Part 1 — Why Flu Season Peaks After Sugar Season

Every year, flu season seems to hit its stride right after the holidays—usually peaking in February. While most people assume it’s just the colder weather, there’s another powerful influence at play: the sugar surge that stretches from Halloween through Valentine’s Day.

The Sweet Season and Your Immune System

From October 31 to February 14, Americans celebrate nearly four months of what could be called “sugar season.” According to the National Confectioners Association, Americans spent $7.4 billion on seasonal chocolate and candy in 2024—about 18% of all confectionery sales—and are projected to spend $3.9 billion on Halloween candy alone within a $13.1 billion total Halloween outlay for 2025. Similarly, Food Manufacturing and NielsenIQ report that Valentine’s Day ranks among the top three candy holidays, with a 512% surge in chocolate sales on that single day.

This long stretch of elevated sugar intake, from Halloween through Valentine’s Day, aligns almost perfectly with the CDC’s documented peak flu months of December through February. During this same time, reviews published through PMC and the New England Journal of Medicine have shown that holiday eating patterns tend to shift toward calorie-dense, sweet foods—resulting in measurable short-term weight gain and inflammation. These are reliable indicators that sugar intake is high and the immune system is under stress.

Even a moderate amount of sugar—roughly the equivalent of a soda or a few holiday treats—can temporarily suppress the ability of white blood cells to fight bacteria and viruses. A landmark 1973 study published in the American Journal of Clinical Nutrition found that ingesting about 100 grams of simple sugars (glucose, fructose, sucrose, honey, or orange juice) reduced neutrophil phagocytic activity for several hours, while starch had no effect. More recent reviews on PubMed confirm that acute hyperglycemia impairs innate immune functions, including neutrophil migration, phagocytosis, oxidative burst, and microbial killing, via cellular mechanisms such as PKC activation—effects observed even outside diabetic populations. Long-term dysglycemia, as discussed in PMC publications, further dysregulates immune responses, compromising antibacterial and antiviral defense.

Why February Is Peak Flu Month

By the time February rolls around, most of us have just come through months of indulgence, less sunlight, disrupted sleep, and richer foods. Our immune defenses are taxed, inflammation is elevated, and our Wei Qi—or protective energy, in TCM terms—is weakened. Add in indoor crowding, dry winter air, and fluctuating temperatures, and we have the perfect environment for viruses to thrive.

This timing isn’t coincidence—it’s biology. After prolonged sugar exposure, the immune system can become sluggish, leaving the body more susceptible to infection. Epidemiological reviews on ResearchGate even note that populations with lower added sugar intake and higher whole-food consumption show fewer upper respiratory infections, though direct, holiday-specific correlations remain limited.

Temperature Swings, Wind, and the TCM Perspective

Traditional Chinese Medicine (TCM) adds another layer of understanding. February often brings unpredictable temperature shifts—warm days followed by sudden, biting cold winds. This is what TCM calls Wind Invasion—an external pathogenic factor that can penetrate the body’s surface when Wei Qi is weak. The body’s outer “shield,” which normally wards off external pathogens, can be disrupted by excess sugar, stress, or fatigue, creating an open doorway for seasonal illness.

Wind tends to enter through the upper back, neck, and nape, which is why TCM practitioners emphasize keeping the neck and shoulders covered during winter transitions. When this defense fails, we may experience chills, sore throat, muscle tension, or the onset of a cold or flu.

How Acupuncture and Herbal Medicine Strengthen Immunity

In TCM, regular acupuncture treatments during the winter months help fortify Wei Qi, regulate circulation, and support organ balance—especially the Lung and Spleen systems, which govern immunity and digestion.
Acupuncture has been shown to modulate the immune response, lower systemic inflammation, and promote better sleep and energy—all vital to ward off seasonal colds and flu.
Chinese herbal formulas such as Yu Ping Feng San (Jade Windscreen Powder) or tonics containing astragalus (Huang Qi) are also traditionally used to reinforce the body’s natural defenses and improve resilience during high-risk months.

Now is the time to give your immune system the support it needs.
✨ Call Alitheia Healing Acupuncture today to schedule your next acupuncture session and strengthen your defenses before flu season peaks.

References:
National Confectioners Association (2024–2025); Food Manufacturing & NielsenIQ (2025); New England Journal of Medicine; PMC Holiday Nutrition Reviews; Sanchez A. et al., Am J Clin Nutr (1973); PubMed Mechanistic Reviews on Hyperglycemia & Immunity; ResearchGate analyses on diet and respiratory infection risk.