What Sugar Actually Does to Your Immune System
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You Should Know: ’Tis the season for Christmas cookies — and colds. You’ve probably heard that sugar “weakens” the immune system. The truth is a little more specific: large sugar loads and high blood sugar can temporarily hamper certain immune defenses, and chronically elevated blood sugar (as in diabetes) is linked to worse immune function.
Going Deeper: The idea traces back to a 1973 study that found neutrophils (a type of white blood cell) became less effective at engulfing bacteria for a few hours after participants consumed 100 grams of sugar (approximately how much you get when drinking a large soda). More broadly, research suggests hyperglycemia can impair neutrophil activity and promote inflammatory signaling. This matters most for people whose blood sugar stays elevated longer — including many people with diabetes.
Takeaway: A common thread here is inflammation and blood sugar control. Acute inflammation helps you fight infection and heal. But persistent inflammation and high blood sugar can make immune defenses less effective.
Bottom Line: A few sweet treats here and there are fine. But if sugar is a daily default — especially alongside poor sleep and stress — it may affect more than your waistline.
