I have read pseudoscience, incorrect advice from social media posts, and speculation lately that synthetic L-ascorbic acid, not natural sourced vitamin C harms your probiotic microbiome.

Where did all this speculation orginate?

My research has concluded that it originated from this article on Natural News.

The article is filled with anecdotal evidence, opinion, and no scientific studies or information to back up the claims.

The author of the article brings up that ascorbic acid is used as a preservative to keep bacteria in apple juice from overgrowing and spoiling the product.1 Yes, this is one of the only statements in the article based on fact. Acids can be used as a preservative to lower the pH of food products to keep bacteria growth to a minimum. Many bacteria have a difficult time surviving in a low pH environment, which is why vinegar, lime and lemon juice, and ascorbic acid which all have a low pH are used as preservatives. You lower pH in canning to prevent the serious medical condition botulism. Botulism is caused by ingesting toxins produced from the bacteria Clostridium botulinum which thrives in an anaerobic (without oxygen), dark, elevated pH environment.2 Does this mean that L-ascorbic acid ingested would reduce colonies of probiotic bacteria in the intestines?

The correct answer is that this is impossible. Ingestion of L-ascorbic acid (pH of 2.4 unless it is buffered) may slightly raise or lower pH levels in the stomach briefly (depending on the pH of your stomach) which if it lowers pH it can be helpful in keeping opportunistic bacteria like H. pylori at bay.3 The very low pH stomach chyme is neutralized by sodium bicarbonate and bile in the duodenum of the small intestine.4 In addition, the acid in your stomach (hydrochloric acid) has a lot lower pH than most ingested acids including L-ascorbic acid. So, if the proposed L-ascorbic acid harms intestinal flora theory is true, anytime you eat and stomach acid is produced all of the microogranisms in your stomach, small intestine, or colon would be eliminated because according to them it would not be neutralized. Buffered vitamin C supplements are not acidic and would negate the issue with the acidity of ascorbic acid affecting the microbiome. Finally, L-ascorbic acid is absorbed completely by the end of your small intestine (unless you are vitamin C megadosing which acts as an osmotive laxative) therefore it would not affect your colonic microbiome.5 6

Now I do recommend that if you are taking a probiotic supplement that it would be best that you take it away from any synthetic L-ascorbic acid supplement because of the possible slight decrease of pH in the stomach might kill some of the probiotic bacteria (which is why I recommend you take probiotics away from meals as well). I also recommend that you do not take a probiotic supplement at the same time as ingesting any acidic food, or during/after a meal. The best time to take a probiotic is three to four hours after eating, when stomach acid is at its lowest point, with a glass of nonchlorinated (diluted chlorine may reduce probiotic colonies it is antimicrobial) water. Bedtime is a good example of an optimal intake time for most people.

Synthetic L-ascorbic acid is not sourced from corn syrup. It is sourced from corn dextrose fermentation which is a very different product.7 Now one thing the author of the article got correct is that most synthetic L-ascorbic acid is sourced from genetically modified corn. However, more than likely there is no genetically modified protein or Bacillus thuringiensis toxin (BT toxin) in the final L-ascorbic acid product, therefore very few probiotic bacteria, if any, would be harmed by the genetically modified produced L-ascorbic acid. Finally, I do not recommend genetically modified sourced L-ascorbic acid products anyway. I recommend Nutribiotic sodium ascorbate, C-Salts, LipoNaturals vitamin C, and Doctor’s Best Quali-C which are all non genetically modified corn sourced.

Finally, the work of Dr. Linus Pauling and a multitude of scientific studies have proved that synthetic L-ascorbic acid is effective.8 If you want to ingest natural whole food sources of vitamin C, I recommend it. I believe for most people this it is the preferred method of ingesting vitamin C. However, I wish people would stop slandering that synthetic L-ascorbic acid (for example intravenous cancer treatments and pulsed dosing for acute viral infections) is harmful.