I hear and read about lots of people making kale smoothies, consuming raw nuts, and munching salads consisting of raw broccoli. So, I decided to take a look at some research to see what the nutritional costs are to eating raw foods. The truth is, it’s better for your body to consume primarily cooked or lacto-fermented vegetables.
Much of the current food science research suggests that cooking food increases the nutrients available from vegetables, meat and fish in humans. Some of the benefits include: improved digestibility of plants, less energy spent on digesting and absorbing food, and most importantly, killing dangerous pathogens present in meat and to some extent, plant matter. Non-thermal processing of food also seems to improve the bioavailability of nutrients, digestibility and even increase the total health benefits of certain foods.
Food has been heat-treated for many centuries, since our ancestors learned, by trial and error, to master fire for cooking purposes approx. 700,000 years ago, to modify the taste and preserve nutritional properties of foods. The invention and continuous development of food treatment has had a substantial, if not major impact on the intellectual, societal and economic development of mankind. The health benefits of fermentation have been known for centuries. In 76 A.D., the Roman historian Plinio advocated the use of fermented milks for treating gastrointestinal infections.
Cooking enhances digestibility of vegetables
Cooking also inactivates anti-nutritional factors such as protease inhibitors and other natural toxins. The second effect is enhanced digestibility of food and bioavailability of nutrients. For example, gelatinization of starch makes possible its hydrolysis by amylase enzymes. Destruction of cell walls in vegetables improves the bioavailability of compounds such as carotenoids and polyphenols. Nuts and seeds contain many anti-nutrients in their raw state. Soaking your nuts overnight, then dehydrating them in a dehydrator or low heat oven will increase the bioavailability of the nutrients in nuts and seeds. Certain foods are associated with disrupted thyroid hormone production. Foods belonging to the cruciferous family are called “crucifers,” and include broccoli, kale, cauliflower, Brussels sprouts, cabbage, mustard, kohlrabi, and turnips. These foods appear to reduce thyroid function by blocking thyroid peroxidase, and also by disrupting messages in thyroid cells. Cooking these vegetables greatly reduces these negative effects.
The thermic effect of food (TEF) is defined as the increase in metabolic rate after ingestion of a meal, due to energy spent on digestion, absorption and metabolizing nutrients. Cooking also appears to have a positive effect on net energy in the body. Humans on vegetarian diets exhibit higher reproductive performance when eating cooked food than raw food. Evidence of low energy intake in women eating predominantly raw food is supported by their having higher rates of amenorrhea or menstrual irregularities than those eating cooked food. In one study, it was found that menstruation was absent in 23% of females of childbearing age who ate at least 70% of their food raw and in 50% of women reporting a 100% raw diet. Although these women were primarily vegetarian, the addition of raw meat to the diet did not change the odds of ovarian suppression. The researchers concluded that women suffered because of their relatively low net energy gain as a consequence of eating their food raw. In another study, a nutritional analysis suggested that in traditional communities, a diet of raw wild foods would render survival and reproduction difficult.
Higher fat meats can lead to better energy balance
It is important to note that eating cooked very lean meats has a nutritional cost. Archaeological evidence suggests that fat derived from bone marrow may have been preferred over muscle tissue as a source of energy and nutrients among early humans. Diets deriving more than 50% of calories from lean protein can lead to negative energy balance, so-called ‘‘rabbit starvation,’’ due to the high metabolic costs of protein digestion.
Cooking kills pathogens
Cooking kills foodborne bacteria, including strains associated with raw meat products such as Escherichia coli, Salmonella, Campylobacter, Staphylococcus, and Listeria. The potential energy savings due to reduced immune maintenance and upregulation could be sizeable. Raw wild meat is possibly less pathogen-bearing on average than raw meat that has been raised and processed for mass-market consumption. When meat is processed at the slaughterhouse, ecoli and other pathogens from the intestines can invade the ground meat. This is why most outbreaks involve burgers and other forms of ground meat but is not usually associated with steaks. These pathogens do not enter the inside of the muscle tissue (steaks). When eating industrially raised red meat, it is suggested to cook burgers well. New processing techniques in industrial meat facilities, such as piercing steaks to improve texture of tougher cuts of meat, can mean that pathogens may be entering steaks as well as burgers. Slow cooking meat appears to be one of the best methods to prepare meat for optimal digestibility.
Lighly cooked fish is healthier than raw or fried
In the case of fish, it appears that lightly cooked is optimal. In one study where edible portions of fresh fish were used raw, fried, cooked and undercooked, the researchers concluded that the breakdown of fish proteins were all fairly complete, but general digestibility was greatest with underdone fish as compared to raw, fully cooked or fried fish.
Fermentation improves gut flora
Fermentation is a non-thermal process that produces chemical changes by enzymes produced from bacteria, microorganisms or yeasts and is one of the oldest known food preservation techniques. During fermentation, the carbohydrate energy source in food, such as lactose in milk is converted to lactic acid. The same happens when pickles are produced from cucumbers. Yeasts convert glucose to ethanol and carbon dioxide. Many health-producing secondary metabolites are produced through fermentation, especially B vitamins and bioactive peptides which can be antimicrobial and immune-stimulatory. In the early 1900s it was realized that bifidobacteria may be effective in preventing infection in infants and the consumption of fermented milks were seen to reverse putrefactive effects of the gut micro flora, leading to the development of the probiotic concept. Probiotics are now used in the treatment of infections and used to promote a healthy immune system. Consuming fermented foods will improve the presence of healthy bacteria in the gut.
Pounding, curing and cooking meat is beneficial
When considering meat, there seems to be some evidence that processing meat either by pounding, drying, curing or cooking is beneficial. Pounding meat and making it soft seems to reduce the cost of digestion, partly because it can pass more quickly through the gut. T
he collagen surrounding each fascicle of muscle fibers generally remains too tough for mastication until heated to 60–70 C, when collagen begins to be hydrolyzed into gelatin, a soluble protein. Although the muscle fibers themselves remain tough, eat meat cooked beyond this temperature leads to gelatinization of the collagen, which separates the muscle fibers and the gelatin.
Improved texture means we eat more protein
Improved texture of meat makes it easier to chew, and easier for our bodies to break down. Also when the fats are heated to oil from a fat, it’s easier for bile to emulsify and ultimately leads to faster absorption. In studies, humans and chimps prefer the taste of cooked meat, leading to us eating more of it. Consumption of more protein meant larger brains and bigger muscles as we evolved.
In summary, it appears that cooking meat and vegetables, consuming lacto-fermented vegetables, and other cured meat is preferable to raw. Well cooked poultry and red meat is safest and easiest to break down, in addition to tasting better. It also appears that the leanest cuts may not be the healthiest to focus on for the bulk of the diet. Regarding fish, lightly cooked fish seems to be optimal, based on the research. Finally, cooking and other methods which improve the texture of meat, make it more palatable leading us to consume more of it. Some studies indicate that our brain size grew at the same time humans discovered fire, and one theory states this could be due to increased protein consumption at that time.
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