The research bears out NR supplement use—several human clinical trials of NR supplements have been completed, including randomized placebo-controlled trials (RCTs), the “gold standard” of clinical research. In one eight-week study4, researchers found that people taking NR had an increase in their blood NAD+ levels. Healthy overweight adults tolerated a daily oral NR dose of up to 1,000 milligrams, with no flushing or serious side effects. Another study5 showed that NR is more bioavailable, or has better absorption, than nicotinamide and nicotinic acid.