By Dr. Mercola

While many people may find themselves succumbing to the common cold and other respiratory illnesses that are so prevalent in the winter, there are several things you can do (and not do) to help keep yourself in top form. Some may not even seem to be an important part of staying healthy, but they are.

When it comes to averting sickness, even while all-around you people might be coughing, sneezing and blowing their noses, successfully running the gauntlet of flu season may be simply a matter of keeping your immune system boosted by applying a few key health strategies. Besides going to school and work, times your immune system might be especially compromised include when you travel or are sleep deprived or stressed out. These are times you want to make sure your immune system is at its best.

Nutrition may be the most vital component in maintaining — or gaining — a healthy immune system. It makes all the difference in the way your body fights off germs, but just as importantly, plays an important role in more minute functions like helping tissues repair and rebuild themselves and how your body reclaims flagging energy.

Foods (and the Nutrients Therein) to Boost Your Immune System

Not just vitamins and minerals, but proteins like collagen and free radical-fighting antioxidants can be introduced to your body through the foods you eat and play vital roles in helping to keep your body functioning at its best. As the Chicago Tribune observes:

“Collagen and its amino acids are essential to healing because they build tissues such as skin, muscles, tendons, ligaments, cartilage, blood vessels, bones and more. Antioxidants remove the harmful free radicals from the bloodstream that can impair the immune system, and vitamins and minerals play specialized roles in healing.”¹

In the same way that crosses training can keep your body fit and toned by working groups of different muscles, eating a variety of foods will target and work toward healing and restoring many different areas of your body, from your brain to your gut to your immune system. Protein found in lean meats, bone broth, fish, eggs, nuts, and seeds help your body repair tissue and fight infection. Studies show that amino acids in protein, such as arginine and glutamine, increase your body’s ability to heal and decrease inflammation.²

Vitamins and Minerals to the Immune System Rescue

Eating foods chock-full of vitamins is an excellent way to strengthen your immune system to stay healthy all season:

• Vitamin A boosts immunity, lowers your risk of infection and supports wound healing through collagen strength. Snack on carrots, squash, sweet potatoes, dark leafy greens, cantaloupe, wild-caught Alaskan salmon, organic pastured eggs and grass-fed beef.
• Vitamin D plays a big part in immune health and can be found in limited quantities in raw grass-fed milk, wild-caught Alaskan salmon, and organic pastured eggs, but the ideal way to optimize your levels is via sunshine
• Some of the most vitamin C-rich foods include citrus fruits, from tangerines to limes, along with leafy greens, bell peppers, and broccoli. Berries are another great source, and they all provide this and other potent antioxidants, which support your immune response and help to rebuild collagen.

Vitamin K1, important for healthy blood clotting, is abundant in dark leafy green vegetables. Vitamin K2 refers to a collection of bacterial menaquinones (MKs) that are found in a variety of different foods, namely animal foods and fermented foods. MK-4 is most abundant in animal foods while you can find MK-7, MK-8, and MK-9 in fermented foods.

Important for collagen production, zinc is another protective antioxidant that helps create and activate your immune system’s white blood cells and is essential in the enzymatic reactions needed for wound healing. Zinc-containing foods include grass-fed red meat (optimal amounts per day range from 5 to 7 ounces), pastured, organic chicken, spinach, nuts and pumpkin seeds.

Selenium is another powerful antioxidant for immune system protection, found in Brazil nuts and organic, grass-fed beef, turkey, and chicken. In addition, as important as any food you eat, drinking adequate water is vital for flushing food through your system, flushing toxins and keeping your body hydrated. Many turns to so-called “sports drinks” for hydrating while working out, but clear, pure water is the ideal beverage.

Immune-Strengthening Vitamins: ‘B’ Is for Boost

B vitamins may constitute a long list, but each one is important for different reasons. Other “B’s” for boosting your immunity are especially effective when you combine the foods containing them so they can all work together for maximum effect. These include vitamin B1 (thiamin), B2 (riboflavin), B3 (niacin), B5 (pantothenic acid) and B7 (biotin).

B12, also known as cobalamin, is a powerful cold- and flu-fighting nutrient in your system, as is vitamin B6, another important, germ-combating vitamin that naturally benefits and strengthens your immune system and even protects against the damaging effects of air pollution.

Vitamin B9 and folic acid help repair tissues and aid in cell metabolism and immune support. They’re found in dark leafy greens, wild-caught, cold water fish like herring, mackerel, sardines, anchovies and wild-caught Alaskan salmon, and pastured organic chicken. Nutritional yeast and other foods fortified with B12 present one-way vegetarians (or anyone else, for that matter) can augment their B12 intake through their diet. Raw, organic grass-fed milk, yogurt, and cheese are additional options with naturally high B12 content.

Optimizing Your Gut Health With Probiotics

The health benefits derived from probiotics are rooted in balancing your intestinal bacteria. One of the easiest and quickest ways to do that is by eating fermented vegetables, which have long been a mainstay in many ancient cultures. However, it’s only been in recent decades that this method of optimizing gut health has reemerged.

The traditional method for preparing fermented vegetables is very much like it was thousands of years ago. Fermenting helps introduce friendly bacteria to your system and is one of the best ways to optimize your immune system, about 80 percent of which resides in your gastrointestinal tract. It’s not an overstatement to say it’s a key line of defense against pathogens, as well as an aid in the production of antibodies.

Aside from fermented vegetables, one of the most healthful fermented foods is kefir, an enzyme-rich food full of friendly microorganisms that help balance your microbiome as well as strengthen your immune defenses. Other beneficial fermented foods include natto, kimchi, pickles, sauerkraut, miso, tempeh and raw grass-fed yogurt, but make sure you watch out for added sugar in most commercial varieties.

The fact that including probiotics in your diet has been shown to reduce incidences of psoriasis, colitis, allergies and many other diseases and conditions is a testament to their effectiveness in protecting your immune system. In addition, pregnant women who take probiotics help reduce their child’s risk of developing allergies.³

Fiber to Optimize Digestion and ‘Up’ Your Immunity

Not only does fiber help balance your gut microbiome, it, too, helps improve your immune system, as resistant starches act as prebiotics to feed healthy bacteria in your gut. As a result, it promotes bowel movements and keeps waste moving smoothly through your colon, while at the same time benefiting your heart health and controlling your blood sugar.

There are two types of fiber: soluble, which easily dissolves in water and becomes gel-like, and insoluble, which doesn’t dissolve but stays basically intact as it moves through your colon; both types are important for digestion.

Eating a fiber-rich diet, which in turn may improve the microbial diversity in your gut, may be linked to better responses during immunotherapy cancer treatment.⁴ In fact, your gut microbiome more directly influences your health and disease than previously thought. The fact is, your diet can make or break not just the ecosystem in which your gut bacteria reside, but your mental health as well.

And it’s not just the food you eat but all kinds of other factors, including the chemicals and pollution you’re exposed to, and all of it can alter the composition of gut bacteria and thereby influence your immune system health. As the Belfast Telegraph notes, “Want to avoid winter flu? Start eating with your gut in mind. Studies have found that having a healthy microbiome is important in fostering a strong immune system and keeping us healthy.”⁵

Getting Your Z’s: Not Optional for Optimal Immunity

Sleep is something that kids may resist, but as adults start the “adulting” that comes with jobs, growing families and paying the mortgage, sleep is something that can all too often go by the wayside. Studies show that not getting the sleep you need — for most people eight hours is the minimum for functioning at your best — can compromise your health in ways you may not have considered.

In fact, several nights in a row with less than restful, adequate sleep puts your body at greater risk for illness. Some of the ways lack sleep manifests itself in disease include:

• Dementia, including Alzheimer’s disease
• Diabetes, which is true even for children⁶
• Increased cardiovascular disease, especially for African-Americans⁷
• Higher incidence of depression and anxiety⁸
• Increased risk of obesity

Another study notes that cutting just one hour of sleep a night increases the expression of genes associated with inflammation, immune excitability, diabetes, cancer risk and stress.⁹ Consistently sleeping less than six hours a night increases your risk for numerous psychological and physical effects. The upshot is, lack of sleep quickly decreases your immune function, leaving your system wide-open for environmental influences, including viruses like colds and flu, that you would feel much better off if you avoided.

Sugar: Just As Bad for You Now as It Ever Was

If you were looking for a food to eat that would compromise your health in numerous ways and absolutely ruin your health, sugar in its many forms — and there are several, thanks to ever-changing food manufacturing gimmicks and money-making strategies — would win the prize. Not only is sugar identified as a carcinogen,¹⁰ it’s also contributing to the ever-increasing rates of chronic disease in the U.S. and throughout the world.

In the last century, sugar has become a daily habit that happens to coincide with increasing rates of obesity, Type 2 diabetes, heart disease, cancer and other chronic illnesses. One of the most insidious ways sugar works in your body is to damage both mitochondrial function and energy production, which triggers cell mutations that are then fed by continued sugar consumption.

What’s amazing is the number of ways sugar can show up, depending on the labels, in the foods you buy at the grocery store, including fruit juices, high fructose corn syrup (HFCS), evaporated cane juice, pancake syrup and cane juice, just to name a few, and the sugar industry has been manipulating the data for decades for the purpose of increasing profits.

To keep your immune system functioning at its best, one of the most effective strategies is to avoid sugar, pure and simple. It’s hard to do, though certainly doable, even if you know you’re suffering from a bad case of sweet tooth; research indicates that sugar impacts the function of dopamine in your brain, the neurotransmitter that triggers your reward system, in the same way, narcotics affect your brain, and may trigger a strong addictive response.¹¹

More Tips for Keeping Your Immune System in Tip-Top Shape

Whether your body is in recovery mode or you want to stave off the bug-of-the-month that might be going around at work or school, there are a few more options to prepare your system to fight back. One way to pack vitamins, minerals and other powerful nutrients into your day are to pack your blender or food processor with the makings for a super smoothie, making use of ingredients like spinach and other dark, leafy greens, carrots, berries like raspberries and strawberries, and even pumpkin seeds and Brazil nuts.

For a different (and more decadent) flavor, try going the chocolate route for your smoothie, but stick with dark chocolate with the lowest sugar content you can find for the antioxidant and anti-inflammatory effects courtesy of beneficial compounds such as epicatechin and resveratrol, known for being neuroprotective. Cacao also benefits your brain, nervous system, heart, and blood vessels while helping to combat diabetes and other inflammation-related conditions.

Eating locally grown foods that are in season is better nutritionally because foods that are picked at peak ripeness and placed on shelves quickly retain the optimal amount of nutrients compared to foods shipped from long distances. These foods are also sometimes injected or sprayed with chemicals to either slow down or speed up the ripening process or otherwise make them appear fresher. Fruits that are “in season” in winter include oranges, kiwifruit, cactus pear, dates, cherimoya, mandarins, red currants and passion fruit.

Vegetables have their own season in which they grow best and offer the highest nutritional profile, and in winter this includes sweet potatoes, leeks, turnips, Brussels sprouts, kale, Belgian endive and winter squash varieties. Last, but certainly not least, keeping stress out of your life, at least to the highest degree possible, will go a long way toward preparing yourself for liver disease- and even flu-free. As Rediff.com¹² maintains, there are several ways you can help protect your immunity:

• Avoid processed foods, as they make you vulnerable to developing chronic conditions
• Avoid excessive alcohol, which can impede the functioning of immune cells
• Avoid obesity, as it can affect the ability of white blood cells to multiply, produce antibodies and prevent inflammation
• Include activity, especially if you know you’re not getting enough; as little as 20 minutes of walking five days a week can increase your immune system function
• Avoid taking unnecessary medications, as even nonprescription drugs, antibiotics and cold and fever fighting medications may weaken your immune system