As oxygen is broken down, poisonous free radicals accumulate in the cell. Through the days of our lives, free radicals slowly attack the mitochondrial machinery. Free radicals also mess with the cell's DNA and proteins. As a result, the cells lose their ability to control the movement of calcium within their own walls, leading to poor muscle function in old age. The cells also can't keep potassium out anymore.
Water rushes in along with the potassium and dilutes what's inside the cell.
In a sense, says KU scientist Fred Samson, old cells drown. Proper diet slows the damage of aging. Foods like broccoli and strawberries contain stuff that reduces the destructiveness of free radicals. The trick is to not eat too many calories. Now that's not the same as eating less, or starving yourself, which is how the message is sometimes received.