The immune system reminds me of technology; when it's running smoothly, everything is up to date and well maintained, it's great - but - when it's lacking what it needs to function optimally, it can be slow or even get a virus. If we eat well, exercise well, keep our stress levels well managed, and more; generally, we can expect to have fewer colds and illness. If we're not getting in activity, not eating enough nutrient-dense foods, and/or we're over-stressed, then we may end up feeling awful.
As a mom of twin toddlers, getting sick is the last thing I want to deal with while chasing them around! But, here's the thing: there are a lot of claims and headlines floating around to hook you onto the latest diet or supplement. How do you know where to put your money and effort?
As a RDN ("Registered Dietitian Nutritionist"), I'll look at some of the evidence-based food-based options to help you keep your immune system functionally well so you can spend more time with friends and family, holiday shopping, out having fun, and less time feeling miserable in bed (if you even get that opportunity!).
Probiotics
These bacteria, which are usually good bacteria, may have health benefits, especially in regard to digestive (1) and immune health, when consumed. Some may even help with reducing symptoms of depression (2) and promoting heart health (3).
Although you can buy these as a supplement, supplements are not regulated which poses additional concern to pregnant and lactating women. In the hospital setting, a couple over the counter versions are used but always check with your MD first. Now, here's a list of foods that contain probiotics:
Yogurt and Kefir: Probably one of the most popular choices because it has a creamy texture, neutral flavor (often sweetened with fruit and nuts) and has its own set of health benefits. It may help reduce diarrhea when on antibiotics, as well (4,5). If you are lactose intolerant, you may find you can still consume certain dairy products such as yogurt or hard cheese. Note: not all yogurt contains live or active cultures due to processing so make sure to check the label. Keep in mind, some yogurt is excessively sweetened and may come in a variety of fat content (0% to 8 % for example). Like yogurt, kefir may help improve bone health, assist with GI issues, and help the immune system (1). Kefir tends to have more probiotics than milk and those with lactose intolerance may still be able to drink it without GI complaints.
Sauerkraut: Shredded cabbage fermented by lactic acid bacteria. Although popular in European cuisine, especially German foods, it also is rich in probiotics and other nutrients (6); Note: it can be high in sodium. Always choose unpasteurized as the pasteurization process kills live bacteria.
Kimchi: Shredded cabbage, but sometimes other vegetables, also fermented with lactic acid bacteria but also made spicy in Korean cuisine. Similar to sauerkraut, kimchi is rich in vitamins, minerals, and antioxidants.
Miso and Tempeh: Although these are different food items, both are a fermented soybean product. Miso is a Japanese seasoning usually found in soup. Because both products contain soy, they are a vegetarian source of protein. The fermentation process in tempeh produces vitamin B12, a nutrient some people may be low in, specially those who are strict vegetarians or vegans (7).
Kombucha: originally popular in Asia, now trending in America, this fermented tea is made with both helpful bacteria and yeast. Research with good methodology currently lacks. Human studies are also lacking. Given this, and that it contains alcohol, it is generally not considered a great option for pregnant and lactating women when there are many other probiotic-rich foods and supplements available (8). This is another one to discuss with your Doctor.
Garlic
Not only does it taste wonderful in warm, savory dishes this time of year, but it can boost immune function and may help prevent and treat the cold and/or flu. Garlic, when crushed or chewed, turns into a sulfur-rich compound called allicin. These compounds have been found to boost the immune response of some white blood cells (WBCs) when they encounter viruses, such as the cold or flu virus (9, 10, 11).
Fish (Oily Fish)
The Omega-3's found in oily fish such as salmon, tuna, trout, and halibut, help fight infections by increasing WBC activity from phagocytes and help fight general inflammation (12) Note: pregnant and lactating women should limit their intake of certain oily fish to 2 portions/week (potentially less with tuna depending if consumed by can or cooked portions). Always check with your MD or personal RD on this one. Other foods high in Omega-3's include: flaxseeds, chia seeds, walnuts, and soybeans. DHA and EPA, other omega 3's, are also being found in dairy products such as milk.
Oatmeal
Perfect on a cold morning, oats contain a soluble fibre, beta-glucan, that is both anti-microbial and antioxidant (13). Note: other foods contain beta glucan such as mushrooms and barley. Consider adding a DHA fortified milk or a probiotic kefir/yogurt and some almonds for additional immune-boosting benefits.
Chicken Soup
It's not just for the soul. The warm liquid, like with hot tea, can help flush out mucus and provide temporary relief when sick and has been found to have a mild anti-inflammatory effect on upper respiratory infections (14).
Yours in Health,
Julie Wallace, RDN, LD, CSP
References below:
https://www.ncbi.nlm.nih.gov/pubmed/22529959https://www.ncbi.nlm.nih.gov/pubmed/25448230https://www.ncbi.nlm.nih.gov/pubmed/24330093https://www.ncbi.nlm.nih.gov/pubmed/25588782https://www.ncbi.nlm.nih.gov/pubmed/19622191https://ndb.nal.usda.gov/ndb/foods/show/45223908?fgcd=&manu=&format=&count=&max=25&offset=&sort=default&order=asc&qlookup=RAW+SAURKRAUT%2C+UPC%3A+654367229552&ds=&qt=&qp=&qa=&qn=&q=&ing=https://www.ncbi.nlm.nih.gov/pubmed/8060790https://www.healthline.com/nutrition/kombucha-while-pregnanthttps://www.ncbi.nlm.nih.gov/pubmed/25153873https://www.ncbi.nlm.nih.gov/pubmed/25961060https://www.ncbi.nlm.nih.gov/pubmed/22280901https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3257651/https://www.todaysdietitian.com/newarchives/050114p16.shtmlhttps://www.ncbi.nlm.nih.gov/pubmed/11035691