How Does Vitamin C Support the Immune System?

Your immune system is an intricate network of organs, specialized cells and proteins that comprise your natural defenses and work together to keep you in top-notch health. Not surprisingly, immune support supplements are popular choices for people who want to support immune function, with vitamin C supplements at or near the top of the list.

However, according to Stephen Tapanes, PhD, people get confused about vitamin C (aka ascorbic acid). Indeed, this vitamin is a cofactor or "helper molecule" in many immune function pathways and helps protect cells from oxidative stress. "But there are some misconceptions about vitamin C," said Dr. Tapanes, a scientist at Life Extension.

For example, people choose high doses of vitamin C supplements, thinking it is the best way to prepare themselves for health challenges. However, a higher dose of vitamin C may not mean more benefits—higher doses may increase plasma concentrations of vitamin C in your bloodstream, but your body will flush out what it doesn't use.

So, how does the body use vitamin C to support immune function? And how do you take it for optimal absorption? Let's peel back the layers of vitamin C's role in immune health.

Vitamin C's role in immune function

As a nutrient, vitamin C is one of the foundations for a healthy immune response, and vitamin C supplements can help strengthen that relationship in three ways:

1. Support various immune function pathways, such as the innate immune system—your body's first line of defense—and the adaptive immune system, which remembers and builds antibodies against previous immune challenges.
2. Promotes the healthy production and function of specialized immune cells, like B and T cells.
3. Help maintain healthy vitamin C levels, necessary for the upkeep and regulation of overall immune health.

 Here's a quick table summarizing how vitamin C works in the body.

You need to have healthy vitamin C levels all the time, not just when a specific challenge comes your way, to ensure it can do this important work.

How does vitamin C support white blood cell activity?

White blood cells are specialized immune cells that are your body's tiny defenders. There are several types of white blood cells, but, in general, they patrol your bloodstream, protect your cells, and keep tissues healthy; more specialized white blood cells remember past immune challenges.

Vitamin C intake helps keep your immune system strong by promoting the production and function of white blood cells. For example, vitamin C supports phagocytosis, a cellular process where macrophages (a type of white blood cell) gobble up and destroy undesirable immune intruders. Vitamin C also helps with cell signaling or "cell communication," so they know what to look for, how to eliminate it, and when to step back, explained Dr. Tapanes.

Why is vitamin C's antioxidant role important for immune health?

As a free-radical scavenger, vitamin C's antioxidant properties support immune and overall health in three ways:

• Protects cells from oxidative stress
• Helps keep tissues healthy
• Supports a healthy inflammatory response during immune function

What happens to the immune system when vitamin C is low

Insufficient vitamin C levels negatively impact how the immune system functions in two specific ways:

• Immune system function: As we've seen so far, vitamin C plays a vital role in the production of immune cells and how efficient they are at keeping you healthy from seasonal and other immune challenges. Its powerful antioxidant properties protect cells from oxidative stress as they perform their duties.
• The body becomes susceptible to immune challenges: Studies have found a link between low vitamin C levels and low vitamin C intake and an increased risk of immune challenges, Dr. Tapanes said. Maintaining adequate levels of vitamin C is crucial to a healthy immune system.

Observational studies have shown that vitamin C intake and exercise, on their own and in combination, are associated with a healthy inflammatory response and robust immune function, Dr. Tapanes added.

But if you do have low levels, one thing that likely will not help is to suddenly start taking it in large doses for a short time. "Taking large doses after facing immune challenges won't make a difference because much of that vitamin C gets excreted from the body. What's important to support your immune health is consistent intake, so your immune response is ready to go when it's needed," Dr. Tapanes said.

What are the best forms of vitamin C to take

Given how important vitamin C is to staying healthy, many people look for the largest possible dose of it when shopping for a supplement—but this is a mistake, said Dr. Tapanes. "Your body will absorb vitamin C from a conventional supplement, but they won't help maintain enough vitamin C plasma concentrations that allow the body to use it before flushing it out," he explained.

An alternative that may keep vitamin C in your bloodstream for up to 24 hours: a liposomal vitamin C supplement, Dr. Tapanes said. Additionally, you can also choose vitamin C supplements in combination with quercetin, elderberry and other nutrients that complement the health-promoting benefits of vitamin C.

Vitamin C supplements come in different shapes and doses, including capsules, drops, effervescent tablets, and even chewables and gummies.

How much vitamin C do you need for immune support?

In general, to maintain healthy levels, you need a certain amount of vitamin C, which will vary by age and gender:

• Adult men: 90 mg daily
• Adult women: 75 mg
• If pregnant: 85 mg
• If breastfeeding: 120 mg

Some lifestyle habits, like smoking, can deplete vitamin C levels in the body. The National Institutes of Health recommends men who smoke to aim for 125 mg of vitamin C, and women who smoke should aim for 110 mg of daily dietary supplementation, Dr. Tapanes noted.

However, the minimum amount of vitamin C that's recommended for daily consumption isn't sufficient to support immune function and overall health. "To get the most of your vitamin C, you will likely need to regularly take a higher dose," Dr. Tapanes said. "Many supplements provide a dose of 250-1000 mg to help maintain optimal levels that are associated with health benefits." You should always follow the instructions on the label when taking a vitamin C (or any) supplement.

What foods are a good source of vitamin C?

Ascorbic acid is packed with health-promoting benefits, says Dr. Tapanes. Nutrient-dense, whole foods should be your primary source of this essential vitamin. Here's a quick list of excellent vitamin C sources:

Vegetables rich in vitamin C:

• Cruciferous vegetables, including broccoli, Brussels sprouts and cauliflower
• Leafy greens like spinach, kale and arugula
• Mushrooms
• Beets
• Turnips
• Sweet potatoes
• Winter squash, kabocha squash

Fruits rich in vitamin C:

• Berries such as strawberries, raspberries, blueberries and cranberries
• Citrus fruits, including oranges, lemons, grapefruits and limes
• Guava
• Kiwi
• Mango
• Papaya
• Pineapple
• Watermelon, cantaloupe
• Tomatoes
• Peppers

Is it safe to take vitamin C every day?

Yes, as Dr. Tapanes explained, it's safe to take vitamin C daily. It's always smart to speak with your healthcare provider to choose the best vitamin C supplement and dosage tailored to your needs.

Should you get vitamin C from foods or supplements?

A balanced diet filled with a variety of whole foods should be your primary source of vitamin C. A vitamin C supplement complements your smart lifestyle choices.

References

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