Should you cook your food?

I work with an advocate of a "raw food diet", and he has really been challenging my views and opinions on nutrition.  You may be asking yourself what a raw food diet is. It's typically a vegan diet (no meat, dairy, or eggs) in which food is minimally cook and/or processed.  I guess someone can be a raw food enthusiast and still eat meat, but that's not very safe.  I've read different statistics, but it sounds like cooked food takes up less than 50% of the what's eaten, and when it is cooked, it's at lower temperatures for short amounts time.

When man was first created, we didn't necessarily have the means to process or cook our foods.  So it got me thinking that maybe we were created to live off the land and not mess with it too much.

My question is:
Should we even be cooking our food at all?

The premises of  a raw food diet is that you choose foods that are higher in nutrients, and you maximize the vitamin and mineral content by not cooking/processing it.  There is another supposed benefit of natural plant enzymes, as well.

Cooking food does cause some vitamin and mineral losses, but it is not apocalyptic.  The water-soluble vitamins (B and C) tend to be the least stable, and many vitamins and minerals can leak out when they're boiled or when the food loses water (Leskova et al., 2006).

As for the plant enzymes, I am having a really hard time finding credible resources as to what those enzymes are and whether or not they can have health benefits.  The assumptions most people make is that if there are enzymes in our food, then they will be digested so it doesn't matter anyway.  I've heard some arguments to that assumption, but since I can't credit or discredit it at this time, I'll choose to ignore it.

Now, there are obvious health benefits to this diet because you will be removing junk  and including more fruits and veggies.  All junk food has been cooked or processed.  Because they are taking out the biggest sources of saturated fat and cholesterol, people on raw food diets tend to have lower LDL cholesterol and triglyceride levels (Koebnick, et al., 2005).  Additionally, high intakes of fruits and vegetables are usually associated with decreased risks for high blood pressure, stroke, type II diabetes, certain types of cancer, and obesity (Craig, 2010)

But we have to keep in mind that eliminating entire food groups can limit nutrients, so raw food diets and even vegan diets are typically not perfect.  For instance, when you take out the dairy group, most people don't get enough calcium.  Dairy is our highest source of calcium.  You can get it from other foods like green leafies and beans, but dairy and (dairy replacers for that matter) have the most calcium.  There has been research that shows that a raw food diet is associated with bone loss (Fontana, et al., 2005).

Also, when meat is restricted, vitamin B12 can be a worry.  Animal products are our biggest source of B12, so many vegetarians/vegans are at risk for B12 deficiency (Koebnick, et al., 2005).  So we worry about a restrictive diet in anyone, especially kids.  Because kids can be picky to begin with, we worry about limiting their available food further.  Statistically, it looks like vegetarian kids may have higher risks for deficiencies in vitamins B12 and D (Dwyer, et al., 1982).

But people can overdo just about anything.  Just like going crazy on the cooked Tastykakes, going crazy on fruits and veggies can sometimes be problematic.  One thing we worry about is the acidity of some fruits and veggies.  People on a raw food diet have a higher risk for dental erosion (Ganss, Schlechtriemen, & Klimek, 1998).  Crazy, huh?  The author of that paper attribute it to the high acidity of some fruits and veggies.  Some processed foods have acid controls (buffers) as additives to control acidity, but raw food doesn't really.

So because a raw food diet (which is usually vegan) is missing out on some important stuff, we can't really recommend it on a long-term basis without supplements. The biggest thing we see long-term is the risk of osteoporosis when calcium intake is not high enough (Appleby, et al., 2007).  Also, some people lose too much weight and actually become underweight, causing a whole mess of other health problems like losing your period (not in a good way) (Koebnick, et al., 1999).

It sounds like an optimal diet contains both cooked and raw foods. Because the raw foods tend to be fruits and vegetables, the health benefits are still seen.  Also, many cooked and processed foods may contain the nutrients that are missing in a raw vegan diet .  It looks like if someone wants to go raw, they should only do it for a short while and then go back to eating some cooked foods (Shetreat-Klein, 2010).

The good news is that there are some benefits to cooking your food.  One really good thing to note is that when you cook food, you kill bacteria, thus making animal products edible.  That means those pesky vitamins B12 and D are no longer a concern.  Killing bacteria makes the food last longer in the fridge, too.  Also, some antioxidants like carotenoids actually work better in your body when they've been heated (Boekel, et al., 2010).

The best way to minimize your losses in vegetables would be to not use direct heat, keep it at medium or lower settings, and don't cook it more than 10 minutes.  I always tell my students to strive for their vegetables to have the texture of Chinese food.  You know, it still has a little crunch to it.  So in theory, as long as you don't turn all of your food into mush, you're still going to have some nutritional value to it if you cook it.

So long (I know this one was long) story short:

Yes, it is perfectly acceptable to cook your food...especially ones that taste nasty raw like potatoes. 

And no, you cannot live off of cooked Twinkies your whole life and think you're going to be healthy.