The relationship between people and food is complex enough to begin with, and it can be a little overwhelming if you're diabetic. In this post, after giving an overview of type one diabetes mellitus, I'm going to talk a little bit about the additional complexities that diabetics have with food.
A non-diabetic person has a working endocrine system that responds to natural increases in blood sugar levels by having portions of the pancreas produce insulin, which causes muscles and especially the liver to store the sugar. The liver acts as a buffer or gas tank; when you eat, it is like putting fuel in your body. The hormone glucagon has the opposite effect of insulin. Glucagon causes the liver to release sugar into the blood. A normal person always has trace amounts of glucagon or insulin in his/her blood. There is a good graph at Wikipedia that illustrates how insulin levels in a normal person's body react to sugar levels caused by eating and activity.
Keeping the blood sugar level below a particular value is important for many reasons that I do not fully understand. When the blood sugar goes too high, above about twice the normal value, the kidneys are overworked from removing all the sugar, and kidney damage can result. There are additional problems with blood vessels being weakened by high blood sugar. Keeping the blood sugar above a certain value is important because otherwise your cells would starve (leading to death). The combination of insulin, glucagon, intaking food, and the energy stored in your liver are all critical to keeping the blood sugar levels at a normal value.
A person with insulin-dependent diabetes mellitus (IDDM or type one diabetes) lacks the ability to produce sufficient insulin. A T1 (I will use this as short-hand for a type one diabetic, and it also makes me sound like a terminator) has the problem that his/her blood sugar would naturally go too high after meals, which can (over a period of years) cause kidney and blood vessel damage. T1s have the short-term problem that their energy reserves are too low. If a T1 performs vigorous physical activity and doesn't eat, the blood sugar will plummet, causing problems.
The way T1s normally solve these problems is by injecting insulin. There are two types of insulin: long-acting (basal) and short-acting (bolus). Long-acting insulin works over a period of roughly 18 to 24 hours, counteracting the "background" stream of sugar from the liver. Long-acting insulin is normally taken once or twice a day; in the Netherlands, doctors only prescribe it before sleep, though in America the dose is usually split between the morning and the night.
Short-acting insulin is taken at the same time as food. The short-acting insulin works over a period of roughly 4 hours. The amount of short-acting insulin I take is related to the amount of carbohydrates (sugars) in the food I eat. Right now I use about 4 units of insulin when I have less than 100 grams of carbs at a meal, 5 units when I have 100 - 110 g, and 6 units when I have above 110 g of carbs (I don't eat more than 110 g of carbs at a meal). This amount of insulin will increase over time, as my pancreas shuts down. Right now my body appears to produce enough insulin to cover about 60 grams of carbs; I need to inject insulin to make up the difference.
Unfortunately there are two big drawbacks to using the short-acting insulin. The first drawback is that the "response curve" of the insulin is set. The sugars in different foods take different amounts of time to absorb, but how and when the insulin acts is not variable. For example, when a T1 drinks 100 grams of caramelized dextrose, which the human body digests very efficiently, the blood sugar increases quickly and rapidly. In comparison, if I drink about 130 grams high-fructose corn syrup (which contains about 100 grams of sugar), my blood sugar would take about twice as long to rise. This is because the human body is less efficient at processing fructose than dextrose. How quickly a food is absorbed is known as the glycemic index, though this varies from person to person. The long and short of this is that foods with easily absorbed sugars (high glycemic index foods) will cause spikes in my blood sugar, which are bad. This is actually true for people in general; the South Beach Diet is a diet that partially focuses on eating low glycemic index foods, causing a lower variation in blood sugar. This type of diet is supposed to be better for you (you can also use it to lose weight, but that isn't the primary purpose of that diet).
Anyways, the important point is that if I'm not exercising (a different post entirely), then my doctor recommends eating food with a lower glycemic index, and eating it slowly. Foods that seem similar actually act very differently. Cherries have a lower index than raisins. Prunes are better for me than dates. Grapefruit is better than pineapple (but this is definitely only true from a glycemic index standpoint; in every other way, fresh pineapple is vastly superior to grapefruit). Anything made with processed, white flour is absorbed very quickly, so things like pancakes will cause spiky blood sugar.
The other drawback to the short-acting insulin is that there can be absorption problems long-term. Scar tissue builds up if a particular site is stressed repeatedly, and if a pocket of insulin isn't absorbed because of scar tissue, and the insulin is released quickly, a sudden drop in blood sugar can occur. Scar tissue is prevented by rotating injection sites; I use half of my body for a month, and then switch. During the month I also rotate within the site itself. I prefer to use the tops of my thighs in the mornings and the evenings, since the large surface area makes site rotation easy. However, it is a bit inconvenient at work, so I normally use my belly at work. Massaging the area before the injection (increases blood flow) helps a little bit, but massaging afterwards seems to cause bruising. Insulin can and does leak if the needle isn't held in the site; I normally count to 10 after injection.
Long-term, lowering the intake of insulin also prevents scar tissue problems. I am trying to eat a low-carb diet by using the Idaho Plate Method. In this method, you split your main plate into a half and two quarters; low-starch veggies occupy half, starch-heavy grains and veggies occupy a quarter, and protein sources occupy the other quarter. One piece of fruit can accompany a meal. The food has been a bigger adjustment than the shots or finger pokes. I ate a lot of pasta before learning I was T1, and right now if I tried to eat a meal with 250 grams of pasta and 500 ml of orange juice (both huge sources of carbs)...well, let's just say a meal like this is a bad idea at this moment. I could eat such a meal if I wanted to, but I'd need about two or three times as much insulin as a much healthier meal.
You'll notice there is no "dessert." Fruit is dessert right now. Sometimes I'll have a square of very dark chocolate with a meal or before I exercise, but right now I'm adjusting to eating less sugar. It isn't easy, but it reduces the amount of insulin I require and is going to be better for me long term.
Well, this post turned out a bit longer than I expected, but I hope it clears up how diabetics view food. We care more about the amount of sugar and how it is absorbed, in addition to the standard concerns about vitamin content and caloric content. All in all, the forced examination of my diet has turned out to be a pretty good thing. It wasn't a great idea to be eating a meal that was 300 g of spaghetti with 500 ml of orange juice as my primary source of energy.
In the next few posts I'll probably cover differences in vitamin sources from America to Europe (you'll be surprised, trust me), along with how diabetics approach exercise.