1. Some Types of Seafood Offer Immune-Boosting Omega-3 Fatty Acids

The omega-3 fatty acids found in some types of fish — such as salmon, sardines, herring, and mackerel — help enhance the functioning of immune cells.

A type of omega-3, may enhance the activity of white blood cells, which further strengthens immunity. That's backed up by a study suggesting that this effect may not only be significant but also happens fairly quickly — within a week, studies found.

2. Healthy Proteins Bolster Disease-Fighting White Blood Cells

The National Institutes of Health (NIH) notes that zinc — a mineral abundant in meats like oysters, poultry, seafood, beef, and lamb — works with the protein found in meat to strengthen the immune system. In fact, certain types of immune cells, including white blood cells, can't function without zinc, according to a review published in December 2016 in the Archives of Biochemistry and Biophysics.

Whether you get your protein from lean meats or vegan or vegetarian options such as tempeh or tofu, making sure you get some at every meal is helpful for keeping your energy and your strength up, suggests McKenzie Caldwell, MPH, RDN, based in Charlotte, North Carolina. She notes that the recommended daily allowance (or minimum amount needed) for protein is 0.8 grams (g) per kilogram of body weight. (To convert to kilograms, divide weight in pounds by 2.2.)

For the most heart-healthy option, choose lean protein. According to the National Heart, Lung, and Blood Institute, lean protein has 55 calories and 2 to 3 g of fat per serving. Examples include 1 ounce (oz) of dark meat chicken with the skin removed, 1 oz of roast beef, and low-fat cheese that has a maximum of 3 g of fat per oz.

Vitamin C may help protect the body against oxidative stress, and that helps support immune functions.

Oxidative stress happens when there is an imbalance of healthy antioxidants and harmful substances called free radicals in the body, research shows. Oxidative stress is associated with an increased risk of various health conditions, including stroke, cancer, and diabetes, a study suggests.

As a type of antioxidant, vitamin C is a free radical scavenger and enhances immunity by supporting cellular function, among other benefits, notes an article published in November 2017 in Nutrients.

Choose foods that are loaded with this vitamin. According to the NIH, foods with vitamin C include oranges, lemons, strawberries, blueberries, tomatoes, broccoli, leafy greens like kale, and bell peppers. To help retain vitamin C in your food, enjoy it raw when possible. Vitamin C is heat sensitive, so cooking can reduce the amount of this nutrient that your body can take in

For a filling snack that's also a big-time help to your immune system, reach for a handful of nuts or seeds. Not only do they have magnesium, but they're also rich with vitamin E, an antioxidant that's been shown to improve the body's ability to fight off bacteria and viruses, according to the NIH.

Options like sunflower seeds, almonds, walnuts, and pecans can give you that vitamin E boost with just a small handful, and they're a tasty addition to salads and other dishes.

They're versatile, too, since you can roast them for a snack or make your own.

One caveat to keep in mind is that portion control is essential when it comes to nuts. They're a healthy food but are calorie dense, so overindulgence could contribute to weight gain

Garlic gets that distinctive smell from sulfur compounds, and regardless of whether you love the aroma, it offers protective benefits to your health and immune response. 

That's because when garlic is crushed or chopped, it produces allicin, which previous research has highlighted for its antiviral and antibacterial properties.

Onions have a substance called quercetin, which may help regulate histamine response and contains antiviral properties, according to a study published in January 2016 in Viruses.

Looking for a powerful immune-driven dinner? Whip up some fresh pasta sauce with garlic and onions, plus tomatoes for that vitamin C addition

6. Yogurt Aids Gut Health, Which May Positively Affect Immunity

"Yogurt is rich in probiotics, the good bacteria that support gut health,"

Johns Hopkins notes that a huge proportion of the immune system is actually in the gastrointestinal tract.

According to a study published in May 2017 in Nutrients, eating yogurt daily can improve immune function because it increases the body's production of antibodies that fight off viruses. 

To avoid added sugar, choose plain, unsweetened yogurt.

Other Tips to Boost Your Immune System

Let's say you load up on all this good stuff and still get socked with the effects of a virus. It happens. But continuing to eat healthily can often help shorten the duration of symptoms if you have a mild case of whatever you've caught.

Keep Eating

Most important is continuing to eat enough food overall especially food in the Mediterranean diet

We might not be able to totally prevent getting sick by eating well, but if you're not getting enough nutrients, and especially not enough protein, you're going to lack the energy to fight it off."

Skip the Sugar and Fat

Also, avoid sugar when you can.

Sugar can trigger inflammation in the body, research indicates, and when your system is fighting against that, your immune system may not have enough power to combat outside stressors such as pathogens and viruses, according to a preliminary animal study published in February 2014 in The Journal of Immunology.

Enjoy Your Food

Whether you're feeling under the weather or not, eating mindfully can be helpful, simply because you'll slow down, feel less rushed, and truly enjoy your food. 

Stress has been linked to poor immune functions, according to a study published in October 2015 in Current Opinion in Psychology, so see your meals as a chance to chill.

Although eating a Mediterranean diet can boost your immunity, it can lift your spirit and nourish your sense of well-being, too.

Final Thoughts

If you are interested in Mediterranean diet and want to learn more?