The nutritional value of Flax seed have been well established.

Flax seeds come in two basic varieties; brown and yellow (also referred to as golden).  Brown and yellow flax have similar nutritional values and equal amounts of short-chain omega-3 fatty acids.

One tablespoon of ground flax seeds and three tablespoons of water may serve as a replacement for one egg in baking by binding the other ingredients together. Ground flax seeds can also be mixed in with oatmeal, yogurt, water (similar to Metamucil), or any other food item where a nutty flavour is appropriate. Flaxseed oil is most commonly consumed with salads or in capsules. Flax seed owes its nutritional benefits to lignans and omega-3 essential fatty acids. Omega-3s, often in short supply in populations with low-fish diets, promote heart health by reducing cholesterol, blood pressure and plaque formation in arteries.

However there is one caveat.
I have recently changed my morning oatmeal to a brand that includes flax seed with the oats. My observation is that I have a dickens of a time removing the flax seed from between my teeth.

Of course, most of the flax seed is chewed and swallowed along with the oatmeal. But, I have observed that most of the breakfast debris left between my teeth consists of the flax seed—even though the seeds represent only a small fraction of the total content of the oatmeal.

Flax seed are just exactly the right size to lodge between the teeth and be insinuated beneath the gum in the crevice that surrounds each tooth.

So while Flax seed has definite medical benefits—it represents a major dental hazard. And they cannot be removed with the toothbrush alone. Floss and/or a Water Pik is required to do the most thorough job of their removal.