A recent open access paper from Japan on the effect of one product of electrolyzed water on nematode life span makes a good point, buried down near the end. The study of antioxidants and metabolism in lower organisms is a challenge:
There are many contradictory reports that [reactive oxygen species (ROS) are or are not] responsible for the regulation of the lifespan of nematodes. It has been reported that many antioxidants cannot extend the lifespan of C. elegans, or can extend the nematode lifespan, but not because of their intracellular ROS-scavenging activities. Because the regulatory mechanisms for lifespan are extremely complication, it is possible that [any given newly evaluated antioxidant] extends the lifespan of C. elegans not only be alleviating ROS accumulation, but also by other mechanisms.
It is comparatively easy to alter the life span of smaller, short-lived animals - and thus hard to separate out meaningful effects that are worth testing in mammals. Things become somewhat more clear once you move up to mice, as in general it seems to be the case that the larger the beast, the less plastic its maximum life span becomes. Researchers can make nematodes live many times longer than normal, mice 50-70% longer, and no-one seems to expect the calorie restriction based techniques that extend mouse life span by up to 40% to do more for humans than provide an extra couple of years. Insofar as antioxidants go, the only things worth talking about in mouse studies are those that target mitochondria - as everything else does nothing.
But back to the electrolyzed reduced water, which may or may not have anything to do with mitochondria, and even if it did, may or may not do anything for life span in mammals. As it is, the researchers had to tilt the playing field to make anything happen in worms. Alterations in the chemistry of the local fluid medium are very different ball game when considering the differences between a nematode and a mouse:
Electrolysis of water typically produces two forms of water: electroyzed reduced water (ERW) or alkaline ionized water, produced at the cathode site, and electrolyzed anode water (EAW), produced at the anode site. ... Recently, ERW has attracted much attention because of its antioxidative potential. ERW scavenged reactive oxygen species in vitro and protected DNA from oxidative damage.
In the present study, a new culture medium, which we designated Water medium, was developed to elucidate the effects of ERW on the lifespan of Caenorhabditis elegans. Wild-type C. elegans had a significantly shorter lifespan in Water medium than in conventional S medium. However, worms cultured in ERW-Water medium exhibited a significantly extended lifespan (from 11% to 41%) compared with worms cultured in ultrapure water-Water medium. There was no difference between the lifespans of worms cultured in ERW-S medium and ultrapure water-S medium. Nematodes cultured in ultrapure water-Water medium showed significantly higher levels of reactive oxygen species than those cultured in ultrapure water-S medium.
If you parse out exactly what the researchers did there, you'll see that they established a growth medium that caused the worms to suffer greater oxidative damage, and then demonstrated that using electrolyzed reduced water prevented a modest fraction of that damage. But on its own, for worms in a normal growth medium, electrolyzed reduced water didn't do much of anything to life span.
This is actually a very representative example of the study of antioxidants and longevity. You can often show some benefit by increasing the levels of ongoing damage and oxidative stress - but under normal conditions, the antioxidant is a wash. I'm usually wary of studies that show that a given approach rescues animals from some form of abnormal engineered deficiency - unless that deficiency occurs in a specific disease, there may be no real application for what is learned. The electrolyzed reduced water research quoted above shows why it is wise to bear this mind.