Multiple studies show that the popular longevity supplement resveratrol blunts the positive effects of exercise and also lowers testosterone levels.

In non-diabetics, metformin shows no benefit on death rates over 21 years and harms exercise adaptations by about 50% while also lowering testosterone.

A study of nearly 50,000 people found that higher iron levels were associated with lower life expectancy, cautioning against blindly taking iron supplements without a blood test.

A 2018 meta-analysis found that high-dose niacin, a form of Vitamin B3, is associated with a 10% increased risk of all-cause death.

There's a strong possibility that popular NAD+ precursors like NMN and NR are converted into niacin by gut bacteria before absorption, raising safety concerns about high doses.

Taking direct antioxidants like high-dose Vitamin C or E after a workout can blunt the positive signaling effects of exercise-induced oxidative stress.

Research suggests that supplementing with Vitamin A and Vitamin E may interfere with the body's natural oxidant balance and potentially increase mortality rates.

Unlike direct antioxidants (Vitamin A, C, E), indirect antioxidants like glycine and NAC may be beneficial by providing the building blocks for the body's own powerful antioxidant, glutathione.