Studying Humans—not Harming Monkeys—Will Solve the Mystery of Menopause

By Dr. Neal Barnard

Last year, the North American Menopause Society delivered welcome news for millions of women: A plant-based diet rich in soy significantly relieves the aversive symptoms associated with menopause.

Specifically, the study found that avoiding animal products, reducing fat, and adding a serving of soybeans alleviated moderate to severe hot flashes by 88 percent—about the same as hormone replacement therapy, which can increase the likelihood of breast cancer, strokes, and blood clots. Participants also lost, on average, eight pounds in 12 weeks.

I was the study’s lead researcher, and I wasn’t surprised that our findings, published in the journal Menopause, again demonstrated why effective, humane, clinical research—in which willing human volunteers, or data or tissue samples collected from them, are studied to understand health and disease—yields the most clinically relevant results.

That’s why I was so troubled to learn of the menopause experiments being conducted on marmosets at the University of Massachusetts-Amherst—scientifically flawed experiments that cause irreversible harm to animals and do not improve our understanding of menopause.

Female marmosets in Agnès Lacreuse’s laboratory have their uterus and ovaries surgically removed. Males are vasectomized and sometimes endure additional surgeries to remove their testes. Telemetry devices are implanted in the bodies of both to monitor brain activity, heart rate, and temperature during sleep and cognitive testing. To implant them, experimenters drill burr holes into the marmosets’ skulls and screw electrodes directly into the bone. Additional incisions are made in their necks and abdomens so that electromyography leads can be implanted.

The marmosets also endure sleep and fluid deprivation, harmful hormonal manipulations, repeated blood, urine, and cerebrospinal fluid collections, and are often restrained before they’re killed and dissected.

If you’re asking how invasive experiments with marmosets can relieve the suffering of women, the answer is simple: It doesn’t. Critical differences in brain size and morphology, development rates, hormone production and responsivity, neurodevelopment, neuroanatomy, and neurodegeneration make marmosets a poor model for human menopause and its effects on the brain.

Marmosets do not experience menopause or its physiological symptoms in humans. Instead, Lacreuse induces the symptoms through surgery, pharmaceutical intervention, sleep deprivation, and heating pads to “model” hot flashes.

Abrupt, surgically induced menopause in captive marmosets cannot elucidate the complex genetic, environmental, or epigenetic factors that influence the transient and protracted menopausal transition in humans. The application of extraneous heat and noise-induced sleep deprivation are not biological simulations of the hot flashes and sleep disturbance that plague women in perimenopause.

Lacreuse cites marmosets’ short life expectancy to justify using them in aging experiments, but their accelerated development makes them inappropriate to study the prolonged, hormone-sensitive changes in the human brain.

If she really wants to help solve the mystery of menopause, she should stop harming animals and utilize the superior, non-animal alternatives being used now to evaluate how menopause and age-related hormonal change can trigger human neurodegeneration.

Large-scale epidemiological studies, postmortem analysis of brain tissues, and in vivo imaging of women in various stages of the menopausal transition are helping researchers understand the role of estrogen in human diseases and behaviors. Cutting-edge technology, including pluripotent stem cell models, three-dimensional cell-culture models, and organ-on-a-chip technologies, are providing more accurate, detailed models of neurodegenerative disease.

By studying human volunteers—as I’ve done for more than two decades—we can shed light on the effects of estrogen on cognition, brain structure and function, mood, hot flash frequency and severity, sleep disturbances, and risk for neurodegenerative diseases. Studies like my own have identified lifestyle changes that can help women now.

Such critical findings are not obtainable in animal “models.”

Dr. Neal Barnard, MD, FACC, is an Adjunct Professor of Medicine at the George Washington University School of Medicine in Washington, DC, and President of the Physicians Committee for Responsible Medicine.