How to build a strong immune system to resist diseases and viral infections.

What exactly should we do to boost our immunity? — Starting with the basics of daily life.

When it comes to immunity, we often look for "something special," but in reality, small daily habits make a big difference. What we always want to convey is to create "sustainable habits." Here, we will explain the four main pillars: sleep, vitamin D, bathing habits, and diet, incorporating scientific insights and practical tips. Honestly, we are not perfect at all of these, but we will share what we have tried and felt effective.

1. Get Quality Sleep: The Foundation for Supporting T Cell Function

Why Sleep Matters

Sleep is the reset time for our immune system. Studies report that T cells in people who get enough sleep activate integrins at higher levels, enhancing their ability to attach to and eliminate infected cells (research by Stoyan Dimitrov, Tanja Lange et al.). Lack of sleep is also associated with a reduced response to vaccines and an increased risk of infection, so prioritizing sleep is an effective first step.

Practical Tips for Improving Your Sleep

• Go to bed and wake up at the same time every day. When your body clock is regulated, your immune function recovers more efficiently.
• Avoid smartphones and bright lights before bed. Blue light disrupts your body clock.
• Do light stretching and deep breathing before bed to relieve tension. We also found it easier to fall asleep with a few minutes of stretching at night.
• Sleep duration varies by individual, but it's good to aim for 7-8 hours.

2. Getting Enough Vitamin D: Combining Sunlight and Supplements

The Relationship Between Vitamin D and Immunity

Vitamin D is an important nutrient involved not only in bones but also in immunity. Clinical studies and reviews have reported multiple times that vitamin D affects both innate and adaptive immunity and is associated with a reduced risk of respiratory infections (review by G. K. Schwalfenberg, meta-analysis by Bergman et al., etc.). It tends to be deficient during seasons with less sunlight or for those who spend most of their time indoors, so caution is needed.

Practical Tips for Sunbathing and Supplements

• On sunny days, try to get direct sunlight for a short time (about 10-20 minutes on your face and hands). Avoid excessive sunburn.
• During periods when you refrain from going out, consider supplements containing vitamin D3 (cholecalciferol). However, it is safer to check your blood levels and consult with a doctor.
• The effect of supplements varies by individual, and excessive intake can be problematic, so adhere to the dosage. We also take D3 after consulting a doctor during the cold season.

3. Boosting Circulation with Heat and Contrast Therapy: How to Use Saunas and Showers

The potential benefits of saunas and hot baths

There are reports that raising body temperature with far-infrared saunas temporarily increases white blood cells and some immune cells. By improving blood flow and lymphatic circulation, the body's circulation improves, which may promote immune responses. However, the strength of the evidence is limited, and caution is required for those with heart disease or high blood pressure.

Contrast Showers: Alternating Hot and Cold Therapy at Home

• The general method is to warm up for a few minutes with a warm shower (or bath), then apply cold water for about 30 seconds to 1 minute, repeating this several times.
• This is said to promote the contraction and expansion of blood vessels and improve lymphatic flow. However, if you are new to this or not feeling well, do not overdo it.
• When we tried it, we felt more refreshed and less prone to cold, but it is stimulating, so we recommend gradually getting used to it.

4. Supporting Th1-Dominant Immunity Through Diet: Specific Foods and Habits

Which nutrients support our cellular immunity?

"Th1-dominant" refers to supporting cellular immunity (T-cell centric) against viruses and bacteria. The following nutrients and foods are thought to support cellular immunity. There is no definitive "superfood," but a balanced diet is the foundation.

• Protein (fish, chicken, soy products, etc.): Immune cells are made of protein.
• Zinc (oysters, red meat, nuts): Involved in the development and function of T cells.
• Selenium (Brazil nuts, fish): A nutrient that helps with antioxidant and immune regulation.
• Vitamins A and C (green and yellow vegetables, fruits): Mucosal defense and antioxidant.
• Mushrooms and seaweeds containing β-glucan, and fermented foods (yogurt, natto, etc.): Beneficial for regulating innate immunity and gut environment.
• Garlic and ginger: Foods traditionally used to support immunity, easy to incorporate into daily seasoning.

Things to keep in mind beyond your diet

• Moderate alcohol consumption and excessive sugar intake can suppress immune function, so be mindful.
• Moderate aerobic exercise helps immune cells circulate, but excessive exercise can be counterproductive, so balance is important.
• Stress management (meditation, deep breathing, hobbies) is also directly linked to immunity. We also found that short meditations improved our sleep.

Summary

You don't need special medicine to boost your immunity. We recommend prioritizing the four basics: "good sleep," "adequate sunlight (vitamin D)," "bathing habits that promote circulation," and "a balanced diet." In addition to these, combining handwashing, vaccination, appropriate use of supplements, and manageable exercise and stress care will lead to building a body that can resist diseases and viruses. We also feel stable in our physical condition by continuing small daily habits. Please try incorporating one thing at a time.

Disclaimer: The information in this article is for general informational purposes only and does not constitute medical advice. Please consult a qualified healthcare professional before making any health-related decisions.