Boost Your Immunity to Combat Cold and Flu Season - Ask a Nutritionist

August 23, 2023

As the weather changes and kids go back to school many families start to worry about what germs are getting brought home. A strong immune system is important all year but especially during cold and flu season. Tune into this week's episode of Ask a Nutritionist with Brandy to learn all about what foods and supplements you can choose to help boost your immunity this cold and flu season.

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Welcome to the “Ask a Nutritionist” podcast, brought to you by Nutritional Weight and Wellness. We are thrilled to have you join us today as we discuss the connection between what you eat and how you feel, and share practical real life solutions for healthier living through balanced nutrition. Now let's get started.

BRANDY: Hello and welcome to Dishing Up Nutrition's midweek segment called “Ask a Nutritionist”. My name is Brandy Buro and I'm a Registered and Licensed Dietitian with Nutritional Weight and Wellness. On today's show, I'll be answering a question we received in our Dishing Up Nutrition Facebook group.

So the question today is, “What are some ways you can boost your immunity to combat cold and flu season this year?” So I think this is a really timely question. A lot of my own clients have been asking the same exact thing as they are getting their kids ready for a new school season. I think many families are worried that their kids go back to school, they're bringing home a lot of germs, and then it puts them at risk for developing cold and flu. So really, when you think about it, the start of a new school season for many families means the start of cold and flu season.

So this is a great topic to discuss. Today, we will cover what foods will support your immune system, the foods that can damage your immune system, and then we'll review a few targeted supplements that you might want to include as part of that real food meal plan to support your immune system.

Foods that boost immune function

So let's start with the foods that will boost your immune system. You know that our motto at Nutritional weight and Wellness is focus on food first. So this means that we believe the best way to support your health and the best way to support your immune system is to eat a variety of real whole foods that are made up of those natural immune boosting nutrients. So first we want to think about fruits and vegetables. Colorful fruits and vegetables of all varieties is going to provide you protective phytonutrients or nutrients from plants. So generally speaking, the brighter and richer the color of the fruit or the vegetable, the more concentrated those nutrients are; nutrients like vitamin C.

Organic fruits and vegetables provide optimal nutrient value

So if you've ever looked at the produce in the supermarket or maybe compared that with the produce you find at the farmer's market or organic produce, you might notice that there is a difference in the color. You're probably going to get more bang for your buck if you go for locally grown and organic produce. Compared to conventionally raised produce that you're more likely to find at the supermarket, it's pretty easy to see the difference in quality. Those organic and locally grown produce are generally going to be more brilliant in color, whereas the conventionally produced produce tends to be a little more dull or faded. And a lot of that has to do with the timeline related to when it was harvested, when it got put on that truck and the journey it has from the field to the supermarket. And then how long has it been sitting in the supermarket?

So the longer it's sitting around, it's losing some of its nutrients, it's losing some of its luster, and it's very easy to see the difference if you compare them side by side compared with like a locally grown or organic produce. Choosing organic or locally produced fruits and vegetables is one way to ensure that you are getting the highest concentration of immune boosting nutrients. It's a little more bang for your buck, so to speak.

However, we understand that buying all organic is not always the most budget friendly. So you can determine or you can prioritize which fruits and vegetables to buy organic by referencing the dirty dozen versus the clean 15 guide. So this is a list that kind of helps you decide which fruits and vegetables are best to purchase organic and those that maybe you could get away with buying conventional. So the dirty dozen refers to produce that has been found to have the highest pesticide levels. So it's best to purchase organic when you can.

The clean 15 are fruits and vegetables that could be okay to buy conventional because they've been found to have the lowest pesticide levels. So this list, the dirty dozen and the clean 15 is updated annually, and it can be found at this website So that is the website for the Environmental Working Group:

High quality protein is critical for immune function

So besides getting a good variety of colorful fruits and vegetables, we also want to include high quality animal-based proteins. So protein is going to provide critical immune boosting amino acids. So a few examples of good quality animal-based proteins would be eggs, fish, beef, turkey, chicken, pork. You could get a high quality grass fed whey protein powder or maybe shellfish if you're someone that lives near the coast. So those are all great examples of high quality proteins.

Natural fats are immune supportive

We also recommend including a variety of healthy natural fats. Healthy fats are rich in antioxidants. So for example, a full fat canned coconut milk is a very good source of lauric acid, a powerful antioxidant. Avocados contain a powerhouse of antioxidants such as vitamin E and lutein and glutathione. Nuts and seeds are actually some of the best sources of antioxidants. More specifically, there's a study done recently that was published in the British Journal of Nutrition that found walnuts, pecans, and chestnuts have the highest content of antioxidants among nuts.

So getting a variety of nuts when you're choosing nuts, not just getting in that rut of almonds or just peanut butter. So all of these foods are going to help support the immune system by fighting off harmful invaders like bacteria and different viruses. So it's a pretty simple meal plan. What we're doing is focusing on three main components: good proteins, natural healthy fats, and a variety of colorful fruits and vegetables. So we want that to be present in every single meal and snack. That is a pretty basic template. So just by following those kind of that mantra, protein, fat carb, you are already doing a lot of good to support your immune system throughout the day.

Sugar weakens immunity

So now that we've discussed, you know what's good for your immune system, let's talk about the flip side. Let's talk about the foods that can weaken your immune system. The most harmful foods for your immune system, and this probably isn't a surprise, is sugar. Sugar is very damaging to the immune system, and it's not just the more obvious culprits like your baked treats like muffins and cookies, but it's also those ultra processed carbohydrates like crackers and chips and pasta.

So those are the types of foods that convert into sugar very quickly and impact our immune system in a very similar way, like straight sugar. Just eating one serving of sugar or highly refined, highly processed carbohydrate can suppress your white blood cells, which is a very important aspect of your immune system. It's suppressing your virus fighting cells basically for several hours. So think about that. Every time you eat a bag of chips or a cookie or maybe that mocha latte, you need to think, this is suppressing my immune system. It's suppressing my white blood cells for several hours. So think about that, and if you're doing that several times a day, especially in the peak of cold and flu season, you could really be doing yourself a disservice.

Healthier swaps for common sugary fall foods

So let's talk about some good swaps for some common sugary fall foods. I think a lot of people when fall hits are getting very excited about that warm latte, that pumpkin spice latte. We all get so excited. But did you know that a medium-sized pumpkin spice latte with whipped cream contains 50 grams of sugar? Knocking it down to a small does not do you much good. A small still contains 38 grams of sugar. So to get a better visual, that medium pumpkin spice latte contains over 12 teaspoons of sugar, and the small contains a little over nine teaspoons of sugar. So that is a ton of sugar. I I highly doubt that anyone is going to sit down with a bowl of 12 teaspoons of sugar and eat it with a spoon. But that is exactly what you're doing in liquid form when you order one of those sugary coffee drinks.

So what are we going to do? How are we going to celebrate the season? So instead of that pumpkin spice latte, maybe instead you could order just a regular coffee with some heavy whipping cream or maybe some full fat coconut milk and you could even add a few drops of stevia to add a little sweetness and a little cinnamon on top, or maybe even some pumpkin spice. That would be delicious. You're cutting out all the sugar, but you're still sort of engaging in that ritual. And the heavy whipping cream is actually, and that coconut milk, they're actually going to help stabilize your blood sugar instead of spiking it like that sugary latte would. So it's a much better swap, much better for your energy and your immune system.

Something else you might get tempted by at the coffee shop are the baked goods, especially something like a pumpkin spice muffin or again, apple cider donut; full of sugar, but also full of those refined carbohydrates. So a much better alternative would be a fall themed baked treat, like our pumpkin spice muffins you can find at

So instead of a bunch of sugar, it's using a little canned pumpkin and some vanilla protein powder for that sweetness. You know, overall it's a balanced snack because it has some protein from that protein powder, a little fat and some carbohydrate from that pumpkin. So that can be a complete balanced snack. So those are just a few ideas to get you started with some healthier fall swaps and a real food foundation.

Vitamin D supports immunity

But even if you're feeling very confident in your meal plan, you may still need an extra boost, a little extra support to get through flu season. So now we'll talk about a few supplements that I recommend to get you through flu season feeling your best. So at the top of this list I'm going to put vitamin D. So Vitamin D is essential for your immune system and it's something that many of us living in these northern regions are deficient in.

And throughout the summer you might be fine without a supplement if you're spending enough time outdoors. We can make some vitamin D through exposure to the sun. But as our daylight hours get shorter and we start moving indoors during the fall season, our vitamin D levels start to drop. And clinically we find here in at Nutritional Weight and Wellness that most people feel their best when their vitamin D level is somewhere between 50 and 80.

So checking your vitamin D level is a very simple blood test that you can request the next time you're in for a physical or at any kind of checkup at your doctor's office. You can even test it at home. There are some at-home testing kits. So that's, that's a nice option. If you've never had your vitamin D level checked and you're kind of curious, well what are the signs of a vitamin D deficiency? Well, here are some things you can watch for: frequent colds and viruses, a low mood, low energy, chronic fatigue, carbohydrate cravings, you could even experience bone and muscle pain. So those are some things to watch for; could be a sign you need to supplement.

And if you do have a a blood test and you find that your vitamin D is low, you absolutely should take a supplement. It's a great way to prevent deficiency and treat deficiency. So just to maintain a healthy vitamin D level, most people need somewhere between 4,000 to 5,000 international units of vitamin D3 every day during the winter months. So I, I normally recommend people start that dose sometime mid-November and continue that through the end of April, maybe even the end of May.

And then during the summertime to maintain a good level, somewhere around 2,000 international units during the summer months is what I suggest. And you may need more than that if you are already deficient, which is why it's really important that you get your levels tested.

Vitamin C is immune boosting

So our next supplement recommendation is vitamin C. So a lot of people think of vitamin C when they think about immune boosting supplements. There's a good reason for that. The highest levels of vitamin C in the body are found in our white blood cells. And our white blood cells are our immune system’s way of fighting disease and infection. And your vitamin C levels may actually become depleted when your immune system is fighting off an infection or if your immune system is already slightly compromised. So this is why it's important to provide ourselves with a continuous supply of vitamin C.

So in addition to getting vitamin C through those colorful fruits and vegetables, we also recommend supplementing with about a thousand milligrams of vitamin C every day just to support a healthy immune system throughout that cold and flu season. If you feel like you already have a cold or if something's coming on, you might want to take a little extra. So think a thousand milligrams every few hours, so maybe four to six times a day. So ramping up your vitamin C dose in the midst of a cold can help lessen the severity and the duration of that infection and help us fight off viruses.

Zinc is immune boosting

All right, so next up and my last supplement that I'll recommend is zinc. So research has found that zinc impacts our immune system in several ways. So it does help increase our T cells, which we we need to fight off illnesses, and it's also boosting our immunity to fight off those viral and bacterial infections.

So if you're deficient, you could be more susceptible to colds and flus. Some other potential signs of zinc deficiency are feeling like you always need that sweet treat after a meal. You may also see white spots on your nails. So those are a couple other signs you could be deficient in zinc. So during cold and flu season, I recommend taking about 50 milligrams of zinc every day. But be sure to take that on a full stomach. If you take zinc on an empty stomach, you will very likely experience a stomachache, nausea. It's very uncomfortable, so be very careful to take it with food.

Another note of caution about supplementing with zinc is that it can compete with copper absorption. So this is a supplement that I recommend taking a break every so often. So I would say like every three months, take a month off. And that can help keep your copper and your zinc levels in a good balance.


So just to recap, you can support your immune system through this cold and flu season and, and all seasons really just by eating real whole foods with lots of colorful fruits and vegetables, high quality animal-based proteins and healthy natural fats. Remember, we want to avoid, eliminate sugar as much as you can, reduce those processed, refined carbohydrates that are weakening your immune system and focus on those immune boosting nutrients: vitamin D3, vitamin C, and zinc. So those are just the basics. Probably easier said than done.

So if you do need help figuring out you know what you should supplement, how much you should supplement, or if you need support in figuring out a meal plan that works for your schedule and your lifestyle and your health history, please give us a call. Meet with one of our licensed dietitians or nutritionists, and we will give you that support. We will figure out a plan that works for you.

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And right now is the perfect time to start ramping up these important supplements and focusing on these meal plan adjustments to help boost your immune system before the cold and flu season really hits you. So thank you so much for listening to Dishing Up Nutrition’s “Ask a Nutritionist” segment. If you have a question that you want us to answer, please join our Dishing Up Nutrition Facebook community. You simply search Dishing Up Nutrition on Facebook and join. We look forward to hearing from you.

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