The cool, seasonal weather has finally settled in, and so has cold and flu season. You knew it was coming, just like Thanksgiving, which is only a week away. While you are busy preparing for good food and good cheer, ask yourself how your immune system is doing. Is your body as healthy as it can be? Will it be able to fend off the cold and flu viruses this season, not to mention other bacterial infections that linger around any time of year? Reports from late September revealed several early cases of the flu in Maine. While we do not know how bad it’s going to get, we do know that more people will be getting sick this fall and winter. The good news is you can decrease your chances of getting sick by boosting your immune system with nutrition.

Keeping our immune systems healthy can help ward off germs like viruses that cause the dreaded cold and flu as well as bacterial infections. If we do get infected, having a robust immune system can still help reduce the severity of symptoms and the duration of the infection. It’s a win-win situation.

The Foundation

A healthy immune system starts with a foundation of a healthy you. This includes getting enough rest; roughly eight hours of high-quality sleep is a good goal. Stress management is important, as chronic stress can take its toll. Hydration is key; our bodies need water even when it’s cold outside. Thirst sensations might be dampened, so be sure to sip on warm beverages regularly, even if you do not always feel thirsty. Staying physically active (not overdoing it, but not lounging on the couch all day) as well as frequent and thorough hand washing both play a key role in warding off infection. Try to maintain a healthy weight; obesity can produce chronic, low-grade inflammation which can decrease immunity. Last but not least, eating a well-balanced diet, including a wide variety of brightly colored vegetables and some fruits, provides vitamins, minerals, antioxidants, phytonutrients, and fiber that our bodies need to function optimally.

Sugar

Avoiding sugar, or decreasing one’s consumption, is one good place to start in boosting immune health. Unfortunately, there are very few studies on this. One key and often-cited study dates back to 1973. After a fast, healthy volunteers were fed 100 grams of sugar in different forms, including table sugar, orange juice, and honey. Their blood was drawn and studied. The white blood cells of those who were given sugar had a two-fold reduced ability to fight a bacterial infection. This effect lasted for five hours, with the greatest effect occurring one to two hours after the sugar ingestion. The same effect was not seen with starch. Clearly, more studies are needed. But because sugar is detrimental to health on so many levels, avoiding it as much as possible is a good place to start.

The Gut

Our gut comprises more than 75 percent of our immune system. Stomach acid can kill ingested pathogens due to its acidity. In addition, the microbial community that lives in our intestines, or the gut microbiota (formerly known as gut flora), plays a key role in immune system functioning. Having healthy microbiota makes it less likely that harmful microorganisms will colonize the gut, by increasing the body’s ability to fend off harmful bacteria and even viruses; the more good bugs there are, the fewer bad bugs can take hold. One interesting study in mice pre-treated with probiotics for three weeks and then infected with a flu virus revealed that they were better able to fight the virus, had less inflammation, and had overall increased survival rates compared to controls. A similar study revealed the opposite: mice pre-treated with antibiotics and subsequently infected with the flu were less able to fight the infection and had decreased survival rates.



Feeding the Gut

While environmental factors are key in shaping the microbial populations in our gut during the early years, other factors like diet (i.e., what we eat) play a role throughout our lives. Some say the food that we eat could actually determine this by up to 57%. This is great news because it means we have a lot of control. The favorite food of healthy microbes is fiber. The easiest way to ensure you are getting good amounts of fiber is to look down at your plate. Make sure at least half your plate consists of colorful plant foods, especially vegetables. This will be easy for some, and more challenging for others. (The average ancestral/hunter gatherer ate a high-fiber diet of 80-100 grams per day. The modern American diet contains 10-15 grams per day.)

Foods that are particularly nourishing include onions, garlic, leeks, Jerusalem artichokes, beans, lentils, cooked-cooled potatoes, plantains, asparagus, jicama, and dandelion greens. We also want to consume foods that naturally contain probiotics or beneficial bacteria found in foods or supplements. Examples include kefir, yoghurt, any fermented vegetables like sauerkraut, kimchi, as well as fermented beverages like water kefir, kombucha, and beet kvass. Probiotic supplements are another good alternative. Make sure the strain of the bacteria is named, and that it has research behind it. Label claims are not a good indication of quality. If you are unsure, consult a health care practitioner who is knowledgeable on the subject.

Lastly, it is just as important to avoid foods that feed harmful bacteria as it is to feed the good bacteria. Harmful bacteria thrive on simple sugars and starchy foods. All processed foods will fall into this category. This includes foods such as cookies, crackers, chips, pastries, white pasta, white bread, deep-fried foods, and sodas, among many others.

Vitamin D

Vitamin D is important for immunity as well as bone health, cell growth, and neuromuscular function, among many other functions. Studies have shown supplementation to be helpful in reducing incidence of the flu as well as protecting against acute respiratory infection. The best source is from sunshine hitting our skin. Unfortunately, above 40 degrees latitude, optimal vitamin D synthesis lasts from mid-March to November. Starting this time of year, many people will need to consume either a supplement or vitamin D-rich foods. If you are supplementing, get your D levels tested regularly. Good food sources include canned salmon and sardines with the bones, pastured eggs, enriched milk, and there is some in liver as well, including cod liver oil. Again, if you supplement, make sure to use a reputable brand; not all supplements are created equal.

Vitamin A

We don’t hear too much about Vitamin A, which is a shame, because it is an essential nutrient and very important for immune health. Deficiency is strongly associated with increased susceptibility to infectious diseases. You may be at increased risk if you have fat malabsorption, bile conditions, inflammatory bowel disease (Crohn’s or ulcerative colitis), pancreatic insufficiency, are a vegan, or have alcoholism. Good sources include organ meats like liver, grass-fed butter or ghee, egg yolks, herring, salmon, fat from grass-fed animals, and cod liver oil. (While green leafy vegetables and orange fruits and vegetables contain beta carotene, they do not contain pre-formed Vitamin A. Beta carotene gets converted into Vitamin A in the body, but conversion rates vary widely from person to person.)

There are a plethora of factors that contribute to a strong immune system. Having the foundation of a healthy lifestyle and diet is a great first step. Nourishing the microbiota with plant foods and probiotic-rich foods, while avoiding processed foods, is equally important. The fat-soluble vitamins D and A likewise are key players in a hearty immune system. While there are a myriad of other foods and nutrients, as well as herbs, that play a role in immunity, the above-mentioned ones will get you well on your way to robust immune health.

The information provided in this article is intended for general use only and is not to be used in place of medical advice from a licensed health professional.