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Surprising Side Effects Carbs Have on Your Immune System, Says Science

Science suggests that carb quality seems to matter over quantity.
FACT CHECKED BY Kiersten Hickman

The rise of the low-carb diet has us all questioning whether or not starch is truly evil. The keto diet has glamorized eating less than 50 grams of carbs per day. Many of us probably know someone who is thriving with lower carb consumption. So, are carbs really causing us harm? The truth is carbs have a place in our diet, but knowing how carbs impact health, specifically our immune system, is vital.

Carbs have a complicated relationship with the immune system that is best described with a Goldilocks analogy. Too few or too many may be damaging, and what's "just right" for you will take some investigating. Here's why, and for even more healthy tips, be sure to check out our list of The 7 Healthiest Foods to Eat Right Now.

They can help improve gut health.


There are some carbs you can consume that will also assist with your overall gut health. Our gut microbiome is made up of trillions of little bugs that work behind the scenes to keep our immunity high. The primary food for the bacteria that live in our gut is prebiotic fiber. Prebiotics get all the credit for supporting a healthy ecosystem inside our GI tract as they act as food for our good bacteria. Feeding healthy gut bacteria stamps out lingering bad bugs in the intestines and restores balance to the microbiome. A gut microbiome with balanced ratio of healthy bacteria positively contributes to overall immune function! Some prebiotic foods that are also starchy include some fruits (bananas, apples), oatmeal, and whole grains.

For more ways to incorporate prebiotics into your diet, check out this dietitian-approved list.

Too many carbs could lead to chronic conditions.

white bread

High carb diets in Americans are correlated with lower quality of life and an increased risk for diet-related diseases. Alzheimer's, Type 2 diabetes, and heart disease have all been linked to a diet high in carbs among other lifestyle factors. This is likely due to the general quality of carbs that Americans consume. Americans aren't eating large amounts of sweet potatoes… but we are downing sodas by the liter.

Choosing higher quality, less processed carbs is shown to improve immune function! Starchy fruits and vegetables are high in immune-boosting vitamins and minerals like Vitamin A, C, and E.

If you're looking for a sign, here is a clear indicator that you are overdoing it with your starchy foods.

You may experience a sugar rush.

whole chocolate cake garnished with mint leaves

Carbs, specifically highly processed sugars, cause spikes in blood sugar that contribute to a domino effect of immune responses in the body. High blood sugar suppresses our natural immune system causing us to be more susceptible to illness—an effect that can last for hours after consuming a sweet treat.

"Spikes in sugar intake when eating a diet high in refined carbs can suppress your immune system," says Lisa Young, PhD, RDN and author of Finally Full, Finally Slim. "If you eat a lot of foods and drinks high in refined carbs, you may reduce your body's ability to fight disease. Foods high in added sugar are the problem, not naturally occuring sugar coming from fruits."

Learn about other ways sugar is sabotaging your health.

Complex carbs can boost immune function.


We know now that quality matters: 100 calories from soda has a drastically different effect on our immune system than 100 calories from berries. Swapping processed foods with their less-processed nutrient-dense counterparts is one way we can improve our immune system through higher quality carb intake.

Less processed complex carbs like whole grains, fruits, and starchy vegetables naturally have higher fiber, vitamins, and minerals that help regulate our immune response.

"Complex carbs in the form of whole grains are very healthy as they are high in fiber and nutrients that help stabilize blood sugar," says Young. Stable blood sugar, in turn, keeps our immune system strong.

Our brain will feel rewarded.

pasta eating

Our brain's pleasure center rewards us for choosing starchy foods. Unfortunately, this can lead to feeling uncontrollably drawn to high-calorie, processed foods as these elicit direct serotonin and dopamine hit in the brain.

We can positively influence this response by choosing high-quality mood-boosting carbs regularly! Healthy carbs stimulate the brain's reward system with the added bonus of improved immune function!

Looking for more good mood foods to incorporate into your diet?

Carbs can help workout recovery.

Female athlete with protective face mask doing plank exercise with hand weights in a gym.

During exercise, we bring about low-grade stress to our bodies. It is a healthy form of stress, however, we can minimize our immune response and improve our post-workout recovery to get the biggest bang for our buck. Science proves that carbs eaten within an hour of exercise directly repair the immune response that took place during activity.

For more immune-boosting tips, check out our list of 30 Best Immune-Boosting Foods.

Caroline Thomason, RDN, RD, LDN, CDCES
Caroline is a women's health Registered Dietitian and diabetes educator based in Northern Virginia. Read more about Caroline
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