Eat honey, agave nectar, or maple syrup. Call it “organic evaporated cane juice,” if you wish. It’s all sugar, and eating too much is unhealthy. But what evidence is there to blame sugar for our maladies? After all, fruits contain sugar, and all carbohydrates—from bread starch to chicory root fiber—are made of sugars. In fact, without one type of sugar—glucose (also known as blood sugar)—which most of our cells continuously use for energy, we would die within minutes.
The problem with sugar is that it is easy to get too much of a good thing. Excess consumption of sugar jeopardizes health by elevating three main conditions: glycemic loads, caloric intake, and inflammation. There are several different types of sugars, and each affects these conditions differently. Here is not the place to describe the chemical differences between different sugars—I encourage you to research these differences on your own; you may start with this link.
High Glycemic Loads and Insulin Resistance
What are glycemic loads? This link explains. When we eat digestible glucose-containing foods, like table sugar (sucrose) and starch, the glucose enters our blood. If blood glucose increases significantly, the pancreas secretes insulin to lower glucose levels; insulin stimulates liver, fat, and muscle cells to absorb glucose out of the blood. The more sugar released, the higher the glycemic load and the insulin response.
Habitually high glycemic loads have been linked to breast cancer, colorectal cancer, and pancreatic cancer, but other studies have not found associations. Interestingly, high glycemic loads have been shown to raise LDL cholesterol (the bad kind), lower HDL (the good kind), and raise triglycerides (fat in the blood), according to Drs. Christian Roberts and Simin Liu in their 2009 article, “Effects of Glycemic Load on Metabolic Health and Type 2 Diabetes Mellitus.” Thus sugar intake affects the amount and types of fat and cholesterol in the blood, and it is therefore important to reduce sugar consumption, along with improving the makeup of fats you eat (have you read my post on fats?), in order to improve cholesterol and triglycerides.
Another important result of high glycemic loads are chronically high insulin levels, which lead to insulin resistance—when cells stop absorbing glucose effectively. Insulin resistance, according to Dr. Gerald Reaven’s article, “Role of Insulin Resistance in Human Disease,” increases one’s risk of diabetes, coronary heart disease (CHD), and possibly hypertension.
Cancer may be related to insulin levels because, according to Dr. Barry Boyd’s 2003 article, “Insulin and Cancer,” insulin and a number of insulin-like growth factors stimulate cell growth, which is bad if those stimulated cells happen to be malignant or pre-malignant.
Caloric Intake
Sugar and insulin work together to make us fat. Sugar, like any carbohydrate, provides 4 calories per gram, and it’s easy to overeat: the CDC reported that between 2005 and 2010, the average adult man consumed 335 calories, and the average woman 239 calories, per day, from added sugars. For men and women, respectively, that works out to 89 and 60 grams of added sugars per day—which doesn’t include natural sugars in fruit, vegetables, and milk (12 grams per cup). Mind you that a 12-oz. Coca Cola has 39 grams of sugar.
When your blood glucose rises, insulin stimulates your liver, muscle, and fat cells to absorb glucose. The liver and muscles convert glucose into glycogen, while your fat cells convert it into—fat. Because of this, and because high sugar intake increases blood triglyceride levels, low-fat foods (and beware—when companies take out delicious fat, they have to replace it with something else delicious, like sugar, so as not to ruin the flavor) may actually lead to obesity if they are high in sugar; always check the nutrition facts label. The World Health Organization has recently recommended that we limit our consumption of added sugars to 25 grams per day.
This may be difficult, however, because Dr. Karen Teff et al. have shown that eating fructose—which is chemically combined with glucose in table sugar (sucrose)—results in higher levels of the appetite-stimulating hormone ghrelin and lower levels of the appetite-suppressing hormones leptin and insulin as compared with eating glucose. Eating a lot of fructose or sucrose, therefore, may make us eat more food—and more calories—than we would eat if we ate only glucose or starches (which are made of long chains of glucose).
Inflammation
Inflammation is a condition when cells produce a lot of chemicals that stimulate cell growth and immune system activity. While acute inflammation following a wound helps us fight off germs and repair tissue, chronic inflammation promotes cancer, autoimmune disorders, and a host of other diseases. Unfortunately, we can blame sugar and insulin for some of our inflammation: Drs. Roberts and Liu, mentioned above, associate high glycemic loads with elevated levels of the inflammatory chemicals interleukin-6, tumor necrosis factor receptor-2, C-reactive protein, adiponectin, and nuclear-factor kappa-B. This is not the place to explain what each of these does (researchers are, in fact, still determining their effects on our bodies), but I encourage you to read into the basics of inflammation.
Roberts and Liu also say that high blood glucose promotes oxidative stress, which is yet another complex condition. It damages DNA, promotes white blood cells to absorb cholesterol particles and stick to blood vessel walls, and contributes to atherosclerosis, cancer, and hypertension.
Learning about all of the problems that sugar-high diets can cause is what fanned my mild interest in healthy eating into a passion for researching nutrition. I credit Dr. Robert Lustig’s lecture, “Sugar: The Bitter Truth,” for first showing me how biochemistry and nutrition are related. In it, he explains that when the liver metabolizes fructose, it produces a number of inflammatory chemicals that ultimately harm the body. Though I think Dr. Lustig is overstating it by blaming fructose alone for the obesity epidemic, watching his lecture motivated me to more than halve my sugar consumption.
A Few Final Notes
High fructose corn syrup
I have to mention high fructose corn syrup (HFCS). HFCS is made of a mixture of chemically uncombined glucose and fructose (its composition varies but is generally around 50-50), whereas table sugar (sucrose) is chemically combined glucose and fructose. We have an enzyme—sucrase—that cleaves the chemical bond between glucose and fructose, so once inside the body, table sugar and HFCS are pretty much identical. And too much of any sugar is unhealthy.
Lactose
Lactose, which is glucose chemically combined to another sugar, galactose, has a lower glycemic index (65) than sucrose (87). People who are lactose intolerant do not produce lactase, an enzyme that, like sucrase, breaks lactose molecules up into individual glucose and galactose molecules, and they can therefore not digest lactose. The undigested lactose is broken down in the intestines by bacteria, which produce the discomfort associated with lactose intolerance.
Added sugar versus natural sugar
Sugar is sugar, as long as the composition of the sugar (glucose, fructose, galactose) is the same. Whenever my parents buy sweetened almond milk, which has 7 grams of added sucrose per cup but almost no naturally-arising sugar, I wonder if it is healthier to drink that or skim milk, which has 12 grams of lactose per cup but no added sugar. I have decided that the healthier sugar source is the one with a lower glycemic load, which is 6 per cup of almond milk and 9 per cup of skim milk. However, I do not just consider which sugar is healthier; I also have to consider the nutrients and toxins that come with the sugar. Skim milk has 8 grams of complete protein per cup, while almond milk has 1, and that single gram is incomplete protein. The almond milk has more calcium and vitamin E, but those were both added as supplements; I could just as well buy fortified skim milk. And what about antioxidants? Or rBST?
This is why nutrition is an endless stream of questions. I look forward to answering more in my next posts. But what can you find out in the meantime?