The crunchy truth: health risks, myths and misinformation about eating clay

If you’ve spent any time in pica or geophagy circles, you’ll know there’s no shortage of “facts” floating around. Some are spot on, others are harmless old wives’ tales… and a few are completely wrong, yet still get shared around like gospel.

When you’re mid-craving, it’s tempting to cling to anything that makes you feel better about giving in. But bad information spreads quickly in these spaces, and once it’s been repeated enough times, it starts sounding true. That’s where the problem is. If people are going to enjoy clay or chalk, it’s worth doing it with clear eyes and a bit of common sense.

This isn’t about spoiling anyone’s fun. It’s about making sure you actually understand the risks so you can make informed choices. Your cravings aren’t going anywhere, so you may as well learn to enjoy them safely.

Myth 1 – Eating chalk causes Calcium Deficiency

No, it doesn’t. If you’re craving chalk (calcium carbonate) or pale clays, it’s usually because your body is already low in calcium. The craving comes first, the deficiency is already there – it’s not the clay causing the problem.

Low calcium can happen for all sorts of reasons: pregnancy, breastfeeding, hormonal changes, kidney issues. If you suddenly start dreaming about a good chalk crunch, it’s worth getting your calcium and vitamin D levels checked before you tuck in. Eating chalk isn’t going to cause the deficiency, but it’s not going to fix the root issue either if your body can’t absorb calcium properly.

Myth 2 – Eating clay gives you Anaemia

Same story here. If you find yourself drawn to deep reds and browns – terracottas, red nakumatts, red khadi – you’re probably craving the iron oxide in them because your body is already low in iron.

Here’s the twist: some clays can actually make anaemia worse. The highly absorbent ones, like white khadi, can bind to nutrients in your gut and stop your body taking in the iron it needs. I stopped eating white khadi for that exact reason – it was dragging my iron levels down. If you’re anaemic, keep a note of what you eat and how you feel afterwards. It’s an easy way to spot which clays work with your body and which don’t.

Constipation – the oldest side effect in the book

Clay has been used for thousands of years to stop diarrhoea, and it does a brilliant job of firming things up in the gut. The trouble is, if you have too much, you’ll be sitting there regretting it. If you’re getting blocked up regularly, you’re overdoing it. Slow down, drink more water, and let your digestive system catch up.

Worms, Ebola and Other nasties

Parasites aren’t a huge risk, but they can happen – especially if the clay’s been dug from areas where animals have been. If you forage your own, stick to clean areas and get it tested if you can.

Ebola’s not a common issue in most places, but in certain parts of Africa, outbreaks have been linked to handling or eating contaminated natural products. Knowing exactly where your clay comes from matters.

Other things to keep in mind

• Yeast infections: Not common, but possible if over-consumption affects your body’s pH balance
• Heavy periods: Some people find that clay cravings increase around their period, especially if they’re already low in iron. Overindulging in certain clays can make iron absorption trickier, so keep an eye on how your body responds during this time.
• Fibres and grit: Poorly processed clays can have plant fibres or small hard particles that irritate the gut
• Toxins and trace metals: Pavement chalk, school chalk, coloured chalk – they might say “non-toxic” but that doesn’t mean “edible.” They can contain binders, dyes or fillers you don’t want in your body
• Mental health myths: Pica isn’t a mental illness. People (and animals) have been doing this for thousands of years. Sometimes it’s about nutrients, sometimes it’s purely sensory. Both are fine
• Autism and sensory differences: Some people on the autism spectrum experience heightened sensory cravings, including for textures and tastes like clay or chalk. This isn’t a mental illness or a problem – it’s just part of how some brains experience the world. Paying attention to texture, crunch, and taste is normal, and enjoying clay safely is possible with awareness of limits.

Know what you’re swallowing

Not all clays behave the same way once they’re in your stomach. Some dissolve quickly, others take their sweet time. AJ Clays once explained this perfectly – raw clays break down faster, shale stone is slower, and slate pencils can take much longer. The slower it breaks down, the longer it sits there, which isn’t always comfortable. If you’re going to swallow, know what you’re dealing with.

Finding your limit

For me, it’s no more than a tablespoon a day. That’s just my personal cut-off. I’m lucky – I can check my bloods at home thanks to my NHS training, so I know when something’s affecting me. Most people can’t do that, so keep your amounts small and give yourself breaks.

Remember, eating clay in small, mindful amounts is not going to kill you. The key is understanding your limits and paying attention to how your body reacts.

If you’re going to crunch, do it safely

1. Stick to trusted, reliable vendors

2. Avoid swallowing large amounts, especially of slow-breakdown clays like slate pencils

3. Learn about the source and processing before you try something new

4. Pay attention to how different clays affect you

5. Don’t beat yourself up – pica is ancient and natural. Just keep it within your limits

Cravings are your body’s way of speaking. Listen to them, but make sure you’re looking after yourself at the same time. The best crunch is the one that satisfies you without sending you to the doctor afterwards.