Keep Yourself Flu-Protected

Influenza-like illnesses (ILI) and upper respiratory tract infections (URTI) typically peak in prevalence during cold months. The media extol the benefits of good hygiene and immunizations, echoing the advice of healthcare professionals. In addition, home remedies and natural products have long been used to prevent and treat common viral illnesses. Here are the few important things you can do to keep yourself flu-protected this season. 

1) Practice good hygiene. Yep, it's as simple as that. Wash your hands. Often, and thoroughly. Transmission of the flu virus can occur through contact -- shaking hands, door knobs, an so on -- and regular hand washing throughout the day can help keep you from becoming infected with the flu. Keeping your hands away from your face helps too, as the flu virus can enter your system through your mouth, nose and eyes.

2) Maintain good hydration. "Drink plenty of fluids" is well-worn advice that may have a basis in its common sense consequences. Dehydration can dry the respiratory mucosal surfaces; however, there is little evidence that drowning in extra fluids improves resistance to viral infections. On the other hand, the frequent trips to the restroom necessitated by larger than usual intake of fluids may promote additional hand washing, thereby reducing the spread of infections.

3) Avoid sleep deficit. "Get plenty of sleep" is another adage voiced by grandmothers as well as clinicians, with the intent of supporting immune function. Sleep deprivation is associated with disruptions of immune function. (1) In laboratory studies, depriving healthy adults of sleep induces a significant increase in both pro-inflammatory and anti-inflammatory markers. Sleep deprivation can also impair the immune response to influenza vaccine. In a study of adult volunteers, influenza immunizations were administered to one group after 4 nights of partial sleep deprivation (sleep restricted to 4 hours per night) and to a second group after 4 full nights (7.5-8.5 hours per night) of sleep. Ten days after vaccination, mean antibody titers in the sleep-deprived volunteers were less than half of those in the volunteers who had normal sleep durations. (2) Because individuals with poorer responses to vaccines also experience higher rates of illness, these findings support the concept that adequate amounts of sleep are important for optimal immunity during respiratory illness seasons. There are no data to suggest that excessive sleep (more than 10-12 hours per night for adolescents and adults) further improves immune function, but it appears prudent to avoid sleep deficits.

4) Take immune-boosting supplements. A growing number of randomized controlled trials have evaluated the effectiveness of natural health products.  

Vitamin C. Vitamin C (ascorbic acid) is the vitamin most often associated with warding off viral respiratory infections. A subgroup analysis of 642 very healthy adults engaged in highly physically stressful activities (marathon runners, skiers, and soldiers on subarctic exercises) showed a 50% decrease in the risk of developing a cold among those who took vitamin C supplements. (3) In the 30 studies that examined the impact of prophylactic vitamin C supplementation on the duration of URTI symptoms, vitamin C conferred a consistent benefit on reduction of cold duration (8% in adults and 14% in children).

Vitamin D. Despite widespread fortification of food with vitamin D and the use of multivitamins, suboptimal vitamin D levels are increasingly reported in adults and pediatric populations. In addition to its well known effects on bone health, vitamin D is an important immune regulator, stimulating innate immunity and moderating inflammation. A secondary analysis of NHANES data from 1988-1994 showed an inverse relationship between vitamin D levels and incidence of URTI.(4) These results have been supported by other studies that show an increased risk for severe acute lower respiratory illness in people with low vitamin D levels.(5)(6) Historically, the association between rickets and risk for severe respiratory infection is well known,(7) and vitamin D deficiency is associated with an increased risk for influenza.(8)(9) 

Zinc. The essential mineral, zinc, plays an important role in immune function. Zinc is a structural component of many enzymes and serves as an intracellular signal between immune cells.(10) The activity of virtually all immune cells is modulated by zinc, and zinc deficiency leads to dysfunction of both humoral and cell-mediated immunity and increases susceptibility to infection. Zinc deficiency is associated with an increased incidence and severity of pneumonia.(11) A meta-analysis of studies reported that zinc supplementation reduced the incidence of acute lower respiratory tract infections in children by approximately 15%.(12) 

Echinacea. Research generally supports the use of high quality Echinacea purpurea products by adults to prevent or treat URTI. A 2007 meta-analysis of 14 controlled trials in adults concluded that E purpurea(13) A 2006 Cochrane review evaluated studies of echinacea as a therapy for URTIs.  A large controlled trial in pediatric patients found that echinacea may help prevent pediatric colds when taken during cold and flu season.(14)
taken prophylactically decreased the odds of the common cold developing by 58% and decreased the duration of a cold by 1.4 days (both statistically significant). 

Garlic. Garlic (Allium sativum) is a commonly used food and folk remedy for preventing and treating the common cold. One high-quality trial of the effect of garlic supplementation on the common cold found that a daily garlic supplement (180 mg allicin content for 12 weeks) significantly reduced the incidence of the common cold.(15) Garlic is generally safe, but its unpleasant effects on breath, belching, and body odor are well known. You may choose an odorless formulation of a garlic supplement. 

Probiotics. Probiotics encompass a large heterogenous group of bacteria that are normal inhabitants of the human gastrointestinal tract. These live microorganisms have undergone intensive study as treatments for gastrointestinal problems such as diarrhea, constipation, and IBS and as therapy for atopic conditions. Recently, research has focused on the potential role of probiotics in preventing respiratory illnesses in adults and children. More than a dozen studies on the effectiveness of probiotics in preventing URTIs have been conducted, with mixed results. Most studies have shown some decrease in the severity and number of illness days in participants randomly assigned to treatment groups.(16) Recent randomized, placebo-controlled, double-blind studies conducted over 3 winter seasons in healthy adult volunteers in Italy evaluated several synbiotic preparations. These preparations contained 3 to 5 strains of Lactobacillus plantarum, L rhamnosus, and Bifidobacterium lactis; lactoferrin; and prebiotics such as short-chain fructooligosaccharides (FOS) or galactooligosaccharides (GOS). The overall incidence, duration, and severity of URTI and ILI were significantly decreased in participants treated with synbiotics vs those in the placebo group.(17)

It is prudent to ensure good hygiene, immunizations, adequate rest, and adequate fluid intake, while avoiding deficiencies of essential nutrients to protect yourself from flu and other respiratory diseases. 

References:

1) Irwin M. Effects of sleep and sleep loss on immunity and cytokines. Brain Behav Immun. 2002;16:503-512. 

2) Spiegel K, Sheridan JF, Van Cauter E. Effect of sleep deprivation on response to immunization. JAMA. 2002;288:1471-1472.

3) Douglas RM, Hemila H, Chalker E, Treacy B. Vitamin C for preventing and treating the common cold. Cochrane Database Syst Rev. 2007:CD000980.

4) Ginde AA, Mansbach JM, Camargo CA Jr. Association between serum 25-hydroxyvitamin D level and upper respiratory tract infection in the Third National Health and Nutrition Examination Survey. Arch Intern Med. 2009;169:384-390.

5) Wayse V, Yousafzai A, Mogale K, Filteau S. Association of subclinical vitamin D deficiency with severe acute lower respiratory infection in Indian children under 5 y. Eur J Clin Nutr. 2004;58:563-567. 

6) Hughes DA, Norton R. Vitamin D and respiratory health. Clin Exp Immunol. 2009;158:20-25.

7) Walker VP, Modlin RL. The vitamin D connection to pediatric infections and immune function. Pediatr Res. 2009;15:438-449.

8) Laaksi I, Ruohola JP, Tuohimaa P, et al. An association of serum vitamin D concentrations < 40 nmol/L with acute respiratory tract infection in young Finnish men. Am J Clin Nutr. 2007;86:714-717.

9) Cannell JJ, Vieth R, Umhau JC, et al. Epidemic influenza and vitamin D. Epidemiol Infect. 2006;134:1129-1140.

10) Haase H, Rink R. Functional significance of zinc-related signaling pathways in immune cells. Annu Rev Nutr. 2009;29:133-152. 

11) Meydani SN, Hamer DH. Serum zinc and pneumonia in nursing home elderly. Am J Clin Nutr. 2007;86:1167-1173.

12) Brown KH, et. al. Preventive zinc supplementation among infants, preschoolers, and older prepubertal children. Food Nutr Bull. 2009;30:S12-S40.

13) Shah SA, et. al. Evaluation of echinacea for the prevention and treatment of the common cold: a meta-analysis. Lancet Infect Dis. 2007;7:473-480.

14) Weber W, Feder-Mengus C, Chiarugi A, et al. Echinacea purpurea for prevention of upper respiratory tract infections in children. J Altern Complement Med. 2005;11:1021-1026.

15) Lissiman E, Bhasale AL, Cohen M. Garlic for the common cold. Cochrane Database Syst Rev. 2009:CD006206.

16) Vouloumanou EK, et. al. Probiotics for the prevention of respiratory tract infections: a systematic review. Int J Antimicrob Agents. 2009;34:197e1-e10.

17) Pregliasco F, et. al. A new chance of preventing winter diseases by the administration of synbiotic formulations. J Clin Gastroenterol. 2008;42 Suppl 3 Pt 2:S224-S233.