Are flax (or linseed) seeds or oils really useful, and are they potentially dangerous to the thyroid?

Flax seeds are very rich in plant omega-3s and in lignans – molecules that block several estrogen receptors and thus reduce the estrogenic stimulation of the body, especially the mammary glands and prostate. They have been linked to potentially beneficial effects on breast cancer (slowing down the growth of tumors) and prostate cancer, as well as to a reduction of cholesterol and the rise of blood-sugar levels. For example, 50g (1.75 oz) of flax-seed bread increases blood-sugar levels by 30% less than the same quantity of white bread.

Looking through one of the biggest American data-bases on natural medicine, which can be accessed only through the libraries of major universities, I found no trace of any potentially damaging effect of flax seeds on the thyroid. The possible side-effects of flax seeds which I did find are these: “Taken orally, flax seeds (or linseeds) may lead to digestive problems comparable to those observed in other foods rich in fiber: bloating, excessive gas, abdominal pain, constipation and nausea. Flax seeds may also significantly increase the number of stools and the risk of diarrhea, and quantities over 45 g per day (1.6 oz) may not be tolerated for this reason. Occasionally allergic or anaphylactic reactions have been reported after ingestion of flax seeds or linseed oil. Some studies suggest an increase in the risk of prostate cancer associated with the consumption of alpha-linoleic acids from foods (meat and dairy products only). However, the consumption of flax seeds has not been linked to a risk of prostate cancer in population studies.”

So, nothing on the thyroid. I don’t know any more about this, but what I’ve learned seems reassuring.