On almost a daily basis, there are new scientific discoveries being published on the important roles microorganisms in our digestive tract play in our health and well-being. These finding have prompted the wide-scale use of probiotics (microorganisms that are considered “good” for your health, often taken in capsule form) in the general population.  Recent scientific publications link the use of probiotics to such benefits as controlling infections (1), boosting the effectiveness of the immune system (2,3 ), modulating responsiveness to anti-cancer drugs (4), controlling obesity (5) and even modulating mental states (6).

In individuals with FD, the microorganisms in the digestive tract play a role in the nausea, vomiting and hypertensive crises that some experience. One of the troubling symptoms of FD is morning periods of nausea and vomiting that seem to resolve as the day progresses. Parents often reflected that their FD children are at their best late at night, but after going to sleep they wake up (again) with symptoms of nausea and vomiting. After studying this phenomenon for a period of time, the researchers in the Laboratory for FD Research at Fordham University realized that during sleep, tyramine is being generated in the gut, which is triggering the nausea. The sensitivity of individuals with FD to the toxic effects of tyramine and related molecules is now well-established.   A major source of tyramine production in the human body has been determined to be the result of the metabolic activity of microorganisms that reside in the digestive tract (7). These bacteria produce an enzyme (known as tyrosine decarboxylase) that converts tyrosine, a normal amino acid present in food, into tyramine, which is toxic to those with FD. These bacteria are very effective at producing tyramine at night because they grow and metabolize best during sleep when the digestive system is quiescent. The tyramine produced is released into the blood stream, where it negatively impacts the neurological system of those with FD. Upon wakening, the digestive system begins its normal movement patterns, which interferes with the ability of the tyramine-producing bacteria to produce tyramine. As the day progresses, the tyramine that was produced during the night-time hours is degraded by the monoamine oxidases in the body and those with FD feel better, only to have the cycle repeat itself with the next night’s sleep. It was these observations that resulted in the recommendation that individuals with FD limit the amount of protein consumed and control the timing of this consumption (see: http://www.fdnow.org/research/treatment-breakthroughs/protein-intake-and-crisis).

To help control the growth of the tyramine-producing bacteria, the Fordham researchers have been working to identify a probiotic that, over time, would encourage the growth of non-tyramine-producing bacteria and thereby “out-compete” the tyramine-producing bacteria. To find such a probiotic, DNA sequence analysis was performed on the microorganisms present in many commercially available probiotic products to: 1) ascertain whether the listing of microorganisms on the product was accurate and 2) evaluate the ability of these bacteria to produce tyramine. The analysis revealed that many of the commercially available probiotics contained microorganisms other than the ones listed on the label and, what was even more troubling, many of the probiotics (including some very popular ones) contain organisms that can produce tyramine. The presence of tyramine-producing bacteria in these probiotics is not usually a problem for the general population, but it is a severe problem for those with FD and likely somewhat of a problem for those who suffer from migraines. This research effort led to the demonstration that the Florajen Digestion (formerly Florajen3) probiotic is suitable for use by those with FD.  This probiotic contains three bacterial strains: Lactobacillus acidophilus, Bifidobacterium lactis and Bifidobacterium longum. Whole genome DNA sequencing performed on each of these organisms reveals that none are capable of producing tyramine and they are therefore safe for use by those with FD. A recently completed small clinical study demonstrated that this product is safe for use by the FD population.

If you would like your child to take a probiotic, this is the only one that the Fordham researchers can certify will not produce tyramine in the digestive system.

Please note: Before making any change to your child’s diet, you should discuss this matter with her/his treating physician.

For commonly asked questions, click here to read a Q&A. 


  1. Wang Y, Li X, Ge T, Xiao Y, Liao Y, Cui Y, Zhang Y, Ho W, Yu G, Zhang T. Probiotics for prevention and treatment of respiratory tract infections in children: A systematic review and meta-analysis of randomized controlled trials. Medicine (Baltimore). 2016 Aug;95(31):e4509
  2. Deng H, Li Z, Tan Y, Guo Z, Liu Y, Wang Y, Yuan Y, Yang R, Bi Y, Bai Y, Zhi F. A novel strain of Bacteroides fragilis enhances phagocytosis and polarises M1 macrophages. Sci Rep. 2016 Jul 6;6:29401.
  3. Wu BB, Yang Y, Xu X, Wang WP. Effects of Bifidobacterium supplementation on intestinal microbiota composition and the immune response in healthy infants. World J Pediatr. 2016 May;12(2):177-82.
  4. Leslie M. MICROBIOME. Microbes aid cancer drugs. Science. 2015 Nov 6;350(6261):614-5
  5. Gérard P. Gut microbiota and obesity. Cell Mol Life Sci. 2016 Jan;73(1):147-62.
  6. Vlainić J, Šuran J, Vlainić T, Vukorep AL. Probiotics as an adjuvant therapy in major depressive disorder. Curr Neuropharmacol. 2016 May 26.
  7. Perry TL, Hestrin M, MacDougall L, Hansen S. Urinary amines of intestinal bacterial origin. Clin Chim Acta. 1966 Jul;14(1):116-23.