PAMF Health Blog

Be Well, Be Well Informed

Foods to Boost Your Immune System

Posted on Dec 3, 2013 | 7 comments



Winter often brings on sniffles, coughs and sometimes the flu. Beyond a flu vaccination, what else can you do to stay healthy? Research suggests you can boost your immune system by getting enough sleep, exercising, and – most importantly – eating key healthy foods.

“The three main antioxidants that help boost our immune systems are vitamin A, vitamin C and vitamin E. And the best way to get those antioxidants is to eat a variety of fruits and vegetables,” says Judy Farnsworth, R.D., CDE, a registered dietitian at the Palo Alto Medical Foundation.

Food That Fight Illness

Antioxidants help stabilize free radicals, which can damage the body’s cells and compromise the immune system. Different fruits and vegetables contain different types of antioxidants, so it’s important to eat a colorful variety, Farnsworth says. Stock up on green leafy vegetables, broccoli, garlic, citrus fruit and berries. Dark berries such as blueberries are especially potent, antioxidant powerhouses.

Vitamin C can help protect you from infection by stimulating the formation of antibodies and boosting immunity. Although vitamin C can’t prevent colds, it may help shorten your cold and make the symptoms milder. So incorporate citrus foods such as oranges and tangerines in your meals. Red bell peppers, papayas, strawberries and tomatoes are also rich sources of vitamin C. Get creative. Put them in salads or enjoy as them as a snack.

Vitamin A (beta carotene) helps keep your skin and tissues healthy. This can help protect you from infections that get in through cuts in your skin. Vitamin A is found in sweet potatoes, carrots, kale and spinach, among other foods.

Vitamin E helps the immune system fight off bacteria and viruses. In addition, vitamin E helps widen blood vessels and prevents blood clots. Vitamin E is found in vegetable oils, nuts, sunflower seeds, greens such as chard, spinach and broccoli, as well as in pumpkin, papaya and mangos.

Be Wary of Supplements

It’s so much easier to pop a vitamin tablet than to eat a healthy diet and exercise. Yet few studies validate the effectiveness of supplements. For example, a major study that reviewed 60 years of published scientific data on the effects of vitamin C tablets on the immune system concluded the tablets offered no benefit in preventing influenza.

Another popular supplement, Super Chlorella, boasts of including all the vitamins and antioxidants needed to strengthen the immune system and prevent the flu. Unfortunately, there is no scientific data to back this up. The same thing goes for many other supplements such as elderberries, garlic tablets and Echinacea.

Despite their contents, supplements don’t mimic all of the nutrients in whole fruits and vegetables. Substituting an orange with a Vitamin C tablet simply doesn’t have the same health benefits.

In general, your best bet is to eat a balanced diet so the immune system-boosting nutrients you need come from real food, Farnsworth says.  “If you’re not sure, see a dietitian to find out which nutrients you’re lacking,” she suggests, “and what you can eat to get that nutrient in your diet.”

And don’t forget to exercise and get enough rest. A healthy diet, adequate sleep, and regular exercise have been scientifically proven to reduce inflammatory markers.

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Judy Farnsworth, R.D., CDE, is a dietitian with the Palo Alto Medical Foundation’s Nutrition Services Department.

Please note that we are unable to respond to personal medical questions through the comments feature below. For information about personalized health care, or if you need help in choosing a PAMF physician, please visit Becoming a PAMF Patient ( or call 1-888-398-5677. If you are a PAMF patient, you can email your doctor securely via our My Health Online program. Thank you


  1. Great. I thought Vitamin C is most important vitamin in winter time. But now I see that others are as important as C. Will have to re-arrange my vitamin course. Thanks.

    • Do your own health research (from MANY different sources), and don’t be afraid to try recommended supplements to find out if they might work for YOU. Many people (including me) have found that elderberry, garlic, and echinacea supplements DO help to significantly reduce the symptoms and duration of a cold, for example. Other herbs and supplements also can help a lot (do your research!). Up through my mid-20s, I had many really bad, long-lasting colds. Then I started taking herbs and supplements that were recommended to me, and I rarely got sick after that. I have sometimes gone 10 years without a cold; and when I do get one, the symptoms are very mild and short-lived. And MANY other people have had similar results!!

      • Indira,
        Thank you for sharing your feedback and we hope you found the article useful. Thanks for visiting our blog!

  2. Both the specific descriptions of the three most important vitamins and the general point that foods are more effective than supplements were helpful. Who would have thought there was Vitamin A in spinach! I try to eat fresh, local and organic. I would be interested in a column on canned and frozen foods. Do canned organic tomatoes like Muir Glen’s, for example, furnish Vitamin C?

    • Hi Joan,

      Eating fresh, local and organic is the best choice when eating fruit and vegetables so you are already making healthy decisions for yourself but there are times when canned or frozen are all that’s available. Frozen vegetables are the next best thing to fresh; they are blanched before freezing so will lose some nutrients but still have most of their nutritional value. Canned produce is cooked more than frozen, so more of the nutrients are destroyed (plus sodium and sugar is often added), but eating canned vegetables is better than eating NO vegetables and some recipies do call for canned foods. So yes, there is vitamin C in your canned organic tomatoes and can be an appropriate choice in a diet that includes mostly fresh foods.

      Thanks for your comment.

      – Judy Farnsworth, R.D.

  3. I have now added green and red peppers to my salad mix.

    • Sounds delicious, Vera! Thanks for your comment and for visiting our blog.

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