Vitamin C and Gut Health

An unexpected partnership...

To the extent to which one could literally take a vitamin for granted, I’m certainly guilty of doing so as it relates to vitamin C.

And why not?

Population level intake data out of my home country of Canada always pointed to the fact that vitamin C intake was adequate in the vast majority of people with citrus fruit and fruit juice being major contributors.

A closer look at data out of the United States, however, tells a slightly different story with vitamin C intake declining in large part due to insufficient fruit/vegetable intake and declining consumption of fruit juice which otherwise represented a significant source of this essential nutrient.

I hope you can C why this changes things a bit.

Now we enter into a discussion of the role of vitamin C and gut health with the knowledge that adequate vitamin C intake is not to be taken for granted.

I will explore this relationship in three distinct areas:

1. Vitamin C & IBD
2. Vitamin C & The Microbiome
3. Vitamin C & Constipation

Let's get to the good stuff.

Vitamin C & IBD

When we think of nutrients of concern for inflammatory bowel disease we often think of iron, vitamin D or B12 and yet emerging evidence suggests that vitamin C is also worthy of consideration.

Whether through reduced absorption or a decrease in fruit/vegetable intake, monitoring vitamin C status in IBD may merit further consideration.

This is especially relevant given that vitamin C enhances the absorption of non-heme iron (eggs, legumes, nuts, seeds, whole grains). 

Vitamin C & The Microbiome

A good deal of evidence exists around the interaction of vitamin C with the human gut microbiome from limited in vitro and human studies. 

A 2021 paper out of Gut Microbes  explored the interaction of various vitamins (A,D,C,B2,E) with the microbiome and determined that vitamin C had the most profound effect on increasing microbiome diversity and short-chain fatty acid production.

In a human pilot study it was observed that high dose vitamin C supplementation for a two week period shifted bacterial populations in the human GI tract, opening the door for further exploration of the utility and relevance of this interaction. 

The quality and totality of the evidence in this area isn’t decisive, but given that both papers cited above were published only last year it’s quite clear that this is an emerging and developing area of scientific inquiry.

Vitamin C & Constipation

While no evidence I’ve come across directly links vitamin C to changes in bowel movements, there are certainly foods out there that are very high in vitamin C and other useful components like soluble fiber.

Kiwi fruit, which has been studied as a potential constipation aid, is among them.

In fact, a 2021 trial published in the American Journal Of Gastroenterology found that two kiwifruit per day over a four week period improved stool consistency and reduced bloating in those with chronic constipation with a lower rate of reported adverse effects as compared to prunes or psyllium fiber. 

Dietary Sources Of Vitamin C

Fruits and vegetables are the primary dietary sources of vitamin C, and of course also contain various types of dietary fiber (particularly soluble & prebiotic) as well as unique antioxidant compounds that have notable positive effects on gut health.

It would be a stretch for me to say that you should eat more fruits and vegetables just to get more vitamin C, but nonetheless there is indeed another good reason to do so.

With that said, here are the top five commonly available fruits and veggie sources of vitamin C:

Fruits: Kiwi, strawberry, mango, orange, pineapple,

Vegetables:  Brussels, bell peppers, broccoli, tomato, kale

Final Thoughts

Vitamin C’s emerging relevance in the world of gut health deserves attention perhaps not necessarily because it is the most important GI tract nutrient but rather because it contributes positively and is paired with a host of other important compounds and delivered via important foods which are generally underconsumed.