Goitrogens

Goitrogens are substances called glucosinolates found in brassica vegetables — broccoli, cabbage, kale, Brussels sprouts, and cauliflower. They can interfere with iodine uptake by the thyroid, and because thyroid function affects bone turnover, it's reasonable to wonder if eating these vegetables could matter for your bones.

In practice, though, the effect is small. Problems only really show up with severe iodine deficiency or truly extreme intakes — the often-cited case involved someone eating well over a kilogram of raw bok choy every day. Cooking these vegetables reduces the active compounds further, and having enough iodine in your diet protects against any issue.

The sensible approach is to keep eating cruciferous vegetables — they're actually one of the best plant sources of calcium, with good absorption since they're low in oxalate. Just make sure you have an iodine source too, like iodised salt, dairy, fish, or seaweed in moderation. If you have a known thyroid condition, keep your intake consistent rather than erratic, and take any thyroid medication away from food, calcium, and iron supplements, since those do meaningfully interfere with its absorption — your prescriber or pharmacist can advise on timing.