The study only used fructose to get the depressive state in place. You may have this state for other reasons, for which the methyl donor substances could still be helpful.
Do note that way overdoing methyl donor foods and supplements can have issues, so take a look at the following two links for more insight.
https://naturallysavvy.com/eat/are-you-eating-methyl-donor-foods/
Methylation: Why It Matters For Your Immunity, Inflammation & More
*
Isn’t it the case that some people need more of the methyl donor and some need less?
This seems to imply a “one-size-fits-all” approach.
Eggs.
.