Tag Archives: kidneys

Neem: nice, nasty or… not sure?

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A few days ago it was sunny and slightly breezy outside (yes, it’s August, but I live in the UK – this isn’t as common as you might imagine) and I thought, I should make the most of this and do something about my orchids.

Now, anyone that reads this blog regularly will know that my Dad is a horticulturist. I, however, am not. My fascination with bright colours, interesting smells and complicated naming conventions went down the chemistry route. But I am, oddly, quite good with Phalaenopsis, aka, moth orchids. I don’t really know why, or how, but I seem to have come to some sort of agreement with the ones that live on my kitchen windowsill. It goes along the lines of: I’ll water you once a week, and you make flowers a couple of times a year, and we’ll otherwise leave each other alone, okay?

Scale bugs secrete honeydew, which encourages the growth of sooty moulds

Well, this was fine for years, until we somehow acquired an infestation of scale bugs. These tiny but extremely annoying pests feed by sucking sap from leaves of plants, and they excrete a sticky substance called honeydew. Trust me, it’s not as nice as it sounds. Firstly, it really is sticky, and makes a horrible mess not just of the orchid leaves, but also the area around the plants.

Then it turns out that certain types of mould just love this stuff, so you end up with black spots on the leaves. And, not surprisingly, all this weakens the plant.

So, what’s the answer? Well, there are several. But the one I tend to default to is neem oil.

This stuff is a vegetable oil from the seeds of the Azadirachta indica, or neem, tree. It has a musty, nutty sort of smell, and is fairly easy to buy.

It’s indigenous to the Indian subcontinent and has been historically important in traditional medicine. In fact, The Sanskrit name of this evergreen tree is ‘Arishtha’, which means ‘reliever of sickness’.

So it’s a natural vegetable oil and people have been using it as a remedy for thousands of years – must be totally safe, right? Right?

Well… I’ve said it before, but some of the very best horribly toxic things are entirely natural, and neem is yet another example. Ingestion of significant quantities can cause metabolic acidosis (finally, something that really does have the potential to change blood pH! Er… but not… in a good way), kidney failure, seizures, and brain damage in children. Skin contact can cause contact dermatitis. It’s been shown to work as a contraceptive and, more problematically, it’s a known abortifacient (causes miscarriage).

Neem oil is easy to buy, but it needs to be handled with caution

All this said, as always, the dose make the poison.

One case study in the Journal of The Association of Physicians of India reported on a 36-year-old man who swallowed 30–50 ml (about three tablespoons) of neem oil, in the hope of treating the corns on his feet. As far as I can tell, it didn’t help his corns. It did cause vomiting, drowsiness, a dangerous drop in blood pH and seizures. There’s no specific antidote for neem poisoning, but the hospital managed his symptoms. Luckily, despite the hammering his kidneys undoubtedly took, he didn’t need dialysis, and was discharged from hospital after just over a week.

Now, okay, you’re unlikely to accidentally swallow three tablespoons of any oil, especially not neem which does have quite a strong, not entirely pleasant, smell and (reportedly – I haven’t tried for obvious reasons) a bitter taste. But nevertheless, it’s wise to be cautious, particularly around children who have a smaller body mass and therefore are much more likely to suffer serious effects – up to and including death. In one reported case, a mother gave a 3-month-old child a teaspoon of neem oil in the hope of curing his indigestion – fortunately he survived, but not without some seriously scary symptoms.

Nimbin, a chemical found in neem oil, is reported to have all sorts of beneficial effects [image source]

Okay, so those are the dangers. Let’s talk chemistry. The Pakistani organic chemist Salimuzzaman Siddiqui is thought to be the first scientist to formally investigate the various compounds in neem oil. In 1942 he extracted three compounds, and identified nimbidin as the main antibacterial substance in neem. He was awarded an OBE in 1946 for his discoveries.

I will confess, at this point, to running into a little bit of confusion with the nomenclature. Nimbidin is described, in some places at least, as a mixture of compounds (collectively, tetranortriterpenes) rather than a single molecule. But either way, it has been shown to have anti-inflammatory properties – at least in rats.

Another of the probably-mostly-good substances in neem is nimbin: a triterpenoid which is reported to have a whole range of positive properties, including acting as an anti-inflammatory, an antipyretic, a fungicide, an antiseptic and even as an antihistamine. Interestingly, I went looking for safety data on nimbin, and I couldn’t find much. That could mean it’s safe, or it could mean it just hasn’t been extensively tested.

Azadirachtin, another chemical found in neem, is a known pesticide [image source]

The substance that seems to do most of the pesticide heavy lifting is azadirachtin. This is a limonoid (compounds that are probably best known for their presence in citrus fruits). It’s what’s called an antifeedant – a substance produced by plants to deter predators from munching on them. Well, mostly. Humans have a strange habit of developing a taste for plants that produce such substances. Take, for example, odoriferous garlic, clears-out-your-sinuses horseradish, and of course the daddy of them all: nicotine.

Azadirachtin is known to affect lots of species of insects, both by acting as an antifeedant and as a growth disruptor. Handily, it’s also biodegradable – and breaks down in a few days when exposed to light and water.

That makes it appealing as a potential pesticide, and it’s also generally described as having low toxicity in mammals – its reported LD50 tends to fall into the grams per kilogram range, which makes it “moderately to slightly toxic“. Wikipedia quotes a value (without a source, as I write this) of >3,540 mg/kg in rats.

But… I did find another page quoting 13 mg/kg in mice. That’s quite dramatically different, and would make it extremely/highly toxic. Unfortunately I couldn’t get my hands on the original source, so I haven’t been able to verify it’s not a transposition error.

Let’s assume it isn’t. It would be odd to have such a big difference between mice and rats. Things that poison mice tend to poison rats, too. There might be some confusion over pure azadirachtin vs. “neem extract” – it could be the case that the mixture of chemicals working together in neem create some sort of synergistic (toxic) effect – greater than the sum of all the individual substances. It could be an experimental error, including a contaminated neem sample, or something to do with the way the animals were exposed to the extract.

Neem soap is widely available online, but that may not be a good thing…

It’s difficult to say. Well, it’s difficult for me to say, because I don’t have access to all the primary sources. (Any toxicologists out there, please do feel free to weigh into the comments section!) But either way, as I’ve already mentioned, several case studies have fingered azadirachtin as one of the substances likely to be causing the well-reported nasty side effects.

If you’re asking this chemist? I say be careful with the stuff. If you decide to use it on your plants, keep it out of reach of children, and wear some good-quality disposable gloves while you’re handling it (I put some on after I took that photo back there). If you’re pregnant, or trying to become pregnant, the safest option is to not use it at all.

Which brings me to neem soap.

Yup. It’s sold as a “natural” treatment for skin conditions like acne. I won’t link to a specific brand, but it’s easy to find multiple retailers with a simple Google search. I looked at one selling soap bars for £6.99 a pop, containing 10% (certified organic, because of course) neem oil. Did I mention back there that neem is known to cause contact dermatitis? I’m fairly sure I did. None of the products I saw had obvious safety warnings, and I certainly found nothing about safety (or otherwise) for pregnant women.

Plus – worryingly, not least because children are more likely to get things in their mouth – you can also buy kids and babies versions, again purporting to contain 10% neem oil.

I even found neem toothpaste. Which… given people often swallow toothpaste… yikes.

My moth orchids are looking much healthier now I’ve got rid of all the scale bugs!

Now again, and for the umpteenth time, the dose makes the poison. The case studies I’ve mentioned involved, at a minimum, swallowing a teaspoon of pure neem oil, and you’re not getting that sort of quantity from smears of toothpaste. But, at the same time, when it comes to pregnancy and babies, it’s generally sensible to apply a precautionary principle, especially for things like soap and toothpaste for which alternatives with well-established safety profiles exist.

Bottom line? Would I use these products? I would not.

But I do use neem to treat the scale bugs on my orchids, and they’re doing much better than they were. Fingers crossed for more flowers!

Do you want something non-sciency to distract you from, well, everything? Why not take a look at my fiction blog: the fiction phial? You can also find me doing various flavours of editor-type-stuff at the horror podcast, PseudoPod.org – so head over there, too!

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Where did our love of dairy come from?

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The popularity of the soya latte seems to be on the rise.

A little while ago botanist James Wong tweeted about the myriad types of plant ‘milk’ that are increasingly being offered in coffee shops, none of which are truly milk (in the biological sense).

This generated a huge response, probably rather larger than he was expecting from an off-hand tweet. Now, I’m not going to get into the ethics of milk production because it’s beyond the scope of this blog (and let’s keep it out of the comments? — kthxbye) but I do want to consider one fairly long thread of responses which ran the gamut from ‘humans are the only species to drink the milk of another animal’ (actually, no) to ‘there’s no benefit to dairy’ (bear with me) and ending with, in essence, ‘dairy is slowly killing us‘ (complicated, but essentially there’s very little evidence of any harm).

Humans have been consuming dairy products for thousands of years.

But wait. If dairy is so terrible for humans, and if there are no advantages to it, why do we consume it at all? Dairy is not a new thing. Humans have been consuming foods made from one type of animal milk or another for 10,000 years, give or take. That’s really quite a long time. More to the point (I don’t want to be accused of appealing to antiquity, after all), keeping animals and milking them is quite resource intensive. You have to feed them, look after them and ensure they don’t wander off or get eaten by predators, not to mention actually milk them on a daily basis. All that takes time, energy and probably currency of some sort. Why would anyone bother, if dairy were truly detrimental to our well-being?

In fact, some cultures don’t bother. The ability to digest lactose (the main sugar in milk) beyond infancy is quite low in some parts of the world, specifically Asia and most of Africa. In those areas dairy is, or at least has been historically, not a significant part of people’s diet.

But it is in European diets. Particularly northern European diets. Northern Europeans are, generally, extremely tolerant of lactose into adulthood and beyond.

Which is interesting because it suggests, if you weren’t suspicious already, that there IS some advantage to consuming dairy. The ability to digest lactose seems to be a genetic trait. And it seems it’s something to do, really quite specifically, with your geographic location.

Which brings us to vitamin D. This vitamin, which is more accurately described as a hormone, is a crucial nutrient for humans. It increases absorption of calcium, magnesium and phosphate, which are all necessary for healthy bones (not to mention lots of other processes in the body). It’s well-known that a lack of vitamin D leads to weakened bones, and specifically causes rickets in children. More recently we’ve come to understand that vitamin D also supports our immune system; deficiency has been meaningfully linked to increased risk of certain viral infections.

What’s the connection between vitamin D and geographic location? Well, humans can make vitamin D in their skin, but we need a bit of help. In particular, and this is where the chemistry comes in, we need ultraviolet light. Specifically, UVB – light with wavelengths between 280 nm to 315 nm. When our skin is exposed to UVB, a substance called 7-dehydrocholesterol (7-DHC to its friends) is converted into previtamin D3, which is then changed by our body heat to vitamin D3, or cholecalciferol – which is the really good stuff. (There’s another form, vitamin D2, but this is slightly less biologically active.) At this point the liver and kidneys take over and activate the chloecalciferol via the magic of enzymes.

We make vitamin D in our skin when we’re exposed to UVB light.

How much UVB you’re exposed to depends on where you live. If you live anywhere near the equator, no problem. You get UVB all year round. Possibly too much, in fact – it’s also linked with skin cancers. But if you live in northerly latitudes (or very southerly), you might have a problem. In the summer months, a few minutes in the sun without sunscreen (literally a few minutes, not hours!) will produce more than enough vitamin D. But people living in UK, for example, get no UVB exposure for 6 months of the year. Icelanders go without for 7, and inhabitants of Tromsø, in Norway, have to get by for a full 8 months. Since we can only store vitamin D in our bodies for something like 2-4 months (I’ve struggled to find a consistent number for this, but everyone seems to agree it’s in this ballpark), that potentially means several months with no vitamin D at all, which could lead to deficiency.

In the winter northern Europeans don’t receive enough UVB light from the sun to produce vitamin D in their skin.

In the winter, northern Europeans simply can’t make vitamin D3 in their skin (and for anyone thinking about sunbeds, that’s a bad idea for several reasons). In 2018, this is easily fixed – you just take a supplement. For example, Public Health England recommends that Brits take a daily dose of 10 mcg (400 IU) of vitamin D in autumn and winter, i.e. between about October and March. It’s worth pointing out at this point that a lot of supplements you can buy contain much more than this, and more isn’t necessarily better. Vitamin D is fat-soluble and so it will build up in the body, potentially reaching toxic levels if you really overdo things. Check your labels.

Oily fish is an excellent source of vitamin D.

But what about a few thousand years ago, before you just could pop to the supermarket and buy a bottle of small tablets? What did northern Europeans do then? The answer is simple: they had to get vitamin D from their food. Even if it’s not particularly well-absorbed, it’s better than nothing.

Of couse it helps if you have access to lots of foods which are sources of vitamin D. Which would be…  fatty fish (tuna, mackerel, salmon, etc) – suddenly that northern European love of herring makes so much more sense – red meat, certain types of liver, egg yolks and, yep, dairy products. Dairy products, in truth, contain relatively low levels of vitamin D (cheese and butter are better than plain milk), but every little helps. Plus, they’re also a good source of calcium, which works alongside vitamin D and is, of course, really important for good bone health.

A side note for vegans and vegetarians: most dietry sources of vitamin D come from animals. Certain mushrooms grown under UV can be a good source of vitamin D2, but unless you’re super-careful a plant-based diet won’t provide enough of this nutrient. So if you live in the north somewhere or you don’t, or can’t, expose your skin to the sun very often, you need a supplement (vegan supplements are available).

Fair skin likely emerged because it allows for better vitamin D production when UVB levels are lower.

One thing I haven’t mentioned of course is skin-colour. Northern Europeans are generally fair-skinned, and this is vitamin D-related, too. The paler your skin, the better UVB penetrates it. Fair-skinned people living in the north had an advantage over those with darker skin in the winter, spring and autumn months: they could produce more vitamin D. In fact, this was probably a significant factor in the evolution of fair skin (although, as Ed Yong explains in this excellent article, that’s complicated).

In summary, consuming dairy does have advantages, at least historically. There’s a good reason Europeans love their cheeses. But these days, if you want to eat a vegan or vegetarian diet for any reason (once again, let’s not get into those reasons in comments, kay?) you really should take a vitamin D supplement. In fact, Public Health England recommends that everyone in the UK take a vitamin D supplement in the autumn and winter, but only a small amount – check your dose.

By the way, if you spot any ‘diary’s let me know. I really had to battle to keep them from sneaking in…

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