RUTH CLARK Staff file photo by Ben Conant

Yup, summer is still here, which means cold and flu season is months away. But right now is the time to be thinking about improving your immunity for the winter. It takes time for your immune system to heal and function optimally.

Here is the good news – one of the most-important ways to feed your immunity is to eat more plant-based foods. Fortunately, this is the season for plenty of local fresh food.

Foods to bolster your immunity

Fruits and vegetables – The brighter and more-colorful your choices the better. Visit your farmers markets and local farmstands for a great selection. Good choices for this time of year include green leafy vegetables, colorful peppers, tomatoes, beets, broccoli, sweet potatoes, winter squash and carrots.

Mushrooms – Some of the best mushrooms for immunity include lion’s mane, chaga, maitake, reishi and shiitake. These mushrooms are a source of antioxidants and polysaccharides, which impact immunity and inflammation. Even button mushrooms are a good source of nutrients for a healthy immune system.

Bitter greens – Kale, arugula, radicchio, romaine, collard greens and broccoli rabe are all great choices. They are chock-full of prebiotics and fiber for gut health and great for digestion.

Garlic and ginger – These are great additions to flavor in cooking, but they both pack a powerful punch when it come to your immunity.

Vitamin D – Good choices include fatty fish like salmon, herring and sardines, cod liver oil, egg yolks, fortified foods like some dairy products, orange juice, soy milk and cereals, along with mushrooms that have been exposed to UV light. Another great source is sunshine, but living in the Monadnock region may curb our exposure during the long winter month so supplements may be in order. Get your blood levels evaluated to be sure.

One of the most-important things you can do right now for your immune system is to improve the health of your gut. Up to 80 percent of your immune system resides in your gut, so the healthier your gut bacteria, the more optimal your immune system. Your microbiome, the 100 trillion microorganisms that reside in your gut and on your skin, protect your body from infection by regulating metabolism and maintaining the mucosal immune system.

Another important reason for maintaining gut health is that these bacteria also play a critical role in nutrient synthesis and absorption. If your mix of bacteria are not healthy, what you eat will not be fully broken down, absorbed and utilized by the body. This is an important point because your immune system is supported by critical nutrients. 

Foods to improve gut health

Fermented foods -- Fermented foods are loaded with healthy bacteria. Sauerkraut, pickles, kimchi, kombucha, kefir and yogurt are great sources of the healthy bugs. Just make sure you are purchasing foods that still contain live bacteria. Pasteurized sauerkraut and pickles in jars in the center aisle of the grocery store don’t make the grade. Look in the refrigerator of the deli department for these foods. You don’t need to eat large quantities to impact your gut. A couple of tablespoons at your lunch or dinner meal will be adequate. 

Focus on prebiotics and fiber -- Prebiotics are food for your healthy bacteria. Great sources include veggies in the allium family like garlic, onion, leeks, scallions, shallots and chives. Other good sources are oats and other whole grains, leafy greens, asparagus, avocado, potato skins and Jerusalem artichokes. Fiber is also a great food for probiotics, so keep your focus on whole foods in the produce department.

Along with foods that you should be eating, there are foods to avoid for an optimal immune system.

Foods to avoid to improve immunity 

Processed food – The importance of minimizing your intake of processed food can’t be emphasized enough. Stick to the outside aisles of the grocery store, spending the most time in the produce department. Avoid foods with long lists of ingredients. If you can’t pronounce the foods on the label, your gut won’t recognize them either. In addition, certain additives and preservatives are harmful to your gut. 

Lessen your sugar intake -- Unhealthy bacteria feed on sugar and refined carbs. A good way to lower these populations is to starve them out. 

Fried foods -- Fried foods are high in a group of molecules called advanced glycation end products (AGEs). AGEs are thought to weaken the immune system in several ways, including by promoting inflammation, depleting your body’s antioxidant mechanisms, inducing cellular dysfunction and negatively affecting gut bacteria. Cutting back on fried foods like French fries, potato chips, fried chicken, pan-fried steak, fried bacon and fried fish will reduce your intake of AGEs 

Fast food – Eating fast food frequently can take a toll on your immune system. Diets high in fast food drive inflammation, increase gut permeability and cause bacteria imbalance in the gut, all of which can negatively affect your immune health 

These few simple steps now can help you create a healthier immune system for the cold and flu season ahead. Start small today so as we move into the challenging months of winter ahead you will be in front of the curve. 

Ruth Clark, author of the best-selling book “Cool the Fire: Curb Inflammation and Balance Hormones,” is a registered dietitian nutritionist with a master’s in public health and over 35 years of experience.  She lives in Sharon and her practice is 100 percent virtual. Clark specializes in midlife and older women who are struggling with weight, mood and fatigue to regain their energy and vitality. You can reach her at ruth@ruthrd.com.

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