Along with winter weather comes the cold and flu season, and there are always general immune health concerns to be on the look-out for any time of year. What can you do to keep your immune system in top shape?
Here are some vitamins and nutrients that support your immune system that can be found in foods and dietary supplements:
Vitamin D is fat-soluble vitamin that is naturally made by the body in response to sunlight and keeps your bones and immune system strong. Studies consistently show that vitamin D levels drop during winter months. This may be due to being indoors more. Average vitamin D levels range between 20-40 ng/ml, and many health care practitioners recommend a level between 30-50 ng/ml.You can request a test by your health care practitioner, and there are even some at home tests now available.Low vitamin D levels increases the likelihood of getting sick. When you aren’t getting enough sun or are prone to having low vitamin D levels, you may consider taking a high-quality dietary supplement. In a meta-analysis of 25 randomized controlled trials including 11,000 participants, vitamin D supplementation is shown to cut risk of respiratory infections by half1.
Zinc is a micronutrient that is essential for our body for a number of diverse roles, including supporting our wound healing response and immune response to infections. As an element (Zn), our bodies cannot make its own zinc, so it needs to come from our foods, such as – whole grains, meats, shellfish, dairy and beans.
While a majority of people in developed countries get enough zinc from foods, certain groups of people are more likely than others to get enough zinc, such as people who have digestive disorders or gastrointestinal surgery or vegetarians, since meat products provide the majority of zinc in diets. Drinking alcohol also decreases the amount of zinc absorbed by the body.
The recommended daily amount of zinc is 8 mg for women and 11 mg for men. Oral zinc supplements may benefit people with low levels of zinc, and if taken soon after cold symptoms, may shorten the length of a cold2.
Vitamin C, or ascorbic acid, is a water-soluble vitamin known for its role in supporting the immune system. Our bodies cannot make vitamin C, so it is another micronutrient that must be obtained from food. Rich sources of vitamin C include papaya, bell peppers, broccoli, brussels sprouts, strawberries, pineapple and citrus fruits.
Most people get enough vitamin C from a healthy diet but vitamin C deficiency can occur in certain groups of people, including people with digestive disorders or certain types of cancer, smokers or those on a limited diet that doesn’t regularly include fruits and vegetables. Vitamin C deficiency can increase your risk of infections as well as lead to a disease called scurvy, which causes anemia, bruising and poor wound healing. The recommended daily amount of vitamin C is 75 mg for women and 90 mg for men.
People susceptible to vitamin C deficiency may benefit from vitamin C supplements. One study show that vitamin C supplementation reduced the risk of catching a cold and cold duration in participants with low vitamin C3. However, taking too much vitamin C (>2000mg/day) can cause side effects such as headaches, fatigue, stomach cramps, and in some populations increases risk for kidney stones.
Elderberries are dark purple berries that come from Sambucus trees. Elderberries have been used for centuries to fight infections and boost immunity, and today they are often cooked down to make elderberry pies, jams, juices or even wine. While research is ongoing investigating its medicinal properties, elderberries are highly nutritious, with one cup boasting a hefty dose of antioxidants, 10 grams of dietary fiber and 52 mg of vitamin C.
In addition to nutrition, elderberry is shown to reduce incidence and duration of colds or flu in some human studies4,5 although another study did not report benefits against the flu6, warranting further research. While no products or medicine to date can completely prevent or cure flu, eating a nutritious diet full of antioxidants is one of the best ways to strengthen the immune system.
Many healthcare practitioners are recommending a protocol combining these dietary supplements for immune health support. Consider morning and evening immune supplements for convenience and cost effectiveness.
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 Martineau AR, Jolliffe DA, Hooper RL, et al. Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ 2017; 356:i6583.
 Rao G, Rowland K. Zinc for the common cold—not if, but when. J Fam Pract 2011; 60(11): 669-671.
 Johnston CS, Barkyoumb GM, Schumacher SS. Vitamin C Supplementation Slightly Improves Physical Activity Levels and Reduces Cold Incidence in Men with Marginal Vitamin C Status: A Randomized Controlled Trial. Nutrients 2014;6(7): 2572-2583.
 Zakay-Rones Z, Thom E, Wollan T, Wadstein J. Randomized study of the efficacy and safety of oral elderberry extract in the treatment of influenza A and B virus infections. J Int Med Res 2004; 32(2):132-40.
 Tiralongo E, Wee SS, Lea RA. Elderberry Supplementation Reduces Cold Duration and Symptoms in Air-Travellers: A Randomized, Double-Blind Placebo-Controlled Clinical Trial. Nutrients 2016; 8(4): 182.
 Macknin M, Wolski K, Negrey J, Mace S. Elderberry Extract Outpatient Influenza Treatment for Emergency Room Patients Ages 5 and Above: a Randomized, Double-Blind, Placebo-Controlled Trial. Journal of General Internal Medicine 2020; 35: 3271-3277.
Dr. Linda May-Zhang has over 10 years of research experience in nutrition, chronic diseases and pharmacology. She has published over 20 peer-reviewed academic papers in scientific journals. She is also a science writer with a passion for educating the lay public.
*These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease.
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