Overview
Vitamin B10, also known as para-aminobenzoic acid or PABA, is no longer considered an essential vitamin for humans, but it has important biological and clinical significance. PABA is recognized mainly for its role in bacterial folate synthesis and has been used clinically for specific diagnostic purposes. It is well known for its ultraviolet light–absorbing properties and has been widely used in sunscreen formulations.
PABA also exhibits antioxidant properties and participates in various metabolic pathways. In laboratory medicine, Vitamin B10 is mainly associated with the PABA test, which is used to assess pancreatic exocrine function and to confirm the completeness of a 24-hour urine collection.
Symptoms
Vitamin B10 deficiency is rare in humans and does not produce a well-defined deficiency syndrome. However, imbalance or reduced availability may be associated with nonspecific symptoms such as fatigue, irritability, hair loss, skin rashes, and photosensitivity.
Neurological symptoms, including mood changes and unexplained anxiety, may be seen in some individuals. In infants and children, hypotonia and developmental delay have been reported in rare cases. Since PABA plays a supportive role rather than an essential vitamin function, symptoms are usually subtle and often linked to underlying metabolic or pancreatic disorders rather than an isolated deficiency.
Causes
Altered Vitamin B10 levels or abnormal PABA test results are commonly caused by impaired pancreatic exocrine function. Conditions such as chronic pancreatitis, cystic fibrosis, pancreatic cancer, and post-pancreatic surgery states can reduce chymotrypsin activity, leading to decreased cleavage and absorption of PABA. Malabsorption syndromes and severe intestinal disorders may also affect PABA absorption.
Drug interactions, particularly with sulfonamide antibiotics, can interfere with PABA metabolism. Inadequate or incomplete 24-hour urine collection may falsely suggest abnormal PABA levels.
Risk Factors
Risk factors associated with abnormal Vitamin B10 or PABA test findings include chronic pancreatitis, pancreatic insufficiency, cystic fibrosis, long-standing malabsorption, and gastrointestinal surgeries involving the pancreas or small intestine. Patients undergoing evaluation for pancreatic enzyme replacement therapy are also at higher risk of abnormal results.
Poor patient compliance with urine collection instructions, dehydration, alcohol intake, smoking, and strenuous exercise before testing can affect test accuracy. Individuals on long-term sulfa drug therapy may also show altered PABA metabolism.
Prevention
Prevention focuses on accurate testing practices and management of underlying pancreatic or gastrointestinal disorders. Proper patient preparation, including avoidance of alcohol, smoking, and strenuous exercise, improves test reliability.
Clear instructions for complete 24-hour urine collection are essential to prevent false results. Early diagnosis and appropriate treatment of pancreatic exocrine insufficiency help normalize PABA metabolism and improve digestive function. Adequate nutrition and management of malabsorption conditions support overall metabolic balance and reduce the risk of abnormal Vitamin B10–related findings.
