Pyridoxine Deficiency · What Is It, Causes, Diagnosis, and More

There can be several causes of pyridoxine deficiency, including consuming less than the recommended dietary allowance (RDA) per day. For men ages 14-50, the RDA is 1.3mg; 51+ years, 1.7 mg. For women 4-18 years, it is 1.2 mg; 19-50 years, 1.3 mg; 51+ years, 1.5 mg. This amount increases to 2.0mg in those who are pregnant or lactating. The richest sources of vitamin B6 include fish, beef liver and other organ meats, potatoes and other starchy vegetables, and non-citrus fruits. In the United States, adults also obtain a lot of their dietary vitamin B6 intake from fortified cereals and poultry. Notably, vitamin B6 found in meats are more easily absorbed and used by the body than vitamin B6 from plants and vegetables, which may be important to those who exclusively follow a vegetarian or vegan diet. 

Individuals with borderline vitamin B6 concentrations or mild deficiency might have no signs or symptoms for months or even years. Those with prolonged or severe pyridoxine deficiency may experience peripheral neuropathy and a pellagra-like syndrome. Pellagra is a disease that occurs when a person does not receive enough of vitamin B3, or niacin. It is characterized by dermatitis, dementia, and diarrhea. In those with pyridoxine deficiency, individuals may often experience skin conditions, such as seborrheic dermatitis, which is characterized by a red, itchy rash on the scalp, face, neck and upper chest. It typically has an oily, flaky appearance and may cause swelling or white patches. One of the functions of vitamin B6 is to produce collagen, a protein in the skin that provides strength and elasticity. Without adequate levels of Vitamin B6, the skin barrier may break down, leading to dermatological conditions. Cheilosis (i.e., scaling on the lips and cracks at the corners of the mouth) and glossitis (i.e., swollen tongue) are also characteristic signs. In the case of glossitis, the tongue becomes enlarged, smooth, and red as it loses the papillae, or raised protrusions, on the tongue. 

Pyridoxine deficiency can be diagnosed by clinical evaluation and physical examination. Clinicians may look for the key signs of deficiency, including dermatological findings, presence of altered mental status, and peripheral neuropathy. They can also take a focused history and obtain records of nutritional intake, supplement use, and medication history. Also critically important is eliciting a history of increased risk, including those with malabsorption syndromes, such as inflammatory bowel disease, celiac disease, or history of bariatric surgery. 

Pyridoxine deficiency can be treated with vitamin B6 supplements. Vitamin B6 is available in multivitamins, in supplements containing other B complex vitamins, and as a stand-alone supplement. It is used by approximately 28%–36% of the general population. Usually, pyridoxine dosed at 50 to 100mg orally once a day will correct the deficiency in adults. 

Supplementation protocols may vary depending on the specific cause of the deficiency. Most people taking isoniazid should be given 30 to 50mg of pyridoxine orally once a day. For metabolic disorders or increased metabolic demand, taking high doses or increasing daily recommended intake of pyridoxine may be required after consulting with a clinician. 

It is important to note that pyridoxine is one of the three water-soluble vitamins that can have toxicity at excessive doses, in addition to niacin (i.e. vitamin B2) and ascorbic acid (i.e. vitamin C).