The immune system helps us to fight off viruses, bacteria, protozoa, and fungi, that can cause disease and keeps them in balance with the health-promoting microbes of our microbiota (the ‘friendly’ bacteria, yeasts, and fungi occurring throughout the body and that are beneficial to health).
While supplements won’t magically prevent or cure the common cold, flu-like viruses or the coronavirus that causes COVID, part of the foundation for a healthy, properly functioning immune system is a good diet that provides sufficient energy, essential fats, protein, and micronutrients. Conversely, diets that are high in processed and refined foods, deficient in micronutrient-density, and especially those high in trans-fats and sugar might worsen responses to infections.
Many nutrients are known to help support immunity, for example:
- Omega 3 fats help us to regulate immunity and inflammation in conjunction with the ‘pro-inflammatory’ omega 6 fats. Omega 3 fats are found in fatty fish and vegan sources like flaxseeds and algae.
- Vitamin A is intricately involved in immunity,  and sufficient Vitamin A is associated with immunity to illness and infections. [2, 3]
- Vitamin C, contrary to popular belief, probably won’t cure the common cold but research suggests that it might help to reduce symptoms of colds and shorten their duration, and might even help to prevent the occurrence of colds in athletes and others prone to higher levels of stress when taken regularly. [5, 6]
- Vitamin E also has immunomodulatory effects. 
- Vitamin D is a key immune regulator and has also shown promise for aiding several auto-immune conditions like systemic lupus and rheumatoid arthritis. 
- Zinc is also a key co-factor for immune responses. Evidence suggests that zinc supplementation might help reduce the duration and severity of the common cold. [9, 10]
- Bioflavonoids from plants might help to reduce upper-respiratory-tract infections.  Other antioxidant-rich foods like grapeseed, rosehips, and cacao improve antioxidant status and immunity and reduce inflammation. [12-17]
- Adaptogens are herbs that are stress ‘tonics’ that help us to respond to stressors more effectively. Among the adaptogens, ginger, ginseng, gotu kola, ashwagandha and astragalus have demonstrated a range of antioxidant, anti-inflammatory and immune-boosting properties. [18-26]
- Common herbs like rosemary are anti-inflammatory and anti-microbial and may benefit immune status. 
- Spices such as turmeric are likely to improve immune function. 
- Medicinal mushrooms help to provide immunity against infections. For example, shiitake mushroom is thought to aid immunity by increasing white blood cell activation. [29, 30]
- Probiotics reduce the incidence and severity of respiratory infections, [31-36] and probiotics are suggested for use to reduce inflammation and infection following several types of surgeries. [37-40]
It should always be remembered that these nutrients (especially the essential vitamins and minerals) work to support immunity by supporting the diet. In other words, many people don’t eat enough of nutrients essential to immunity like pre-formed vitamin A and zinc, and so, supplementing these can support immunity by restoring sufficiency.
Top 3 Supplement Picks to Support Immunity
Good Green Vitality (previously ‘Good Green Stuff’) by Nuzest, is a broad-spectrum multinutrient that contains the best quality essential vitamins and minerals including those required to support immunity (such as pre-formed vitamin A, vitamin C, full-spectrum vitamin E, and zinc) along with adaptogens, mixed whole-food derived phytochemicals and ‘greens’. It’s been called “much more than a multi and waaay more than just greens”…by me.
Omega 3 fatty acids from fish oil help to modulate the immune-inflammatory cascade. While Good Green Vitality contains a good dose of vitamin D, many people might benefit from a little extra, especially during winter, and Melrose Fish Oil + Vitamin D is a great way to get the benefits of both easily.
All of the medicinal mushrooms are awesome for health but Reishi is the great all-rounder and is thought to have profound immune benefits in traditional medicine. It can be added to the diet as a powder, liquid extract (for ease of use), or in an herbal elixir or cacao drink (which is also great for relaxing and unwinding at night). Special mention should also be made of Chaga which is touted as an immune-supporting ‘shroom that can be used periodically.
Check out the full report on immunity and health at http://cliffharvey.com/all-about-immunity/
Treat all claims of ‘cures’ and ‘preventatives’ with caution, especially in the current climate of emerging threats like novel flu viruses and other similar viruses like the current COVID-19 novel coronavirus pandemic.
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