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With cold and flu viruses seemingly stronger than ever, the thought may have crossed your mind more than once: How to boost your immune system? Studies have proven that these eight dietary supplements are among the most effective at enhancing your immunity to infectious diseases.
There are nine different species of Echinacea, although three are used for medicinal purposes:
- Echinacea angustifolia
- Echinacea pallida
- Echinacea purpura
Echinacea purpura extract is the most widely used for the treatment and prevention of various infectious diseases, especially for children, the elderly, and immunocompromised patients.
Echinacea has various medicinal properties. First, it is antimicrobial against pathogens such as viruses and bacteria that cause colds, flu, sore throats, and other respiratory illnesses. However, it has been shown to enhance the growth of gut flora (healthy bacteria in the gut), specifically increasing the healthy Bifidobacterium species. Therefore, echinacea may enhance the effects of priobiotics containing Bifidobacterium. Echinacea also has anti-inflammatory properties, supports wound healing, and has been shown to improve the immune systems’ resistance against infection.
For dehydrated powders (including encapsulated echinacea), the species of purpuera is most popular with oral doses from 300 mg to 500 mg, three times per a day (900 to 1,500 mg daily). Tinctures of an ethanolic extract of the aerial parts (leaves and stems) are used in the concentration of 2.5 mL, three times per day, or up to 10 mL daily.
NAC (N-acetyl L-cysteine) is a form of the amino acid cysteine. It supports immune system function in four ways:
- First, it replenishes glutathione, a potent antioxidant needed for optimal immune system function. Interestingly, when glutathione is already at a healthy level in the body, then NAC supplementation will not raise it any further. This helps explain why NAC supplementation seems to be most effective in older adults, as they are more likely to have low glutathione levels.
- Second, NAC clears mucus in respiratory conditions such as bronchitis.
- Third, research shows that NAC protects against the flu. In one study, a total of 262 older adults were given placebo or 1200 mg NAC tablets daily for six months. The NAC group saw a significant decrease in flu frequency and severity, and improvement of symptoms. In addition, only 25 percent of the people infected with H1N1 influenza in the NAC group developed symptoms, compared to 79 percent for placebo.
- Last, NAC has been shown to disrupt the biofilms of harmful bacteria and yeast such as Staphylococcus aureus, Candida albicans, and Helicobacter pylori.
3. Vitamin D3
Vitamin D deficiency is one of the most common vitamin deficiencies seen in adults. In fact, one study from the Mayo Clinic found that as many as 57 percent of adults are deficient in this “sunshine” nutrient. And, research has proven a deficiency in vitamin D3 specifically is associated with increased autoimmunity (the body attacks itself) as well as an increased susceptibility to infection. Adults can take vitamin D3 (cholecalciferol) in regular capsule form at levels between 1,000 IU and 5,000 IU daily. (Note: Children should not take extra vitamin D supplements without consulting a family doctor or pediatrician.)
4. Vitamins B12 and B6
Two B vitamins are primarily responsible for immune support: B12 and B6. Vitamin B12 manages cell division and growth. Therefore, a lack of this vitamin may obstruct the growth of white blood cells. Vitamin B6 is vital to supporting biochemical reactions in the immune system. A deficiency in this nutrient can lead to reduced white blood cell response.
Additionally, the B vitamins help protect gut microbiota from pathogens.
5. Vitamin C and Zinc
Several cells of the immune system accumulate vitamin C and need the vitamin to perform their tasks, especially phagocytes and T-cells. And, zinc has been demonstrated to fight infections and help heal wounds.
Despite these therapeutic properties, for quite some time there has been a controversy on whether vitamin C and zinc can contribute to the prevention and therapy of the common cold. However, a large number of randomized controlled intervention trials have settled this debate. These trials document that adequate intakes of vitamin C (up to 1 g) and zinc (up to 30 mg) ameliorate symptoms and shorten the duration of respiratory tract infections including the common cold. Furthermore, vitamin C and zinc reduce the incidence and improve the outcome of pneumonia, malaria, and diarrhea infections, especially in children in developing countries.
6. Black Elderberry
The elderberry plant, Sambucus nigra, is a good source of protein, amino acids, unsaturated fatty acids, fiber, vitamins, and minerals. In addition, elderberry contains antioxidants called polyphenols, mostly in the form of anthocyanins, flavonols, phenolic acids and proanthocyanidins, as well as terpenes and lectins.
The antioxidant effect of the polyphenols in elderberry has been shown to have beneficial effects on blood pressure, glycemia (blood sugar) reduction, and immune system stimulation with anti-viral and even anti-tumor potential. The most well-known manufacturer of black elderberry is Sambucol, which makes an elderberry syrup; the dosage is 2 teaspoons per day.
Of all of the aforementioned supplements, probiotics probably rank as the most effective immune boosters. This is because their mechanism of action is so far-reaching; probiotics impact dendritic cells, epithelial cells, T-cells, lymphocytes, and B-cells.
In sum, probiotics in the GI tract help to reinforce the barrier function of the intestinal lining, lowering the chance of bacteria in the intestines entering into the blood stream. Of all the healthy bacterial strains, four have been proven by research studies to significantly impact the immune system:
- Lactobacillus rhamnosus GG
- Bifidobacterium animalis
- Lactobacillus paracasei
- Lactobacillus acidophilus
8. Astragalus Root
Last, but certainly not least, of all the powerful immune boosting supplements is astragalus root. Astragalus root comes from the Astragalus membranaceus plant, a hairy-stemmed plant native to China. Astragalus root is loaded with beneficial flavonoids that have potent antioxidant properties enabling it to support the health of many organs as well as reduce the effects of aging. The primary benefit of taking astragalus root is as an adaptogen, a natural substance that works to regulate the effects of stress and fatigue on the body. But, studies have also shown the herb to be an impressive immune booster.
Astragalus root can be consumed as an extract, tea, powder, or tincture. For adults, the recommended dosage is 250 to 500 mg of standardized extract, three to four times daily. As a fluid extract, a 1:1 ratio of 2 to 4 mL, three times per day is recommended. In tincture form, a 1:5 ratio of 3 to 5 mL, three times per day is recommended.
Astragalus tea can be consumed as 6 to 12 g of dried root in 12 ounces of water up to three times daily. The oral dosage of powdered root is 500 to 1,000 mg, three to four times a day.
This article was originally published in 2018. It is regularly updated.
 Journal of Agricultural Science. 2017;9(4): 1.
 J Med Food. 2007 Sep; 10(3): 423–434.
 Free Radic Biol Med. 2008 Nov 1;45(9):1252-62.
 G. (2017, February 25). N-Acetylcysteine for Immunity. Retrieved March 30, 2018, from https://supplementsinreview.com/immune/n-acetylcysteine-immune/
 Mayo Clin Proc. 2006 Mar;81(3):353-73.
 J Investig Med. 2011 Aug; 59(6): 881–886.
 Cell Host & Microbe. 2017;21(2): 130-131.
 Med Monatsschr Pharm. 2009 Feb;32(2):49-54.
 Ann Nutr Metab. 2006;50(2):85-94.
 J of Functional Foods. 2015 Oct; 18(B):941-958.
 Current Opinion in Gastroenterology. 2015 March; 31(2): 153-158.
 Int J Mol Sci. 2017;18(12).