4 Foods That Are Lowering Your Immune System — and 7 Delicious Foods to Support It

A robust immune system might be the most in-demand item of 2020 and 2021. But even without a pandemic, a properly functioning immune system can help us combat  the flu, common colds, and those little 24-hour viruses that tend to circulate any time of year. 

If you find yourself coming down with every last bug, it may be time to take stock and see what immune-boosting healthy habits you should start incorporating into your daily life. The best things you can do for your immune system are to be physically active, manage your stress levels, get adequate sleep, and eat a healthy diet. 

While making big adjustments in all of these categories can feel like a tall order, taking small steps to improve them will absolutely help. We checked in with integrative medicine dietitian Robin Foroutan, MS, RDN, HHC and Mascha Davis MPH, RDN, author of Eat Your Vitamins, for their thoughts on how to best boost our immune systems.

Immunity-boosting foods:

1. Oysters

One oyster provides an entire day’s worth of zinc. This mineral can prevent viruses from replicating in our bodies, and is required for our bodies to make antibodies, Foroutan says. If you don’t like oysters, other high-zinc foods include pumpkin seeds, beef, hemp hearts, and chickpeas.

2. Shiitake mushrooms

Eating four ounces of shiitakes a day may boost your immunity, according to a recent study, which showed that participants who did this had better-functioning gamma delta T-cells (cells that leap into action when they detect a pathogen). Their immune systems produced less inflammation, as well, which may be because shiitakes contain beta glucan, an anti-inflammatory fiber that protects against infection.

3. Turmeric

This goldenspice contains the compound curcumin, which has powerful anti-inflammatory and antioxidant properties. Plus, curcumin intake may lower cortisol levels. “This is important due to the fact that elevated cortisol levels — often as a result of chronic stress — can weaken the immune system,” Davis says.

4. Garlic

Go ahead and mince an extra clove for dinner tonight: allicin and other compounds in garlic stimulate cells that fight viruses. Plus, garlic is antimicrobial, so it supports gut health. 

“Basically, whatever is good for the gut is good for the immune system,” Foroutan says. This is because our gut contains lymphoid tissues, which are part of our immune system. 

5. Fatty fish

“Salmon, trout, and tuna contain three essential nutrients for immune function: protein, omega-3 fatty acids, and vitamin D,” says Davis. “Protein is used to create and repair immune cells in the body. Omega-3s have anti-inflammatory effects that help support immune function, and vitamin D is important for regulating and activating the immune response in the body.” 

6. Kefir

Since a change in our gut microbiome can affect our immune response, it makes sense that probiotic-rich foods like kefir, yogurt with live cultures, and kimchi are good for immunity. Probiotics directly fight pathogens and boost the gut immune system. In fact, a Cochrane meta-analysis of 12 trials found that probiotics appear to be better than a placebo at reducing the chances of getting an upper respiratory virus as well as decreasing the duration of the cold if someone comes down with one.

7. Citrus fruit

Oranges, grapefruit, and other citrus are known for their vitamin C. This antioxidant helps our bodies kill microbes, fights oxidative stress, and supports the physical cell barrier that keeps pathogens out. Although some studies suggest that vitamin C supplements may help reduce the duration and severity of the common cold, not all research shows this benefit, and a 2016 analysis concluded that it’s best to get your Vitamin C from your diet.

Immunity Busters

1. Processed carbs

White bread, pasta, and other refined carbs lack fiber, and fiber helps regulate the immune cells in our digestive tract. When the “good” bacteria in our gut eat prebiotic fiber from our diets, the bacteria release short-chain fatty acids. These acids also play a role in our immunity. So if you’re not getting enough fiber because you’re filling up on processed carbs, you’re potentially hurting your immune system’s ability to fight pathogens.

2. Added sugars

Just in case you need another reason to be mindful of sweet stuff: Diets high in added sugars may increase inflammatory proteins in the body, which decrease immune function, Davis says. Additionally, sugar limits the ability of white blood cells to kill pathogens. Even worse, it changes our gut microbiome, in turn changing how our immune systems react to microbes.

3. Fried and charred foods

As much as we love french fries, burgers, bacon, and charred steaks — and oh, do we love them — your immune system doesn’t. These foods contain “advanced glycation end” products (AGEs), which increase inflammation and may negatively impact gut bacteria, Davis explains. You can still enjoy your cookouts while being immunity-friendly, though: Marinating meats in lemon juice or vinegar, herbs, and spices appears to decrease the formation of AGEs, Foroutan says.

4. Alcohol

Another bummer: excessive drinking can throw off the balance of “good” and “bad” bacteria in the gut microbiome and damage immune cells in the GI system, Davis says, which can make it harder to fight off infections and viruses.