Most people are going to take their thyroid med first thing in the morning, and
probably wouldn't eat the veggies and
(have to research that) until later in the day. I wonder how many walnuts you'd have to eat to get that effect.
The health benefits of things like broccoli, cauliflower, walnuts, etc are much greater than the harm they might do, when eaten in moderation and separated from the medication, by a few hours.