Can Tortoises Eat Kale?

Yes, in moderation. Our records rate kale feed in moderation for every species group, meaning a useful green in rotation rather than a daily staple.

Kale is one of the better supermarket greens available to a British keeper in winter. The limit on it is a sensible precaution rather than a warning.

Species considerations

The verdict does not change by species group. Kale is rated moderation for Mediterranean Testudo tortoises, for grazing species like the Sulcata and leopard, and for tropical forest species alike.

For grazing species there is a separate point: kale is a supplement to grass and hay, not a substitute. A Sulcata filling up on kale is one not eating the fibre it actually needs.

What goitrogens actually do

This is where most tortoise pages either overstate the risk or wave it away, so it is worth being precise.

Kale contains glucosinolates, principally progoitrin and sinigrin. When the leaf is damaged, an enzyme called myrosinase converts these into thiocyanates. Thiocyanates compete with iodine for uptake at the sodium-iodide symporter on thyroid cells. If that competition is sustained and iodine intake is low, thyroid hormone production can be affected.

That mechanism is real. Three things temper it:

1. Dose matters enormously. The documented human cases involve extreme intakes. The most cited example, reported in the New England Journal of Medicine, involved a woman eating roughly a kilogram or more of raw bok choy daily for months.
2. The threshold in tortoises is not established. Even in human nutrition, the thiocyanate content of kale is not well characterised and the intake associated with adverse thyroid effects is unknown. Nobody has determined the equivalent figure for a tortoise. Any site giving you a precise safe quantity is inventing it.
3. Iodine offsets it. The effect depends on iodine status. Kale itself contributes some, which is part of why it compares favourably to other brassicas.

Our position: moderation is a precaution based on a plausible mechanism and the general principle of dietary variety, not on documented cases of tortoises harmed by kale. We would rather say that plainly than imply a certainty that does not exist.

One thing not to do: cooking reduces goitrogen content substantially in human food preparation. That is irrelevant here. Tortoises eat raw plant material, and cooking their food serves no purpose.

Kale is not spinach

A myth worth killing. Plenty of tortoise pages group kale with spinach and chard as high-oxalate greens to be avoided.

Kale is a low-oxalate green. Spinach and chard are not.

This is the whole reason kale and spinach sit in different bands on our chart despite both being dark leafy greens. Kale’s calcium is genuinely available to the animal. Spinach’s largely is not, and it interferes with calcium from the rest of the meal as well.

If you have been avoiding kale because you read that it blocks calcium, you were reading about the wrong vegetable.

How often, and why we will not give you a number

There is no defensible gram figure, and pages that supply one are guessing.

Portion depends on species, age, body size, season, what else is in the diet that week, and the individual animal. A hatchling Hermann’s and a 5kg leopard tortoise do not share a serving size.

What we can give you is a usable rule:

• Rotate, do not repeat. Kale should be one of several greens across a week, not the green.
• Never the base of the diet. Weeds and flowers do that job. Kale supports it.
• Do not stack brassicas. Kale plus spring greens plus pak choi in the same week is a lot of the same compound. Vary the family, not just the item.
• Winter is when it earns its place. From November to March, when British forage disappears, kale is one of the better things in a supermarket. See winter feeding.
• A practical test: if you could write down everything your tortoise ate last week on one line, the diet is too narrow regardless of how good each item is.

Preparation

• Raw, always.
• Wash it, including bagged kale sold as pre-washed.
• Do not chop or shred finely. Fibre length matters. Tortoises swallow leaves whole and only the cut ends are exposed to gut bacteria, so chopping speeds fermentation from identical ingredients. Offer whole leaves where you can. The reasoning is in Mediterranean tortoise diet.
• Stalks are fine and carry more fibre than the leaf.
• Cavolo nero, curly kale and red kale are all the same species and carry the same rating.

Alternative greens

Kale is a good option among a weak category. These are better.

The underlying point: of the sixteen leafy greens in our records, exactly one is rated for regular feeding, and it is not kale. Weeds and flowers supply eleven of the fourteen everyday foods on the whole site. See best weeds for tortoises and what vegetables can tortoises eat.

To check anything else, the tortoise food checker gives a verdict for your species group with the reasoning behind it. Spring greens behave much the same way as kale, and the complete banded list is in the tortoise food chart.

Ratings follow our own food records, built from the Tortoise Trust, the British Chelonia Group, The Tortoise Table plant database and published veterinary and nutritional research, and checked as described in our sources and review policy. This is husbandry information rather than clinical advice. See our veterinary disclaimer.

Last reviewed: September 2026.