Q “I have an underactive thyroid (hypothyroid issue), and I am wondering if I am safe to have your Fibre Balancing Greens Smoothie mix or your Flax Plus Oil blend”. Both of these contain kale to boost Vitamin K levels – vital for supporting your calcium metabolism
A: Brassicas, like kale, all contain sulforaphane, which is a wonderful health-promoting compound, which helps to protect against cancer and to support your bodies ability to detox via your livers powerful detox system. The downside of this compound is that it can potentially negatively impact the functioning of your thyroid gland.
So should you eat your kale, broccoli etc. or not?
There is a lot of misinformation about this question on the internet, so I check out the peer-reviewed published science.
A recent review of the science around this question concluded that at a reasonable level of consumption, the sulforaphane occurs “at concentrations far lower than those likely to impair thyroid function”.
So not eating your brassicas, because you are worried about your thyroid, would be depriving yourself with the very powerful health benefits you gain by having more brassicas in your diet.
Another important factor is that the effect of sulforaphane on your thyroid is that it can reduce the rate at which your thyroid absorbs iodine. This means you can minimise the small negative effect of eating brassicas by having plenty of iodine and selenium in your diet.
When I was designing Balancing Greens and Flax Plus, I was very mindful of these potential conflicts, so I made sure there was a good balance between achieving the optimum Vitamin K and Iodine levels for your health and any minor negative impact on your thyroid.
Conclusion – eat lots of brassicas for your health.