The reason niacin substitutes are an issue is that the amount of this B vitamin needed to lower cholesterol is typically about 3,000 mg a day, but taking very high dose of any vitamin, especially this vitamin, can throw other vitamins out of balance.
If you take high-dose niacin by itself, you may just be trading one factor for heart disease, high cholesterol, for another, high homocysteine. Taking more than 1,000 mg of niacin a day can raise homocysteine levels, especially if niacin is not balanced by folic acid (400-1,000 mg a day), vitamin B6 (10-50 mg a day), and vitamin B12 (50-300 micrograms a day). If you take more than 1,000 mg of niacin daily, you need additional B vitamins.
There have been no trials of niacin for lowering cholesterol in persons who have not had a heart attack, but the Coronary Drug Project followed 8,000 men who had had a heart attack for eight years. Taking 3,000 mg of nicotinic acid every day resulted in:
- 10% lowering of total cholesterol,
- 26% lowering of triglycerides,
- 27% lowering of the rates of second heart attacks, and
- 27% lowering of the rates of stroke.
Other studies of both men and women have found that taking niacin raises HDL levels and transforms LDL cholesterol from the sticky apo-A form to the lighter, less harmful apo-B form. Taking beta-carotene, vitamin C, vitamin E, and selenium, however, reduced the benefits of niacin.
Unfortunately, a number of things can go wrong when you take niacin for your health health. Niacin side effects include:
- Liver damage, detected by changes in blood tests for the cell damage markers ALT and AST, and, in extreme cases, by tenderness and enlargement of the liver. Like statin drugs, niacin sometimes damages the liver. Hepatitis has been observed from taking dosages as low as 500 mg a day for a period as short as two months, although most cases of liver damage occurred when the dosage was 3,000 to 9,000 mg for several years.
- Higher blood sugar levels. Diabetics usually should not take high-dose niacin. The vitamin can cause insulin resistance and raise blood sugars.
- Occasional side effects have included blurred vision, migraine, peptic ulcers, disturbances of heart rhythm, and gout.
The best use of niacin for type 2 diabetics is in lowering very high triglyceride levels, so high that they are causing pancreatitis. In this case, however, the niacin is usually given by intravenous injection under a doctor's supervision.
Jialal I, Amess W, Kaur M. Management of hypertriglyceridemia in the diabetic patient. Curr Diab Rep. 2010 Aug;10(4):316-20.