Worldwide, infertility affects 15% to 30% of couples trying to conceive. In about half of those cases, the trouble lies with the male partner, the authors noted. Sperm cells are highly sensitive to reactive oxygen species, so reducing oxidative stress has been postulated as a mode of action for reducing apoptosis, increasing sperm cell motion parameters, and improving sperm integrity.
Oxidative stress postulated as infertility mechanism
The authors, associated with an agricultural university in Hefei, looked at a wide variety of research on green tea and other polyphenolic and antioxidant compounds. They included references to in vitro and in vivo studies and included research on animal models as well as those done on human tissue and in humans directly. The base idea was looking at how these natural compounds can help protect delicate sperm cells.
“The sperm membrane comprises polyunsaturated fatty acids which are highly susceptible to a chain reaction of ROS [reactive oxygen species] known as lipid peroxidation. Lipid peroxidation results in the loss of membrane integrity which disrupts cell function and damages sperm motility by inducing apoptosis,” they noted.
The authors said their review of the research also shows that oxidative stress can cause DNA damage in sperm cells.
Groundbreaking 2017 study
The authors noted that Indian researchers showed for the first time in a 2017 study that polyphenols can have an effect in interrupting this damaging feedback loop.
“Antioxidant supplementation has been specified as a possible approach to treat reproductive diseases and improve fertility. In 2017, it was proven, for the first time, that polyphenols found in significant amounts within the seminal plasma act as natural antioxidants,” they said.
A wide variety of antioxidant compounds have been studied in this connection, the authors noted. To some degree, that variability complicates the task of coming up with a coherent view.
“Many previous studies have lacked randomization and placebo-controlled arms. The kind, amount, and period of antioxidant treatment has also varied significantly. Some researchers studied a few antioxidants, while others altered the duration of the therapy or used different combinations,” they said.
More data backs green tea constituents
For green tea polyphenols (GrTPs), the evidence is more compelling, they said. This ingredient, with a long history of use, has been studied enough that the confounding factors of study design, length, etc., have tended to even out and provide a clearer picture of these ingredients’ potential benefits in this area.
For example, the authors noted that, “An animal model study conducted by Awoniyi and colleagues examined the modulation of ROS by GrTPs in rat semen. They found that GrTP supplementation significantly increased the sperm count and motility. GrTPs have also been shown to decrease lipid peroxidation, protein carbonylation, and DNA damage.”
The authors noted that the research they cited shows possible combinations of GrTPs and could improve the effects on supporting sperm health.
Among the ingredients they mentioned as showing promise are Rooibos extracts (Aspalathus linearis) and the fertility herb Vitex Agnus castus, commonly known as chasteberry.
“A consensus is still required regarding the type and quantity of GrTPs required to gain the maximum effect. Although GrTPs have demonstrated utility in treating male and female infertility and alleviating OS their precise actions and mechanisms remain to be determined. At the molecular level, GrTPs may represent a complementary treatment to improve fertility and treat infertility or related diseases.
"It should also be determined whether polyphenols or their composite extracts have supplementary effects on fertility. Furthermore, future studies should combine GrTPs with different extracts or herbs to determine their effects on semen motility and the pregnancy rate as key outcomes,” they concluded.
2018, 10(7), 834; doi:10.3390/nu10070834
“Therapeutic Role of Green Tea Polyphenols in Improving Fertility: A Review”
Authors: Rahman SU, Huang Y, Zhu L, et al.