VIP

Vasoactive Intestinal Peptide, or VIP, is a 28 amino acid peptide hormone that your body produces naturally, particularly in the gut, pancreas, and central nervous system. Despite its name suggesting it only affects the intestines, VIP actually has widespread effects throughout your entire body — influencing blood vessels, the immune system, circadian rhythms (your internal clock), and multiple organ systems.

Your body relies on VIP for some very important jobs: regulating inflammation, dilating blood vessels, relaxing smooth muscle, and coordinating communication between your nervous system and immune system. Scientists consider VIP part of the third branch of your autonomic nervous system, distinct from both the fight-or-flight (sympathetic) and rest-and-digest (parasympathetic) branches.

VIP has gained significant attention in functional medicine for its role in treating Chronic Inflammatory Response Syndrome, commonly known as CIRS. This is a complex multi-system illness often triggered by exposure to water-damaged buildings and mold. Dr. Ritchie Shoemaker pioneered the use of VIP nasal spray as the final step in his CIRS treatment protocol, documenting its effects in over 10,000 patients. In these patients, VIP levels are typically low while inflammatory markers are elevated, and restoring VIP helps rebalance the immune system.

VIP works through two main receptors called VPAC1 and VPAC2, which are found throughout the body. When VIP binds to these receptors, it triggers cascades of cellular activity that reduce inflammation, promote tissue repair, and help restore normal function to systems that have been disrupted by chronic inflammation. VIP is typically administered as a nasal spray, which allows direct delivery to the brain and systemic circulation. In the United States, it is a compounded medication that requires a prescription.

VIP works by binding to specialized receptors called VPAC1 and VPAC2 on the surface of cells throughout your body. These are G protein-coupled receptors, meaning that when VIP attaches to them, they trigger a chain reaction inside the cell. Specifically, they activate an enzyme called adenylate cyclase, which increases levels of a signaling molecule called cyclic AMP (cAMP). This in turn activates proteins that influence gene expression and change how the cell behaves.

One of VIP's most important functions is calming inflammation. It reduces the production of pro-inflammatory cytokines — chemical messengers that drive inflammation — including TNF-alpha, IL-6, and IL-12. At the same time, it increases the production of anti-inflammatory cytokines like IL-10. VIP also suppresses Th17 immune responses, which are associated with autoimmune disease, and promotes the development of regulatory T cells (T regs) that act as the immune system's peacekeepers, helping to keep inflammatory responses in check.

VIP has significant effects on blood vessels. It causes vasodilation, meaning it relaxes the smooth muscle in blood vessel walls, allowing them to open wider and improving blood flow. It specifically reduces pressure in the pulmonary arteries (the vessels leading to the lungs), which is why it has been studied for pulmonary arterial hypertension. It also stimulates the growth of new blood vessels through a process called angiogenesis.

In the brain and endocrine system, VIP regulates your circadian rhythms through actions in the suprachiasmatic nucleus — the brain's master clock. It influences the release of hormones from the pituitary gland, including growth hormone, prolactin, and luteinizing hormone. It regulates insulin and glucagon release from the pancreas, and it acts as a neurotransmitter affecting cognition and mood.

In the gut, VIP promotes the health of intestinal lining cells, regulates stomach acid secretion, controls water and ion absorption in the colon, supports the integrity of the gut barrier, and even has antimicrobial properties against certain pathogens. This wide range of actions explains why VIP deficiency — as seen in CIRS patients — can cause such diverse and widespread symptoms.