(NaturalNews) It forms a big part of most modern-day diets, but research suggests that sugar consumption can impair immune function for a significant period of time, by as much as 50%.
Indeed, sugar has been described as "one of the food components most damaging to our immune system." 
What research suggests about sugar and immune function
Studies previously published in the American Journal of Clinical Nutrition and Dental Survey revealed that consuming 100 grams (3.5 ounces) of carbohydrates, such as fructose, glucose, sucrose, pasteurized orange juice and honey, inhibited the ability of white blood cells to engulf and destroy harmful microorganisms and particles which were foreign to the body.
The impairment of immune function began within less than 30 minutes after sugar ingestion and remained that way for more than five hours. At the height of immune suppression, which typically took place about two hours after sugar consumption, this important function of white blood cells was lowered by as much as 50%. 
The role of white blood cells form a significant part of the body's defense mechanism against infections. As such, when the capabilities of white blood cells are impaired, the body's overall immune response is greatly affected. 
Further, consuming about 75 grams of glucose has also been shown to reduce lymphocyte activity.  Lymphocytes are white blood cells produced by the tonsils, spleen and thymus that scavenge for microorganisms and toxic compounds in the body. 
More sugar means greater immune suppression
Importantly, the amount of glucose consumed has a corresponding adverse effect on the function of white blood cells. In other words, the higher the amount of sugar ingested, the higher the degree of immunity impairment. 
What some experts say about sugar and immunity
Joseph Pizzorno, ND, who founded Bastyr University in Kenmore, Washington, listed numerous factors which impair immune system in his book Total Wellness. These included toxic chemicals, stress, inadequate rest, candida overgrowth in the bowels, air pollution, vaccinations, heavy metals, pesticides and nutritional deficiencies, among others. At the top of his list was the "intake of sugar and other concentrated carbohydrates." 
Dr. Joseph Mercola also wrote that sugar consumption impairs the immune system and makes people more susceptible to disease. 
Simple sugars, even those present in fruit juice, suppress immunity - it is thus imperative to avoid sugar while fighting an infection. Short-term fasting can give the immune system a boost by keeping blood sugar levels low; this is especially useful during the first one to two days of acute infections. Prolonged fasting, however, would deplete energy levels and become counterproductive. 
Considering the amount of sucrose and other refined sugars present in typical modern-day diets, particularly in the Standard American Diet, it follows that many persons have significantly compromised immune systems, which then opens them up to higher risks of numerous chronic diseases, including cancer.
With its adverse effect on immune function in mind, sugar consumption should be carefully watched by the health conscious. This is especially true of processed food products that contain refined sugars, which are typically devoid of important nutrients that support and nourish the immune system.
Sources for this article include:
 Murray, Michael, ND., Pizzorno, Joseph, ND., and Pizzorno, Lara, MA, LMT. The Encyclopedia of Healing Foods. New York, NY: Atria Books, 2005. Print.
 Murray, Michael, ND, and Pizzorno, Joseph, ND. Encyclopedia of Natural Medicine. 2nd ed. New York, NY: Three Rivers Press, 1998. Print.
 Trivieri, Jr., Larry, and Anderson, John W. Alternative Medicine: The Definitive Guide. 2nd ed. New York, USA: Celestial Arts, 2002. Print.
 Mercola, Joseph, Dr., and Pearsall, Kendra, Dr. Take Control of Your Health. Schaumburg, IL: Mercola.com, 2007. Print.
About the author: Reuben Chow has a keen interest in natural health and healing as well as personal growth.