Higher niacin levels linked to lower cardiovascular risk, but not in those with diabetes

Key takeaways:

• Vitamin B3 may protect against death from all causes and CVD, especially in patients without diabetes.
• The effect of niacin on cardiovascular death may vary for different populations.

Higher intake of dietary niacin decreased the risk for all-cause mortality and cardiovascular-related death, according to results of a retrospective cohort study published in Scientific Reports.

However, researchers reported a steeper reduction in the risk for death in adults without diabetes.

Niacin, or vitamin B3, is common in Western diets, “with many individuals consuming niacin levels far exceeding the recommended dietary allowance, particularly in the U.S. where intake surpasses the recommended dietary allowance by threefold,” Ling Lin, from Chongqing University in China, and colleagues wrote.

Greater intake of niacin has previously been associated with several health benefits, including risk reductions for COPD and glaucoma, but the impact of the vitamin on CVD risk and long-term health “remains contentious” amid limited research, the researchers wrote.

The study conducted by Lin and colleagues assessed the effects of niacin intake on cardiovascular and all-cause death among a cohort of 26,746 adults aged 20 years or older from the 2003 to 2018 National Health and Nutrition Examination Survey.

Researchers categorized participants into four groups based on the quartiles of the average dietary niacin intake for 2 days.

The analysis showed3,551 all-cause deaths and 1,096 cardiovascular deaths during a median follow-up of 9.17 years.

Participants in the highest quartile of dietary niacin intake had a lower risk for all-cause mortality (HR = 0.74; 95% CI, 0.63-0.86) and cardiovascular mortality (HR = 0.73; 95% CI, 0.57-0.95) vs. those in the lowest quartile.

The researchers noted that the effect of niacin intake on cardiovascular death may vary in different populations, as they observed lower HRs in older adults, women and participants with obesity.

They also highlighted significant interaction between diabetes and niacin intake. The investigators reported HRs for all-cause mortality in the highest quartile of niacin intake of 1.01 (95% CI, 0.76-1.35) for adults without diabetes and 0.66 (95% CI, 0.56-0.79) for those with diabetes vs. participants in the lowest quartile.

Regarding possible mechanisms behind this interaction, Lin and colleagues explained that prior research has suggested that niacin may increase both blood sugar and diabetes risk.

“Niacin may impair insulin sensitivity through several pathways,” they wrote. “Therefore, higher dietary niacin is recommended to reduce the risk of all-cause death in non-diabetic people, but not in diabetic patients.”

The researchers added that the effects of niacin on the mortality risk may come from the improvement of nicotinamide adenine dinucleotide, or NAD, metabolism.

“As a precursor of NAD, niacin can increase the level of NAD and improve cell capacity metabolism, DNA damage, inflammation, mitochondrial function, cell aging, and cell death through multiple mechanisms,” they wrote.

The researchers identified several study limitations. For example, using niacin intake estimates based on self-reported data, while acknowledging that a 2-day period may not have been long enough to accurately capture dietary patterns.

“Further research is needed to clarify the variations in the impact of dietary niacin intake on cardiovascular mortality across different populations,” Lin and colleagues concluded.