Health is Chemistry, Not Math
In America we seem to have an over-abundance of faith in our ability to control the natural world. Because of America’s early industrialization, large amount of natural resources, and privileged position during World War 2, we got lucky and were able to exploit a lot of cheap energy to build our country. Our victory over the Earth seemed official when America landed astronauts on the moon. This early industrial success seems to have permeated our national psyche and infused us with the false faith that every problem can be solved with the right engineering solution.
But health is not an engineering problem. Science and technology are not always the right tools to use to make a person “healthy.” A person isn’t healthy just because they have all the right parts in all the right places. A sick person can’t always be fixed just by taking out bad parts and putting in good parts. Nor can a sick person be fixed by subtracting “bad” substances and adding “good” substances. When used correctly, some “bad” substances can be good for you, and some “good” substances can harm you.
Many approaches to health seem to simply be “add up all the calories I eat in a day, if I keep it under 1,800, I am healthy” or “add up all the nutrients I take in in a day, if I am around 100, I am healthy.” While the numbers you see on packaging are good guidelines for behavior, it is by no means the whole story.
If you are growing or trying to build muscle or just have a high metabolism, you will need more calories than other people. If you are old or sedentary or just have a slow metabolism, you will need fewer calories than other people. If you are a pregnant young woman, your nutritional needs will be different than if you are an old man.
The way your body processes what you eat isn’t simple, either. You absorb fat more- or less-readily based on your body chemistry and how stressed you are. You absorb calcium more -or less-readily based on your hormonal makeup and on how much Vitamin D you have. You process protein more or less-effectively based on what types of protein it is and how much energy your body spends digesting it.
The nutrition facts on food labels are not equivalent to what your body actually gets out of those foods. For example, the levels of vitamins you actually absorb from preparing and eating a can of vegetables are far lower than the levels of vitamins you absorb from eating those vegetables fresh.
The Calorie information is also just an estimate. A Calorie is actually a unit of heat, which represents the amount of heat that it takes to heat 1 kilogram of water by 1 degree Celsius. Calories were originally measured by direct calorimetry, which meant a scientist would dehydrate the food and burn it underneath of a container of water, then see how much the temperature of the water rose as a result. By this crude measure, wood and dynamite would both be very Calorie-rich foods.
The modern measure takes into account what the average human can/can not digest effectively. The modern Calorie takes the total amount of stored chemical energy in the food and then adjusts the number down based on how hard it is for humans to digest the substance, with fat being the most-digestible substance and fiber being the least-digestible substance. The modern number is also an estimate and not completely accurate, however, because the way that the stomach chemically breaks down food is not the same in all people or all circumstances. If your stomach is particularly cold or particularly hot it won’t digest the food as effectively. If you eat food in a very cold or very hot environment, up to 20% of the Caloric energy you would absorb from the food is wasted on your less-efficient digestion.
The converse is also true—if you eat comfortably-warm foods in a comfortable environment, your stomach has to do less work getting that food at the right temperature for chemical reactions, and you will absorb more of that food’s energy. In fact, a lot of what makes food appealing to us is when it has been prepared in a way that makes digestion efficient for our stomachs. Breads and cakes, for example, are easily-digested because we expand their surface area as much as possible, which lets the stomach acids coat them and work at them from many angles. Harder, flatter breads make your stomach work harder, and therefore deliver less energy to your body successfully, and that is why they don’t taste as good to us, even if they actually contain the same amount of chemical energy as fluffier breads.
Digestion is a complicated chemical process. I don’t think anyone can claim to understand the way that every person’s body will process every food, and I certainly don’t. But I know that I can’t trust the tally-sheets of Nutrition Facts to tell me the whole story about whether or not my diet is healthy.