Can watermelon seeds germinate inside your stomach?

Monday, July 10, 2006
When you were a youngster, did your mum tell you to eat the watermelon but to leave the seeds out or they will grow in your stomach?

But everyone knows it's almost impossible to eat a juicy watermelon and avoid every single seed — therefore eating melons has become a nervous adventure.

It's 92 percent water and by the looks of things, 92 percent seeds. But watermelon is basically a multivitamin in itself, full of vitamins A, B6 and C. We humans have also been chomping on watermelons for over 5000 years, but does this gigantic fruit harbour a dark secret?

What if some of the seeds got stuck inside and germinated? It's a horrific thought, imagine, a crop of fruit growing in your stomach? It's a theory that's been doing the rounds for a while, so our reporter Michael Slater wants to find out the inside information — literally.

As part of his mission, Michael's going to take a journey deep inside his stomach. He visits Dr Katie Ellard, a gastroenterologist, who has just the gadget for the job.

Now what you need to do is swallow a small capsule … and what this will do over eight hours is transmit pictures from inside your stomach and small bowel," says Dr Ellard.

What Michael will swallow is called a pill cam. A tiny camera that will film the journey a seed would normally make through his stomach, while a computer stores the images.

Eight hours later …

Michael returns to see what's really inside his stomach.

"The stomach is where the food initially gets mixed up with the acid, and then it goes into the small bowel where the calories are absorbed," says Dr Ellard.

The camera travels into the hydrochloric acid into Michael's stomach and then the alkali in his small bowel. The PH shows the strength of the acid or alkali. It takes around 24 hours for a seed to pass through the seven-and-a-half metres of stomach.

Michael also wants to do his own experiment, so to get some help he calls in the big guns: a year eight science class.

First, Michael needs the seeds, so a heavy-duty watermelon chow-down is needed.

First sample
The first sample will be a seed put into a couple of solutions to mimic the conditions in the stomach and digestive system.

The seed first has some hydrochloric acid mixed with water poured on top of it in a beaker. This has a PH level of approximately one to mimic the stomach. The seed will stay in the beaker for four hours, which is roughly how long it will take before any food can travel through the stomach.

Afterwards the seed heads into the small intestine. So to mimic that, the seed is transferred to a solution of sodium bicarbonate and water (with a PH level of approximately 7.5).

Second sample
Another sample will mimic normal growing conditions — cotton wool soaked in water.

Both samples are placed in a darkened room for 24 hours to see if they sprout.

First up, the sample left in an alkali solution that mimicked the stomach's conditions is put under a magnifying glass. There are no changes whatsoever, no germination taking place. This is exactly the same result with the seeds on damp cotton wool.

So as we're clear on all counts, it's safe to say that watermelon seeds are not going to germinate in our stomachs.

But why didn't the seeds sprout? Dr Gordon Rogers is a horticultural expert at the University of Sydney. He conducts research to assist farmers produce higher and better quality watermelon yields, so he's the green thumb when it comes to watermelons.

The seeds need three things to germinate. They need moisture, they need the right temperature range, they need oxygen," he says.

Well here's another revelation from Michael's pill camera experiment. In the dark gurgling depths of his stomach there is no oxygen. So a seed could never grow there.

But what about the other sample on the cotton wool? For seeds to actually start producing the shoot they usually take about three to five days. Therefore, the second sample eventually sprouted after six days. And the timing is all part of the watermelon's clever plan for survival.

"The whole purpose really of the watermelon fruit is for seed dispersal," says Dr Rogers. "And the idea is that the animal, the hope that the animal eats the fruit in one place then deposits the seed somewhere else and so spreads the plant species into new areas. So they're really designed to pass through the animal's gastrointestinal tract intact."

So watermelons aren't bad, they want to be loved. Some cultures even roast them before eating as they're full of amino acids that are very good for you.

But if you're still not convinced, there's a simple solution to worry-free watermelon eating — just choose the seedless variety!

  • We're used to watermelons looking like giant soccer balls, but have you ever seen a square shaped one? In Japan they grow melons inside glass boxes to make the fruit square. Why? Because they're easier to stack — but they're also double the price.

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