Scientists have previously shown that nanoparticles of the carbon black type, which can be found in printer toners and certain foods, cause DNA damage in the liver – which increases the risk of cancer. A new study now suggests that nanoparticles in the stomach and the intestines, possibly from foods with black colourants, are also bad for our blood vessels. (Photo: Colourbox)

Nanoparticles travel through the stomach and intestines

Nanoparticles impair blood vessels’ ability to change size – a precursor to arteriosclerosis. Surprisingly, they not only affect the lungs, but they also travel through the stomach and intestine – and thus possibly through food too.

Thomas Hoffmann

Published 25 October 2012 - 06:21

It may not be such a great idea to consume activated carbon to reduce your flatulence or your hangovers.

Activated carbon contains the widespread nanoparticle known as carbon black, which is also used in various forms as a colourant in tyres, printer toners and food.

Carbon black now appears to affect blood vessels in rats – not just through inhalation, which scientists have known for a long time, but also through the stomach and the intestines.

"We can see that the blood vessels become less able to expand. The effect is located on the innermost layer of the blood vessels, and that’s actually very critical. This makes it difficult to control the blood flow, and it’s typically an early sign of arteriosclerosis," says Peter Møller, a professor of environmental medicine at the Department of Public Health, University of Copenhagen.

Still unclear how nanoparticles travel from bowel to body

Nanoparticles come in many different shapes and sizes, but common to them all is that they are all smaller than 0.000000001 metre.

Scientists have known for a while that nanoparticles, just like particles in air pollution, can affect our body when we breathe them into our lungs.

But this is the first time that a study proves the likelihood of nanoparticles also affecting us through the stomach and the intestines.

“We don’t really know why it happens, but that’s something we’re aiming to study further,” says Møller.

Carbon black also present in candy

We’re exposed to various types of carbon black particles from a host of everyday products ranging from makeup and activated carbon, which is available over the counter in pharmacies to fight flatulence and hangovers, to food and black candies such as Turkish Pepper.

Carbon black in foods

The researchers have repeatedly applied for funding to study the effect that nanoparticles in food have on humans. But without luck.

It’s possible that carbon black is present in all black-coloured foods that contain E153. According to Peter Møller, a ‘food version’ of carbon black appears to be slightly less harmful than the ‘printer toner version’, which was used in the new study.

He is, however, keen to point out that the measurements are inconclusive, and that it’s very difficult to find studies of how humans react to foods with nano content.

It’s also unclear exactly which particles are used in foods, and for that reason he cannot substantiate the consequences of eating foods with added E153.

The professor does, however, point out that the study was made with a carbon black particle that is primarily found in printer toners.

Since carbon black nanoparticles are made in a variety of ways and come in various shapes and sizes, it’s not certain that the new findings can be said to apply to carbon black in other products such as Turkish Pepper and other foods in which carbon black is represented by the name E153.

“We have only studied a single particle, so we cannot generalise. But if you’re presented with the choice between a product with nano and one without and you worry about the health implications, then it makes sense to pick the product with no nanoparticles,” says the professor.

Findings are likely to apply to humans

Møller and his research team carried out their experiments on so-called Zucker rats, which are said to be particularly good models for how the human body can be affected in the direction of serious diseases such as diabetes and cardiovascular diseases.

It’s always tricky to transfer results from animal studies directly to humans. However, when it comes to how nanoparticles affect our bodies, there is good reason to believe that we respond in the same way as rats.

“We have clearly seen similar effects in the lungs of laboratory animals, and we can also see that people exposed to air pollution lose their ability to dilate their blood vessels,” he says.

“This provides us with a direct correlation, which makes it likely that the particles may have a dangerous intrinsic property in humans.”

Harmful effect vanished with the nanoparticles

The study, published in the journal Toxicological Sciences, shows that a single dose of carbon black in the stomach or intestines has no effect on rats. But ten doses over a ten-week period affected the blood vessels’ ability to regulate their own size.

When the researchers removed the particles and examined the rats again after 13 weeks, the effect had disappeared.

The result corresponds perfectly with the researchers’ own expectations, based on previous studies with nanoparticles in animal lungs.

Does carbon black affect intestinal bacteria?

However, when it comes to explaining how the nanoparticles affect our bodies through the stomach or the intestines, the researchers still have some way to go.

“We have some theories, ranging from the particles being absorbed in the body to the particles creating a kind of inflammation of the gastrointestinal tract, and thereby affecting the whole system,” he says.

“It’s also possible that the particles cause the intestinal bacteria to release toxic substances, but that’s something we would like to take a closer look at in the future.”

The team has backed up these findings in another study, published in the journal Toxicology Letters. This study takes a more detailed look at what happens at the cellular level when animals are exposed to nanoparticles through the stomach or the intestines.

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Read the Danish version of this article at videnskab.dk

Translated by: Dann Vinther