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I have just bought a flowerpot of sage - Salvia officinalis. I know that the leaves can be used for tea. But can they also be eaten fresh, as a snack or as part of the salad? Is there any limit on the amount of fresh Salvia leaves that is safe to eat per day?

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    I love adding sage to pasta. The easiest way I found is to put sage leaves in a small cup, add some butter on it and put it in the microwave, for maybe 30s. The leaves become very crispy and keep their strong taste. You can then break the leaves on pasta, and not much else is needed. Since 1 or 2 leaves per person are enough, I wouldn't like to eat a whole sage salat. – Eric Duminil Mar 23 at 8:45
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    What we all have ignored so far: The assumption is that your pot was indeed sold as kitchen herb and not as decorative plant. With the latter, fertilizers and pesticides could be an issue. – Stephie Mar 23 at 9:41
  • Btw, the flowers are also edible. – Stephie Mar 23 at 14:12
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Sage (Salvia officialis) is a staple herb in various cuisines. It pairs with veal in an Italian Saltimbocca or pork in the British sage and onions stuffing and is eaten even on its own, e.g. battered and fried. So yes, it’s clearly edible. However, personally I would not serve it as a salad leaf, it’s probably too pungent to be truly enjoyable, but taste is of course personal preference. There are recipes that use sage in vinaigrette, though.

As the flavor is quite intense and a little goes a long way, most consumers will never nibble on enough to get in the range where the thujone content matters (similar to the amygdalin in apple pips). But let’s do a rough estimation to get a ballpark number. The amount of oil that can be extracted from S. officinalis leaves is between 0.5 and 1 %. That oil can contain up to 50% thujone, so we can just use the 0.5% as thujone content of fresh leaves. Considering that the LD50(mice) of thujone is 45mg/kg and that 30mg/kg gives a 0% mortality, a healthy 75kg “average person” could probably eat 2g of thujone or 400g sage leaves and be fine - but it wouldn’t be a good idea nevertheless, taste-wise. Excessive, especially habitual/long term use is sometimes discouraged.

The EU has limited the amount of thujone from sage a food product may contain to 25mg/kg. That would equal 50g sage leaves in 1 kg prepared food.

Conclusion: Enjoy cooking with your sage, forget about the salad leaves idea.

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Further reading: https://pubmed.ncbi.nlm.nih.gov/20727933/

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    No matter how good your cooking is: if there's 50g of sage in there per kilogram of food it'll be far too nasty for anyone to eat a relevant amount of it – Hobbamok Mar 23 at 8:35
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    @Hobbamok the percentage is obviously way higher for sage tempura (which are delicious), but the serving size is so small, it’s still harmless. – Stephie Mar 23 at 8:37
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    There are also (@Hobbamok) recipes for sage pesto. Most seem to measure the sage in cups, but where I've found weights they're no more than about 50g per serving. It's apparently metabolised quickly (in mice) so shouldn't accumulate, but anyway several servings per day for a couple of days would be needed to reach the total above. – Chris H Mar 23 at 9:57
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    @Hobbamok I used to love sage tempura as a child and would have certainly eaten loads of it if I could have gotten that much. Now I'm thinking I should really get me a flowerpot of sage too, to freshen up those old memories (and potentially get poisoned, apparently :D). ... wait, does that EU limit mean I couldn't buy sage tempura in a restaurant in the EU? – Nobody Mar 23 at 16:19
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    @Nobody probably, that would explain why I haven't ever seen it anywhere. Also: a) get you some sage! and b) then get your sage a big enough pot. I bought a bundle and replanted a single plant for my window still and it never grows. My mom (who took the other plant) has hers growing to insane sizes because her pot is twice the size. The ones in the garden are doing very well though, so if u can just drop them there. They need half a year to really take root but from then it's a quite hardy and fas growing plant. Survived this winter as well (I'm making Liquor from it hence I need a lot) – Hobbamok Mar 24 at 9:21
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If you were a human-sized rat, it seems that in the worst case, 2 kg of leaves might be enough. That's a rather handwavy amount, of course.

To go into more depth: the presence of papers like "Toxicity of Salvia officinalis in a newborn and a child: an alarming report" means that dying from eating sage isn't common - apparently, two very young children having seizures after ingesting sage essential oil is news enough to get published as a cautionary case report. So it is unlikely that anybody has ever measured the exact amount needed for an adult human to die from sage poisoning.

What people have measured is the composition of the essential oil extracted from sage. A good example is "Composition of the essential oil of Salvia officinalis L. from various European countries", which makes a good comparison of samples - because of course, there is huge variation between plants of the same species.

If we make several assumptions, we can make a back-of-the-envelope calculation:

  • the only toxic compound we are interested in is thujone
  • the conversion ratio for fresh to dry sage is 3:1 by weight
  • the sage you eat produces as much essential oil as the highest-yield sage in the paper (the range was 2.2 to 24.8 ml per kg dried leaves)
  • the sage you eat has as much thujone as the highest-thujone sage in the sample (50% alpha and 13% beta thujone)
  • both alpha and beta thujone count equally
  • the LD50 dose for rats (192 mg/kg) is relevant for humans
  • your weight is 70 kg

then my calculation is that you would have to consume 13.44 g of thujone to reach the LD50, while a kilogram of fresh sage will have a bit over 6 grams of thujone.

This is of course a very inaccurate calculation, please do not rely on the exact numbers. But if should give you an idea of the rough range of dangerous amounts.

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    Lol, we were obviously thinking along the same lines! (Different numbers, but hey...) – Stephie Mar 22 at 21:50
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    @Stephie it seems you took the mouse LD50 from Wikipedia, while I used the rat LD50 from the paper - and yes, there is a 4x difference, and that's normal (and why I list the relevancy of the rat LD50 as unproven assumption). Else it lines up nicely - and your calculation of reaching the highest allowed dose is quite pertinent. – rumtscho Mar 22 at 21:55
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    Jep. I was too lazy to go much father than Wikipedia - knowing that even with a whole lot of hand waving and rounding up the conclusion would still be “unless you start munching down a whole shrub, you’ll be fine”. – Stephie Mar 22 at 21:57
  • tl:dr: Any food will be absolutely disgusting long before the sage content becomes any dangerous – Hobbamok Mar 23 at 8:36
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    “If you were a human-sized rat” - that alone deserves an upvote! – Stephie Mar 23 at 9:37

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