What really makes a difference in managing your immune system during seasonal changes is sleep time, humidity of the mucous membranes of your nose and throat, and hand hygiene. High-dose vitamin supplements or immune supplements that often come to mind first do not make as much of a difference as expected unless people have deficiencies.
Below, we divide items into items with relatively clear evidence and items with shallow evidence compared to their popularity. The goal is not to find one more supplement, but to protect the routines that support normal immune function.
Summary
- Studies repeatedly show that if you sleep less than 6 hours, your vulnerability to infection increases.
- When the mucous membrane dries, ciliary movement, which is the first line of defense, decreases. Indoor humidity of 40-50% is the baseline
- Hand hygiene is still the most cost-effective because it reduces the contact path rather than droplets.
- There is a significant difference only in those with vitamin D deficiency, and high doses of vitamin C are based on shortening the period rather than prevention.
- It is safe to administer the influenza vaccine 2-4 weeks before the outbreak begins.
1. Measures with clearer evidence
1-1. Sleep — The Most Underrated Item
Sleep deprivation has a relatively consistent impact on markers of immune function. In a controlled rhinovirus challenge study at Carnegie Mellon University, the infection rate was clearly higher in the group with short sleep duration, and subsequent studies generally point in the same direction. It has been reported that antibody formation after vaccination also tends to decrease with sleep deprivation.
If you listen to the daily routine of people in the clinic who say, “I live with a sore throat every time the season changes,” there are many cases where the sleep time is fixed to 5 hours. In this state, it is natural that adding a few nutritional supplements does not bring much change in sensation.
1-2. Mucosal moisture — the nose’s first line of defense
The cilia of the nasal mucosa act as a conveyor to push incoming foreign substances to the back of the throat. This movement is sensitive to the viscosity of the mucus, so when it dries, the speed decreases and the virus stays on the mucous membrane longer.
In many homes, when heating is started, the indoor humidity drops to around 20%. Keeping a hygrometer at 40-50% is a better response than looking for candy after your throat is sore. If it exceeds 60%, mites and mold will increase, so it is not a good idea to increase it recklessly.
1-3. Hand hygiene
Respiratory viruses don’t just spread through the air. It passes through doorknobs, elevator buttons, and cell phones and enters the hands, and from the hands to the mucous membranes of the eyes and nose. The basic method is to wash with soap for at least 20 seconds, and when water is not available, alcohol hand sanitizer is an alternative.
1-4. Vaccination
The influenza vaccine takes about two weeks for antibodies to rise after vaccination. Domestic epidemics generally occur between December and March of the following year, so vaccination between October and November is acceptable. Priority is given to those over 65 years of age, people with chronic diseases, and pregnant women.
2. Measures with less evidence than expected
| Item | Common expectations | Actual level of evidence |
|---|---|---|
| High dose of vitamin C | Prevent colds | The preventive effect on the general public is not clear. When taken regularly, the duration of illness is shortened by about a day or so. |
| Vitamin D | Taking it boosts immunity. | A reduction in respiratory infections has been observed in people with low blood levels. Additional benefit is uncertain in people whose levels are already adequate |
| Zinc | Great for colds | There are reports of a shortened period when taken within 24 hours of symptom onset, but there is a large variation in dosage form and dosage. Long-term high doses inhibit copper absorption |
| Probiotics | Strengthen immunity | Difficult to generalize due to large variation among strains |
| Red ginseng and immune supplements | Prevents infection | There is a large difference in individual perception, and it is insufficient to use as a basis for infection prevention. |
To summarize, nutritional supplements are a tool to make up for deficiencies, not a tool to boost immunity beyond the normal range. If you do a lot of indoor activities and have little exposure to ultraviolet rays, it is worth checking your vitamin D levels.
3. A two-week routine for seasonal transitions
3-1. Every day
- Fixed bedtime and wake-up times. Regularity often breaks down before the total sleep time.
- Check indoor humidity of 40-50%
- Wash your hands immediately after returning home and wash your face afterwards.
3-2. Weekly
- About 150 minutes of aerobic exercise per week. However, there are reports that you become temporarily vulnerable to infection immediately after marathon-level high-intensity exercise, so there is no reason to overdo it on days when your condition is poor.
- Bedding washing and ventilation
3-3. When symptoms started
In the early stages of a sore throat, hydration and rest are priorities. Since saline nasal rinsing is not a drug, there are few restrictions on its use, and it is helpful when you feel like runny nose is going down the back of your throat.
4. Signs that should not be overlooked
- Fever over 38 degrees Celsius lasting more than 3 days
- Accompanied by shortness of breath or chest pain
- Only one tonsil is severely swollen, difficulty swallowing, and difficulty opening the mouth.
- Voice change lasts for more than 2 weeks
- The cold gets better but then gets worse again, causing yellowish runny nose and facial pain.
The third, in particular, may be a time-sensitive condition such as a peritonsillar abscess, so it is not appropriate for watchful waiting at home.
Frequently Asked Questions
Q. Are there any foods that boost immunity? A. The evidence that one specific food boosts immunity is weak. A more practical variable is whether a diet balanced in protein and micronutrients is maintained, and if an extremely low-calorie diet is followed, it can work in the opposite direction.
Q. Is there a reason why a sore throat comes first every season? A. This is because dry, cold air irritates the pharyngeal mucosa first. When you breathe through your nose, the air is humidified and warmed, but if your nose is blocked and you breathe through your mouth, this process is skipped and the pharynx is directly exposed. This is also the reason why sore throat symptoms occur frequently in people with nasal congestion.
Q. Can you tell the difference between a cold and the flu on your own? A. There are differences in trends. Influenza often begins with sudden high fever and generalized muscle aches, and nasal symptoms tend to follow later, while a cold starts slowly with a runny nose and sore throat. However, since there are many cases of overlap, a definite distinction may require testing.
This article is general health information and is not a substitute for individual medical care. If symptoms persist or worsen, please seek treatment at a medical institution.