Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

The changing epidemiology of iodine deficiency


Globally, about 2 thousand million people are affected by iodine deficiency. Although endemic goitre is the most visible sign of iodine deficiency, its most devastating consequence is brain damage causing mental retardation in children. The relationship between iodine deficiency and brain damage was not clearly established until the 1980s when the term iodine deficiency disorders (IDDs), which encompass a spectrum of conditions caused by iodine deficiency, was introduced. This paradigm shift in the understanding of the clinical consequences of iodine deficiency led to a change in iodine deficiency assessment. The median urinary iodine excretion level has been recommended as the preferred indicator for monitoring population iodine deficiency status since 2001. The 2007 WHO urinary iodine data in schoolchildren from 130 countries revealed that iodine intake is still insufficient in 47 countries. Furthermore, about one-third of countries lack national estimates of the prevalence of iodine deficiency. The picture that has emerged from available data worldwide over the past two decades is that IDDs are not confined to remote, mountainous areas in developing countries, but are a global public health problem that affects most countries, including developed countries and island nations. The recognition of the universality of iodine deficiency highlights the need to develop and apply new strategies to establish and maintain sustainable IDD elimination and strengthen regular monitoring programmes.

Key Points

  • Despite efforts to monitor changes in the magnitude of iodine deficiency worldwide, prevalence data are crude and are still not available for many countries

  • Iodine deficiency is re-emerging in some developed countries; therefore, public awareness and government policies on iodine fortification, supplementation and surveillance of iodine deficiency are warranted

  • Currently, the WHO, UNICEF and ICCIDD recommend using median urinary iodine concentration in school-age children as a proxy for the iodine nutrition status of the general population

  • The applicability of this recommendation for the most vulnerable population groups, such as pregnant women and young children, needs to be reviewed

  • At the population level, close monitoring and surveillance of iodine intake is an important public health measure to ensure optimal iodine nutrition

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.


  1. 1

    Zimmermann, M. B., Jooste, P. L. & Pandav, C. S. Iodine-deficiency disorders. Lancet 372, 1251–1262 (2008).

    CAS  Article  Google Scholar 

  2. 2

    Hetzel, B. S. Iodine deficiency disorders (IDD) and their eradication. Lancet 2, 1126–1129 (1983).

    CAS  Article  Google Scholar 

  3. 3

    Bleichrodt, N. & Born, M. P. in The Damaged Brain of Iodine Deficiency (ed. Stanbury, J. B.) 195–200 (Cognizant Communications, New York, 1994).

    Google Scholar 

  4. 4

    Qian, M. et al. The effects of iodine on intelligence in children: a meta-analysis of studies conducted in China. Asia Pac. J. Clin. Nutr. 14, 32–42 (2005).

    CAS  PubMed  Google Scholar 

  5. 5

    Zimmermann, M. B. Iodine deficiency. Endocrine Rev. 30, 376–408 (2009).

    CAS  Article  Google Scholar 

  6. 6

    de Benoist, B., McLean, E., Andersson, M. & Rogers, L. Iodine deficiency in 2007: global progress since 2003. Food Nutr. Bull. 29, 195–202 (2008).

    Article  Google Scholar 

  7. 7

    Andersson, M., de Benoist, B. & Rogers, L. Epidemiology of iodine deficiency: salt iodisation and iodine status. Best Pract. Res. Clin. Endocrinol. Metab. 24, 1–11 (2010).

    CAS  Article  Google Scholar 

  8. 8

    UNICEF. Sustainable Elimination of Iodine Deficiency (UNICEF, New York, 2008).

  9. 9

    Freake, H. in Biochemical and Physiological Aspects of Human Nutrition (ed. Stipaunk, M. H.) 761–781 (W. B. Saunders Company, Philadelphia, 2000).

    Google Scholar 

  10. 10

    Brown-Grant, K. Extrathyroidal iodine concentrating mechanisms. Physiol. Rev. 41, 189–213 (1961).

    CAS  Article  Google Scholar 

  11. 11

    WHO, UNICEF & International Council for the Control of Iodine Deficiency Disorders. Assessment of Iodine Deficiency Disorders and Monitoring Their Elimination: A Guide for Programme Managers 3rd edn [online]. (2007).

  12. 12

    Institute of Medicine & Academy of Sciences. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium and Zinc (National Academy Press, Washington, 2001).

  13. 13

    Fisher, D. A. & Oddie, T. H. Thyroid iodine content and turnover in euthyroid subjects: validity of estimation of thyroid iodine accumulation from short-term clearance studies. J. Clin. Endocrinol. Metab. 29, 721–727 (1969).

    CAS  Article  Google Scholar 

  14. 14

    Stanbury, J. B. et al. (Eds) Endemic Goiter: The Adaptation of Man to Iodine Deficiency (Harvard University Press, Cambridge, 1954).

    Book  Google Scholar 

  15. 15

    DeGroot, L. J. Kinetic analysis of iodine metabolism. J. Clin. Endocrinol. Metab. 26, 149–173 (1966).

    CAS  Article  Google Scholar 

  16. 16

    Cavalieri, R. R. Iodine metabolism and thyroid physiology: current concepts. Thyroid 7, 177–181 (1997).

    CAS  Article  Google Scholar 

  17. 17

    Lamberg, B. A. Iodine deficiency disorders and goitre. Eur. J. Clin. Nutr. 47, 1–8 (1993).

    CAS  PubMed  Google Scholar 

  18. 18

    Delange, F. M. & Dunn, J. T. in Werner and Ingbar's The Thyroid: A Fundamental and Clinical Text 9th edn (eds Braverman, L. E. & Utiger, R. D.) 264–287 (Lippincott, William & Wilkins, Philadelphia, 2005).

    Google Scholar 

  19. 19

    WHO. Endemic Goitre (WHO, Geneva, 1960).

  20. 20

    WHO, UNICEF & International Council for the Control of Iodine Deficiency Disorders. Global Prevalence of Iodine Deficiency Disorders (WHO, Geneva, 1993).

  21. 21

    Aghini-Lombardi, F. et al. Effect of iodized salt on thyroid volume of children living in an area previously characterized by moderate iodine deficiency. J. Clin. Endocrinol. Metab. 82, 1136–1139 (1997).

    CAS  PubMed  Google Scholar 

  22. 22

    Zimmermann, M. B. et al. Thyroid size and goiter prevalence after introduction of iodized salt: a 5-y prospective study in schoolchildren in Côte d'Ivoire. Am. J. Clin. Nutr. 77, 663–667 (2003).

    CAS  Article  Google Scholar 

  23. 23

    Li, M. et al. Iodine nutritional status of children on the island of Tanna, Republic of Vanuatu. Public Health Nutr. 12, 1512–1518 (2009).

    Article  Google Scholar 

  24. 24

    Selamat, R. et al. Iodine deficiency status and iodised salt consumption in Malaysia: findings from a national iodine deficiency disorders survey. Asia Pac. J. Clin. Nutr. 19, 578–585 (2010).

    PubMed  Google Scholar 

  25. 25

    Assey, V. D. et al. Tanzania national survey on iodine deficiency: impact after twelve years of salt iodation. BMC Public Health 9, 319 (2009).

    Article  Google Scholar 

  26. 26

    WHO, UNICEF & International Council for the Control of Iodine Deficiency Disorders. Assessment of Iodine Deficiency Disorders and Monitoring Their Elimination: A Guide to Programme Managers 2nd edn (WHO, Geneva, 2001).

  27. 27

    Zimmermann, M. B., Aeberli, I., Torresani, T. & Bürgi, H. Increasing the iodine concentration in the Swiss iodized salt program markedly improved iodine status in pregnant women and children: a 5-y prospective national study. Am. J. Clin. Nutr. 82, 388–392 (2005).

    CAS  Article  Google Scholar 

  28. 28

    Li, M. & Eastman, C. J. Neonatal TSH screening: is it a sensitive and reliable tool for monitoring iodine status in populations? Best Pract. Res. Clin. Endocrinol. Metab. 24, 63–75 (2010).

    Article  Google Scholar 

  29. 29

    WHO. WHA43.2 Prevention and Control of Iodine Deficiency Disorders [online]. (1990).

  30. 30

    United Nations. World Declaration on the Survival, Protection and Development of Children [online]. (1990).

  31. 31

    International Council for the Control of Iodine Deficiency Disorders. Ending hidden hunger: the Montreal Micronutrient Conference. IDD Newsletter 7, 1–10 (1991).

  32. 32

    Food and Agriculture Organization of the United Nations and WHO. World Declaration and Plan of Action for Nutrition [online]. (1992).

  33. 33

    WHO. Iodine and Health: Eliminating Iodine Deficiency Disorders Safely Through Salt Iodisation: A Statement by the World Health Organization (WHO, Geneva, 1994).

  34. 34

    Delange, F., Bürgi, H., Chen, Z. & Dunn, J. T. World status of monitoring iodine deficiency disorders control programs. Thyroid 12, 915–924 (2002).

    Article  Google Scholar 

  35. 35

    WHO. Iodine Status Worldwide: WHO Global Database on Iodine Deficiency (WHO, Geneva, 2004).

  36. 36

    Andersson, M., Takkouche, B., Egli, I., Allen, H. E. & de Benoist, B. Current global iodine status and progress over the last decade towards the elimination of iodine deficiency. Bull. World Health Organ. 83, 518–525 (2005).

    PubMed  PubMed Central  Google Scholar 

  37. 37

    WHO. WHA58.24: Sustaining the Elimination of Iodine Deficiency Disorders (WHO, Geneva, 2005).

  38. 38

    UNICEF. The State of the World's Children 2009 (UNICEF, New York, 2009).

  39. 39

    Andersson, M., de Benoist, B., Delange, F. & Zupan, J. Prevention and control of iodine deficiency in pregnant and lactating women and in children less than 2-years-old: conclusions and recommendations of the technical consultation. Public Health Nutr. 10, 1606–1611 (2007).

    CAS  Article  Google Scholar 

  40. 40

    Eastman, C. J. Where has all our iodine gone? Med. J. Aust. 171, 455–456 (1999).

    CAS  Article  Google Scholar 

  41. 41

    Li, M., Ma, G., Boyages, S. & Eastman, C. J. Re-emergence of iodine deficiency in Australia. Asia Pac. J. Clin. Nutr. 10, 200–203 (2001).

    CAS  Article  Google Scholar 

  42. 42

    Gunton, J. E., Hams, G., Fiegert, M. & McElduff, A. Iodine deficiency in ambulatory participants at a Sydney teaching hospital: is Australia truly iodine replete? Med. J. Aust. 171, 467–470 (1999).

    CAS  Article  Google Scholar 

  43. 43

    McDonnell, C. M., Harris, M. & Zacharin, M. R. Iodine deficiency and goitre in schoolchildren in Melbourne, 2001. Med. J. Aust. 178, 159–162 (2003).

    PubMed  Google Scholar 

  44. 44

    Hamrosi, M. A., Wallace, E. M. & Riley, M. D. Iodine status in pregnant women living in Melbourne differs by ethnic group. Asia Pac. J. Clin. Nutr. 14, 27–31 (2005).

    CAS  PubMed  Google Scholar 

  45. 45

    McElduff, A. et al. Neonatal thyroid-stimulating hormone concentrations in northern Sydney: further indications of mild iodine deficiency? Med. J. Aust. 176, 317–320 (2002).

    PubMed  Google Scholar 

  46. 46

    Travers, C. A. et al. Iodine status in pregnant women and their newborns: are our babies at risk of iodine deficiency? Med. J. Aust. 184, 617–620 (2006).

    PubMed  Google Scholar 

  47. 47

    Guttikonda, K., Travers, C. A., Lewis, P. R. & Boyages, S. Iodine deficiency in urban primary school children: a cross-sectional analysis. Med. J. Aust. 179, 346–348 (2003).

    PubMed  Google Scholar 

  48. 48

    Guttikonda, K. et al. Recurrent iodine deficiency in Tasmania, Australia: a salutary lesson in sustainable iodine prophylaxis and its monitoring. J. Clin. Endocrinol. Metab. 87, 2809–2815 (2002).

    CAS  Article  Google Scholar 

  49. 49

    Hynes, K. L., Blizzard, C. L., Venn, A. J., Dwyer, T. & Burgess, J. R. Persistent iodine deficiency in a cohort of Tasmanian school children: associations with socio-economic status, geographical location and dietary factors. Aust. N. Z. J. Public Health 28, 476–481 (2004).

    Article  Google Scholar 

  50. 50

    Li, M. et al. Are Australian children iodine deficient? Results of the Australian National Iodine Nutrition Study. Med. J. Aust. 184, 165–169 (2006).

    PubMed  Google Scholar 

  51. 51

    Li, M., Chapman, S., Agho, K. & Eastman, C. J. Can even minimal news coverage influence consumer health-related behaviour? A case study of iodized salt sales, Australia. Health Educ. Res. 23, 543–548 (2008).

    Article  Google Scholar 

  52. 52

    Li, M., Waite, K. V., Ma, G. & Eastman, C. J. Declining iodine content of milk and re-emergence of iodine deficiency in Australia. Med. J. Aust. 184, 307 (2006).

    PubMed  Google Scholar 

  53. 53

    Skeaff, S. A., Thomson, C. D. & Gibson, R. S. Mild iodine deficiency in a sample of New Zealand schoolchildren. Eur. J. Clin. Nutr. 56, 1169–1175 (2002).

    CAS  Article  Google Scholar 

  54. 54

    Skeaff, S. A., Thomson, C. D. & Gibson, R. S. Iodine Deficiency Disorders (IDD) in the New Zealand population: another example of an outmoded IDD control programme. Asia Pac. J. Clin. Nutr. 12 (Suppl.), S15 (2003).

    Google Scholar 

  55. 55

    Mulrine, H. M., Skeaff, S. A., Ferguson, E. L., Gray, A. R. & Valeix, P. Breast-milk iodine concentration declines over the first 6 mo postpartum in iodine-deficient women. Am. J. Clin. Nutr. 92, 849–856 (2010).

    CAS  Article  Google Scholar 

  56. 56

    Pettigrew-Porter, A., Skeaff, S., Gray, A., Thomson, C. & Croxson, M. Are pregnant women in New Zealand iodine deficient? A cross-sectional survey. Aust. N. Z. J. Obstet. Gynaecol. 51, 464–467 (2011).

    Article  Google Scholar 

  57. 57

    Vanderpump, M. P. et al. Iodine status of UK schoolgirls: a cross-sectional survey. Lancet 377, 2007–2012 (2011).

    CAS  Article  Google Scholar 

  58. 58

    Delange, F. Iodine deficiency in Europe and its consequences: an update. Eur. J. Nucl. Med. Mol. Imaging 29 (Suppl. 2), S404–S416 (2002).

    CAS  Article  Google Scholar 

  59. 59

    Zimmermann, M. B. Symposium on 'Geographical and geological influences on nutrition': Iodine deficiency in industrialised countries. Proc. Nutr. Soc. 69, 133–143 (2010).

    Article  Google Scholar 

  60. 60

    Vitti, P., Delange, F., Pinchera, A., Zimmermann, M. & Dunn, J. T. Europe is iodine deficient. Lancet 361, 1226 (2003).

    Article  Google Scholar 

  61. 61

    Zimmermann, M. B. & Andersson, M. Prevalence of iodine deficiency in Europe in 2010. Ann. Endocrinol. (Paris) 72, 164–166 (2011).

    CAS  Article  Google Scholar 

  62. 62

    Pearce, E. N. Iodine nutrition in the UK: what went wrong? Lancet 377, 1979–1980 (2011).

    Article  Google Scholar 

  63. 63

    Food Standards Australia New Zealand. Australia New Zealand Food Standards Code Amendment No. 103–2008 (Commonwealth of Australia, Canberra, 2008).

  64. 64

    Seal, J. A., Doyle, Z., Burgess, J. R., Taylor, R. & Cameron, A. R. Iodine status of Tasmanians following voluntary fortification of bread with iodine. Med. J. Aust. 186, 69–71 (2007).

    PubMed  Google Scholar 

  65. 65

    Burgess, J. R. et al. A case for universal salt iodisation to correct iodine deficiency in pregnancy: another salutary lesson from Tasmania. Med. J. Aust. 186, 574–576 (2007).

    PubMed  Google Scholar 

  66. 66

    Mackerras, D., Powers, J., Boorman, J., Loxton, D. & Giles, G. G. Estimating the impact of mandatory fortification of bread with iodine on pregnant and post-partum women. J. Epidemiol. Community Health 65, 1118–1122 (2011).

    Article  Google Scholar 

  67. 67

    Buttfield, I. H. & Hetzel, B. S. Endemic goitre in eastern New Guinea with special reference to the use of iodized oil in prophylaxis and treatment. Bull. World Health Organ. 36, 243–262 (1967).

    CAS  PubMed  PubMed Central  Google Scholar 

  68. 68

    Temple, V., Mapira, P., Adeniyi, K. & Sims, P. Iodine deficiency in Papua New Guinea (sub-clinical iodine deficiency and salt iodization in the highlands of Papua New Guinea). J. Public Health (Oxf.) 27, 45–48 (2005).

    Article  Google Scholar 

  69. 69

    Kumar, B., Moriarty, H., Khan, N. & Kishore, K. Progress in the Fijian iodine supplementation program. Network for Sustained Elimination of Iodine Deficiency [online], (2009).

    Google Scholar 

  70. 70

    Zimmermann, M. B. et al. New reference values for thyroid volume by ultrasound in iodine sufficient schoolchildren: a World Health Organization/Nutrition for Health and Development Iodine Deficiency Study Group Report. Am. J. Clin. Nutr. 79, 231–237 (2004).

    CAS  Article  Google Scholar 

  71. 71

    Delange, F. The role of goitrogenic factors distinct from iodine deficiency in the etiology of goiter [French]. Ann. Endocrinol. (Paris) 49, 302–305 (1988).

    CAS  Google Scholar 

  72. 72

    Glinoer, D. The regulation of thyroid function during normal pregnancy: importance of the iodine nutrition status. Best Pract. Res. Clin. Endocrinol. Metab. 18, 133–152 (2004).

    CAS  Article  Google Scholar 

  73. 73

    Zimmermann, M. B. Iodine deficiency in pregnancy and the effects of maternal iodine supplementation on the offspring: a review. Am. J. Clin. Nutr. 89, 668S–672S (2009).

    CAS  Article  Google Scholar 

  74. 74

    Pharoah, P. O., Buttfield, I. H. & Hetzel, B. S. Neurological damage to the fetus resulting from severe iodine deficiency during pregnancy. Lancet 1, 308–310 (1971).

    CAS  Article  Google Scholar 

  75. 75

    Haddow, J. E. et al. Maternal thyroid deficiency during pregnancy and subsequent neuropsychological development of the child. N. Engl. J. Med. 341, 549–555 (1999).

    CAS  Article  Google Scholar 

  76. 76

    Rajatanavin, R. Iodine deficiency in pregnant women and neonates in Thailand. Public Health Nutr. 10, 1602–1605 (2007).

    Article  Google Scholar 

  77. 77

    Jaruratanasirikul, S. et al. Maternal iodine status and neonatal thyroid-stimulating hormone concentration: a community survey in Songkhla, southern Thailand. Public Health Nutr. 12, 2279–2284 (2009).

    Article  Google Scholar 

  78. 78

    Ojule, A. C. & Osotimehin, B. O. Maternal and neonatal thyroid status in Saki, Nigeria. Afr. J. Med. Med. Sci. 27, 57–61 (1998).

    CAS  PubMed  Google Scholar 

  79. 79

    Chakraborty, I. et al. Iodine deficiency disorders among the pregnant women in a rural hospital of West Bengal. Indian J. Med. Res. 123, 825–829 (2006).

    CAS  PubMed  Google Scholar 

  80. 80

    Hollowell, J. G. et al. Iodine nutrition in the United States. Trends and public health implications: iodine excretion data from National Health and Nutrition Examination Surveys I and III (1971–1974 and 1988–1994). J. Clin. Endocrinol. Metab. 83, 3401–3408 (1998).

    CAS  PubMed  Google Scholar 

  81. 81

    Caldwell, K. L., Makhmudov, A., Ely, E., Jones, R. L. & Wang, R. Y. Iodine status of the U.S. population, National Health and Nutrition Examination Survey, 2005–2006 and 2007–2008. Thyroid 21, 419–427 (2011).

    Article  Google Scholar 

  82. 82

    Hollowell, J. G. & Haddow, J. E. The prevalence of iodine deficiency in women of reproductive age in the United States of America. Public Health Nutr. 10, 1532–1539 (2007).

    Article  Google Scholar 

  83. 83

    Perrine, C. G., Herrick, K., Serdula, M. K. & Sullivan, K. M. Some subgroups of reproductive age women in the United States may be at risk for iodine deficiency. J. Nutr. 140, 1489–1494 (2010).

    CAS  Article  Google Scholar 

  84. 84

    Limbert, E. et al. Iodine intake in Portuguese pregnant women: results of a countrywide study. Eur. J. Endocrinol. 163, 631–635 (2010).

    CAS  Article  Google Scholar 

  85. 85

    Andersson, M. et al. The Swiss iodized salt program provides adequate iodine for school children and pregnant women, but weaning infants not receiving iodine-containing complementary foods as well as their mothers are iodine deficient. J. Clin. Endocrinol. Metab. 95, 5217–5224 (2010).

    CAS  Article  Google Scholar 

  86. 86

    Kibirige, M. S., Hutchison, S., Owen, C. J. & Delves, H. T. Prevalence of maternal dietary iodine insufficiency in the north east of England: implications for the fetus. Arch. Dis. Child. Fetal Neonatal Ed. 89, F436–F439 (2004).

    CAS  Article  Google Scholar 

  87. 87

    Lazarus, J. H. & Smyth, P. P. Iodine deficiency in the UK and Ireland. Lancet 372, 888 (2008).

    Article  Google Scholar 

  88. 88

    Luton, D. et al. Iodine deficiency in northern Paris area: impact on fetal thyroid mensuration. PLoS ONE 6, e14707 (2011).

    CAS  Article  Google Scholar 

  89. 89

    González Mateo, M. C. et al. Assessment of iodine nutritional status and thyroxine levels in pregnant women from different geographic areas of the Castile and Leon [Spanish]. Endocrinol. Nutr. 58, 416–421 (2011).

    Article  Google Scholar 

  90. 90

    Kung, A. W., Lao, T. T., Low, L. C., Pang, R. W. & Robinson, J. D. Iodine insufficiency and neonatal hyperthyrotropinaemia in Hong Kong. Clin. Endocrinol. (Oxf.) 46, 315–319 (1997).

    CAS  Article  Google Scholar 

  91. 91

    WHO & UNICEF. Reaching Optimal Iodine Nutrition in Pregnant and Lactating Women and Young Children (WHO, Geneva, 2007).

  92. 92

    Becker, D. V. et al. Iodine supplementation for pregnancy and lactation—United States and Canada: recommendations of the American Thyroid Association. Thyroid 16, 949–951 (2006).

    CAS  Article  Google Scholar 

  93. 93

    National Health and Medical Research Council. Iodine Supplementation for Pregnant and Breastfeeding Women (NHMRC, Canberra, 2010).

  94. 94

    Gallego, G., Goodall, S. & Eastman, C. J. Iodine deficiency in Australia: is iodine supplementation for pregnant and lactating women warranted? Med. J. Aust. 192, 461–463 (2010).

    PubMed  Google Scholar 

  95. 95

    Yan, Y. Q. et al. Attention to the hiding iodine deficiency in pregnant and lactating women after universal salt iodization: A multi-community study in China. J. Endocrinol. Invest. 28, 547–553 (2005).

    CAS  Article  Google Scholar 

  96. 96

    Gowachirapant, S. et al. Urinary iodine concentrations indicate iodine deficiency in pregnant Thai women but iodine sufficiency in their school-aged children. J. Nutr. 139, 1169–1172 (2009).

    CAS  Article  Google Scholar 

Download references

Author information




M. Li researched the data for the article. Both authors wrote the article, provided substantial contributions to discussions of the content and reviewed and/or edited the manuscript before submission.

Corresponding author

Correspondence to Mu Li.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Li, M., Eastman, C. The changing epidemiology of iodine deficiency. Nat Rev Endocrinol 8, 434–440 (2012).

Download citation

Further reading


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing