The ingestion of olive leaf extract alters the population of the microorganisms residing in the colon and restricts the growth of the tyramine-producing bacteria. Daily ingestion of olive leaf extract reduces the incidence of hypertensive crises in individuals with FD.


The fact that what we eat impacts the organisms present in our digestive system is well-known. In an invited review that was published in the journal Pharmacological Research, Scott and coworkers (2013) recently described the influence of diet on the microorganisms inhabiting the gut (1). The article contains a great deal of very important and fascinating information, some of which is summarized below:

  1.  The volume of the bacteria in the colon of an adult is approximately a quarter of a liter.
  2.  The types of microorganisms residing in the gut are strongly influenced by a range of factors, including the foods consumed.
  3. Changes in the foods consumed can have a profound impact on the organisms residing in the colon.
  4.  In individuals who are not taking stomach acid-reducing drugs, approximately 10% of the ingested protein makes it to the colon where it is degraded by the resident microorganisms. (From other sources: The use of acid-blocking drugs decreases the efficiency of the digestive process and increases the percentage of undigested protein that enters the colon.)
  5. The bacteria present in the colon convert the protein by-products into amines, such as tyramine.
  6. The ingestion of certain foods can prevent the establishment of various microorganisms, including pathogenic microorganisms.

In 2010, based on the facts presented above, as well as on other observations that we had made, we posted on the FD Now website a recommendation that individuals with FD should not consume more than the recommended daily allowance of protein. As we have continued our research efforts, we have come to further understand and appreciate the medical impact of the bacterial residents of the colon on individuals with FD. Control over the growth of pathogenic organisms in the colons of individuals with FD is made even more challenging by the use of acid-blocking medications that facilitate the growth of pathogenic organisms such as clostridium difficile (2, 3).
Since our discovery of the impact of bacteria present in the digestive tract on the onset of hypertensive crises, physicians dealing with FD patients experiencing nausea in the mornings or ongoing hypertensive crises have prescribed antibiotics to inhibit the growth of these organisms. These treatments have been successful at reducing morning nausea and, in those experiencing them, reducing the number of crises. While the antibiotic administration works for a period of time, the problematic/pathogenic microorganisms (PM) eventually re-establish themselves in the colon and the course of antibiotics has to be repeated. We have been actively seeking a mechanism to control the establishment of the PM.
Ingested materials that can prevent the establishment of PMs in the colon are referred to as prebiotics. Prebiotics confer benefits upon the host’s health and well-being by causing specific changes in the populations of gastrointestinal microorganisms (4). Knowing the critical importance of reducing the presence of the tyramine-producing bacteria in the colon of those with FD, we looked to identify a prebiotic that would reduce the likelihood of the establishment of tyramine-producing bacteria in the colon of these individuals. As the intestinal organisms belonging to the genus clostridium have been demonstrated to produce tyramine (5) and, as the establishment of these organisms in the colon is enhanced by the use of acid-blocking medications (2, 3), we have focused on the identification of prebiotics that restrict the growth of clostridium.

In 2006, Medina and coworkers demonstrated that olive oil, which contains phenolic compounds, has a strong antibacterial effect against clostridium (6). In a paper entitled “Effect of Olive Leaf Extracts on the Growth and Metabolism of Two Probiotic Bacteria of Intestinal Origin”, the authors state that “olive leaf extracts may well have a beneficial role in promoting probiotic bacteria and inhibiting harmful bacteria such as clostridium”(7). Based on these reports and the anecdotal observations that those with FD who consumed large amounts of olive oil had fewer crises, several years ago we began examining the effect of the ingestion of olive leaf extract on the number of hypertensive crises experienced by those with FD. A clear corresponding decrease in the incidence of crises was observed by those ingesting olive leaf extract.

Based on our observations, we are pleased to announce to the FD community this latest breakthrough. Please note: Before making any change to your child’s diet, you should discuss this matter with her/his treating physician.

We are recommending the inclusion of olive leaf extract in the diet of those with FD. After considering several of the olive leaf extracts that are commercially available, we are recommending the Olive Leaf Extract produced by ProHealth. A description of this product is located at the following web address: https://www.prohealth.com/shop/product.cfm/product__code/PH123. We are recommending the daily ingestion of one capsule of this olive leaf extract in the morning and one in the evening.

1. Scott KP, Gratz SW, Sheridan PO, Flint HJ, Duncan SH. The influence of diet on the gut microbiota. Pharmacol Res. 2013; 69(1):52-60.
2. Kwok CS, Arthur AK, Anibueze CI, Singh S, Cavallazzi R, Loke YK. Risk of Clostridium difficile infection with acid suppressing drugs and antibiotics: meta-analysis. Am J Gastroenterol. 2012; 107(7):1011-9.
3. Janarthanan S, Ditah I, Adler DG, Ehrinpreis MN. Clostridium difficile-associated diarrhea and proton pump inhibitor therapy: a meta-analysis. Am J Gastroenterol. 2012; 107(7):1001-10.
4. Roberfroid M, Gibson GR, Hoyles L, McCartney AL, Rastall R, Rowland I, Wolvers D, Watzl B, Szajewska H, Stahl B, Guarner F, Respondek F, Whelan K, Coxam V,Davicco MJ, Léotoing L, Wittrant Y, Delzenne NM, Cani PD, Neyrinck AM, Meheust A. Prebiotic effects: metabolic and health benefits. Br J Nutr. 2010; 104 Suppl2:S1-63.
5. Karlsson S, Banhidi ZG, Albertsson AC. Detection by high-performance liquid chromatography of polyamines formed by clostridial putrefaction of caseins. J Chromatogr. 1988; 442:267-77.
6. Medina E, de Castro A, Romero C, Brenes M. Comparison of the concentrations of phenolic compounds in olive oils and other plant oils: correlation with antimicrobial activity. J Agric Food Chem. 2006; 54(14):4954-61.
7. Haddadin MS. Effect of olive leaf extracts on the growth and metabolism of two probiotic bacteria of intestinal origin. Pakistan J Nutr. 2010; 9(8):787-793.