The holidays are upon us, and there are more than just visions of sugar plums dancing in our heads. Sugary foods are everywhere you look. In fact, retail sales of sugar historically double during the month of December.
But our sugar intake isn't only thing that spikes this time of year. ‘Tis the season for cold, flu, and other respiratory infections, too. And while weight gain might be the first thing you worry about when it comes to sweet treats, too much sugar can also pose a serious threat to your immune system.
Researchers first discovered a correlation between sugar intake and immunity in the early 1900s while studying glucose levels and infection frequency among diabetes sufferers. This was corroborated in later studies conducted at Loma Linda University in California, which found that diabetics’ neutrophils were more sluggish than normal (Challem 1997). Neutrophils are white blood cells: defenders of the immune system that are designed to attack and dispose of alien bodies, including bacteria, viruses and cancer cells.
Researchers noted that after ingesting glucose, fructose, sucrose, honey—even orange juice—neutrophils exhibited a “significantly decreased capacity to engulf bacteria” in all test subjects (Sanchez, Reeser, et al. 1973). This impairment was strongest within the first two hours of eating sugar, but lingered on for a least five hours more. More recent studies have corroborated the diabetes-infection connection (Lin 2006).
But what about the rest of us? It turns out that the debilitating effects of sugar on neutrophil activity is not limited to those with diabetes. Studies have shown that even short-term hyperglycemia—more commonly known as a “sugar rush”—can affect all the major components of your body’s innate immune system and impair its ability to combat infection (Turina 2005). In other words, the more you indulge your sweet tooth, the greater your risk of getting sick.
In the United States, the commercial food industry has been more than willing to satisfy America’s craving for sugar—so it’s no wonder that we’re collectively getting sicker. At the beginning of the 20th century, Americans consumed only about five pounds of sugar per year. In the 1950s, that number jumped to almost 110 pounds, and increased a further 39 percent by 2000 as consumption of corn sweeteners octupled, according the USDA.
High fructose corn syrup was initially marketed as a healthful replacement for sugar; but in fact, the biological effects are the same. Not only do they completely lack nutritional value—no vitamins, protein, minerals, antioxidants, or fiber—they displace the healthier foods in our diets that do. And because they are such empty calories, we consume more than we need to. The same is true for artificial sweeteners, which trick your body into producing insulin. Once the insulin realizes there is no sugar to carry to your cells for energy, it sends a message to your body to eat more—even though you aren’t really hungry (Mawhinney 2011) .
But this displacement causes more than weight gain. Mineral deficiencies contribute to immune dysfunction by inhibiting all aspects of the system, including the body’s ability to produce T-cells and raise effective antibodies. Magnesium, which is especially important to both our innate and acquired immune responses (Tam. 2003), can decrease incidence of respiratory infections (PDR. 2000); while zinc improves immune responses and may shorten the duration of the common cold (Haase 2009) (Bogden 2004) (Bondestam 1985). These and other microminerals are all displaced by sugar-laden fast foods (Milne 2000), which only increases risk of infection.
Does this make all sugar evil? On the contrary, our body needs certain amounts of sugar—especially glucose—for energy. However, different sugars utilize different metabolic pathways and trigger different body responses. Glucose, a monosaccharide, triggers the release of insulin, which carries it to every cell in our body to be converted to energy. Fructose, on the other hand, gets processed by the liver, does not trigger insulin, and is more likely to be converted to fat. And sucrose (or table sugar) is a disaccharide containing both glucose and fructose, meaning metabolism will trigger both pathways. So even though the amount of glucose in a slice of bread can be measured against an equal amount of table sugar, they have different effects on the body.
Yes, it’s complicated—but the American Heart Association (and BodyBio) believe in one simple rule. Rather than deducing what kind of sugar is in it and how many calories it is, simply avoid foods that contain added sugar and stick to the sugar found in natural foods. Not only will you find it easier to maintain a healthy weight, you’ll be strengthening your immune system. And if you stick to the ADA’s recommendation of 100-150 calories per day, you can still enjoy this season's holiday cookie.