Understanding Colds and Flu
- The Common Cold: No Cure
There is currently no cure for the common cold because it is caused by over 160 different serotypes (types) of rhinovirus. Due to the varied shapes of these viruses, antibodies developed against one serotype are often ineffective against another, meaning individuals can catch multiple colds within a year or even a season.
- Cold Transmission and Survival
Colds are primarily spread by breathing, sneezing, coughing, or by people touching surfaces after contact with respiratory droplets, then touching their own eyes, nose, or mouth. The cold virus is quite stable and can survive on surfaces (non-human or human) for up to 24 hours.
- Flu Virus Types and Survival
The flu (influenza) virus also has different serotypes and general categories (A, B, C), distinguished by surface proteins (e.g., H1N1, which caused the Spanish Flu). Unlike the cold virus, the flu virus can only exist on surfaces for about 2 hours, making human-to-human contact its most typical mode of transmission.
- Flu Vaccines
Flu vaccines exist because there are a limited number of predominant flu virus types in a given year, allowing specific vaccines to be generated. These shots can reduce the risk of contracting the targeted flu strain by about 40-60% and can also lessen symptom severity. The decision to get a flu shot is personal, based on individual risk factors and exposure levels.
- Contagion Periods
For both colds and flu, individuals can be contagious about 24 hours before symptoms appear. They are most contagious when feeling at their worst (peak symptoms like coughing, sneezing, fever). However, the myth that one is no longer contagious after a few days or once they start feeling better, despite still exhibiting symptoms, is incorrect; continued symptoms mean continued contagion.
- Symptoms and Onset
Cold symptoms typically develop one to two days after exposure. The severity of both cold and flu can vary from mild to very severe, and they can exacerbate other health issues.
The Immune System: Three Lines of Defence
The immune system has an elegant and logical structure, comprising three main lines of defence:
- Physical Barriers
These are the initial defences between the body's organs and the outside world. They include the skin, which has antibacterial and antiviral substances. Other critical barriers are the mucosal lining of the nose and mouth (which traps and neutralises viruses) and the tears on the surface of the eyes (containing antibacterial agents). The nasal microbiome is particularly effective at combating incoming viruses.
- Innate Immune System
This is a rapid, generalised, and non-specific response system. If a virus breaches physical barriers, the innate immune system deploys white blood cells (e.g., neutrophils, natural killer cells, macrophages) and neurochemicals. The complement system marks infected cells with an "eat me" signal, while infected cells release "help me" signals, prompting the release of cytokines (like interleukin 1, interleukin 6, tumor necrosis factor alpha). This response causes inflammation, swelling, and increased blood flow to the infected area. The innate system can often fight off an infection before full-blown symptoms develop.
- Adaptive Immune System
This is the highly specific and targeted defence. It produces antibodies (immunoglobulins like IgM, then highly specific IgG) that precisely match the shape of the specific viral intruder (serotype or strain). Crucially, the adaptive immune system maintains a memory of past infections, allowing for a rapid and effective response if the same virus is encountered again.
- The lymphatic system also collaborates with the vascular system by filtering waste, combating infection, and producing useful chemicals.
Behavioural Tools for Immune System Support
- Avoid Touching Your Face
A significant route of infection is touching one's eyes, nose, or mouth with contaminated hands. Studies show people unconsciously touch their face, especially their eyes, shortly after shaking hands. Being mindful of this and practising hand hygiene can significantly reduce the risk of infection.
- Prioritise Quality Sleep
Adequate, quality sleep is foundational for mental and physical health and performance. Sleep deprivation (e.g., less than 50-75% of required sleep) significantly compromises the innate immune system's effectiveness.
- Ensure Adequate Nutrition
Maintaining adequate nutrition is crucial. Being in a chronic caloric deficit, such as when dieting heavily, can compromise innate immune system function. Post-exercise carbohydrate intake (complex carbs, fruit) can help attenuate inflammation, especially after fasted training.
- Manage Stress Effectively
Chronic stress (day after day) or acute stress that disrupts sleep can reduce innate immune function. However, short, acute bouts of stress (that don't inhibit sleep) can actually enhance immune function by transiently increasing cortisol and promoting inflammation, which are tools the immune system uses to combat infection.
- Practise Nasal Breathing
Consciously breathing through the nose (rather than the mouth) most of the time is highly beneficial. Nasal breathing creates a healthy environment (milieu) for the nasal microbiome, helps regulate air temperature, and strengthens the primary defence against viruses.
- Support a Healthy Microbiome
A healthy gut microbiome is crucial for a robust innate immune system. This can be supported by consuming two to four servings of low-sugar fermented foods daily, such as refrigerated sauerkraut, kimchi, kefir, kombucha, or live-culture yogurts. Additionally, a simple practice of swishing and swallowing water first thing in the morning (prior to brushing teeth) can support the oral and gut microbiomes.
- Engage in Appropriate Exercise
Moderate to high-intensity exercise of 60 minutes or less can bolster the innate immune system by increasing the circulation and activity of immune cells and chemicals for up to 24 hours post-exercise. Even 12-20 minutes of high-intensity training can be beneficial. However, excessive exercise (e.g., marathons, or workouts exceeding 75 minutes) can severely compromise immune function, diminishing immune cell activity and elevating stress hormones and inflammatory molecules. If feeling unwell with whole-body malaise or a sore throat, rest is the best response; exercising while sick can prolong illness and is not recommended.
- Utilise Deliberate Heat Exposure (Sauna)
Regular sauna sessions can increase innate immune system activity. For instance, three rounds of 15 minutes in a sauna (176-210°F) with 2-minute cool-down breaks, conducted over several weeks, can significantly increase cortisol and leukocyte counts, thereby boosting the innate immune response. However, if already sick, avoid very hot saunas to prevent adding further stress to the body.
Supplements for Prevention and Treatment
Always consult a physician before taking any supplements, especially for children, pregnant women, or those with existing health conditions.
- Vitamin C
Despite popular belief, high doses of Vitamin C (6-8 grams per day) show only a small and not robust effect on delaying or shortening colds, and can cause gastric distress. A key meta-analysis supporting its benefits was retracted due to data analysis flaws. For most people, sufficient vitamin C from food or a foundational supplement is adequate, and high doses are unlikely to be effective for cold/flu prevention or treatment.
- Vitamin D
Vitamin D deficiency is linked to diminished immune function and increased susceptibility to acute respiratory infections. Supplementing with 1,000 to 2,000 IU of vitamin D daily is generally safe and can reduce the risk of acute respiratory infections (though the degree of prevention is small to moderate). Regular sunlight exposure is also vital for vitamin D production and overall immune health. Blood tests are recommended to determine individual vitamin D needs, as some people may require higher doses, while excessive intake can be detrimental.
- Echinacea
Scientific data suggest that echinacea offers little to no benefit for avoiding or treating colds and flu. Furthermore, regular high doses might even impede innate immune system function by reducing white blood cell and natural killer cell counts. Its use is generally not recommended, or at least should be reserved for short periods in winter months.
- Zinc
There is strong scientific evidence supporting zinc for combating colds. A dosage of 100 milligrams or more per day (divided, taken with food to avoid gastric distress) has been shown to be effective. One study noted a three times faster recovery rate from colds with 90 milligrams per day of zinc acetate. Zinc is particularly beneficial for older individuals (over 65). While most studies focus on colds, physicians generally do not see a reason to avoid it for flu.
- N-Acetyl Cysteine (NAC)
NAC is a precursor to glutathione, a master antioxidant, and acts as a powerful mucolytic, helping to loosen mucus. This can relieve congestion associated with colds and flu, and is a preferred alternative to over-the-counter decongestants which can cause rebound congestion and be habit-forming. A 1997 study showed that taking 600 milligrams of NAC twice daily for six months significantly reduced the probability of contracting influenza (79% of placebo group got sick versus 25% of NAC group). Clinicians have also used NAC as a preventative. For prevention, a dosage of 1,200 milligrams per day (e.g., two 600mg doses) is suggested. For treatment of active colds, 600-900 milligrams three times per day, avoiding doses close to bedtime due to increased mucus flow, has been used. NAC is currently available over-the-counter.