A study from CU Anschutz published in iScience finds that stress experienced by fathers before conception can influence offspring growth and bone development through the molecule let 7f 5p in sperm, without changes to DNA. The research adds to evidence that a father's life experiences shape early…
Researchers at the University of Colorado Anschutz Medical Campus have found that stress experienced by fathers before conception may influence the growth and bone development of their offspring. The study, published in iScience on July 17, 2026, focuses on biological signals carried in sperm that are not related to changes in DNA. According to the research, a small stress responsive molecule called let 7f 5p increases in sperm when a person is under stress, and this molecule may help shape how an embryo develops in its earliest stages. Those early changes can later influence growth after birth.
The findings suggest that sperm carry more than just genetic material. They carry molecular signals shaped by a father's life experiences, including stress. The study was led by Tracy Bale, PhD, who holds the Anschutz Foundation Endowed Chair in Women's Integrated Mental and Physical Health Research at the Ludeman Center at CU Anschutz. Co-author Neill Epperson, MD, professor and chair of the CU Anschutz Department of Psychiatry, also contributed to the work. The research builds on earlier work from the same team that showed stress can change molecules in sperm and affect how offspring develop.
To test the role of let 7f 5p, scientists increased levels of this molecule in fertilized mouse eggs to mimic the biological effects of paternal stress. They observed that male offspring exposed to higher levels of the molecule grew larger and developed longer bones compared to controls, even though they ate a normal diet. This finding indicates that the molecule alone, apart from other stress-related factors, can influence physical development.
The study adds new evidence that the same biological system previously linked to changes in offspring brain development, behavior, and metabolism may also influence physical growth, including body size and bone development. The researchers note that ongoing or repeated stress before conception may play a role in these biological changes. Bale explained that prolonged stress, such as caring for a seriously ill family member, working in a high-pressure job, or coping with financial strain, could increase levels of let 7f 5p in sperm. That molecule may then subtly influence how a child's body develops before birth. "It is like a father's stress quietly nudges the body's growth settings, with effects that show up later in life," Bale said.
The study highlights that health before conception may matter not only through genetics but also through biological signals influenced by life experience. Epperson emphasized that the findings strengthen evidence that stress biology in the germline is not fixed. "It seems to change in response to life experiences in ways that can influence early development," he said. Bale added, "This study shows that sperm carry more than DNA. They carry information about a father's experiences that can shape early development and long-term health."
While the research is based on mouse models, the findings suggest that similar mechanisms may occur in humans. The researchers recommend that individuals manage stress, get enough sleep, eat well, and seek support during difficult times to help support healthier biological conditions before conception. Bale concluded, "This research is about understanding that our experiences can have biological effects. Taking care of ourselves before conception is an important part of planning for healthy children."
The study was conducted at the University of Colorado Anschutz Medical Campus and is part of a growing body of evidence showing that paternal preconception health can influence offspring development across generations. The research was published in the journal iScience and builds on prior work from the same team that found links between stress and changes in offspring brain development, behavior, and metabolism. The current findings extend that work to include physical growth and bone development, suggesting that the biological effects of paternal stress are broad and may have implications for understanding intergenerational health.
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