Tiago Villanueva: Quaternary prevention and disease mongering

Tiago_VillanuevaOne of the major advantages of being an active member of listservers, particularly international ones, is that I am in touch with leading colleagues around the world, and also I can learn about issues and think in ways that I would not otherwise have become aware of. I’ve had the chance to cross paths a few times with Dr Juan Gérvas, a towering figure of international general practice based in Spain, and a professor of primary care, public health, and management at several Spanish universities.

Participating in his primary care innovation seminars and doing a rotation with him in Madrid were some of the highlights of my general practice vocational training program, and we keep in touch regularly since we are members of several general practice listservers in Portugal, Spain, and Brazil. I often learn a lot from Dr Gérvas’s posts on the listservers regarding subjects such as health services research in primary care or limits to the power of medicine (prevention of too much medicine, errors, limits of screening), which are some of his main scientific topics of interest. He is very interested in quaternary prevention (the need to protect patients from unnecessary and potentially harmful medical intervention), and he recently co-authored a very interesting article about it in a swiss primary care journal.

Furthermore, an issue that caught my eye thanks to a message posted by Dr Gérvas on the listservers were the recent findings from a Spanish research group that iodine supplements in pregnancy could be potentially harmful to both the mother and the fetus. I had the chance afterwards of debating this issue with him personally via email, and with his permission, I reproduce below the electronic discussion I had with him, and invite you to draw your own conclusions.

Tiago: Juan, do you have any idea of how widespread the practice of recommending systematic iodine supplementation early in pregnancy is, even in areas considered iodine sufficient for the general population such as the US? Textbooks,  guidelines, and protocols concerning pre-natal care always mention the importance of supplements of folic acid, and eventually, iron, but there’s usually much less talk about iodine supplementation.

So, are we actually talking about a “current common practice?” Is this practice perfectly avoidable? If so, why?

Juan: Supplements of folic acid might make sense only in the first stages of pregnancy, i.e. the first 21 days before the neural tube is closed. Even then, we do not know the exact mechanism of action (not excluding, teratogenia and the increase of abortion of “errors”). Supplements of iron are generally not indicated, and its use is not recommended. With supplements of iodine, just have a look on the internet and see how many “advocates” are around the world, from New Zealand and Australia, to Poland and Spain. In Spain it is common practice to recommend supplements of iodine to pregnant women. It is a practice with no scientific basis in countries and regions that ensure sufficient iodine for the general population.

Tiago: The author’s 2010 results show potential harm for the mother, [1] while the 2011 results show potential harm for the fetus. [2] Is it still too early or premature to talk about disease mongering?

Juan: The first results of the Spanish group (Rebagliato et al) were published in 2009. They confirm in 2010 the previous findings about worse outcomes in pregnancy, [1]  but their interest in iodine supplements started in the early 2000 with the INMA project (Infancia and Medio Ambiente, Environment and Childhood) (3,4). In 2011 they confirm their previous findings about the potential harm of iodine supplements in  pregnancy.[2] We can speak, no doubt of disease mongering, in this case helping to transform “normal” pregnancy into a “disease” that should be under the care of specialists.

Tiago: The authors (Rebagliato et al) have said that the 2011 results corresponded to “the first known report of a potentially deleterious effect of maternal consumption of multivitamins containing iodine during pregnancy on psychomotor achievement in infants” and that “these results should be evaluated with caution.” [2] In the meantime, what should we tell our patients at the practice?

Juan: Rebagliato et al indeed started their work to support the supplements of iodine. So their findings were a surprise, even for them. They are scientific and ask for caution. They recommend that women in general, and during pregnancy, eat healthy diet which help them to enjoy life and obtain the nutrients they need. Healthy means fruit, vegetables, fish, meat,  olive oil and so on (the Mediterranean diet).

Tiago: This is a cohort study, so we’re likely to see more results in 2012. In your opinion, what else could we still expect?

Juan: I guess we can expect confirmation of the previous findings.

Tiago Villanueva is a newly qualified general practitioner and former BMJ Clegg Scholar and editor, studentBMJ


1. Iodine intake and maternal thyroid function during pregnancy.
Rebagliato M, Murcia M, Espada M, Alvarez-Pedrerol M, Bolúmar F, Vioque J, Basterrechea M, Blarduni E, Ramón R, Guxens M, Foradada CM, Ballester F, Ibarluzea J, Sunyer J. Epidemiology. 2010 Jan;21(1):62-9.

2. Effect of Iodine Supplementation During Pregnancy on Infant Neurodevelopment at 1 Year of Age.
Murcia M, Rebagliato M, Iñiguez C, Lopez-Espinosa MJ, Estarlich M, Plaza B, Barona-Vilar C, Espada M, Vioque J, Ballester F. Am J Epidemiol. 2011 Mar 8. [Epub ahead of print]

3. Ribas-Fito N, Ramon R, Ballester F, et al. Child health and the environment: the
INMA Spanish Study. Paediatr Perinat Epidemiol 2006;20:403e10.

4. Murcia M, Rebagliato M, Espada M, et al. Iodine intake in a population of pregnant women: INMA mother and child cohort study, Spain. J Epidemiol Community Health. 2010;64:1094-99.