You don't have to consume flaxseed to get alpha-linolenic acid. Notably, it is the richest source of lignans, which provide fiber. In the process of digestion, bacteria convert lignans into estrogen-like substances called enterodiol and enterolactone. These may have anti-tumor effects. Phytoestrogens are also found in other plants, including soy, certain herbs, whole grains, and other seeds.
Studies have shown that flaxseed can reduce tumors in lab animals.
So far there's no convincing evidence of a similar action in humans, though some ongoing studies may provide answers. In addition, lignans may play some role in lowering cholesterol and possibly in maintaining bone density. Flaxseed oil usually does not contain lignans, though some processors do add some lignans back into the oil. It is increasingly difficult to single out any one plant food as unique or miraculous. All plant foods have good things to offer.