Niacin – also known as vitamin B3 or nicotinic acid – is a natural compound (formula C
2 ) and an essential nutrient for humans. It is water-soluble, which means it is not stored in the body. Excess amounts of the vitamin leave the body through the urine. That means we need a continuous supply of niacin in your diet.
Niacin is found in variety of foods, including liver, chicken, beef, fish, cereal, peanuts and legumes. It can also be synthesized from tryptophan, an essential amino acid found in protein. Niacin has long been an accepted treatment for high cholesterol. It is well-documented to increase the levels of high-density cholesterol (HDL or “good cholesterol”) and to decrease the levels of low-density cholesterol (LDL or “bad cholesterol”).
But what do these effects really mean? Do they translate into true health benefits? A brand-new study casts doubt on the value of niacin therapy:
After a pre-randomization run-in phase to standardize the background statin-based LDL cholesterol-lowering therapy and to establish participants’ ability to take extended-release niacin without clinically significant adverse effects, the researchers randomly assigned 25,673 adults with vascular disease to receive 2 g of extended-release niacin and 40 mg of laropiprant or a matching placebo daily. The primary outcome was the first major vascular event (non-fatal myocardial infarction, death from coronary causes, stroke, or arterial revascularization).
During a median follow-up period of 3.9 years, participants who were assigned to extended-release niacin-laropiprant had an LDL cholesterol level that was 10 mg per deciliter (0.25 mmol/l) lower and an HDL cholesterol level that was 6 mg per deciliter (0.16 mmol/l) higher than the levels in those assigned to placebo. Thus the lipid-effects of previous studies were confirmed.
However, assignment to niacin-laropiprant, as compared with assignment to placebo, had no significant effect on the incidence of major vascular events Niacin-laropiprant was associated with an increased incidence of disturbances in diabetes control that were considered to be serious and with an increased incidence of diabetes diagnoses as well as increases in serious adverse events associated with the gastrointestinal system, the musculoskeletal system, the skin and infections and bleeding.
Based of these data, the authors arrived at the following conclusion: among participants with atherosclerotic vascular disease, the addition of extended-release niacin-laropiprant to statin-based LDL cholesterol-lowering therapy did not significantly reduce the risk of major vascular events but did increase the risk of serious adverse events.
This extremely well-done trial is a poignant reminder of the fact that, in health care, we must never take our assumptions for granted. Here the underlying assumption was that the Niacin-induced lipid changes lead to a reduction of cardiovascular risks. Not only it proved to be erroneous but, through serious adverse effects, Niacin actually decreased patients’ health status.
The lessons from all this are straight forward, I think:
- ‘Natural’ does not necessarily mean safe.
- Long-established does not necessarily mean efficacious.
- Assumptions are merely assumptions, nothing more; if we want to make sure that they hold, we need to test them.
- When we finally do test assumptions, we better do it rigorously.