It is a frailty food manufacturers are very good at manipulating, Gardner says. “Lots of food products are advertised as low in salt, fat, or sugar, but nearly always when manufacturers reduce one of the three, they boost the other two to compensate. Or they put some omega 3 in a brownie, and emphasize that in large letters on the packaging as if it is a health product. But it’s still a brownie! The problem for society is that we eat a lot of crappy foods. Even food banks mostly give out processed foods. We just have to change people’s habits.”
Gardner thinks that’s happening, albeit slowly. “I’m really confident that the ground is moving,” he says. “But you don’t change habits overnight.”
As we part, he adds an afterthought. “There’s a really easy way to do food shopping in supermarkets,” he says. “Just stick to the outside aisles. The aisles in between are almost entirely filled with processed foods. If you stick to the outside, you will automatically have a healthier diet.”
It is easy to make risk sound scary. It is often written that eating a daily helping of processed meat increases your risk of colorectal cancer by 18 percent, which is doubtless true. But as Julia Belluz of Vox has pointed out, “A person’s lifetime risk of colorectal cancer is about 5 percent, and eating processed meat every day appears to boost a person’s absolute risk of cancer by 1 percentage point, to 6 percent (that’s 18 percent of the 5 percent lifetime risk).” So, put another way, if a hundred people eat a hot dog or bacon sandwich every day, over the course of a lifetime one of them will get colorectal cancer (in addition to the five who would have gotten it anyway). That’s not a risk you may want to take, but it’s not a death sentence.
It is important to distinguish between probability and destiny. Just because you are obese or a smoker or couch potato doesn’t mean you are doomed to die before your time, or that if you follow an ascetic regime you will avoid peril. Roughly 40 percent of people with diabetes, chronic hypertension, or cardiovascular disease were fit as a fiddle before they got ill, and roughly 20 percent of people who are severely overweight live to a ripe old age without ever doing anything about it. Just because you exercise regularly and eat a lot of salad doesn’t mean you have bought yourself a better life span. What you have bought is a better chance of having a better life span.
So many variables have been implicated in heart health—exercise and lifestyle, consumption of salt, alcohol, sugar, cholesterol, trans fats, saturated fats, unsaturated fats, and so on—that it is almost certainly a mistake to pin the blame decisively on any one component. A heart attack, as one doctor has put it, is “50 percent genetic and 50 percent cheeseburger.” That exaggerates matters, of course, but the underlying point is valid.
The most prudent option, it seems, is to have a balanced and moderate diet. A sensible approach is, in short, the sensible approach.
*1 There is a surprising lack of consensus on who actually invented the calorie with respect to diet. Some food historians say Nicolas Clément of France came up with the concept as far back as 1819. Others say it was a German, Julius von Mayer, in 1848, and still others credit two Frenchmen working together, P. A. Favre and J. T. Silbermann, in 1852. What is certain is that it was all the rage among European nutritionists by the 1860s, when Atwater first encountered it.
*2 The eight are isoleucine, leucine, lysine, methionine, phenylalanine, tryptophan, threonine, and valine. The bacterium E. coli is unusual among living things in its ability to utilize a twenty-first amino acid, called selenocysteine.
15 THE GUTS
Happiness is a good bank account, a good cook and a good digestion.
—JEAN-JACQUES ROUSSEAU
INSIDE, YOU ARE enormous. Your alimentary canal is about forty feet long if you are an average-sized man, a bit less if you are a woman. The surface area of all that tubing is about half an acre.
Bowel transit time, as it is known in the trade, is a very personal thing and varies widely between individuals, and in fact within individuals depending on how active they are on a given day and what and how much they have been eating. Men and women evince a surprising amount of difference in this regard. For a man, the average journey time from mouth to anus is fifty-five hours. For a woman, typically, it is more like seventy-two. Food lingers inside a woman for nearly a full day longer, with what consequences, if any, we do not know.
Roughly speaking, however, each meal you eat spends about four to six hours in the stomach, a further six to eight hours in the small intestine, where all that is nutritious (or fattening) is stripped away and dispatched to the rest of the body to be used or, alas, stored, and up to three days in the colon, which is essentially a large fermentation tank where billions and billions of bacteria pick over whatever the rest of the intestines couldn’t manage—fiber mostly. That’s why you are constantly told to eat more fiber: because it keeps your gut microbes happy and at the same time, for reasons not well understood, reduces the risk of heart disease, diabetes, bowel cancer, and indeed death of all types.
Nearly everyone equates the location of the stomach with the belly, but in fact it is much higher up and markedly off center to the left. It is about ten inches long and shaped like a boxing glove. The wrist end, where the food enters, is called the pylorus, and the fist part is the fundus. The stomach is less vital than you might think. We give it way too much credit in popular consciousness. It contributes a bit to digestion both chemically and physically, by squeezing its contents with muscular contractions and bathing them in hydrochloric acid, but its contribution to digestion is helpful rather than vital. Many people have had their stomachs removed without serious consequence. The real digestion and absorption—the feeding of the body—happens further down.
The stomach holds about one and a half quarts, which is not very much compared with other animals. The stomach of a big dog will hold up to twice as much food as yours does. When food reaches the consistency of pea soup, it is known as chyme (pronounced “kime”). The rumblings of your gut, incidentally, come mostly from the large intestine, not the stomach. The technical term for gut rumblings is “borborygmi.”
One thing the stomach does do is kill off many microbes, by soaking them in hydrochloric acid. “Without your stomach, a lot more of what you ate would make you ill,” Katie Rollins, a general surgeon and lecturer at the University of Nottingham, told me one day in the dissecting room there.
It is a miracle that any microbes get through, but some do, as we all know to our cost. Part of the problem is that we bombard ourselves with a lot of tainted stuff. An investigation by the Food and Drug Administration in 2016 found that 84 percent of chicken breasts, nearly 70 percent of ground beef, and getting on for half of pork chops contained intestinal E. coli, which is not good news for anything but the coli.*1