Marks Daily Apple
Serving up health and fitness insights (daily, of course) with a side of irreverence.
16 May

Safe Cooking Temperatures

If you can't stand the heat...Let’s face it. Some of us grew up in houses where our fathers habitually burned the toast and set off the smoke alarm on a daily basis. Perhaps our mothers roasted the Thanksgiving turkey until you could weave an absorbent bath towel with its fibers. Or maybe grandpa’s grilling style charred every piece of meat beyond visual recognition. Yes, comparative tales of over-cooking are the stuff of familial nostalgia and domestic comedies. We knew it tasted bad (O.K., wrenchingly bad), but was it that bad for us?

Let’s first say that MDA is not about to go raw foodie. We love our veggies and meats, and we say this first and foremost: eat ‘em any way you can. Nonetheless, the bulk of research seems to suggest that cooking, specifically with certain temperatures and methods, can do a real number on the food we eat.

Raw Veggies

First let’s get the arguments on the table. There’s Grandma Mabel in her house dress sitting in one corner spouting off on how all her relatives lived to 90+ and had two sides of cooked vegetables and well done meat (of course!) at every meal, thank you very much. On the other side is the raw foodie in slouchy jeans saying carcinogenic compounds are waiting to attack your every cell if you dare put that spoonful of cooked carrots in your mouth. O.K., that’s not exactly how it is on either side of the food fence, but we love the visual

Much of the argument for “raw” boils (teehee) down to this. When food is cooked, the natural enzymes and micro-organisms are eliminated, nutrient levels plummet, and harmful compounds such as heterocyclic amines are formed.

Hmmm. Grandma? “Ha! Then what about my homemade cooked tomato sauce and the increase in lycopene and overall antioxidant activity?” (Never underestimate Grandma.)

Saute

Well, we’ll leave you two to duke it out in the corner with that basket of raw beets. As for the rest of us, why don’t we just take a closer look. When it comes to cooking, what’s lost? What’s gained? If we tend to side with Grandma, are there things we can do to maintain or enhance the healthfulness of the foods we cook?

Before we move onto the specifics, one overall principle seems to be this: low temperatures are generally better for retaining the highest nutrient content of food and for reducing oxidation and its associated toxic by-products. High heat, prolonged cooking? Not so good. But we’ll get to that.

Negating Nutrients?

First, the nutrient question. As we reported in January, Italian scientists had found that different cooking methods had varying impact on the vegetables tested. Sometimes cooking depleted nutrients (as in frying) and sometimes it enhanced them (boiling and especially steaming). But that doesn’t tell the whole story. Other researchers at the University of Warwick found that steaming, microwaving and brief stir frying of Brassica vegetables (e.g. broccoli, cauliflower, Brussel sprouts) maintained the veggies’ anti-cancer properties otherwise known as glucosinolates.

Boiling Water

Boiling, however, resulted in significant loss of glucosinolates: “broccoli 77%, Brussel sprouts 58%, cauliflower 75% and green cabbage 65%.” The researchers in the Warwick study boiled the vegetables for 30 minutes, which was a much longer duration than that used with the other cooking methods. High, direct heat and long duration both contribute to the leeching of nutrients into the water. Other cooking methods such as frying and broiling use very high heat as well and are not recommended. Another tip: hold off on adding lemon juice and other acids for flavoring. Acids can break down vegetables, particularly more delicate varieties, encouraging additional nutrient loss.

To maintain nutrient levels (PDF), let your senses be a guide. Remember those dull, anemic, limp little mushy cylinders that passed for green beans in school lunch? There’s a reason they looked gross to you then (and now). It turns out the more appealing a bean looks, the healthier it probably is. Green beans, for example, that are briefly steamed or “poached” in a few tablespoons of water will be even more vibrantly colorful than they were before that quick dip in the pot. The texture will be tender but still a bit crisp. This is what you’re looking for when cooking produce: when they look like they belong on the cover of Bon Appetit, they’re done. (Hint: you may even want to briefly blanch them in some ice water to completely halt the cooking process.) And, as a general rule, keep the lid on while you’re cooking/steaming. The food will cook faster, and less time subjected to the heat is good). Low and enclosed does it.

Cooking, as in the example of Grandma’s lycopene-rich tomato sauce, can “activate” nutrients, and can even make them more bioavailable. Certain foods are to some degree poisonous or unhealthy to humans in their raw state. Many tubers, for example, must be cooked to be a healthy and digestible nutrient source for humans.

Transferring Toxins?

The question of cooking involves not just retaining the good but avoiding formation of the bad. One of the foremost toxins associated with cooking are heterocyclic amines (HCAs), a variety of carcinogenic compounds formed during the cooking of muscle meats through a reaction involving creatine and amino acids. (HCAs form with the “carmelization” and charring we see most prominently when grilling.) Studies have linked the intake of HCAs with cancer of the stomach.

Barbecue

High heat cooking such as frying, broiling and grilling produces higher levels of HCA. In fact, HCA levels can triple when temperatures are raised from 392 degrees to 482 degrees Fahrenheit.

A better cooking option for meat is oven roasting. Even better yet are stewing or braising, which keeps temps at or below boiling (212 degrees). With these slower, lower cooking methods, it’s still advisable to cook meats to “medium” doneness. Check the meat rather than let the crock pot decide when it’s ready.

Other harmful substances associated with high heat cooking are AGEs (a.k.a. glycotoxins), which have been associated with inflammation, oxidative stress and aging. A diet that contains meats cooked with high heat methods such as grilling, broiling and frying has been associated with higher levels of AGEs.

Another word on oxidation and cooking. While stir frying at low to medium temperatures offers a good option for veggies and meat strips, it’s important to not undo the good by using oils that will be cooked rancid in the process. Use broth, coconut oil, clarified butter or refined oils that are appropriate for higher temperatures.

Mitigating Measures

Some of us love our grills and cooked foods of all varieties. And, as we mentioned earlier, we’re all about meat and vegetables in a pot, on a house, with a spork, etc., etc. So, are there “measures” we can take to minimize the damage our cooking methods and their accompanying temperatures may cause?

Oven Knobs

Using the microwave to partially cook meats before grilling or broiling can cut HCAs by as much as 90%. Likewise, using marinades with herbs such as rosemary, thyme, oregano, garlic, basil or parsley can lower HCAs by up to 87% (and adds some antioxidant action to boot).

Our final word: Eating a diet rich in vegetables and meats is what we’re all about. But we’re always looking for ways to make a good thing even healthier. We think there’s enough reason to eat raw when it makes sense to and when you prefer it that way. Yet, cooking figures into the picture for most of us, and we think a little information can make a healthy (and tasty) difference.

Comments, suggestions for cooking? We’d love to hear them.

kpishdadi, In Praise of Sardines, feministjulie, canonsnapper, . SantiMB . (toobusy), bennylin0724 Flickr Photos (CC)

Further Reading:

When Do Foods Really Go Bad?

DIY Household Cleaners

13 Simple, Timeless Kitchen Hacks (Banish Tears, Cuts, Burns, Smells & Stains!)

Diet Hack: Practical Tips for Cooking Vegetables

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You want comments? We got comments:

Imagine you’re George Clooney. Take a moment to admire your grooming and wit. Okay, now imagine someone walks up to you and asks, “What’s your name?” You say, “I’m George Clooney.” Or maybe you say, “I’m the Clooninator!” You don’t say “I’m George of George Clooney Sells Movies Blog” and you certainly don’t say, “I’m Clooney Weight Loss Plan”. So while spam is technically meat, it ain’t anywhere near Primal. Please nickname yourself something your friends would call you.

  1. I rarely cook anything on the indoor range at a temp higher than medium anymore; usually I turn the burners down to low or very low once the pan is hot and cooking has commenced. If I do use a higher temp (medium-high), it is just for a very short time, for browning or to reduce a sauce. Even for steaming or using a double boiler, once the water is hot enough to make steam, lowering the temp to just below medium is usually adequate. Saves energy and the pots are easier to clean, too.

    I never liked fried eggs very much but now I realize that I always had them cooked too fast over heat set too high, which rubberizes and hardens the whites on the edges, doesn’t set the whites in the middle (ugh), or overcooks it all, especially the yolks (which I like runny or semi-runny).

    Now I heat the butter in the pan on medium until the butter stops foaming (water in butter has evaporated), add my 2 or 3 eggs, season (seasoned sea salt & pretty green kelp granules), cover with a lid (sometimes adding a TBL of water for steaming), and reduce temp to med-low or low. Covering allows moisture to gently steam the whites without crisping the edges or overcooking the yolks (adding the water is great when not flipping eggs over because it perfectly sets the whites without overcooking the yolks). I turn off the heat when the egg whites are not quite set in the center, gently flip the eggs over for just a second or two to finish setting the egg whites, then flip them back for perfectly cooked egg whites, and nicely warm and runny egg yolks.

    A good thin flexible spatula with an angled front edge is important for flipping without breaking the yolks. Mine is a cheap flimsy plastic white one that I would be lost without.

    If I’m feeling really decedent, I’ll top the hot eggs with a small pat of butter to melt on top. Yum!

    Living in So California, I do grill a lot throughout the year, too. But I rarely cook anything over direct heat the entire time.

    I heat the grill on high, sear for a few minutes on medium-high or high heat, then move the food to the “off” side of the grill (where the temp is cooler) and close the cover; the cooking continues via indirect heat.

    “Low and slow” is best for the typically lean pastured foods I use anyway. Even if some juice or fat drips below (minimal amounts), it isn’t onto the heat source so flare-ups are minimal (searing and not poking the meat surface keeps the juices from dripping, too). I love my “pigtail” meat turner or very long tongs. Additionally, I tend to cook most meats to no more than medium rare (which is almost too well done for pastured meats). Lately I’m leaning toward outright rare meat. I also avoid sugary BBQ sauces on the grill, which just burn and char unless applied in the final moments (plus who needs the sugar?).

    Anna wrote on May 16th, 2008
  2. I recently bought a vegetable steamer for just this reason. Short of being a “raw foodist” the steamer keeps the vegetables fresh and crisp, I’d argue better than boiling. Plus, it’s the only decent way I know how to do Asparagus without being one of those fancy ridiculous asparagus cookers.

    Marty wrote on May 16th, 2008
  3. I’m glad you mentioned that cooking reduces toxicity in certain foods. I think that point is underappreciated, because people tend to focus exclusively on nutrient content. I also think it’s the main weakness of the raw food philosophy.

    Brassicas contain goitrogens that are destroyed by cooking. Beans, grains and other seeds contain anti-nutrients and toxic lectins, some of which are destroyed by cooking. Other vegetables are just too tough without cooking.

    I do think we’re well adapted to eating raw meat, although cooking it probably isn’t so bad either. One of the things Weston Price noticed was that all the healthy cultures he studied had at least a little bit of uncooked meat in their diet.

    Sasquatch wrote on May 16th, 2008
  4. You see the transferring of toxins at tali gaiting1 events all over this country and it seems as though that this sort of thing is promoted rather than frowned upon. I am not saying people should stop grilling food if they want, what I am saying is there is a responsible way of cooking your meals and that these things should be taken into account even at events with large gatherings.

    Cal wrote on May 16th, 2008
  5. I have a rather laborious recipe for bread/muffins that is a nutritional masterpiece, and for at least some of the batches that I make for a friend of mine, the requested final topping before going into the oven is a sprinkling of NAC (N-acetyl cysteine), to inhibit browning and reduce the volume of AGEs created during baking.

    Now that’s using science to tweak your cooking!

    More on browning here:
    http://www.alive.com/747a2a2.php?subject_bread_cramb=111

    Andrea wrote on May 16th, 2008
  6. Two things:

    1) I had an amazing pork ossobucco last night at a local restaurant. They had slow cooked it at low temps for over 24 hours. If I had the time (or Anna’s patience) I would do more of that myself.

    2) I do grill a fair amount of meat, trying to be careful not to overdo it…and I prefer it rare anyway. But the whole HCA / AGE thing is a major reason that I take the high amounts of supplemental antioxidants that I do on a daily basis.

    Mark Sisson wrote on May 16th, 2008
  7. Interesting post. I also think it is important to choose the right kind of oil for the cooking temperture and the ingeredients of the food being cooked. When I make an omlete I use olive oil and when I want to stir fry veggies in higher tempertures I usually use grape seed oil. The latter is supposed to be more resistant to higher tempertures. I never heat flaxseed oil, just for dressings and sometimes with yogurt and berries.

    Al wrote on May 16th, 2008
  8. I agree, slow & low for meat, however this issue of goitrogens & nitriles in crucifers is rather concerning even alarming, i eat loads of raw cabbage & brocolli (in salads) & kale or sinich/banana smoothies but maybe this is unhealthy? what ? even boiling only reduces the content by one 1/3, there’s so much confusion in the nutritional world but one rule usually stands – ‘veg is good’ now even this is an issue, sometimes i wonder if there is anything you can actually eat without compromise.

    JC wrote on May 17th, 2008
  9. If you are cooking at low temperatures (braising comes to mind), then you are not cooking hot enough to break down any refined oil.

    If you are cooking at higher temperatures even for fairly short periods of time, the coconut oil you recommend is one of the worst choices, because it has one of the lowest smoke points (350F). The smoke point is the temperature at which a fat or oil begins to break down (and taste bad).

    Consequently, I use the following refined oils:

    Up to 350F: Olive oil, or if I don’t want the olive flavor then canola oil.

    350F – 400F: Extra virgin olive oil (aka EVOO) or canola oil. EVOO has a higher smoke point than regular olive oil.

    > 400F: Safflower oil or, as you suggest, ghee (clarified butter).

    Also, in support of your article, there is no real need to use raging high heat to sear meat. You can get a better, healthier (I think), juicier, tastier light brown “sear” (if done with spices this is sometimes known as “bronzing”) at medium heat; you don’t need raging high heat. It just takes longer

    The idea that searing meat locks in its juices was debunked empirically in 1984 in Harold McGee’s “On Food and Cooking: The Science and Lore of the Kitchen”, a book highly praised by no less than Thomas “French Laundry” Keller himself. Here is a quote from an article about Mr. McGee:

    For the original [edition of his book], McGee set out to debunk various kitchen myths. A big misconception, McGee said, is the belief that by searing meat, juices are locked in. Not so.

    “It’s not an old wives’ tale. It’s an old chemist’s tale,” McGee said, referring to 19th-century German scientist Juntus von Liebig.

    “Take two steaks, sear one and cook it medium-rare, and then cook the other to medium-rare, gently, without searing it,” he said. “They’ll both be done to the same end-point. But the one that’s seared loses more moisture. Far from sealing in the juices, it squeezes them out.”

    Full article:

    http://www.paloaltoonline.com/weekly/morgue/2004/2004_11_19.mcgee19ja.shtml

    Curtis Jackson wrote on July 15th, 2008
  10. What about roasting vegetables? There’s a big trend now to roast vegetables to maximize flavor, etc. It’s high heat – 400 to 450 – but not so long. Is that a total burn of nutrients? Thanks.

    Marla Johnson wrote on March 26th, 2009
  11. Marla, roasting sure makes them taste good! So I say roast’em and just eat more.

    Mark Sisson wrote on April 1st, 2009
  12. I can’t help but I always cook my entrecote stakes in a raging heat on a cast-iron pan. About 1.5min per side and the stakes are nicely seared and medium-rare. I wonder if cooking for such a short duration is really detrimental to the meat?

    Steven wrote on May 31st, 2009
  13. ” … using a microwave to partially cook meats…”

    Uh…NO! Why would I pay for grassfed/finished meat and then destroy the nutrients by rendering them worthless in a microwave…no no no.

    Whoever does that don’t make me come and slap you.

    suvetar wrote on June 26th, 2010
  14. Im interested in grilling/BBQ. Would using wood from nearby trees be the best/healthiest source of fuel? As opposed to charcoal, propane, wood chips, etc.

    Jason wrote on July 1st, 2010
  15. What’s the best way to cook a beef tenderloin (filet mignon)? I just got 10 pounds of grass fed tenderloins. I was going to grill them but now I’m worried that I eat too much grilled food and well-done food.

    Does the microwaving method work with this cut of meat? Suvetar, are you sure that microwaving does away with the nutrients? Last I heard, microwaves preserve nutrients better than most other methods of cooking…

    Any advice much appreciated!

    Ashley wrote on October 5th, 2010
  16. If our bodies are really adapted for pre-agricultural hunter/gatherer lifestyles, wouldn’t that mean that our bodies are also adapted for open flame cooking which is probably how our very remote ancestors cooked their meat for millennia? They more likely than not fired up some logs and threw meat on the fire, HCA be damned. I doubt that they hauled around pottery in which to stew their food. For that reason, could it be that high temperature cooking actually does us no harm?

    MetaCynic wrote on February 13th, 2012
    • good point! i often wonder about how bad HCA can be for this very reason too. When I was in Australia that was exactly how they were cooking a kangaroo under a tree in the middle of nowhere – big chunks straight on the fire. I don’t worry too much about a bit of HCA.

      Damien wrote on April 10th, 2012
      • not disparaging the aboriginees, but many other societies globally that had relatively complex cooking methods, also had relatively complex learning and other progress that the aussies did not have.

        ian wrote on April 12th, 2012
    • Modern humans are exposed to a much much greater load of toxic chemicals, so i have no doubt there bodies could rid it much easier then ours

      Chris wrote on November 2nd, 2012

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