"To moderate the effects" means to lessen or control the impact or consequences of something, usually in order to make it more manageable or less severe. Full definition
In truth, they have a relatively moderate effect on your blood glucose levels. (healthyeating.sfgate.com)
Notably, maternal depression moderated this effect such that infant sleep problems correlated with bonding only in those mothers who were depressed. (link.springer.com)
The times we feel we can't avoid sugar we can at least moderate its effects. (connectionparenting.com)