Why Pregnant Rats Should Avoid Apples

By Jim McVeagh 12/02/2011

No, that’s not what the headline was on the front page of the Weak-end Herald today – it was considerably more alarmist:

Fruit juice, apples linked to fetus harm

An expectant mother could be putting her unborn child at risk by drinking as little as three glasses of juice a day or eating five apples.

Scientists at the University of Auckland’s Liggins Institute have found a connection between sugars such as fructose and impaired fetal development.

You only learn that this study involved rats in paragraph seven

Now, I’m not one of those strange people who think that animal studies are a waste of time. Rats are useful little creatures in experimental research. Their physiology is reasonably similar to a human’s. They have short life cycles, meaning we can easily work out if their lives are shortened by our experiments. And, in general, animal rights people do not go all gooey over them because they are not endangered and not cute. This means that scientists can do relatively disgusting things with rats that they could not do with dogs, cats or chimps. Above all, working with rats is relatively cheap.

However, rats are not humans. This means that a result we obtain experimenting on rats really does need to be verified in humans. You can’t just extrapolate.

In the study in question, (Vickers MH, Clayton ZE, Yap C, and Sloboda DM  Maternal Fructose Intake during Pregnancy and Lactation Alters Placental Growth and Leads to Sex-Specific Changes in Fetal and Neonatal Endocrine Function Endocrinology 152: 0000—0000, 2011 – publication ahead of print), the female offspring of pregnant rats fed a diet of 20% fructose had raised plasma leptin, fructose, and blood glucose levels at birth indicating a possible predisposition to both obesity and, eventually diabetes. This sounds considerably less scary than 5 apples a day (the equivalent of 20% fructose) is linked to fetal harm.

Similar results have been obtained before in rat studies but this particular study models a more “normal” consumption level of fructose (previous studies were of 50% and higher levels of fructose in the diet). While this is certainly something that needs further study, we are a long way from extrapolating this to humans. It may be that rats are particularly sensitive to fructose in their diet, or that they are not as efficient as humans in metabolising it. It may be that the source of the fructose is important, with apple consumption being better than drinking fructose-laden corn syrup. There are many factors that could lead to an entirely different result in humans.

The authors of the study cite a Finnish cohort study that found that an increase in sugar- sweetened beverages from childhood to adulthood was associated with being overweight in women but not men, bolstering the sex specificity of their findings but not otherwise adding to the idea that fructose may case metabolic problems in children. There are plenty of other studies ably demonstrating that excessive sugar consumption in childhood and adolescence predisposes people to develop diabetes in adulthood. There are plenty of reasons to moderate our sugar intake. But to blindly suggest that pregnant woman maybe putting their babies at risk by eating fruit is dubious in the extreme. Unfortunately that is exactly the message that mums will get from this article. After all, it’s on the front page. It must be important.

I can understand the desire of researchers to get their research in the news. Generate enough concern about something and you guarantee that you will get sufficient funding to continue the research to the next level. But this type of premature ejaculation of scientific results panders to excitable journalists looking for sensational headlines and predisposes them to generate messages that are entirely unhelpful, if not dangerous. I can guarantee you I am going to be spending valuable consultation time with pregnant women explaining why it is safe to eat apples, rather than spending it addressing their real concerns. Worse still, there will be pregnant women who stop eating fruit altogether, putting themselves at possible risk of vitamin deficiencies.

And all because scientists want funding and journalists want headlines. How sad.


Related posts:

  1. Comparing Apples with Frogs
  2. Vitamin Victims?
  3. Just Don’t Look at My Liver

0 Responses to “Why Pregnant Rats Should Avoid Apples”

  • I thought much the same as you – that it was a particularly poor, alarmist piece of reporting. But I’d want to see the original press release before slating the scientists concerned; it could well be the press that have got all overwrought with this, rather than the researchers. If it _was_ the latter, then they need some serious media training…

    • Fair enough. Although the quotes from Dr Deborah Sloboda in the newspaper article indicate that she was certainly “fanning the flames” as it were.

  • Ah, Jim McVeigh jumping in again 🙂

    Those who want to read the abstract for themselves, the link is:


    The full article is subscription only.

    Leaving aside criticism of the research (I haven’t time to read it yet), I’d be wary of jumping in and pinning the resulting media report on the researchers in quite the way that you have. The journalist and editor have roles in getting this to print too. There are plenty of examples of researchers having their results over-generalised presented in an over-reaching manner, etc. in the media (not necessarily intentionally – sometimes problem is simply that science really wants specialist writers).

    Although the quotes from Dr Deborah Sloboda in the newspaper article indicate that she was certainly “fanning the flames” as it were.

    Not necessarily. You’re reading the final article, not what happened during the interview.

  • Jumping in is what I do best, Grant 🙂

    I don’t have any great criticism of the research (I have read the full article – access to the Uni library is a wonderful thing). It seems solid enough – though endocrinology is an obscure subject to me.

    While I don’t think Dr Slobada was saying anything like the final slant of the journalist, I do think she was not as cautious as she should have been – judging from the quotes in the article. Journalists are excitable creatures and we should be more cautious when talking to them.

  • It appears that the distinction between fructose in natural foods like apples etc and fructose used to sweeten highly-processed foods went out the window during the editing stage at the Herald, hence the focus in the headline and intro on apples and fruit juice. Currently trying to figure out a way at the Science Media Centre to work with media companies to try and cut down on these editing abortions on science-related stories, but it is very tricky, especially given the outsourcing of sub-editing functions for the newspapers… the SMC in the UK is trialing a new service Before the Headlines, which involves an expert issuing an analysis of new research that goes to journalists as the research is released…