How to keep your immune system strong?

Healthy ways to strengthen your immune system:^[1]

• Keep your kidney healthy
• Having kidney disease and kidney failure can weaken your immune system, making it easier for infections to take hold.^[10,11]
• Read Kidney Disease—All Things Considered
• Keep your liver healthy
• The liver is a key, frontline immune tissue. Ideally positioned to detect pathogens entering the body via the gut, the liver appears designed to detect, capture, and clear bacteria, viruses, and macromolecules.^[14]
• Read Risk Factors of Liver Diseases
• Avoid toxins such as PCB, pesticide, or Arsenic 
• PCBs are ubiquitous environmental toxicants, for which animal studies demonstrate immunotoxic effects.^[12]
• Arsenic has been shown to affect not only the immune response, but also behavior in rats.^[13]
• Read The dangers of pesticides to humans.  But, the gist is that pesticides are immunosuppressive agents.
• Micronutrients supplementation
Micronutrients such as vitamin C, D, zinc, and selenium play roles in antioxidant, anti-inflammatory, antithrombotic, antiviral, and immuno-modulatory functions and are useful in both innate and adaptive immunity.^[26,28,29]
• Take selenium supplementation (especially prior to the vaccination)
• Inhibition of ferroptosis via selenium supplementation promotes the survival of follicular helper T cells, boosting the germinal center and antibody response following vaccination in mice and people.^[25]
• Don't smoke or vape
• Eat a diet high in fruits, vegetables, and whole grains
• 30 good reasons for eating plant-based diets
• Among COVID-19 patients, propolis and combinations of bee honey with herbal plants were associated with improved viral clearance and symptom recovery.^[21]
• The cells rely on nutrients as an energy source and for building blocks.  A study shows that nutrients are also involved in inhibitory pathways, and that deprivation of certain nutrients or metabolites might be good for adaptive immunity.^[19]
• Take a multivitamin if you suspect that you may not be getting all the nutrients you need through your diet
• Health benefits of Vitamin D
• Vitamin-rich foods
• Vitamin B assists in proper activation of both the innate and adaptive immune responses, reduces pro-inflammatory cytokine levels, improves respiratory function, maintains endothelial integrity, prevents hypercoagulability and can reduce the length of stay in hospital.^[23,24]
• Therefore, vitamin B could be used as a non-pharmaceutical adjunct to the treatment of patients with COVID-19.^[22]
• A study found that taking multivitamins, omega-3, probiotics or vitamin D supplements may lessen the risk of testing positive for SARS-CoV-2. But taking vitamin C, zinc, or garlic supplements did nothing to reduce the risk of catching Covid-19.^[20]
• Exercise regularly
• Exercise and its benefits
• Maintain a healthy weight
• Control your stress level
• How to manage stress
• Control your blood pressure
• If you drink alcohol, drink only in moderation
• No more than one to two drinks a day for men, no more than one a day for women.
• Alcohol can weaken the immune system and make the body more susceptible to infections.^[9]
• Get enough sleep
• Good night sleep
• Hours of sleep — How long is too little or too much?
• Avoid sugar or HFCS
• Niket Sonpal, a board-certified internist and gastroenterologist, stated that the suppression of the immune system starts as soon as 30 minutes after the consumption of sugar and can last up to five hours.^[16-18]
• Take steps to avoid infection, such as washing your hands frequently and trying not to touch your hands to your face, since harmful germs can enter through your eyes, nose, and mouth.]
• Avoid high-salt diets
• Research has found that besides being bad for blood pressure, a high salt diet is also bad for the immune system.^[27] 

References

1. Preventing the spread of the coronavirus - Harvard Health
2. List of Risk Factors for Covid-19
3. Melatonin — A Promising Candidate for Prevention and Treatment of COVID-19
4. Top Zinc-Rich Foods For Better Immunity
5. Immunosenescence — Weaker Immune System of the Elderly Explained
6. Hesperidin — a promising adjuvant treatment option against SARS-CoV-2 infection
7. Immune systems are like our fingerprints
8. Natural Immunity
• What Can Cause Depressed Immunity?
• Immune System Boosters
9. 6 Surprising Ways Alcohol Affects Your Health — Not Just Your Liver
10. Chronic Kidney Disease and Pneumococcal Disease: Do You Know the Facts?
11. The immune system and kidney disease: basic concepts and clinical implications
12. Prenatal PCB exposure and thymus size at birth in neonates in Eastern Slovakia
13. Arsenic ecotoxicology and innate immunity
14. Immune Responses in the Liver
15. Vitamin D3 — A Promising Candidate for Prevention and Treatment of COVID-19
16. A high-sugar diet affects cellular and humoral immune responses in Drosophila
17. Eating Sugar Can Weaken Your Immune System
18. The Effect of Short-Term Hyperglycemia on the Innate Immune System
19. Researchers map metabolic signaling machinery for producing memory T cells
20. Which Vitamins Actually Reduce Your Risk Of Getting Covid-19?
21. Propolis, Bee Honey, and Their Components Protect against Coronavirus Disease 2019 (COVID-19): A Review of In Silico, In Vitro, and Clinical Studies
22. Be well: A potential role for vitamin B in COVID-19
23. Michele C.A., Angel B., Valeria L., Teresa M., Giuseppe C., Giovanni M., Ernestina P., Mario B. Vitamin supplements in the era of SARS-Cov2 pandemic. GSC Biol. Pharm. Sci. 2020;11(2):007–019.
24. Zhang L., Liu Y. Potential interventions for novel coronavirus in China: a systematic review. J. Med. Virol. 2020;92(5):479–490.
25. Selenium saves ferroptotic TFH cells to fortify the germinal center
26. Nutritional risk of vitamin D, vitamin C, zinc, and selenium deficiency on risk andclinical outcomes of COVID-19: a narrative review
27. A high-salt diet compromises antibacterial neutrophil responses through hormonal perturbation
28. The Role of Minerals in the Optimal Functioning of the Immune System
29. Zinc Levels Affect the Metabolic Switch of T Cells by Modulating Glucose Uptake and Insulin Receptor Signaling
30. Myths vs. Facts About Your Immune System