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Thursday, January 9, 2014

Nutrition in the first 1,000 days: How strong is the data?

The first 1,000 days represents the development of a child from conception through to 2 years of age. Maternal and infant nutrition during this period has become the corner stone of many international programmes to combat malnutrition. The message relayed within this area is simple: Optimal height for age and optimal cognitive function are largely determined during the first 1,000 days. If a child suffers poor nutrition during this period, then there is permanent reduction in stature and a permanent loss of cognitive function. The UN initiative “Scaling Up Nutrition” (SUN) which has now been adopted by 45 countries has the first 1,000 days and maternal-infant nutrition as its core. However, a recent review and analysis published in the American Journal of Clinical Nutrition and led by Andrew Prentice of the London School of Hygiene and Tropical Medicine[1], would certainly demand a more rigorous review of a policy which effectively espouses the view that the first 1,000 days is the make-or-break period for physical development.

The paper begins by describing the data upon which the first 1,000 days theory is based. These data show that in 54 countries with low incomes, children are born with heights below the WHO growth standards and that this height deficit deteriorates over the first 2 years of life and then remains stable for the remainder of the study, which lasted 5 years. The authors point out that these data come from an “amalgamation of large-scale nationally representative data sets that were not collected for research purposes”.  They also point out that the original data from Africa does show some, albeit modest recovery in height between 24 and 48 months.

The second point made by the authors is that whereas most brain and neuronal development takes place in the first 1,000 days, most other tissues show significant growth after this period, all of which are driven by hormonal development, differing for males and females. The peak growth of lymphoid tissue occurs between 5 and 10 years of age while muscles, bones and reproductive organs show a surge in growth in the early to mid teens. If different organs grow at different rates at different ages, then it is logical to assume that sub-optimal nutrition can modify this growth well outside the first 1,000 days. The authors present data from Brazil, Guatemala, The Philippines and South Africa, which clearly shows recovery in height after the first 1,000 days and that this recovery is not based on any special nutrition intervention. India is exceptional in not showing any post 2-year height recovery. The research base of Andrew Prentice is in rural Gambia and over 6 decades, the growth of children from local subsistence farming villages has been recorded. The data show the expected fall in height in the first 1,000 days of these poor children. However, it shows very good recovery thereafter. Then as growth demands are increased in puberty, there is a temporary fall in height for age, which again shows recovery and plateaus in the second decade of life.  All of these data challenge the concept that the first 1,000 days is the only critical period of growth and that interventions outside that period are unlikely to have any effect.

The authors now move on to look at the actual evidence of the effects of nutritional intervention during pregnancy and early childhood. As regards pregnancy, the authors cite the Cochrane Review of 23 protein-energy supplement trials reached the following conclusion[2]: “Dietary advice appears effective in increasing pregnant women's energy and protein intakes but is unlikely to confer major benefits on infant or maternal health. Balanced energy/protein supplementation improves fetal growth and may reduce the risk of fetal and neonatal death. High-protein or balanced protein supplementation alone is not beneficial and may be harmful to the infant. Protein/energy restriction of pregnant women who are overweight or exhibit high weight gain is unlikely to be beneficial and may be harmful to the infant.” The authors also cite meta-analyses of pre-natal trials involving 17 with zinc supplementation and 49 with iron and folic acid supplementation. The outcome of the meta-analyses was that these nutritional supplements produced non-significant effects on birth outcome. As the authors point out, these trials cannot be dismissed and furthermore cannot be considered to be flawed by design. They then cite a meta-analysis of 42 trials, which involved nutritional intervention in childhood involving complimentary feeding. Whereas some benefits were seen such as reduced rates of anaemia and improved micronutrient status, the authors argue “ in the context of the current discussion their analysis underscores the fact that the range of interventions before 24 months reported to date could only make a limited contribution to reducing stunting in poor populations”. Disappointing as they may be, again these studies cannot be dismissed. It may well be, as the authors argue, that a combination of poor hygiene, infection and infestation may negate any nutritional impact and they point out that trials combining both dietary and hygiene interventions are underway.

This is a very important paper and one that will trouble the first 1000-day proponents. It is also a very thoughtful paper because it emphasizes that that the first 1,000 days remains a very important period for potential life long impacts on growth. However, it is a paper that challenges both the strength of evidence of the first 1000 days and the concept that other critical periods of growth are of lesser importance. The authors did not consider cognition as an outcome of the first 1,000-day nutritional intervention. However, they do cite 2 papers, which challenge the view that cognitive development is again, confined to the first 1,000 days.

[1] Prentice AM et al (2013) AJCN, 97:911-918

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