Olive leaf tea may have hematological health benefit over green tea

Clin Nutr. 2019 Dec;38(6):2952-2955. doi: 10.1016/j.clnu.2018.11.009. Epub 2018 Nov 20.


Olive leaf extracts are rich in several polyphenols having potential health benefits. We conducted the current parallel-group randomized controlled trial to compare the effects of long-term consumption of olive leaf tea (OLT) and green tea (GT) on hematological parameters in 31 female volunteers aged between 40 and 70 years of old. We found that RBC count, hemoglobin, and hematocrit were increased significantly in the OLT group than those of in the GT group at 6 and 12 weeks of intervention. Within-group comparison showed that hematocrit was significantly increased in the OLT group at 6 weeks of intervention, whereas RBC count and serum iron was significantly decreased in the GT group at 12 weeks of intervention. This is the first clinical study reporting the beneficial effects of continuous intake of OLT on hematological parameters. This observation is supported by our previous in vitro study reporting the differentiation-inducing effect of certain olive leaf components on human hematopoietic stem cells. However, further investigations in larger cohorts with a careful consideration of target population are required to confirm the preventive effect of OLT against anemia and other red cell disorders.

Keywords: Anemia; Hemoglobin; Olive Polyphenol; Olive leaf tea; RBC.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Erythrocyte Count / statistics & numerical data
  • Female
  • Hematocrit / statistics & numerical data
  • Hemoglobins / drug effects*
  • Humans
  • Iron / blood
  • Middle Aged
  • Olea*
  • Plant Extracts / administration & dosage
  • Plant Extracts / blood*
  • Plant Extracts / pharmacology*
  • Plant Leaves
  • Polyphenols / administration & dosage
  • Polyphenols / blood
  • Polyphenols / pharmacology
  • Tea*


  • Hemoglobins
  • Plant Extracts
  • Polyphenols
  • Tea
  • Iron