Your body needs fuel to do its work. It gets it from three sources, carbohydrates, fat and protein. Carbohydrates are anything that comes from a plant or tree, including fruit, vegetables, flour products, potatoes, rice and sugar. You get fat and protein from animal sources–eggs, meat, dairy products and certain fatty vegetables, such as nuts, avocados and olives.
Each of the three sources of fuel has its own building block. For carbohydrates it’s the sugar glucose. For fat, it’s fatty acids. For protein, it’s amino acids.
Your digestive system breaks down each kind of fuel to its basic building block–glucose, fatty acid or amino acid– before it is absorbed into your bloodstream. Once in your system you need insulin to transport glucose out of your blood and into your cells. You need only small amounts of insulin to handle fat and protein. Bottom line: The amount of insulin you produce is mainly determined by how much and what type of carbohydrates you eat.
Modern humans get most of their carbohydrate fuel from so-called refined carbohydrates–mainly flour products, potatoes and rice. These foods provide more calories with less investment of land, labor and capital than any other kind of food because they’re packed with a tasteless white powder called starch.
Starch is comprised of chains of glucose molecules linked end-to-end like railroad cars. Its purpose in nature is to provide energy for seeds to sprout. Seeds contain enzymes that, when water is added, break starch down to pure glucose. Many animals including humans also have digestive enzymes that break starch down to glucose and releases into the gut. It turns out that the amount of glucose you get from eating a serving of potatoes or rice or a slice of bread is about the same as what you’d get from eating a pile of sugar the same size. As one researcher put it, “You can put a teaspoon of sugar on a bowl of Wheaties or a teaspoon of Wheaties on a bowl of sugar. Once it arrives in your digestive system, it’s all the same.”
This is something new for humans. For millions of years, prehistoric humans had no way of processing grains. They got most of their fuel from fat and protein, which they got from eating small animals, large animals, carrion, fish, bugs and nuts. The carbohydrates they ate consisted mainly of crude vegetation–grasses, roots, bark and occasionally fruit when in season. These contained plenty of vitamins, minerals and fiber and could stave off starvation but were meager sources of fuel. Their digestive systems could put to use small amounts of starch, but they consumed only miniscule amounts of it.
Because of our dependency on starch as a major source of calories, we modern humans consume hundreds of times more glucose molecules than our prehistoric ancestors did. It is not surprising that the amount of starch we consume is toxic to many of us. Since humans began cultivating grains about ten thousand years ago, they have become smaller, less muscular and prone to what has been called diseases of civilization, including obesity, diabetes and heart disease.
What Doctors Mean by the Word “Sugar”
When doctors talk about sugar, as in “blood sugar,” they’re not talking about the white stuff in your sugar bowl; they’re referring to glucose. The sugar in your sugar bowl is actually sucrose, a double molecule of glucose and another sugar–fructose. Sucrose is sweeter than glucose, so we like to add it to things to sweeten them up. Because sucrose is half glucose, it contributes to glucose consumption. However, most of the glucose in our diet comes from eating other carbohydrates, including fruits, vegetables,flour products, potatoes and rice.
You might feel guilty about eating sweets because you know they’re full of sugar–sucrose–, and indeed sugar-containing soft drinks are a big problem among kids. However, by far the largest source of glucose in the modern human diet, especially for adults, is starch.
