Holiday Immune Support

Sugar + Stress = Vulnerability to Colds and Flu
By Nieske Zabriskie, ND
The strength of the immune response changes based on several variables such as diet, stress, and mood. Thus, around the holidays, when people are more prone to eat sugary foods and refined carbohydrates, there is a direct and unfavorable effect on immune function. In addition, the stress of the holiday season can also have detrimental effects on the immune response. Adults average 2-4 colds per year, with increased occurrence during the fall and winter when the air is colder with decreased humidity.1 Consequently, many people have an increased susceptibility to colds and flu during the holiday season.

Sugar and the Immune System

Animal models have shown that increasing sucrose intake increases the neurotransmitter serotonin, important for mood balancing, suggesting that eating sugar can make us feel better when depressed.2 Although consuming sugar may result in enhanced mood, anyone who experiences this “sugar high” must pay a steep price. This is because numerous studies have shown that increased sugar intake dramatically decreases the immune response.

Short-term hyperglycemia (elevated blood sugar) affects all major components of innate immunity and impairs the ability of the individual to fight infection.3 The white blood cells are the primary mediators of the immune response. Neutrophils are a type of white blood cell that act as an important first-line-of-defense in the immune system by engulfing (phagocytizing) pathogens. Hyperglycemia has been shown to decrease neutrophil activity in numerous studies.4 One study showed that increased glucose levels decreased neutrophils’ ability to engulf several pathogens such as Staphylococcus epidermidis, Staphylococcus aureus, and Escherichia coli.5 A similar study showed that poor blood sugar control in diabetic patients decreased neutrophil activity against Klebsiella pneumoniae.6 Specifically, neutrophils experienced a decrease in their movement and their ability to engulf and kill pathogens, an increase in leukocyte apoptosis (programmed cell death), and a reduction in lymph node retention capacity. Additionally, lowering of blood glucose has been shown to significantly improve neutrophil activity.7


Sugar’s harmful effect on the immune system was further demonstrated in a study that showed a significant decrease in neutrophil activity in blood samples from healthy adults at 30 and 60 minutes following ingestion of 75 grams of glucose.8 Another similar study examined the activity of neutrophils after a 100 gram dose of various simple carbohydrates including glucose, fructose, sucrose, honey, and orange juice in humans. The results indicated that all simple carbohydrates tested significantly decreased the capacity of neutrophils to engulf bacteria. The greatest effects occurred between 1 and 2 hours after ingestion of the carbohydrates, and the values were still significantly below the fasting control values five hours after glucose ingestion.9 Thus, increasing intake of sugary foods will have a profound impact on the immune response.

Stress and the Immune System

Around the holidays, not only do individuals increase their consumption of sugary foods, they also often experience increased stress levels. Stress, through the hypothalamic-pituitary-adrenal (HPA) axis, can modulate the immune system. Cortisol, released from the adrenal glands, is the primary hormone that mediates the stress response. Cortisol, in response to stress, suppresses the immune response.10 Research has shown that stress can affect the immune system in several ways such as reduced neutrophil activity, changes in types of chemical mediators (cytokines) produced by the white blood cells, and decreased cytotoxic T-lymphocytes and natural killer cell activities.11-12 Studies suggest that an elevated cortisol:DHEA ratio is a contributing factor to this reduced immunity, particularly in elderly patients. DHEA (dehydroepiandrosterone) is a steroid hormone secreted from the adrenal glands). More specifically, an elevated cortisol:DHEA ratio significantly decreases neutrophil activity.

One particularly interesting study evaluated the perceived life stress and risk of upper respiratory infections (URI). The study found that those individuals with high levels of negative life events and who showed high cortisol reactivity had increased numbers of URIs. Also this study showed that during times of increased perceived stress, lower reactivity of natural killer cells and CD8 T-lymphocytes were also correlated with increased URIs.13


In addition, studies have shown that anxiety affects immune function. Anxious subjects were found to have increased cortisol levels with impaired immune function and changes in cytokines released from the white blood cells.14

When Defenses are Down

EpiCor® is widely used for its ability to act as a potent immune system modulator. It has been shown to modulate the number and activity of immune cells known as lymphocytes including T-lymphocytes and natural killer cells, as well as antibody production.15 Additionally, EpiCor has been shown to significantly decrease the duration and number of reported symptoms in individuals suffering from colds and flu in a clinical trial.16 However, under times of increased vulnerability and decreased resistance to infection, such as during the holidays, pathogens may gain the upper hand. Consequently, even those individuals who regularly take Epicor for immune enhancement may need additional support this time of year. When defenses are down and the first signs of a cold or flu are felt, adding Fast Response™ can be a particularly powerful tool to enhance immunity.

Fast Response supports the immune system using a combination of vitamins and minerals with traditional Chinese herbs. These ingredients modulate white blood cells including B-lymphocytes, T-lymphocytes, macrophages, and natural killer cells, as well as decrease inflammation, which causes many of the symptoms associated with colds and flu.

The traditional Chinese botanicals in Fast Response have shown efficacy in supporting immunity. Forsythia suspense has been shown to have anti-viral and anti-bacterial activity.17-18 Lonicera japonicus inhibits the pro-inflammatory cyclooxygenase (COX)-2 and 5-lipoxygenase (LOX) enzymes,19 which is important as infection with the cold virus increases the activity of these two inflammatory enzymes.20 In traditional Chinese medicine, Platycodon grandiflorum has been used for clearing the lungs, resolving phlegm, and soothing the throat,21 and research has shown that constituents of Platycodon stimulate macrophage proliferation and activity.22 Arctium lappa (Burdock) contains arctigenin, which has been shown to prolong the survival time of mice infected with influenza virus as well as inhibited lung consolidation in mice pneumonia caused by the influenza virus.23 Arctium lappa decreases coughing, and was equally active as some synthetic preparations in studies using animal models.24 Research indicates that both Arctium lappa and the essential oils of Mentha arvenis inhibit the growth of several strains of pathogenic bacteria.25-26 Constituents of Glycyrrhizae uralensis have anti-inflammatory properties,27 can activate macrophages,28 and have been shown to decrease replication of coronavirus from patients with severe acute respiratory syndrome (SARS).29 Schizonepeta tenuifolia has been shown to regulate inflammatory responses by modulating T-lymphocyte activity.30 This combination of nutrients and botanicals can provide the extra support needed during times of increased vulnerability to colds and flu.

Taking a formula that combines the above botanicals with immune-supporting vitamins and minerals can be a particularly effective approach. Vitamins A, C, B6 and the mineral zinc are critical for optimal immune function. Vitamin A is required for the growth and activation of B-lymphocytes, increases macrophage activity, and is important in maintaining a sufficient level of natural killer cells. Deficient levels of Vitamin A can reduce lymphocyte numbers, natural killer cells, immunoglobulin responses, and impair T-lymphocyte function.31 Vitamin C has been shown in multiple studies to significantly reduce the duration of episodes and the severity of common cold and flu symptoms.32 Vitamin B6 is important for normal immune function as deficiencies have been shown to alter lymphocyte differentiation and maturation and impair antibody production.33 Zinc is required for normal development and function of white blood cells such as neutrophils and natural killer cells, and zinc deficiency adversely affects T-lymphocyte function, B-lymphocyte development, antibody production, and macrophage activity.34 Clinical trials indicate that zinc supplementation can significantly shorten the time to complete resolution of symptoms in patients with the common cold.35

Adding a vitamin D3 supplement to the immune-boosting regimen above also is important during cold and flu season. Researchers have theorized that the reason why the cold and flu season occurs in winter is because vitamin D deficiency is widespread during this time of year when exposure to sunlight is minimal.36 One explanation for vitamin D’s role in immunity is that it up-regulates an important gene called cathelicidin, a naturally occurring broad-spectrum antibiotic.37


Stress and poor dietary habits such as increasing intake of sugary foods and refined carbohydrates increase susceptibility to infection, particularly this time of year. Supplements such as EpiCor (see source link below) are ideal for general immune support. However, under times of increased vulnerability and decreased resistance to infection, products such as Fast Response may be necessary for extra immune enhancement. Adding a vitamin D3 supplement to this regimen will further strengthen immunity and provide additional defense against colds and influenzas. 


1. National Institutes of Health. Common Cold. Available at: Accessed on: 09-22-08.

2. Smolders I, Loo JV, Sarre S, et al. Effects of dietary sucrose on hippocampal serotonin release: a microdialysis study in the freely-moving rat. Br J Nutr. 2001 Aug;86(2):151-5.

3. Turina M, Fry DE, Polk HC Jr. Acute hyperglycemia and the innate immune system: clinical, cellular, and molecular aspects. Crit Care Med. 2005 Jul;33(7):1624-33.

4. Patel KL. Impact of tight glucose control on postoperative infection rates and wound healing in cardiac surgery patients. J Wound Ostomy Continence Nurs. 2008 Jul-Aug;35(4):397-404.

5. Van Oss CJ. Influence of glucose levels on the in vitro phagocytosis of bacteria by human neutrophils. Infect Immun. 1971 Jul;4(1):54-9.

6. Lin JC, Siu LK, Fung CP, et al. Impaired phagocytosis of capsular serotypes K1 or K2 Klebsiella pneumoniae in type 2 diabetes mellitus patients with poor glycemic control. J Clin Endocrinol Metab. 2006 Aug;91(8):3084-7.

7. Alba-Loureiro TC, Munhoz CD, Martins JO, et al. Neutrophil function and metabolism in individuals with diabetes mellitus. Braz J Med Biol Res. 2007 Aug;40(8):1037-44.

8. Bernstein J, Alpert S, Nauss KM, et al. Depression of lymphocyte transformation following oral glucose ingestion. Am J Clin Nutr. 1977;30:613 (abstract).

9. Sanchez A, Reeser JL, Lau HS, et al. Role of sugars in human neutrophilic phagocytosis. Am J Clin Nutr. 1973 Nov;26(11):1180-4.

10. Butcher SK, Killampalli V, Lascelles D, et al. Raised cortisol:DHEAS ratios in the elderly after injury: potential impact upon neutrophil function and immunity. Aging Cell. 2005 Dec;4(6):319-24.

11. Reiche EM, Morimoto HK, Nunes SM. Stress and depression-induced immune dysfunction: implications for the development and progression of cancer. Int Rev Psychiatry. 2005 Dec;17(6):515-27.

12. Godbout JP, Glaser R. Stress-induced immune dysregulation: implications for wound healing, infectious disease and cancer. J Neuroimmune Pharmacol. 2006 Dec;1(4):421-7.

13. Cohen S, Hamrick N, Rodriguez MS, et al. Reactivity and vulnerability to stress-associated risk for upper respiratory illness. Psychosom Med. 2002 Mar-Apr;64(2):302-10.

14. Arranz L, Guayerbas N, De la Fuente M. Impairment of several immune functions in anxious women. J Psychosom Res. 2007 Jan;62(1):1-8.

15. Jensen GS, Hart AN, Schauss AG. An antiinflammatory immunogen from yeast culture induces activation and alters chemokine receptor expression on human natural killer cells and B lymphocytes in vitro. Nutrition Research. 2007 Jun;27(6):327-335.

16. Moyad MA, Robinson LE, Zawada ET Jr, et al. Effects of a modified yeast supplement on cold/flu symptoms. Urol Nurs. 2008 Feb;28(1):50-5.

17. Zhang GG, Song SJ, Ren J, et al. A new compound from Forsythia suspensa (Thunb.) Vahl with antiviral effect on RSV. J Herb Pharmacother. 2002;2(3):35-40.

18. Kong B, Wang J, Xiong YL. Antimicrobial activity of several herb and spice extracts in culture medium and in vacuum-packaged pork. J Food Prot. 2007 Mar;70(3):641-7.

19. Rall LC, Meydani SN. Vitamin B6 and immune competence. Nutr Rev. 1993 Aug;51(8):217-25.

20. Seymour ML, Gilby N, Bardin PG, et al. Rhinovirus infection increases 5-lipoxygenase and cyclooxygenase-2 in bronchial biopsy specimens from nonatopic subjects. J Infect Dis. 2002 Feb 15;185(4):540-4.

21. Guo L, Zhang C, Li L, et al. Advances in studies on Platycodon grandiflorum. Zhongguo Zhong Yao Za Zhi. 2007 Feb;32(3):181-6.

22. Choi CY, Kim JY, Kim YS, et al. Augmentation of macrophage functions by an aqueous extract isolated from Platycodon grandiflorum. Cancer Lett. 2001 May 10;166(1):17-25.

23. Yang Z, Liu N, Huang B, et al. Effect of anti-influenza virus of Arctigenin in vivo. Zhong Yao Cai. 2005 Nov;28(11):1012-4.

24. Kardosová A, Ebringerová A, Alföldi J, et al. A biologically active fructan from the roots of Arctium lappa L., var. Herkules. Int J Biol Macromol. 2003 Nov;33(1-3):135-40.

25. Gentil M, Pereira JV, Sousa YT, et al. In vitro evaluation of the antibacterial activity of Arctium lappa as a phytotherapeutic agent used in intracanal dressings. Phytother Res. 2006 Mar;20(3):184-6.

26. Imai H, Osawa K, Yasuda H, et al. Inhibition by the essential oils of peppermint and spearmint of the growth of pathogenic bacteria. Microbios. 2001;106 Suppl 1:31-9.

27. Shin EM, Zhou HY, Guo LY, et al. Anti-inflammatory effects of glycyrol isolated from Glycyrrhiza uralensis (Leguminosae) in LPS-induced RAW264.7 macrophages. Int Immunopharmacol 2008 Jul 10. Published online ahead of print.

28. Nose M, Terawaki K, Oguri K, et al. Activation of macrophages by crude polysaccharide fractions obtained from shoots of Glycyrrhiza glabra and hairy roots of Glycyrrhiza uralensis in vitro. Biol Pharm Bull. 1998 Oct;21(10):1110-2.

29. Cinatl J, Morgenstern B, Bauer G, et al. Glycyrrhizin, an active component of liquorice roots, and replication of SARS-associated coronavirus. Lancet. 2003 Jun 14;361(9374):2045-6.

30. Kang H, Oh YJ, Choi HY, et al. Immunomodulatory effect of Schizonepeta tenuifolia water extract on mouse Th1/Th2 cytokine production in-vivo and in-vitro. J Pharm Pharmacol. 2008 Jul;60(7):901-7.

31. Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, DC: National Academy Press, 2002. Available at:

32. Gorton HC, Jarvis K. The effectiveness of vitamin C in preventing and relieving the symptoms of virus-induced respiratory infections. J Manipulative Physiol Ther. 1999 Oct;22(8):530-3.

33. Rall LC, Meydani SN. Vitamin B6 and immune competence. Nutr Rev. 1993 Aug;51(8):217-25.

34. Shankar AH, Prasad AS. Zinc and immune function: the biological basis of altered resistance to infection. Am J Clin Nutr. 1998 Aug;68(2 Suppl):447S-463S.

35. Mossad SB, Macknin ML, Medendorp SV, et al. Zinc gluconate lozenges for treating the common cold. A randomized, double-blind, placebo-controlled study. Ann Intern Med. 1996 Jul 15;125(2):81-8.

36. Cannell JJ, Vieth R, Umhau JC, Holick MF, Grant WB, Madronich S, Garland CF, Giovannucci E. Epidemic influenza and vitamin D. Epidemiol Infect. 2006 Dec;134(6):1129-40.

37. Cannell JJ, Hollis BW. Use of vitamin D in clinical practice. Altern Med Rev. 2008 Mar;13(1):6-20.

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