Bryan Johnson Stores Girlfriend's Menstrual Blood at -80°C, Sparks Debate
Tech entrepreneur Bryan Johnson's latest biohack involves freezing his girlfriend's period blood. Experts say menstrual samples have research value, but freezing period blood is not an established fertility-preservation method.
Bryan Johnson's Period Blood Freezing Sparks Debate
The world of biohacking often pushes boundaries, but Bryan Johnson, known for his extreme longevity experiments, recently made headlines for an unusual venture: freezing his girlfriend Kate Tolo's period blood.
Kate’s period blood is in my -80 °C freezer.
Around 10 mL. pic.twitter.com/OdLxO9qyJu— Bryan Johnson (@bryan_johnson) July 31, 2026
Johnson, who is known for spending millions of dollars on experiments aimed at slowing ageing, said the 10 ml sample from his girlfriend Kate Tolo is being stored for research.
The unusual disclosure quickly drew attention online, with some users questioning how far Johnson's approach to longevity research should go. Others said there was a genuine scientific reason to study menstrual samples.
Johnson has said the sample could help researchers study different types of cells and look for possible exposure to substances that may affect human health.
Why is menstrual blood being studied?
Menstrual blood is not simply blood. It can contain endometrial cells, immune cells and other material shed during menstruation.
This has made menstrual samples an area of growing scientific interest. Researchers are studying whether they could provide useful information about conditions affecting the reproductive system.
One area of research is endometriosis, a painful condition that can take years to diagnose. Scientists are exploring whether menstrual samples could eventually help develop less invasive ways of detecting the condition.
Dr Prajna Shetty, founder of Dr Shetty's Fertility Clinic and director of the Assisted Reproductive Technology department at Cloudnine Fertility in Nerul, Mumbai, told India Today the idea behind studying menstrual samples is not unusual from a research point of view.
She said menstrual effluent could provide a non-invasive way of studying the uterine environment and could potentially help researchers understand reproductive health.
What about microplastics and PFAS?
Johnson has also highlighted the possibility of testing the sample for contaminants such as microplastics, PFAS and endocrine-disrupting chemicals.
PFAS, sometimes known as "forever chemicals", are a large group of chemicals that can remain in the environment for long periods. Researchers are studying possible links between exposure to such chemicals and reproductive health.
Dr Shetty said looking for these substances in menstrual samples is a legitimate area of scientific research, particularly as scientists continue to study how environmental exposures may affect reproductive health.
However, finding something in one person's sample would not by itself prove that it is causing a health problem.
One sample is not a medical study
This is one of the biggest points experts have raised around Johnson's experiment.
A sample from one person can be interesting, but it cannot establish that a particular test is useful for the wider population.
For a medical test to become part of routine healthcare, researchers need much larger studies involving many people. They also need to establish how accurate the test is and whether the results can actually improve diagnosis or treatment.
Dr Shetty stressed that Johnson's personal experiment should therefore be viewed as an example of scientific curiosity rather than proof that menstrual blood testing has been validated for everyday medical care.
Can freezing period blood preserve fertility?
This is where experts draw a clear line between research and established fertility treatment.
Menstrual blood can contain menstrual blood-derived stem cells, often referred to as MenSCs. These cells have attracted scientific interest because of their possible regenerative properties.
Researchers are studying their potential use in areas including neurological and cardiovascular conditions. However, much of this work remains at the laboratory or early research stage.
There are currently no established fertility treatments in which a woman freezes menstrual blood as a proven way of preserving her future fertility.
Dr Sarla Kumar, a fertility specialist in Delhi, has raised strong reservations about using cryopreserved period blood for fertility purposes, saying there is currently no established clinical utility for the practice in reproductive medicine.
The distinction is important because research into stem cells should not be confused with a proven treatment.
What are the established options for fertility preservation?
People looking to preserve fertility have established medical options that have been studied and used in clinical practice for years.
For women, egg freezing and embryo freezing are recognised fertility-preservation procedures. Eggs are collected after ovarian stimulation and rapidly frozen using a technique called vitrification.
Embryos can also be frozen after fertilisation. For men, sperm freezing is a widely used method of preserving reproductive material.
These procedures are different from freezing menstrual blood. They are specifically designed to preserve reproductive cells or embryos that can potentially be used later.
The significance of distinction
The interest in menstrual blood is not without scientific basis. Researchers are studying the cells and biological material found in menstrual samples for possible future uses.
But a promising area of research is not the same as a proven medical treatment.
Experts say people should be careful about claims that suggest freezing menstrual blood today could protect their fertility or provide future health benefits. Such claims need to be supported by strong clinical evidence before they can be considered reliable.
For Johnson, the sample appears to be part of his wider interest in collecting data and exploring unconventional approaches to health and ageing.
His disclosure has certainly attracted attention, but the science behind menstrual blood research is more measured than the viral reaction might suggest.
The research potential is real. What remains unproven is whether these samples can eventually lead to reliable medical tests or treatments.
Experts say established fertility-preservation methods such as egg, embryo and sperm freezing remain the evidence-based choices for people seeking to preserve reproductive options.
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