Taking niacin, also known as nicotinic acid, would be about 50 times more efficient than taking

the amino acid triptophan to boost NID, because only about 2% of triptophan is converted into

niacin. Also, tritophant didn't work to improve mitochondrial or muscle function and physically compromised

older adults, even when combined with niacin or nicotinamide.

And side effects of taking tryptophan include belching and gas, blurred vision, diarrhea, dizziness,

drowsiness, dry mouth, headache, heartburn,

and potentially a life-threatening condition known as eosinophilia myalgia syndrome, or EMS.

There was an epidemic of EMS tied to tryptophan supplements from a single supplier back in

1989 that led to their removal from the market for about 15 years.

Some sort of contaminant was suspected, but the cause remains a mystery.

To this day, triptophan supplements continue to be tainted with impurities,

with at least one case of EMS reported decades after the initial epidemic.

A case of EMS tied to a bizarre weight loss diet involving hundreds of cups of cashews,

a rich source of tryptophan, suggests the syndrome can be caused by excess triptophan directly.

If anything,

tryptophan restriction may be beneficial.

Nearly 50 years ago was demonstrated that restricting dietary

triptophan reduced cancer rates and increased the lifespans of rats and subsequently mice.

Vegetarians and vegans both appear to have significantly lower intakes of triptophan,

but only in vegans does this translate to lower tryptophan blood levels, though presumably

not if they were to take tryptophan supplements.

What about taking NAD directly?

...