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Vitamin C and It’s Role in the Gut Immune System

Vitamin C is a water-soluble micronutrient, which means that it dissolves in water and is transported to the body’s tissues. Since humans are unable to synthesize it, it’s necessary that vitamin C be ingested from an external source - preferably foods, although the human body can accept synthetic, supplemental sources just as well.

Despite the source of vitamin C, it’s like all water-soluble vitamins and is not well stored, so we must take it in daily.

The purpose vitamin C serves is to act as an antioxidant, helping to protect cells from the damage caused by free radicals. This, along with encouraging the production of new white blood cells that fight infection, is how vitamin C strengthens the immune system. We also need vitamin C to make proteins such as collagen, and it plays an important role in the production of neurotransmitters like serotonin and norepinephrine.

In some way or another, ALL of these processes relate back to the gut. But the most notable role of Vitamin C that I want to focus on is its role in the immune system.

Vitamin C Specifically for the Gut Immune System

Seeing as it is so important for gut and immune health, AND with all the C-Virus chatter currently happening, there has been a focus on vitamin C.

Your gut is home to 70% of the immune cells in your body, so the health of your immune system and your gut are closely intertwined.

The foods we eat affect the diversity and composition of bacteria in the gut, which in turn affect immune cells - this is one reason why keeping your gut healthy is so important! On the flip side, immune cells in the gut communicate with and influence the microbiome.

Implications for Vitamin C

In the 1970s Linus Pauling suggested that Vitamin C could successfully treat and/or prevent the common cold. Results of subsequent controlled studies have been inconsistent, resulting in confusion and controversy, although public interest in the subject remains high.

We know that vitamin C is a powerful antioxidant which assists our ability to ward off and deal with infection, meaning vitamin C may help to reduce the SEVERITY and DURATION of the common cold.

Vitamin C does not PREVENT or CURE sickness or the common cold.


One reason is that the human body cannot utilize limitless amounts of vitamin C. For example, the recommended daily intake of vitamin C is 90 mg for adults, and absorption decreases to less than 50% when taking amounts greater than 1000 mg.

This is why “megadosing” Vitamin C (think: Emergen-C every 2 hours) may not be as helpful as it appears,

While excessive intake is likely not toxic, for some, megadosing vitamin C can actually trigger gut upset, stomach pain, diarrhea, and gas.

Make note, for those who are constipated, vitamin C can be very useful. However, on the contrary, if you have diarrhea, it is recommended that you limit vitamin C.

All this to say - vitamin C is important, but more is not always better. I’m not anti-vitamin C supplements (I’ll cover some of my favorites below), but I am pro- food-first approach.

Vitamin C Foods

Here is a list of foods that naturally contain vitamin C:

  1. potatoes

  2. broccoli

  3. Brussels sprouts

  4. cabbage

  5. cantaloupe

  6. cauliflower

  7. guava

  8. grapefruit

  9. bell peppers

  10. kale

  11. kiwifruit

  12. lemons

  13. mango

  14. oranges

  15. papaya

  16. spinach

  17. strawberries

  18. tomatoes

Who Should Supplement

There are various “risk” groups for not getting enough vitamin C. As stated by The NIH, they are “individuals with limited food variety” and “people with malabsorption and certain chronic diseases.”

Both of these are categories you might fall under.

In a recent exclusive e-newsletter I sent, I discussed more about absorption. In the newsletter, I stated, “Nutrient absorption ranges from 10-90%. That’s a huge range. The determining factor? Of course, how your digestive system is functioning. Are there overgrowths? Do you have a digestive disease? Is there scarring? Are you chewing your food? And so many more things.”

You can take all the vitamin C in the world, but if you are not absorbing it for any digestive reason, it won’t matter.

Even though deficiency is rare, the lack of vitamin c in the body inhibits the synthesis of collagen, which leads to symptoms like:

  1. swelling and bleeding of the gums

  2. fatigue

  3. muscle weakness

  4. bruise easily

  5. joint and muscle aches

  6. bleeding gums

  7. leg rashes

  8. ulcers in mouth and intestines

If you have any of these symptoms, are at risk of malabsorption, or if you have severely limited vitamin C foods for whatever reason, you may want to supplement vitamin C through a simple power. See more on that below.

What is a Good Vitamin C Supplement?

First, here are the recommended daily amounts.

And this is what the upper limits are.

Knowing that and how much you estimate you’re getting from food per day, could help determine supplement quantity. But do remember, if you are having signs and symptoms of a deficiency, be sure to talk to your doctor, as you might not be absorbing it properly.

Here are my top 4 vitamin C supplement recommendations:

  1. Thorne Vitamin C with Flavonoids

  2. Nuun Immunity Tablets

  3. Nordic Naturals Vitamin C Gummies (gotta admit, I’m a big fan of gummy vitamins lol!)

  4. Carlson Mild-C Powder

Like with everything else, proceed slowly and go and consult with your doctor and/or nutritionist on the appropriate amount for you and your condition.

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