Niacin gastrointestinal effects

Adverse effects of niacin are most commonly seen when this vitamin is used at pharmacological doses above I g/day in the treatment of dyslipidemia. Notable adverse effects include flushing due to vasodilatation dermatological effects including dry skin pruritus and hyperkeratosis gastrointestinal effects including peptic ulcer,. stomach pain, nausea. and diarrhea elevations in serum uric acid and glucose and hepatotoxicity. ... 

The effects of most vitamin B overdoses have not been documented, although large dosages of pyridoxine have been reported to cause peripheral neuropathies. Ataxia and numbness of the hands and feet and impairment of the senses of pain, touch, and temperature may result. Excessive niacin intake may result in flushing, pruritus, and gastrointestinal disturbances. These symptoms are due to niacin s ability to cause the release of histamine. Large dosages of niacin can result in hepatic toxicity. 

Niacin deficiency is known to produce pellagra, which presents dermatological, gastrointestinal, and neurological symptoms (19,93,96). Niacin has also been implicated in several nonvitamin functions, which are still under investigation. These include the reduction of serum cholesterol levels, vasodilation, and modulation of the effects of cancer and diabetes (93,96-99). 

Niacin has also been trialled in combination with a statin and its safety compared with a statin alone [64 ]. Flushing occurred in 67% of patients and was the most common treatment-related adverse effect 21% of patients stopped taking niacin for a variety of symptoms and the incidence of adverse effects apart from flushing was 85%. There were three cases of chest pain, which were regarded as serious adverse events. Gastrointestinal discomfort was not uncommon. Fasting blood glucose concentrations rose by 7.7% over the 12 weeks of the study. In contrast in another study there was improved whole-body insulin sensitivity in an open study over 6 months [65 ]. 

---