What do actress Gwyneth Paltrow, tennis star Venus Williams, and pro quarterback Tom Brady have in common? All of them have followed a raw food diet at some point.

Raw food diets include foods, mainly fruits,  vegetables, nuts and seeds (ideally organic), that can be eaten without cooking or with minimal heat (no more than 104 to 118 degrees F, say some raw-food websites). For non-vegans, the diet may include raw (unpasteurized) milk, sashimi, ceviche, cheese, yogurt and carpaccio (raw meat or fish).

Supporters claim that eating foods raw preserves valuable nutrients, enzymes and even oxygen that cooking destroys. "Cooking is a process of food destruction from the moment heat is applied to the foodstuff,” writes raw foods advocate T.C. Frye on rawfoods.com. Eating raw, advocates say, “detoxifies” the body. Some people also argue that eating raw is more natural because prehistoric people evolved to digest raw, not cooked, food.

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Nutrition experts say raw food diets do offer certain health benefits — but you may lose out in other areas. SafeBee talked to Vandana Sheth, RDN, CDE, a nutrition consultant and spokesperson for the Academy of Nutrition and Dietetics, to see how the diet measures up.

The pluses

More fiber and beneficial plant chemicals. A well-balanced raw food diet virtually guarantees you’ll be eating more nutrient-rich fruits and vegetables and more fiber — because you really have no other choice. “Most Americans don’t meet the requirement for fruits and vegetables, especially fiber,” says Sheth. “A raw food diet would also have nuts and seeds, so you may have some heart health benefits as well.”

Weight loss. A raw food diet, with its emphasis on fruits and vegetables, will probably help you lose weight, says Sheth.

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The minuses

Losing nutrients enhanced by cooking. While eating produce raw preserves some nutrients that are degraded by cooking, eating raw also reduces the availability of others that are enhanced by cooking. With some nutrients, such as the lycopene in tomatoes, “we actually enhance the nutrients or concentrate the nutrients when it comes to cooking process,” says Sheth. “So lycopene is higher in cooked tomatoes and tomato sauce compared to raw tomatoes. The beta carotene in carrots is significantly higher when it’s in a cooked form rather than the raw form. As far as some other nutrients, like vitamin C, we might lose some from the heating process, but we usually get plenty of that from other foods.”

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Difficulty getting several key nutrients. Eating a raw food diet can make it difficult to get several important nutrients, including vitamin B12, vitamin D, selenium, zinc, iron and two of the omega-3 fatty acids, according to Sheth. “B12 primarily comes from animal products. Some raw vegan sources could be nutritional yeast. That might be a good way to satisfy it,”says Sheth. “But it’s a concern for sure. Vitamin D is definitely a concern. Most of us tend to be deficient on it.” For this reason, people on a raw food diet might need to take supplements, she said.

Lack of protein. “If you’re having beans and lentils,” says Sheth, “if you have them in the sprouted form, the germinated form, you might be able to meet your nutritional needs that way on a raw vegan diet. But you open up many more choices when you have the cooked form.” Cooking is also a simple way to kill bacteria and parasites. Without some kind of cooking, eating meat, fish, eggs, and milk becomes much riskier. Some people on a raw food diet eat yogurt and cheese — good sources of protein — but vegans don’t.

Time, and potential social isolation. Besides simply picking up a fruit and eating it, raw food advocates prepare foods by soaking, sprouting, juicing, dehydrating, fermenting and pickling them. “It’s definitely a big time commitment, for sure,” says Sheth. And depending on your skills and commitment, your food may or may not taste very good. “Unless you very comfortable doing the prepping, the dehydrating, the fermenting, the sprouting, the germinating, it may not be very flavorful. That can be a big setback.”

Dining out with friends, unless you happen to have a raw foods restaurant nearby, may also pose a problem. “Eating out would be a huge issue, because yes, we could get a salad, but what about the dressing? You would have to be really careful with it if you’re very strict.”

“Food is not just nourishment, it is also a part of our lives,” say Sheth. “It’s a part of social settings. So it does put people in sort of a bind when they’re with other people.”

Lower bone mass and density. A raw vegan diet often leads to lower bone density and mass, according to a study by Luigi Fontana of Washington University in St. Louis published in JAMA Internal Medicine. But, as Sheth points out, no one has connected a raw food diet with osteoporosis. “We see the same thing in other studies that look at long-term vegan diets — not raw food diets, but vegans in general,” Sheth says. “They found that they tended to have lower bone mass, but they didn’t have any higher risk for osteoporosis.”

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A word about enzymes and detoxifying

What about the idea that you get enzymes you need for digestion from raw foods? “As far as the suggestion of the enzymes goes, most of us don’t need the plant enzymes for the digestive process,” Sheth says. “Our digestive process takes care of it.”

As for claims that a raw food diet can “detoxify” your body, they’re a no-starter, says Sheth. “We have organs in our body that can do the detoxification process. We have our liver, our kidneys. That’s their job. So if you’re doing the right things in terms of eating a variety of food, we don’t need to have a specific product or a specific diet to cause that detoxification.”

The bottom line

Eating plenty of fruits and vegetables is the way to go for better health, no question. But there’s little scientific evidence to support the claims behind raw food diets or concerns that cooking food does any harm, according to Sheth. Humans have had plenty of time to adapt to using fire and heat to treat food — more than a million years, in fact, since our ancestors first discovered fire.

“In my practice I don’t push for this diet. I say yes, there are some pros and cons to it, and you need to be very educated and careful with it. I’m especially concerned with families taking this on when they have young children. I feel that going more plant-based — yes, there are many positive benefits. But when you take away the cooking process, it eliminates some of the key resources you might otherwise have.”

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Greg Breining is a Minnesota-based journalist who writes about science, travel and nature for national and regional magazines, including Audubon and National Geographic Traveler. His books about the natural world include Wild Shore and Paddle North.