Biological Anthropologist, Richard Wrangham’s new book Catching Fire: How Cooking Made Us Human explores the role of cooking in the evolution of what and how humans eat. Almost two million years ago, when Homo erectus lit the bonfire, the species began to consume a greater amount of calories.

The Softening of Foods
Wrangham explains that the larger molecules of raw food, meat or otherwise, take longer to digest, and therefore require more energy to be spent, than those which have been reduced in size due to the heat process of cooking. Think of it simply as “digestion math.” Softer foods are easier to digest and therefore you net more calories from the food because your body is spending less energy breaking them down. For example, digesting fibrous celery results in a zero net calorie gain since the energy output is equal to the energy input.

Wrangham highlights a study, that I now call the “Hamburger Python” study, which used digestion math. When pythons were given raw meat to eat in a ground up form like hamburger, the scientists saw a 12% reduction in energy required to digest. Taking it a step further, the scientists noticed by cooking the raw meat there was also a 12% reduction in energy required on behalf of the python.


Sample Problem:
12% reduction in digestion energy by grinding the meat before eating
+12% reduction in digestion energy by cooking the meat before eating
______
23% (When combined – like a cooked hamburger – it did not yield a simple 24% reduction; there must be some overlap between the two processes molecularly speaking.)

The python “consumed” more calories because the processing did not require as much calorie expenditure to digest the hamburger.



Because heat has the ability to break down the larger, more fibrous food molecules, food is softened to the point that it significantly reduces the amount of time it takes to chew. According to Wrangham, Chimpanzees take about six hours a day just to chew their (raw) food. The still more tightly bound molecules of food are then sent through the Chimps’ GI tract where oxygen (more than required for human digestion) is rerouted from the ambulatory muscles to the GI.

Nutritionally, the effect of cooking has a big impact. Immense! Some might say, obese!
Wrangham cites a study completed by Japanese dentists where four-week-old lab rats were separated into two groups. One group was given typical rat food while the experimental group were given the same food but it was processed to be softer by the addition of air. Everything else was kept constant, like a good scientific experiment. Both diets had the same water content, calorie count and nutritional profile. The rats also had the same daily routine filled with whatever kind of rat exercise they previously received. The rats fed the “air puffed” food grew at a faster rate and ultimately had 30% more body fat than their rat counterparts.

What the dentists concluded was that the softened food texture affected energy metabolism by lowering post-prandial (after eating) thermogenesis (heat production), which is a fancy way of saying the amount of energy the body spends to finish digesting the food. Because of the reduced energy cost of digestion, think “digestion math” again, the metabolic rate of the experimental rats was lower than that of the control.

What does this mean for us?
The researchers believed that the long-term deficiency of thermogenesis, associated with soft foods, results in a greater tendency toward obesity. Our food is becoming softer all the time and not just through cooking. Bread used to be crunchy and have a short shelf life, now it is made with heavily refined grains and can last weeks on top of your refrigerator. We eat linguini instead of cooked barley. We drink fruit juice and smoothies instead of whole fruit. This is just one more bullet point for the whole foods movement!

End of the Line: End of Eating Fish?

The year 2009 is ripe for food documentaries thanks to the growing “foodie” movement. Just this month both Food, Inc. and End of the Line were released. As a student of nutritional science, the latter made me frustrated by the message that was sent – stop eating fish. (To be fair the message at the end of the film was actually, “Ask before you buy: only eat sustainable seafood” however if you’ve seen the movie, fish eating is portrayed as a “guilty” pleasure.) So how can we be conscious fish eaters while not sacrificing the health benefits of this most appetizing and healthy food item?

1.Diversify
Try types of fish that are new to you, in particular those listed as “Best Choices” according to your region’s Seafood Watch Guide. According to Charles Clover (who cited marine scientist Dr. Albert Tacon) it takes 5 times as many kilograms of anchovies to grow 1 kilogram of farmed salmon. During the scene where this is explained, a woman looked frankly at the camera and said, “Why don’t we just eat the anchovies?” With that in mind, try these recipes to diversify your palate:

1. Spaghetti with Sardines, Dill and Fried Capers – use whole wheat pasta and Sardines from the US Pacific waters to get the maximum benefit.
2. Broiled Mackerel with Ginger and Garlic
3. Baked Trout with Shiitake Mushrooms, Tomatoes, and Ginger

2. Substitute If Chilean Seabass and Atlantic Cod are the only fish you like (both are on the “Avoid” list) perhaps it is time to look to non-fish alternatives as a way to obtain some of the benefits of fish. Fish are one of the most nutrient dense food items on the planet. The current buzz about their benefit usually includes their high levels of Omega-3 Fatty Acids, in the bioavailable forms of EPA and DHA. However, what is often overlooked is the rich composition of many vitamins and minerals found in fish and seafood. Recent research has linked adequate selenium intake to lower cancer rates because of its antioxidant properties. It is also known for its assistance in healthy pancreatic and immune system function, prevents oxidative stress of cells, DNA repair and enzyme activation. Selenium is most readily found in a variety of seafood, fish and other animal sources like liver and eggs. Though selenium can be found in plant-based sources, the amount of this mineral present in the food is highly dependant on the level of selenium found in the soil in which the vegetable was grown. Impossible for a consumer to know! Thus, seek organic produce rich in selenium (Brazil nuts, shiitake and crimini/button mushrooms, barley and brown rice) and keep your fingers crossed.

Note: Selenium is a trace element and is very toxic if taken in excess, therefore never supplement with selenium.