When did eating get so complicated? I remember when my grandfather would go out back behind his Chicago bungalow and pick vegetables for dinner while cursing at the bunny as it slipped out through a hole in the chicken wire fence. Then later that day, we’d savor the flavors of fresh-picked, organic produce nurtured from seed to table by his weather-beaten hands and expertly prepared by my grandmother in her eternally aromatic, cozy kitchen.
Back then it was simple. We ate fresh whole foods, and nothing processed. Today, it seems much more complicated, but is it really? With any number of specific diets bombarding the internet and diet books filling bookstore shelves claiming to have the secret for a long and healthy life, we’re left wondering if the claims really hold up. You know the diets I’m talking about -keto, paleo, macrobiotic, raw, vegan, vegetarian, pescatarian, wildatarian, South Beach, Weight Watchers and the Mediterranean, for example. In this article, I’ll take a closer look at just one diet in particular - the raw food diet and see how it holds up to the science.
So what if you eat a carrot raw or roasted, an onion raw or sautéed, a tomato raw or stewed? Well, it turns out that when your using food as medicine, how you prepare your food makes a huge difference in which nutrients your body absorbs.
When it comes to the raw food diet, many enthusiasts operate on the notion that cooking food destroys nutrients and enzymes which are vital to boosting digestion and fighting chronic disease. A minority even go as far as to say that cooking food makes it toxic. Rest assured, that is not the case.
In terms of lost enzymes, it is true that enzymes are heat sensitive and deactivate when heated over 117°F, but no studies have been successful in proving that the result is enzyme deficiency in humans. Some scientists even point out that the enzymes are there only to nourish the plant not help people digest them. Furthermore, humans produce their own enzymes to digest food, making enzyme deficiency unlikely.
On the point of cooked food toxicity, Kathleen Zelman, MPH, RD says, “Contrary to the claims of many raw food fans, cooking does not make food toxic but instead makes some foods digestible, boosting nutrients like beta-carotene and lycopene, and kills bacteria, which helps you avoid food poisoning.”
Andrew Weil, M.D. points out, “Another disadvantage of eating raw foods is that many of the natural toxins in edible roots, seeds, stems and leaves are destroyed by cooking them in water. For example (when raw), alfalfa sprouts contain canavanine, a natural toxin that can harm the immune system; button mushrooms contain natural carcinogens, and celery produces psoralens, compounds that sensitize the skin to the harmful effects of ultraviolet radiation in sunlight. Most of these detrimental compounds are broken down by simple cooking.”
What is the raw food diet exactly?
The rules are flexible and there is no one raw food diet. Vegans, vegetarians and omnivores can choose it, and some allow for a percentage of foods to be cooked to a temperature no higher than 188°F even though the raw food diet doesn’t allow heating food over 116°F. Essentially, those following a raw food diet will take in at least 70% of their food raw, including uncooked and unprocessed organic fruits, vegetables, nuts, seeds, fermented foods and sprouted grains. Some will also include unpasteurized dairy, raw eggs, meat and fish. However, nutrient-rich super foods such as beans, whole grains and lean proteins, which are not eaten raw will likely be left off the list entirely. In truth, the raw food diet is inadequate in many essential nutrients such as protein, iron, calcium, vitamin B12, fatty acids, vitamin D3 and more, which means buying expensive supplements will likely be necessary.
If you’re concerned about food poisoning with the raw food diet, you’re not alone. There absolutely is a higher risk of food poisoning with raw or undercooked foods, which is why most healthcare professionals will conclude that the risks outweigh any benefits. In fact, eating certain foods raw such as spinach, lettuce, tomatoes and sprouts puts you at higher risk of contamination from E. coli, Salmonella, Listeria and Campylobacter bacteria, all of which cannot survive the cooking process. Medical practitioners recommend against the raw food diet for pregnant women, young children, seniors and people with a compromised immune system or other chronic medical conditions like cancer and kidney disease.
How does cooking help us out?
Some vitamins are lost through cooking, however, others are enhanced and become more available to our bodies. Cooking can boost the flavor profile of foods and make the nutrients easier to digest. A 2002 study, was the first to recognize that the way foods are prepared dictates which nutrients humans are able to absorb and at what levels. For example, cooking certain beneficial phytochemicals aids our ability to absorb them more efficiently. For example, Cis-Lycopene, which is found in tomatoes increased 35% after 30 minutes of cooking, according to Rui Hai Liu Professor in the Department of Food Science at Cornell University. That’s big, since lycopene has been found to help reduce the risk of heart disease, macular degeneration and cancer.
The cooking process breaks down the thick cell walls of the plant allowing your body to better absorb the nutrients. Cooked carrots, spinach, mushrooms, asparagus, cabbage, peppers and many other vegetables supply more antioxidants to the body, such as carotenoids (which give them their red, yellow and orange colors), and ferulic acid than they do when eaten raw, says Liu. A report in the Journal of Agriculture and Food Chemistry specifically looked at the preservation of antioxidants through cooking, particularly carotenoid, in carrots, zucchini and broccoli.
Indole, another cancer fighter, is formed when plants such as broccoli, cauliflower and cabbage, are cooked. A study published in The Journal of Nutrition reported that indole helps kill precancerous cells before they turn malignant. Dark leafy greens such as spinach and kale contain both calcium and iron. In their raw state, a natural compound called oxalic acid blocks the ability for the body to absorb these important nutrients, but when cooked even slightly the heat breaks it down so your body can absorb these critical minerals.
As you’ve likely heard, a diet rich in antioxidants lowers a person’s risk of chronic disease. Your body changes beta-carotene into vitamin A, which plays an important role in vision, reproduction, bone growth and regulating the immune system. In fact, immediately after being cooked, a carrot’s antioxidant levels increased more than 34%. On the contrary, another study found that cooking carrots also leads to a total loss of polyphenols, another important group of chemicals found in raw carrots. Specific polyphenols have been shown to reduce the risk of cardiovascular disease and cancer, according to a report in The American Journal of Clinical Nutrition.
Furthermore, vitamin C levels dropped dramatically during cooking since it is easily broken down when exposed to heat. However, the trade-off may be worth it since vitamin C is readily found in more fruits and vegetables, including broccoli, oranges, cauliflower, kale and carrots, and is retained more readily by some cooked vegetables than is lycopene, Liu asserted.
Another study published in the International Journal of Food Science & Technology determined that cooking asparagus increased several natural phytochemicals, including quercetin, lutein and zeaxanthin. Quercetin helps fight inflammation and may help prevent certain types of cancer and protect the heart. Lutein, helps keep eyes, skin and hearts healthy, and is thought to help protect against breast cancer. Zeaxanthin helps protect your eyes from age-related macular degeneration.
There have to be benefits to the raw food diet, right?
The good news for raw foodies out there is that they don’t have it all wrong. Research shows quite clearly that some veggies, including broccoli, are better eaten raw. According to a study in the Journal of Agricultural and Food Chemistry, the enzyme myrosinase, which breaks into a compound known as sulforaphane, is damaged when heated. A study published in the journal Carcinogenesis found that sulforaphane might block the proliferation of and kill precancerous cells while another study published in The Proceedings of the National Academy of Sciences found that sulforaphane may also help fight the bacterium helicobacter pylori that causes ulcers and increases a person's risk of stomach cancer.
One popular reason to go raw does have merit. Weight loss is possible and even likely for some since the diet is based on clean, whole-plant foods, which are high in fiber and low in calories, fat, and sodium. Moreover, most of what a raw foodie eats will be high in vitamins, minerals and disease-fighting phytochemicals. Research has even shown that the types of calories you consume do make a difference to your waistline as outlined in THE CONVERSATION.
Unfortunately, like with most things moderation is the key with eating raw foods. Essentially, it’s best to eat a variety of raw and cooked foods. More specifically, certain foods are best raw, others are best cooked, and others offer benefits prepared both ways with one caveat. When eating your produce raw, add a healthy oil to help your body better absorb fat-soluble nutrients.
“A mix of raw salads and cooked veggies is the best way to ensure you’re getting the most from these foods. If you’re cooking them don’t cook too much or you’ll destroy other vitamins and beneficial compounds. Cooking lightly retains the most nutrients while enhancing others.” Lauren McGuckin dietitian and spokesperson for the Dietitions Association of Australia.
To make it easy, follow these general rules and the chart below.
General rules of thumb:
1. Buy local produce and store food properly. Oddly enough, the antioxidant levels in some produce can increase in the first few days of storage with the exception of broccoli, bananas and apricots which begin to lose their antioxidants within days of being picked. However, overall there will be a 30% loss of other nutrients within three days of picking.
2. Store fruits at room temperature, including tomatoes.
3. Prepare produce just before you use them.
4. Avoid boiling most produce and losing water soluble vitamins. If you do boil, save the water for use in soups and sauces.
5. Avoid deep-frying, which can create free radicals from extremely hot oil while veggies will lose most of their antioxidants.
6. A light sauté, steam and roast are great ways to preserve nutrients in your food.
7. Increase the availability of fat-soluble vitamins by eating your veggies with healthy oils, such as olive, avocado, flaxseed, grapeseed, coconut and sesame.
8. Eat nuts raw since cooking increases their calories and fats while decreasing important minerals.
9. When fresh produce is not available, substitute with frozen since freezing helps retain nutrients better than canned or other forms of processing.
Get your copy of the Keep It Simple Raw/Cooked Food Chart
Read more:
Check out an article by Marlynn Wei, MD,JD, Psychiatrist in theHuffington Post that details how to prepare 11 fruits and vegetables to maximize their health benefits.