Niacin: Surprise! Niacin Safely Improves Lipid Profile in Diabetics
By Ward Dean, MD
I have always considered nicotinic acid (niacin, vitamin B3) to be the premier lipid-lowering substance of choice. Niacin cheaply and effectively reduces cardiovascular risk and optimizes the blood lipid profile for most people. Niacin reduces total cholesterol, increases HDL-C (good cholesterol), and lowers LDL-C (bad cholesterol) and triglycerides. As an added bonus, niacin also is a powerful growth hormone secretagog, and to top it off, is very inexpensive.
The only potential downsides to niacin use in most people is the distinctive (and unpleasant, to some people) niacin flush, a transient redness of the skin (due to a harmless dilation of capillaries in the skin), and itching. Fortunately, this effect resolves after several days or weeks in most people with careful dosage titration and continued use. In addition, niacin has been implicated in occasional mild to severe elevations of liver enzymes and even hepatotoxicity (especially involving the timed-release variety). There has also been a generally accepted belief that niacin should be avoided by diabetics, due to a purported tendency to cause elevations of blood sugar, thereby worsening glucose tolerance and actually exacerbating the abnormal lipid profile, for which it was ostensibly being taken to correct.
Recently, the results of a fairly large study appear to indicate that this bit of conventional wisdom, which I have observed myself, in a number of patients, causing me to discourage diabetics from taking niacin, may not be universal, and may in fact, be wrong (Elam, et al, 2000). In this 5-month study, the effects of niacin on lipid and glucose levels were observed on 468 hyperlipidemic patients (125 of whom suffered from Type II or non-insulin dependent diabetes mellitus [NIDDM]).
All subjects in the study participated in an active niacin run-in period. During this period, niacin was administered in progressively increasing doses of 50, 250 and 500 mg twice daily, at 4 week intervals. Upon completion of the run-in period, niacin was increased to 750 mg twice daily, and subsequently increased to 1,000 mg and then 1,500 mg twice daily, or until maximum tolerated dose was reached for the remainder of the 48 week treatment period. The researchers also ingeniously provided placebos, only 15% of which contained 50 mg of niacin. This was designed to cause intermittent flushing to minimize the likelihood of inadvertent unblinding of the study.
Both diabetic and non-diabetic participants experienced a progressive decrease in both total and LDL-Cholesterol as niacin dosage was increased to 3,000 mg/day (Fig. 1). HDL-C levels continued to increase, and triglycerides decreased further in participants both with and without diabetes. The researchers found, surprisingly, that niacin therapy was effective in modifying lipoproteins in participants both with and without diabetes.
Effect of Niacin on Blood Sugar and Safety Parameters
Niacin use resulted in a small increase in average glucose levels in all participants. Fig. 2 depicts changes in glucose values during the niacin treatment period. However, despite these transient increases, with continued use, plasma glucose subsequently returned to baseline. Hemoglobin A1c (another indicator of glucose tolerance) slightly increased in diabetics treated with niacin, but not in non-diabetics.
The authors stated that they believed this slight increase of HbA1c could have been eliminated if other means of controlling blood sugar had been instituted simultaneously. Nevertheless, there was no requirement for those patients using insulin to alter their insulin dosage. The researchers also found that liver enzymes were not affected by niacin.
Despite its proven ability to increase HDL and lower triglycerides, niacin has been discouraged for patients with diabetes. This is due to reports of niacin induced deterioration of glucose tolerance in subjects both with and without diabetes. The authors confirmed that blood glucose levels may rise slightly in both diabetics and non-diabetics treated with lipid-modifying doses (1,500-3,000 mg/day) of niacin. However, over 60 weeks of high dose niacin, the glucose-worsening effects were minimal, and did not require reduction in niacin dosages, nor alteration of other anti-diabetic therapy. The authors concluded that lipid-modifying doses of immediate-release niacin can be used safely in patients with stable, controlled type 2 diabetes mellitus. Based on these findings, I believe that niacin may be considered for use to reduce elevated blood lipids in diabetics as well as non-diabetics.
Elam, M.B., Huninghake, D.B., Davis, K.B., Garg, R., et al. Effect of niacin on lipid and lipoprotein levels and glycemic control in patients with diabetes and peripheral arterial disease. The ADMIT Study: A randomized trial. JAMA, 2000, 284: 10, 1263-1270.