Are Food Preservatives Bad for Gut Health?

Calcium propionate, potassium benzoate, sulfites, are just a few of the preservatives that we see on our everyday food labels. There have been claims that these are harmful for for our health, specifically where the gut is concerned. So, let’s dig a little deeper into the research done on if food preservatives are bad for you gut health.

Some of the preservatives of interest are:

  • Calcium propionate
  • Natamycin
  • Potassium benzoate
  • Sodium benzoate
  • Sodium nitrite
  • Sodium propionate
  • Sulfur dioxide
  • Sorbic acid
  • Sulfites
  • Potassium sorbate
  • TBHQ
  • EDTA
  • BHT

In addition, salt and sugar are natural food preservatives due to their effect on water activity in food.1,2,3

Appropriate benzoic acid levels might improve gut functions, while excess levels will hurt gut health

So far, a few studies based on animal models have been conducted and released on the effect of food preservatives on gut health. Rats or mice and pigs are reported to be quite similar in physiology and anatomical structures to humans. So, they are considered as good representative models for humans.4,5

Preservative Tested concentration of preservative Animal model Result
Calcium propionate6 3 mg/kg diet Broiler chicken Lowered bacterial and fungal count in gut.
Epsilon-polylysine7 0.025% w/w Mice Diversity of bacteria in the gut microbes of mice was temporarily changed recovered  and returned to normal.
Sodium propionate8 3.3 g/50 g diet Healthy subjects Increased the fecal bulk and bifidobacteria, indicating beneficial effect on gut health.
Sorbic acid9 5 g/kg diet Piglets Activated immune and inflammatory responses.
Benzoic acid10 5 g/kg diet Piglets Reduced fecal score (incidence of diarrhea and fecal samples for apparent total tract digestibility), indicating promoting gut health.

Many preservatives studied with in vivo methods have not shown a long term negative effect on gut health. In addition, appropriate benzoic acid levels might improve gut functions, while excess levels will hurt gut health.4

To date, limited research has been conducted to study the effect food preservatives on gut health. Rats, pigs and ruminants are applied to study the impact of certain food preservatives on gut health. However, there are no available studies on potassium sorbate, sorbic acid, sulfites, EDTA and BHT in animal models.

We cannot draw a conclusion based on current limited research

So far, most research has been conducted in vitro and in vivo on animal models, lacking clinical trials. In vitro testing is a good investigation method to discover underlying mechanisms. However, it cannot represent animal data or clinical data due to lacking physiological natures.

In vivo experiments can closely mimic the physiological effect of humans, but still cannot completely represent the clinical data. Results with regards to the effect of food preservatives on gut health are still inclusive, due to various types of animal models such as rats, pigs, or ruminants, various food preservatives, and various target microorganisms in the gut. Therefore, we cannot draw a conclusion based on the current limited research. More studies are needed to fulfill this research gap for a better understanding.

Is it true our digestive systems can’t keep up with all preservatives added to our diet since the 1950s?

The ’50s saw the peak of the Baby Boomer years, following the end of the great depression and World War II. It was a time where consumers found more choices and jobs were abundant. It signified an era of tremendous changes to our diets and our environment. Therefore, many things have evolved, other than our diets. It is hard to justify this statement because of this shift in spending and eating habits.

With an increase in the variety and quantity of foods, we increased obesity rates, diabetes and coronary diseases. These has more impact on our overall health, than do preservatives have on our gut health. In addition, many preservatives in the following table, break down in our digestive system to small metabolites and get excreted by our kidneys.

Food preservative Excreted through Test subject Reference
Benzoic acid Urine Healthy subjects 11
Sodium benzoate Urine Healthy subjects 12
Sodium nitrite Urine Healthy subjects 13
Sulfite Urine Rats 14
TBHQ Urine Rats 15
EDTA Urine Rats 16
BHT Urine Healthy subjects 17

In summary, there is no scientific evidence that supports the claim that preservatives have a negative effect on gut biome.  One of the reasons is because many of these preservatives break down into smaller metabolites in our gastrointestinal systems and are excreted.

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  1. Salt. Last accessed by Mar 19. 2020.
  2. Sugar. Last accessed by Mar 20. 2020.
  3. Water activity. Last accessed by Mar 20. 2020
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As a research scientist, Jing is responsible for lab activities and technical writing for publication. She received her B.S. degree in China and started her M.S. degree and PhD. degree in Department of Grain Science and Industry and Food Science, at Kansas State University, respectively. Jing’s expertise is functional food & nutrition. Driven by strong motivation and interests, she enjoys this job and wants to contribute more to food industry.