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There is very little evidence that deodorants are linked to breast cancer

A few years ago, an email started bouncing around the Web, claiming that underarm deodorant use caused breast cancer. Over the years this has caused widespread anxiety, as seen here by the volume of inquiries to our cancer information helpline from women worried about their risk of developing cancer.

We get so many inquiries, we even wrote a page about the email on CancerHelp UK.

A large part of the supposed evidence for this idea comes from a single laboratory that investigated the claim, and which continues to assert that deodorants might cause breast cancer, despite mounting evidence to the contrary.

This group’s thinking starts with the observation that slightly more breast cancers occur in the ‘upper outer’ region of the breast – the bit near the armpit. This, they speculate, is a sign that exposure to deodorants might cause this difference.

Their work has focused on several components of deodorants. One of them, the aluminium salts, are a key ingredient of most underarm sprays and roll-ons.

In laboratory tests, aluminium has been found to be a weak oestrogen mimic, and to be able to interact with DNA. There is weak evidence, from laboratory studies, that it might cause cancer. But a huge leap to say that, just because you see something happening in cells in a lab, it also occurs in living, breathing human beings.

This week a new piece of research, also carried out in part by the team, supposedly adds new evidence to the aluminium/breast cancer story.

But does it?

The paper looked at the aluminium levels in breast tissue samples taken from 17 breast cancer patients.

In each case, a series of samples was taken from different regions of the breast. The researchers found that levels of aluminium were ‘significantly’ raised in breast tissue nearer the skin.

They didn’t look at aluminium levels in the breast compared to other parts of the patients’ bodies.

They didn’t look at aluminium levels in the patients compared to people without cancer.

They didn’t reference their results against any ‘accepted’ or ‘safe’ level of aluminium in humans.

In short, they didn’t have any ‘control’, or reference point, against which to judge their results.

Based on their findings, they concluded:

“We have confirmed the presence of aluminium in breast tissue and its possible regional distribution within the breast. Higher content of aluminium in the outer breast might be explained by this region’s closer proximity to the underarm where the highest density of application of antiperspirant could be assumed.” (Emphasis ours).

You can see for yourself the degree of speculation in their conclusions.

Interestingly, the fact that more cancers occur nearer the armpit can be explained by basic biology – there is just more breast tissue there. More tissue = more cells. More cells = more things that can go wrong = higher chance of a cancer developing.

Now let’s look at another type of evidence – population-based studies that look at large numbers of people. One such study, in 2002, looked at 1,600 women. It found no increase in breast cancer risk in the women on the study who regularly used deodorants.

Other large population studies, as we’ve said before on this blog, have uncovered other things that do clearly affect a woman’s risk of breast cancer.

But these turn out to be either things beyond a person’s control, such as the age a woman starts and finishes her periods; or things she’d rather not change, such as how many children she has or whether she takes HRT to control menopausal symptoms.

Nevertheless, we all understandably want to ‘do’ something about our cancer risk, and know more about how our environment affects it. So when papers come out such as this one, which holds up the spectre of ‘things in the environment’ that we don’t really understand, we tend seize on them, and worry.

But when you look at all the evidence, the ‘controllable’, non-genetic causes of breast cancer are, in the main, fairly mundane things to do with modern childbirth and reproductive cycles. In short – our modern western family patterns are responsible. And we don’t really want to change them.

There are, though, a few everyday things that a woman can do that slightly reduce her breast cancer risk, that are based on sound, validated science.

And

But really – other than how they smell, and whether that’s an improvement on how you smell – don’t worry too much about the chemicals you spray under your arms.

Henry

Comments

Ed August 31, 2007

You just know that he spent as long writing the headline as the post…

Kat August 31, 2007

Terrible pun, Henry!