The TARGET-D randomized clinical trial involving 630 adults with heart disease found that personalized vitamin D supplementation significantly reduced heart attack risk by 52% compared to standard care over approximately four years. Participants in the treatment group had their vitamin D levels regularly monitored and adjusted to maintain blood levels between 40–80 ng/mL, while the control group received standard care without vitamin D management. Notably, 85% of participants started with vitamin D levels below 40 ng/mL, and about half of those receiving treatment needed more than 5,000 IU daily—over six times the FDA’s recommended 800 IU—to reach target levels. While the personalized dosing reduced heart attacks specifically, it did not significantly lower the combined risk of death, heart failure, stroke, or heart attack overall. The researchers emphasize these preliminary findings need confirmation through additional clinical trials, particularly in more diverse populations, as 90% of participants were white.
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