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Building Immunity Through Diet

You’ve heard it time and time again. Eat a balanced diet rich with fruits, vegetables, whole grains, and lean protein to stay healthy. 

This is of utmost importance during cold and flu season to keep your immune system working at its prime.

Many people believe to build immunity that you should consume more antioxidants. It is true antioxidants are found in many foods that have been proven to help keep you healthy like berries, tomatoes, sweet potatoes, citrus fruits, etc.

But, half of your plate at each meal should be filled with fruits and vegetables anyhow. So, just by eating a well-balanced diet*, you will be delivering beta carotene, lycopene, and vitamins C, E, and A to your body to help your cells defend itself from illness and infection.

Of course, diet alone won’t keep you well.  Other great strategies to stay well include getting plenty of sleep, dressing appropriately for the weather, washing your hands, avoiding other sick people and getting the annual flu vaccine.

Want to know more about an immunity boosting through diet?  Here are the answers to some common questions we dietitians receive every cold and flu season.

Over-the-Counter Supplements
These are over-the-counter products that contain vitamins, antioxidants, and herbs marketed to help prevent or fight infection, including Emergen-C and Airborne. Both of these supplements contain concentrations of vitamins A, B, E, selenium, and zinc. They also contain between 1,000 mg to 2,000 mg per of vitamin C, which is equivalent to approximately 11 glasses of orange juice. The recommended daily allowance of Vitamin C is 90 mg for men and 75 mg for women.  Mega doses of any vitamin is not proven to provide any benefit and may actually have an adverse effect.   If you are interested in these products, ask your doctor before taking these supplements.

Vitamin C
Vitamin C, also known as ascorbic acid, is a water soluble vitamin, meaning that it is hard to achieve a toxic effect by taking too much of the vitamin. However, high doses of vitamin C can cause gastrointestinal disturbances and diarrhea as well as possibly contribute to the formation of renal oxalate stones. Many people believe that mega doses of Vitamin C can help prevent or treat colds, but several studies have found that vitamin C is no more effective than placebo.

Zinc, just like most vitamins/minerals, will help protect immune function.  However, supplementing with just zinc is not the answer to a healthy immune system.  The answer is eating a well-balanced diet and making sure you receive all of the daily recommended amounts of vitamins and minerals.

Zinc is found in meat, fish, poultry, fortified breakfast cereals, and milk/milk products. Toxicity from zinc is rare, but excessive intake of zinc can interfere with copper and iron absorption. Therefore, Zinc should not be taken for more than 5 days at a time.

Echinacea is an herb that is available over-the-counter that has been used to help boost the immune system and reduce severity of illness. The studies examining Echinacea’s effectiveness boosting the immune system are inconsistent.  Extracts of Echinacea have been shown in some studies to boost immune cells.  However, a study published in 2005 in the New England Journal of Medicine, found that Echinacea was not effective in preventing colds and did not help alleviate cold symptoms. Additionally, two studies conducted by the National Center for Complementary and Alternative Medicine also did not find any benefit taking Echinacea for colds in either children or adults.

Remember, herbs and supplements are not approved by the U.S. Food and Drug Administration, so products could be mislabeled or contain varying amounts of the product in which you would not be aware.  It is always a good idea to consult a physician before taking any herb for medical advice and also due to possible side effects with other medications or toxicity.

*Guidelines for a Healthy Balanced Diet
We’ve talked a lot about consuming a balanced diet to stay well (or to get well if you are sick.)  A healthy adult diet comprises…
Approximately 2 cups of fruit per day
Approximately 2-3 cups of vegetables per day
Approximately 3-4 oz of grain (1/2 of your daily servings should be whole grains per day)
Approximately 5-6 oz of protein per day
Approximately 3 cups of dairy per day
Approximately 5-6 teaspoons of oils per day
Don’t forget to drink plenty of fluids to keep hydrated. For more information go to

Kelly Washington is a clinical dietitian on WakeMed Raleigh Campus.