History

Food Processing: It's What Makes Us Human

Turning raw ingredients into something more has played an important role in our evolution. Continue reading →

The idea of food processing these days conjures up images of excess sugar and unhealthy fats, but humans and our ancestors have been processing food for millions of years.

In fact, as DNews' Jennifer Viegas reports today, food processing plays an important role in our evolution, according to new research from Harvard University published in the journal Nature.

Between 2 million and 3 million years ago, human ancestors worked with stone tools to process their meals, pounding or slicing their food to break it down before chewing. Around this time, early humans began adding meat to their diets, a high-calorie food difficult to chew effectively when it's raw or in big chunks. Processing food -- even just cutting it into smaller pieces -- outsources some of the work of digestion so more energy can be extracted from meals.

How the American Diet Has Changed: Photos

Thanks to cooking and other means of food preparation, it's easy to take for granted just how much time and energy food processing saves us.

Consider the efforts other mammals go through simply to chew their food. Our closest relatives, chimpanzees, spend much of their day chomping away at their food, and with much greater bite force at that. Most mammals eat a lower-quality diet and take their time with their meals. Other animals, like reptiles, put even more work into each meal because they swallow their food whole.

Testing how much of a difference in effort was required with chewing raw vs. primitively processed food proved a decidedly unappetizing challenge for the study's participants. Volunteers sampled a small buffet of foods inspired by Paleolithic Era cuisine, which included raw, sliced, pounded and cooked goat as well as a selection of vegetables. Goat was chosen by the researchers because of its similar texture to game. With special devices meant to measure the effort involved, the volunteers chewed until they would normally swallow and then spat each morsel out.

Original Paleo Diet Included Red Meat, Starchy Veggies

According to the researchers' data, the muscular effort and number of chews required by processed food was almost 20 percent less than its raw counterparts over the course of an entire day.

Time and energy expenditure aside, cooking or otherwise processing food comes with other benefits as well. Processed food can be consumed in smaller, more digestible pieces, providing an extra nutrition boost thanks to a higher surface area to volume ratio.

Over time, food processing began to have an impact on human physiology. "Eating meat and using stone tools to process food apparently made possible key reductions in the jaws, teeth and chewing muscles that occurred during human evolution," study author Katie Zink said in a statement.

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When metabolically expensive organs don't require as much energy to do their jobs, they shrink in size. Smaller guts, for example, are only compatible with diets rich in high-quality, easy-to-digest food. This extra resource bandwidth can then be taken up by other organs, specifically the brain. This trade-off is known as the "expensive-tissue hypothesis," first proposed in 1995.

Food processing allowed for larger brains and the ability to communicate through speech, according to paleoanthropologist Daniel Lieberman, who worked on the Harvard study. "We are partly who we are because we chew less."

"A characteristic of the American dietary that has persisted throughout years has been its abundance." This sentence is no less true today than when it was

published in the American Journal of Clinical Nutrition in 1959

. That abundance, however, comes with a cost: Americans eat too much. That excess consumption and often poor nutrition has brought with it a multitude of life-changing and often life-threatening diseases and conditions, including obesity, diabetes, heart disease, cancer and more. Although the number of Americans who are overweight or obese has been on a steady climb since the middle of the 20th century,

a recent report by the New York Times suggests

that efforts to abate this health crisis might be gaining ground thanks to a shift in public attitudes. For the first time since the federal government began tracking dietary intake over more than four decades of data collecting, the daily calorie intake of the average American showed a sustained decline. Read on to see how the American diet has changed since the middle of the 20th century.

Americans Falsely Believe Their Diet Is Healthy

While calorie counts have been on the downswing, calorie intake is still far above where it once stood. Americans' daily average caloric intake is over 500 calories higher than it was in 1970, when the average hovered around 2,169 calories per day. What does a more than 20 percent increase in caloric intake mean for the average American? Consider that a pound a fat contains 3,500 calories. Assuming that even a quarter of those calories represent excess energy beyond what's needed for daily maintenance levels, that translates into a pound of stored fat gained every month, or 12 additional pounds per year. Portion sizes have seen a similar increase over time.

According to the U.S. Department of Health & Human Services

, in the last two decades alone, food portions in American restaurants have doubled or in some cases tripled. Portion sizes began increasing in the 1970s and rose sharply in the 1980s. Many food portions greatly exceed USDA and FDA standard servings,

according to a study published in the American Journal of Public Health

. "The largest excess over USDA standards (700 percent) occurred in the cookie category, but cooked pasta, muffins, steaks and bagels exceeded USDA standards by 480 percent, 333 percent, 224 percent and 195 percent, respectively," the study found.

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According to the U.S. Department of Agriculture (PDF)

, between the 1950s and 2000, Americans consumed on average 39 percent more refined sugars. Consumption of corn sweeteners, with high-fructose corn syrup leading the charge, octupled. On average, Americans consume an estimated 156 pounds -- yes, pounds -- of added sugar per capita every year. Excessive sugar intake can lead to all kinds of negative health outcomes, including but not limited to dental problems, obesity, diabetes, liver failure and more. These concerns are what led the

Food and Drug Administration (FDA) recently to propose

a change in food labeling that would recommend the daily intake of calories from added sugars not exceed 10 percent of total consumption. More than 70 percent of U.S. adults get over 10 percent of their daily calories from sugar.

7 Facts About Sugar That May Surprise You

Americans aren't just eating more sugars than they used to; we're also drinking more.

According to the Harvard School of Public Health

, before the 1950s, the standard soft drink size was 6.5 ounces. That decade, manufacturers started selling larger sizes, and by 1960 the 12-ounce can was everywhere. Fast forward 30 years, and 20-ounce bottles are ubiquitous. Today, single-use soft drinks can reach up to 64 ounces and have up to 700 calories. Since the 1970s, sugary drinks have grown from 4 percent of Americans' daily calorie intake to 9 percent. A quarter of Americans get at least 200 calories a day from soft drinks. Teens and children are particularly high consumers, too. Sugar drinks are the top calorie source for teenagers, and are consumed daily by an estimated 91 percent of children.

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Beginning in 1980, when USDA issued the first federal dietary guidelines implicating fats and cholesterol as a major source of Americans' health woes, particularly heart disease, the food industry began shifting formulas in their products that moved away from saturated fat and toward vegetable oils and carbohydrates. Low-fat diets became all the rage, with a bevy of product lines offering low-fat alternatives. What happened after Americans got turned on to low-fat foods? They got even fatter and less healthy. Foods may not have had as much saturated fat, but they made that up with an increase in sugar and refined grains, which kept calorie counts the same. The switch to hydrogenated vegetable oils and margarines also only increased health risks. Heart disease is still the number one killer in the United States, and we also have rising numbers of diabetes and obesity to contend with. In fact, despite numerous studies since the 1990s showing that low fat diets are ineffective at best and harmful at worst, the government continues to recommend a low fat diet.

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Go to the snack aisle of any supermarket or convenience store in the United States, and you'll find a wide array of potential options to satisfy any junk food craving. What do all of these foods have in common? They're all made of refined grains, in addition to other nutritionally deficient ingredients. Refined grains do not offer the same nutritional benefits as whole grains. The process by which refined grains are produced removes fiber, iron, vitamins and other nutrients,

according to the American Heart Association

. Examples of refined grains include white flour, corn flour and white rice. Not only have Americans turned to unhealthier grains for a greater share of their calories; modern wheat is also less nutritious than heritage grain varieties.

Why You Should Probably Stop Eating Wheat

As Americans increasingly eat out at restaurants more and consume more processed foods, salt intake has steadily increased across all age groups. The average American between ages 20 and 74 consumed close to 1,500 mg more sodium per day in 2006 than in 1971,

according to the Institute of Medicine of the National Academies

. The Centers for Disease Control and Prevention (CDC) recommends everyone ages 2 and up consume less than 2,300 mg per day, which is about a teaspoon a day. Some people with certain health risks, such as diabetes or high blood pressure, should limit that further to 1,500 mg per day. Eating too much salt increases water intake in the body, which leads to high blood pressure. Kidneys work overtime to deal with the excess sodium, and the increased blood volume puts a strain on the heart and blood vessels. At worst, a lifetime of a sodium surplus could lead to heart failure or stroke,

according to the Harvard School of Public Health

.

Fast Food Is Less Salty Abroad

In 1929, presidential candidate Herbert Hoover ran under the slogan "a chicken in every pot and a car in every garage." These items might seem common enough today, but Hoover was basically promising what were then considered luxuries to every American household. At the time of Hoover's campaign, "the few chickens raised for meat were sold directly to high-end restaurants, first-class dining cars, and luxury caterers,"

according to the Smithsonian Museum of American History

. Chickens were instead kept for their eggs, which are a valuable source of protein and other nutrients. Egg consumption peaked mid-century, and has been in decline ever since. The overblown connection between cholesterol in eggs and heart disease certainly contributed to Americans turning their back on eggs. But a decline in prices of another protein source, specifically chicken, also contributed to eggs falling out of favor. In the last half of the 20th century, poultry consumption went up more than three-fold, according to USDA data. Red-meat consumption saw a steady decline over the same period, with Americans eating roughly 10 percent fewer pounds per capita every year.

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