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Rapid response to:

Clinical Review

Genetically modified foods

BMJ 1999; 318 doi: https://doi.org/10.1136/bmj.318.7183.581 (Published 27 February 1999) Cite this as: BMJ 1999;318:581

Rapid Response:

GM foods and the Pusztai affair

Editor,

In the Clinical Review by Leighton Jones (1) it is implied
that Dr Pusztai's experiments had only tested the effects
of potato spiked with ConA lectin. It was the initial
dissemination of this incorrect information followed by the
inappropriate suspension of Dr Pusztai and the implied
fraud that was suggested by the institution of an audit
according to MRC guidelines that led myself and other
scientists to allow our names to be included in the
memorandum defending Dr Pusztai, whom we know to be an
honourable and careful scientist. It is clear from the
report of the Audit conducted at the Rowett Institute in
August 1998, and so far only incompletely released
(http://www.rri.sari.ac.uk/press), that experiments
involving transgenic potatoes containing the gene for the
snowdrop lectin (GNA) had already been performed at the time
of Dr Pusztai's World in Action television interview. If the
Rowett Institute had simply released a statement that the
work was preliminary and allowed the work to continue it is
unlikely that such a potentially damaging media storm would
have resulted.

There has been little clarity surrounding the subsequent
media debate and this situation has unfortunately been
exacerbated by some misleading statements from fellow
scientists.

Firstly: not all lectins are toxic. They are ubiquitous
carbohydrate-binding proteins. All mammalian cells and
blood and all plant nuts, seeds and bulbs, including many
non-toxic food components contain lectins (2). Some of
these, red kidney bean lectins for example, are toxic and
need to be destroyed by heat before consumption but others
such as tomato lectin are apparently harmless when eaten
raw. Some of these food lectins have very interesting
biological effects - our group has recently reported the
selective inhibition of
nuclear-localising-sequence-dependent nuclear protein
import by the common edible mushroom lectin which we often
eat raw (3). Many of these plant lectins serve an
insecticidal or antifungal role in the plant. The snowdrop
lectin (GNA) binds to mannose which is minimally expressed
in mammalian intestine but extensively expressed in the
intestine of sap-sucking insects. It is therefore
plausible that expression of this lectin in food plants
might render them unattractive to insects but safe for
human consumption, particularly if the food (potato) is
always cooked before ingestion.

Secondly: the experiments performed by Dr Pusztai, whatever
their results, would not imply that all genetically modified
foods were unsafe. The message which Dr Pusztai was trying
to put across was simply that such foods require very
careful testing. As with the testing of new pharmaceuticals,
some such transgenic foods will prove toxic or otherwise
unsatisfactory and be discarded at an early stage of
development.

Thirdly: the fact that Dr Pusztai has been barred from
continuing his experiments since the time of his initial
suspension has resulted in a very unsatisfactory situation
in which his data although interesting remain preliminary
and further experimentation will probably need to be done
before any final conclusions can be drawn about the effects
of the transgenic GNA potato or its promoter.

One lesson to be learnt from this episode is that all
scientists need to be careful to ensure that their comments
serve to inform rather than confuse when handling issues
that carry such extreme public interest.

Jonathan M Rhodes

Professor of Medicine,
University of Liverpool,
rhodesjm@liverpool.ac.uk,
tel 0151 706 4073,
fax 0151 706 5802

1. Jones L. Genetically modified foods. Science, medicine, and the future. Clinical Review. British Medical Journal 1999, 318:581-84.

2. Rhodes JM. Beans means lectins. Commentary. Gut 1999 in press.

3. Yu L-G, Fernig DG, White MRH, Spiller DG, Appleton P, Evans RC, Grierson I, Smith JA, Davies H, Gerasimenko OV, Petersen OH, Milton JD, Rhodes JM
Edible mushroom (Agaricus bisporus) lectin, which reversibly inhibits epithelial
cell proliferation, blocks Nuclear Localization Sequence-dependent nuclear protein
import. J Biol Chem 1999; 274: 4890-99.

Competing interests: No competing interests

05 March 1999
Jonathan M Rhodes