All food is fuel, but your children’s physiologies will founder if you fill their tanks with low-grade octane — especially during cold and flu season. (The most effective way to battle the winter ills? Get your children a flu shot and make sure they wash their hands regularly.) Give them premium nourishment and they’ll zoom along happily with souped-up immune systems primed to defeat bacteria and viruses.

For the healthiest “sick season” ever, here are five tips on what to add — and what to subtract — from your child’s diet right now:

  1. Sugar = Subtract it

    Sugar is demonized for many well-founded reasons, but did you know it’s bad for your child’s immune system, too? Slurping in the simple carbohydrates found in glucose, fructose, sucrose, honey, and — yes — orange juice, will suppress your child’s immune response for up to five hours. According to a Loma Linda University study, these simple sugars reduce the army of white blood cells, rendering your children’s bodies unable to prevent bacterial and viral invaders from thriving and pillaging their bio-systems. Advice? Try to keep sugar to a minimum during the winter holiday season. Now at least you know that monitoring that squirreled-away Halloween candy, minimizing late-night raids on Thanksgiving pies, and buying beverages low in sugar is doing your child’s body good.

  2. Probiotics = Add ‘em

    Probiotics, also known as “friendly bacteria,” are live, beneficial microorganisms that battle pathogens and toxin-producing bacteria in our intestines. Their outstanding powers are becoming increasingly apparent. A 2009 study in Madison, Wisconsin, of 3 to 5 year olds discovered that youngsters developed excellent cold and flu resistance simply by ingesting two probiotic supplements: lactobacillus acidophilus and bifidobacterium animalis subsp lactis. The children’s incidences of fever were reduced by 72.7 percent, coughing by 62.1 percent, and sneezing and nasal congestion by 48 percent. Kids taking probiotics also missed approximately 30 percent fewer days of child care, and their use of antibiotics was slashed by a whopping 84.2 percent. As in the study, you can give your child probiotics through supplements (available in the refrigerated section of most health food stores), but excellent food sources include yogurt, kefir, and even some types of kim chee; before purchasing, be sure to read the labels to ensure they contain these friendly bacteria.

  3. Fruits and vegetables = Add ‘em

    Another weapon in your “eat your veggies” arsenal: They can stave off icky symptoms. According to a 2011 study in Berlin, dietary supplements from fruits and vegetables provided a 20 percent reduction in days ruined by moderate or severe cold symptoms. While fruits are an easier sell for most children, many veggie-adverse kids won’t find this so compelling — so you’ll probably need to present them with a cornucopia of options. Even kids can appreciate that spending five minutes eating broccoli to ensure they get to that special event, outing, or party can be worth it (or at least you can try to get them to see it that way).

  4. Orange juice = Subtract it

    Yes, fruits are good for you, and mom and granny may have pulled out the orange juice every time you got the sniffles. But recent findings suggests that if life hands you an orange, don’t make orange juice. While oranges themselves are bursting with vitamin C, healthful fiber, and micronutrients, when squeezed into juice, sugar levels surpass those of most other fruit juices. Loaded with about 24 grams of sugar in an 8 oz. glass, orange juice sugar levels are nearly as high as the same size serving of Coca Cola (which has only 2 more grams of sugar in the same size serving). And sugar, as we know (see #1), is a no-go when it comes to staying healthy.

  5. Vitamin D = Add it

    Colds and flu strike harder in winter because we’re sun-deprived: Limited sunlight means less vitamin D. Numerous studies have discovered that low levels of vitamin D in the bloodstream significantly increase the risk of respiratory infection. An American Journal of Clinical Nutrition article asserts that Vitamin D is far superior to vaccines at preventing the flu because it activates the killer T cells that protect us. While taking vitamin D in the winter can do the trick, egg yolk, fortified milk, cheese, and breakfast cereals; fatty fish like salmon, mackerel, and tuna (a caveat: fatty fish tend to have more mercury); and fish liver oil supplements are all great sources, too — and they may be easier for your child to swallow. (Learn more on safe ways to get vitamin D in your child’s diet.)

  6. Water = Add it

    Glug, glug, glug. Keep your children hydrated with eight to 10 glasses of H2O each day. Water strengthens the body’s immune system by transporting oxygen to our cells, moving nutrients to our tissues and organs, and flushing out toxic impurities.