The Blood-Brain Barrier: Barricading the Aging Brain

By Shannon Kasun, Neuroscience Specialist

The brain requires a carefully controlled environment to function properly. One of the systems responsible for maintaining the neuronal microenvironment is the blood-brain barrier, a highly selective, semi-permeable barrier that separates circulating blood from brain tissue.

(Ding et al., 2025)

Rather than simply acting as a wall, the blood-brain barrier functions more like a sophisticated security system. Specialized endothelial cells lining blood vessels in the brain work alongside pericytes, astrocytes, and tight junction proteins to create a protective cellular network. Together, these structures help prevent harmful substances, including toxins and pathogens, from entering the brain, while allowing essential molecules to cross through mechanisms such as diffusion and active transport.

Like many biological systems, the blood-brain barrier becomes less effective with age. Age-related changes including the loss or dysfunction of pericytes and tight junction proteins, vascular dysfunction, oxidative stress, and inflammation compromise the integrity of the blood-brain barrier (Kim et al., 2025). The result is often described as a "leaky" blood-brain barrier, in which substances that would normally be tightly regulated more readily enter brain tissue. This "leakiness" contributes to neuroinflammation, neurotoxicity, and the accumulation of pathological proteins associated with neurodegenerative disease (Kim et al., 2025).

Importantly, certain brain regions may be particularly susceptible to blood-brain barrier dysfunction. Research identified early age-related blood-brain barreir breakdown in the hippocampus, a region essential for memory consolidation and particularly vulnerable in Alzheimer’s disease (Montagne et al., 2015). Greater leakage in this neuroanatomical area may contribute to age-related cognitive impairment and dementia (Hussain et al., 2021). 

Several lifestyle and nutritional factors may support blood-brain barrier health. Regular physical activity helps protect and repair the blood-brain barrier through multiple pathways, including reductions in oxidative stress and inflammation and beneficial effects on vascular signaling and endothelial function (Sun et al., 2025). These mechanisms provide another potential explanation for the strong relationship between physical activity and long-term brain health. Experimental research suggests magnesium supplementation reduces blood-brain barrier permeability and influences the transport and clearance of amyloid-beta, a protein strongly associated with Alzheimer’s disease pathology (Zhu et al., 2018). Higher omega-3 levels were associated with better measures of blood-brain barrier integrity in healthy aging adults, implying omega-3 fatty acids play a role in maintaining the structure of the blood-brain barrier (Barnes et al., 2021). 

Maintaining the integrity of the blood-brain barrier is an important strategy for protecting the brain as we age. Regular exercise and proper nutrition are tactical ways to reinforce this critical defense system and promote long-term brain health and cognition.

References 

• Ding, L., Kshirsagar, P., Agrawal, P., & Murry, D. J. (2025). Crossing the Blood-Brain Barrier: Innovations in Receptor- and Transporter-Mediated Transcytosis Strategies. Pharmaceutics, 17(6), 706. https://doi.org/10.3390/pharmaceutics17060706 

• Kim, S., Jung, U. J., & Kim, S. R. (2025). The Crucial Role of the Blood-Brain Barrier in Neurodegenerative Diseases: Mechanisms of Disruption and Therapeutic Implications. Journal of clinical medicine, 14(2), 386. https://doi.org/10.3390/jcm14020386

• Montagne, A., Barnes, S. R., Sweeney, M. D., Halliday, M. R., Sagare, A. P., Zhao, Z., Toga, A. W., Jacobs, R. E., Liu, C. Y., Amezcua, L., Harrington, M. G., Chui, H. C., Law, M., & Zlokovic, B. V. (2015). Blood-brain barrier breakdown in the aging human hippocampus. Neuron, 85(2), 296–302. https://doi.org/10.1016/j.neuron.2014.12.032

• Hussain, B., Fang, C., & Chang, J. (2021). Blood-Brain Barrier Breakdown: An Emerging Biomarker of Cognitive Impairment in Normal Aging and Dementia. Frontiers in neuroscience, 15, 688090. https://doi.org/10.3389/fnins.2021.688090 

• Sun, Z. X., Xie, F., Zhao, Y., Wang, X., Sun, Z. W., Qian, L. J., & Feng, H. (2025). Exercise and the blood-brain barrier: Mechanistic insights and therapeutic implications. Neurobiology of disease, 217, 107166. https://doi.org/10.1016/j.nbd.2025.107166

• Zhu, D., Su, Y., Fu, B., & Xu, H. (2018). Magnesium Reduces Blood-Brain Barrier Permeability and Regulates Amyloid-β Transcytosis. Molecular neurobiology, 55(9), 7118–7131. https://doi.org/10.1007/s12035-018-0896-0 

• Barnes, S., Chowdhury, S., Gatto, N. M., Fraser, G. E., & Lee, G. J. (2021). Omega-3 fatty acids are associated with blood-brain barrier integrity in a healthy aging population. Brain and behavior, 11(8), e2273. https://doi.org/10.1002/brb3.2273