The winter months are filled with many fun activities — snowboarding, skiing, sitting by the fire with a good bottle of wine. But, as with most things, there is a downside — the dreaded flu season. Whether it's the flu itself, or just a common cold, many of us find ourselves spending the inclement season battling to maintain our health. Though there are recommended preventive measures one can take to protect against the flu — flu shot, anyone? — there still exists no single 100 percent non-fallible solution so we should take all the help we can get. While no diet remedy or nutritional supplement has been scientifically-proven to effectively prevent the flu, here are five nutritional tips that may help boost your immune system.

Hydrate. When I'm trying to fend off the sniffles, my first line of defense is to hydrate. Your body requires extra hydration when fighting off infection. Try drinking half of your body weight in ounces of water per day. For example, a 130-pound woman, aim for 65 ounces of water daily.

Add lemon and ginger to your diet. A Harvard study found that 200 mg of vitamin C a day may reduce the duration of cold symptoms. You can increase your intake of vitamin C by adding citrus fruits such as lemon to your diet. Whole ingredients such as lemon and ginger also work well as natural anti-microbial foods.

If you find that you don't have these ingredients on hand, try one of my favorite immunity-boosting shots from one of these Philly go-to spots. Just remember that when juice of any kind is over-consumed and not balanced with a proper diet, weight gain and additional sugar cravings can occur.

Sip-N-Glo Juicery Immunity Shot: lemon, ginger, elderberry and apple cider vinegar The Healer Shot: lemon, turmeric, oregano oil and black pepper

Animo Juice Bar Lemon Ginger Shot: lemon, ginger, apple and cayenne pepper

Whole Foods Market Lemon Snap Power Shot: lemon, ginger, and tumeric

Consume healthy bacteria. A healthy gut leads to a robust immune system so I encourage clients to always include a level of good bacteria in their diet. You can do this by adding whole food sources of probiotics into your daily routine such as yogurt (avoid flavored yogurt or brands that contain >10 grams of sugar), kefir, kombucha or fermented vegetables like kimchi and sauerkraut. I also recommend taking a probiotic supplement, especially during the winter months and always after antibiotic use to aid in gastrointestinal function. Be sure to purchase a supplement that has greater than 10 billion live strands such as Garden of Life or Advanced Naturals Ultimate Floramax.

Eat foods rich in antioxidants. To make sure your immune system is functioning at its peak — especially during flu season — you'll want to load up on foods rich in the antioxidants and beta-carotene, such as clementines (they're in season), cabbage, broccoli, pumpkin, sweet potatoes, and spinach. Vegetable soups are another great way to get more produce into your diet on these cold winter days. Lentils, quinoa, and dried beans are a great winter staple, and there are many ways to use them. Add quinoa to a vegetable soup or toss 1/2 cup of edamame, garbanzo, or cannellini beans atop a salad.

Try my favorite winter chili recipe here. This recipe is a great way to fill up on both protein and fiber. I usually add extra vegetables such as peppers and mushrooms.

Get enough sleep. Lack of sleep suppresses the immune system making you more susceptible to getting sick. Research shows that people who do not get enough sleep are more likely to get sick after being exposed to a virus. Adults should aim for seven to nine hours of sleep every night. Try sticking to a sleep schedule even on weekends, and refrain from using devices such as cell phones or tablets 30 minutes to an hour before bed.

Regular sleep habits can lead to more energy throughout the day, a stronger immune system, and a better quality of life. Sleep trackers such as Polar A370 or other apps available on smart phones not only track your sleep duration but quality as well.

To relax before bed, sip decaffeinated chamomile or green tea. The polyphenols — especially catechins found in green tea — may stimulate the production and activity of specific cells associated with combating viruses. I'm also loving Tumeric Wellness Tea, which is a blend of turmeric, rosemary, citrus peel, ginger and black pepper. All herbs and spices that help to safeguard your immune system!

Theresa Shank, RD, LDN, is a Philadelphia based registered dietitian and the founder of Philly Dietitian.