Horizon’s Longitude Prize episode: overselling the benefits of GM crops and fish oil

Horizon’s recent Longitude Prize episode discussed interesting research using Genetically Modified (GM) crops to make omega 3 fish oil (not found naturally in plants). Horizon stated that fish oil is “thought to protect against…cancer”. This surprised me, so I asked Longitude Prize for the source of Horizon’s fish oil claims. The sources they provided aren’t adequate to support the claims made – Horizon oversold the benefits of fish oil and of GM crops that produce it.

The Longitude Prize helpfully responded to my questions by tweeting that the sources of Horizon’s fish oil claims were Danaei et al.’s PLOS Medicine article and Frank Sack’s article on Harvard’s website, but these sources don’t adequately support the claim that fish oil protects against cancer. The Danaei et al. article isn’t relevant to this claim*, while Sack’s article does not adequately support it because:

  • Sack states that “New studies are identifying potential benefits for…cancer”. This is very different from fish oil being thought to protect against cancer – small studies have reported cancer risks or benefits for so many foods that Schoenfeld and Ionnidis find that “cancer risk or benefits have been claimed for most food ingredients”. Some of these risks/benefits will be found to be significant when larger studies are done, but many won’t.
  • Sacks’ article is discussing ALA (found in things like rapeseed oil) as well as the EPA and DHA found in oily fish. There is no need to use GM crops in order to get the benefit of eating ALA – for example, the cheap veg oil in my cupboard is a good source of this fatty acid.
  • Relying on the opinion of a single expert – as posted on a university website – isn’t particularly robust, even where the expert is very well-respected. There is plenty of published, peer-reviewed research on fish oil and I would have hoped Horizon could have drawn on this.

Overselling the benefits of a GM crops matters. Research suggests that a lack of perceived benefits is an important aspect of public rejection of GM crops. It also appears that trust is important in shaping public attitudes to GM foods (and to public assessment of their benefits). Those of us who support research in this field should push for a robust account of the actual and potential benefits of GM crops – overselling the benefits like this is not good public engagement.

* The article does not attribute any reduction in cancer deaths to fish oil consumption – see Fig. 1. It does argue that fish oil reduces deaths from cardiovascular causes (which supports another claim in that Horizon show).

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