

The pros: More fruit and vegetables, less junk

Associate Professor Tim Crowe, a practicing dietician and researcher in nutrition at Deakin University, said the raw food diet was certainly healthier than the average Australian diet.

Australian Bureau of Statistics (ABS) data suggests most of us get more than a third of our daily energy intake via discretionary "junk foods" like chips, cake and pizza.

"It's an extremely healthy diet. You are eating almost all plant-based food, very little overly processed food," Associate Professor Crowe said.

But it's unclear whether the raw food diet delivers more health benefits than a normal vegan diet that includes cooked food, as very little research has been conducted.

Associate Professor Crowe said one likely benefit was weight loss, but not because of any properties inherent to raw foods.

"You'll probably lose weight if you follow it (the diet). But the reason you'll lose weight is because of how restrictive it is," he said.

Ms Saxelby agreed the main benefit of raw food eating was the focus on fruit and vegetables.

And for the environmentally conscious, there are several benefits. Animals and animal products are off the menu, and you'll likely use less gas or electricity, further reducing your carbon footprint.

The cons: Prep time, calorie-dense treats

Ms Saxelby recently road-tested the diet herself for a week. She found, oddly enough, that eating raw meant more time in the kitchen preparing food, in order to make it palatable.

"You're doing a lot of chopping and mixing and making your raw food dressings," Ms Saxelby said.

"Once you made it, it was good … but it did need a lot of preparation."

For Associate Professor Crowe, the main drawback was that you would be cutting out food groups.

As well as cutting out meat, dairy and grains, you would also be cutting out many vegetables that simply cannot be eaten raw.

"A completely raw food diet does reduce how many foods you can eat," he said. "There are some foods that may be more difficult to eat. A lot of legumes may be difficult to eat and digest without cooking … some foods are just not palatable or enjoyable to eat in a raw state — potatoes for example."

Ms Saxelby said as is often the case with restrictive diets, cutting out entire food groups like meat and dairy means you are probably not going to get all the important nutrients your body needs.

"You just don't get enough calcium and iron and zinc and omega 3 on a vegan diet," she said.

The restrictions can also have an impact on your social life. While there are some great raw food cafes and restaurants, most places don't really cater for raw foodies.

Another factor to consider is food safety and hygiene, as cooking kills many of the bacteria responsible for food poisoning. But on the plus side, if you're not eating meats — especially chicken and eggs — then you'll be avoiding some of the leading causes of food-borne illness.

And those sweet raw food treats at your local cafe also come with a warning.

"Nuts and dried fruits, and coconut fat — even if it's raw and uncooked — are still very calorie dense," Ms Saxelby said.

"You need to listen to your stomach and stop eating when it's full … so maybe you have one bliss ball, you don't have six."

The verdict: All things in moderation

Overall, Associate Professor Crowe said the raw food diet was not a way of eating that he would endorse.

How does the paleo diet stack up nutritionally?

The paleo diet is based on the notion that our bodies have not evolved to cope with our modern diet, so we must eat the way our hunting and gathering paleolithic ancestors ate. But is it nutritionally sound?

"For people that enjoy being very obsessive about the food they eat, and people that are overly focused on their health, then the raw food diet would appeal to them," he said.

"But it's not one I would be recommending to many people at all. You can eat just as healthily with having some level of cooking in your food, and eating more of a traditional vegetarian style diet — without taking it one step further and not cooking food. You just don't need to go that far."

While Ms Saxelby doesn't recommend a 100 per cent raw food diet, she does believe we can benefit by increasing our raw food intake and boosting the amount of fruit and vegetables we consume.

"I think 50 per cent [raw food] is fine," she said. "Some people have an 80-20 rule. They eat 80 per cent raw, 20 per cent cooked and that's good because you can have a little bit of cheese or meat or fish … It's good to incorporate it partially. Like a lot of these diets, take the best from it."

Another approach is to adopt a "raw before four" diet, eating only raw food before 4:00pm and then having a cooked dinner.

"Then hopefully you can sit with the rest of the family … you're not sitting by yourself with a big salad at the other end of the kitchen," Ms Saxelby said.

-来自 ABC NEWS

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