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Long-chain polyunsaturated fatty acids, infant formula, and breastfeeding
CORRESPONDENCE
COMMENTARY
CORRESPONDENCE Long-chain polyunsaturated fatty acids, infant formula, and breastfeeding Sir—P Willatts and colleagues (Aug 29, p 688)1 interpret their data as suggesting “that term infants may benefit from long-chain polyunsaturated fatty acids (LCPUFA) supplementation and that the effects persist beyond the period of supplementation”. They might also have argued that term infants would benefit from receiving breast milk, which is naturally rich in LCPUFA, and that the benefits would be expected to persist beyond the period of breastfeeding. Other researchers have found long-term advantages in intellectual and retinocortical development for infants fed breast milk, and have associated these with breast milk LCPUFA.2,3 Breastfeeding is the standard against which artificial feeding should be measured. It is therefore surprising that Willatts and colleagues included no reference group of breastfed infants in their study. It may be relevant that the study was supported by Milupa Ltd, UK, a firm with an interest in marketing its LCPUFA-supplemented products but not in the promotion of breastfeeding. Research design and interpretation need to be rigorously protected from the subtle pressures of commercial sponsorship. Carol Campbell Community Paediatric Department, Foyle H and SS Trust, Bridgeview House, Gransha Park, Londonderry BT47 1TG, UK 1
2
3
Willatts P, Forsyth JS, DiModugno MK, Varma S, Colvin M. Effect of long-chain polyunsaturated fatty acids in infant formula on problem solving at 10 months of age. Lancet 1998; 352: 688–91. Lucas A, Morley R, Cole TJ, Lister G, Leeson-Payne C. Breast milk and subsequent intelligence quotient in children born preterm. Lancet 1992; 339: 261–64. Makrides M, Neumann M, Simmer K, Pater J, Gibson R. Are long-chain polyunsaturated fatty acids essential nutrients in infancy? Lancet 1995; 345: 1463–68.
Authors’ reply Sir—Carol Campbell observes that we included no reference group of breastfed infants in our study of the effect of LCPUFA in infant formula
THE LANCET • Vol 352 • November 21, 1998
on problem solving at age 10 months. The aim of our randomised trial was to find out whether dietary LCPUFA in term infants during the first months of life confers any later cognitive advantage. We therefore compared problem-solving scores in groups of infants differing in only one characteristic—whether they received formula supplemented with LCPUFA or non-supplemented formula. Inclusion of a group of breastfed infants was an inappropriate design for the study aim. Comparisons of formula-fed and breastfed infants involve non-random assignment to these groups, and factors such as genetic and social-demographic variables, parenting skills, or quality of parent-child interaction may also contribute to differences in cognitive abilities. Attempts to statistically control for the potentially confounding effects of these factors may be inadequate.1,2 For comparison, taking into account these differences, we report the problem-solving scores in 23 term infants who were breastfed for at least 4 months and tested at age 10 months on the three-step, means-end problem described in our previous study. The percentage of families in social classes I and II, maternal age, maternal education, and percentage of home owners did not differ significantly between the formula-fed groups, but were significantly higher in the breastfed group (table). We previously reported that the problemsolving scores were higher in the LCPUFA group than in the noLCPUFA group (Mann-Whitney U test p<0·05). Intention scores were
slightly higher in the breastfed group than in the LCPUFA group but the difference was not significant, and neither did these groups differ on a number of intentional solutions. By contrast, intention scores and number of intentional solutions were higher in the breastfed group than in the noLCPUFA group (p<0·05). After adjustment for social class and maternal education, intention scores no longer differed significantly between the breastfed and no-LCPUFA groups (p=0·08), but number of intentional solutions remained higher in the breastfed group (p<0·05). *P Willatts, J S Forsyth Department of Psychology, University of Dundee, Dundee DD1 4HN, UK 1 2
Wright P, Deary IJ. Breastfeeding and intelligence. Lancet 1992; 339: 612. Jacobson SW, Jacobson JL. Breastfeeding and intelligence. Lancet 1992; 339: 926.
Sir—P Willatts and colleagues1 report that term infants fed in the first period of extrauterine life with LCPUFAenriched formulae obtained higher scores in problem solving at age 10 months than infants receiving a traditional formula. Others have shown an association between smoking in pregnancy and lower birthweight of infants2 and subsequent deficits in measures of cognitive development up to advanced childhood.3 To investigate the relation between maternal smoking habits and fattyacid composition of milk, which contains substantial amounts of LCPUFA, we have analysed the total lipid composition of milk from 44 mothers fully breastfeeding for up to 3
LCPUFA (n=21)
No LCPUFA (n=23)
Breastfed (n=23)
Demographic characteristics % in social classes I & II (n) Maternal age (years)* Maternal education (years)* Housing (rent/own)
5 (1)† 25·4 (0·9)† 16·2 (0·1)† 13/8†
4 (1)† 27·1 (1·0)† 17·0 (0·4)† 9/14†
61 (14)‡ 30·8 (0·6)‡ 18·7 (0·3)‡ 4/19‡
Problem-solving scores Intention score* Intentional solutions*
13·5 (0·9)† 2·0 (0·3)†
11·1 (0·9)‡ 1·0 (0·3)‡
13·9 (0·7)† 2·0 (0·3)†
*Mean (SE); †p>0·05; ‡p<0·05.
Demographic characteristics and problem-solving scores on entire problem in formula-fed and breastfed groups
1703
COMMENTARY
CORRESPONDENCE Long-chain polyunsaturated fatty acids, infant formula, and breastfeeding Sir—P Willatts and colleagues (Aug 29, p 688)1 interpret their data as suggesting “that term infants may benefit from long-chain polyunsaturated fatty acids (LCPUFA) supplementation and that the effects persist beyond the period of supplementation”. They might also have argued that term infants would benefit from receiving breast milk, which is naturally rich in LCPUFA, and that the benefits would be expected to persist beyond the period of breastfeeding. Other researchers have found long-term advantages in intellectual and retinocortical development for infants fed breast milk, and have associated these with breast milk LCPUFA.2,3 Breastfeeding is the standard against which artificial feeding should be measured. It is therefore surprising that Willatts and colleagues included no reference group of breastfed infants in their study. It may be relevant that the study was supported by Milupa Ltd, UK, a firm with an interest in marketing its LCPUFA-supplemented products but not in the promotion of breastfeeding. Research design and interpretation need to be rigorously protected from the subtle pressures of commercial sponsorship. Carol Campbell Community Paediatric Department, Foyle H and SS Trust, Bridgeview House, Gransha Park, Londonderry BT47 1TG, UK 1
2
3
Willatts P, Forsyth JS, DiModugno MK, Varma S, Colvin M. Effect of long-chain polyunsaturated fatty acids in infant formula on problem solving at 10 months of age. Lancet 1998; 352: 688–91. Lucas A, Morley R, Cole TJ, Lister G, Leeson-Payne C. Breast milk and subsequent intelligence quotient in children born preterm. Lancet 1992; 339: 261–64. Makrides M, Neumann M, Simmer K, Pater J, Gibson R. Are long-chain polyunsaturated fatty acids essential nutrients in infancy? Lancet 1995; 345: 1463–68.
Authors’ reply Sir—Carol Campbell observes that we included no reference group of breastfed infants in our study of the effect of LCPUFA in infant formula
THE LANCET • Vol 352 • November 21, 1998
on problem solving at age 10 months. The aim of our randomised trial was to find out whether dietary LCPUFA in term infants during the first months of life confers any later cognitive advantage. We therefore compared problem-solving scores in groups of infants differing in only one characteristic—whether they received formula supplemented with LCPUFA or non-supplemented formula. Inclusion of a group of breastfed infants was an inappropriate design for the study aim. Comparisons of formula-fed and breastfed infants involve non-random assignment to these groups, and factors such as genetic and social-demographic variables, parenting skills, or quality of parent-child interaction may also contribute to differences in cognitive abilities. Attempts to statistically control for the potentially confounding effects of these factors may be inadequate.1,2 For comparison, taking into account these differences, we report the problem-solving scores in 23 term infants who were breastfed for at least 4 months and tested at age 10 months on the three-step, means-end problem described in our previous study. The percentage of families in social classes I and II, maternal age, maternal education, and percentage of home owners did not differ significantly between the formula-fed groups, but were significantly higher in the breastfed group (table). We previously reported that the problemsolving scores were higher in the LCPUFA group than in the noLCPUFA group (Mann-Whitney U test p<0·05). Intention scores were
slightly higher in the breastfed group than in the LCPUFA group but the difference was not significant, and neither did these groups differ on a number of intentional solutions. By contrast, intention scores and number of intentional solutions were higher in the breastfed group than in the noLCPUFA group (p<0·05). After adjustment for social class and maternal education, intention scores no longer differed significantly between the breastfed and no-LCPUFA groups (p=0·08), but number of intentional solutions remained higher in the breastfed group (p<0·05). *P Willatts, J S Forsyth Department of Psychology, University of Dundee, Dundee DD1 4HN, UK 1 2
Wright P, Deary IJ. Breastfeeding and intelligence. Lancet 1992; 339: 612. Jacobson SW, Jacobson JL. Breastfeeding and intelligence. Lancet 1992; 339: 926.
Sir—P Willatts and colleagues1 report that term infants fed in the first period of extrauterine life with LCPUFAenriched formulae obtained higher scores in problem solving at age 10 months than infants receiving a traditional formula. Others have shown an association between smoking in pregnancy and lower birthweight of infants2 and subsequent deficits in measures of cognitive development up to advanced childhood.3 To investigate the relation between maternal smoking habits and fattyacid composition of milk, which contains substantial amounts of LCPUFA, we have analysed the total lipid composition of milk from 44 mothers fully breastfeeding for up to 3
LCPUFA (n=21)
No LCPUFA (n=23)
Breastfed (n=23)
Demographic characteristics % in social classes I & II (n) Maternal age (years)* Maternal education (years)* Housing (rent/own)
5 (1)† 25·4 (0·9)† 16·2 (0·1)† 13/8†
4 (1)† 27·1 (1·0)† 17·0 (0·4)† 9/14†
61 (14)‡ 30·8 (0·6)‡ 18·7 (0·3)‡ 4/19‡
Problem-solving scores Intention score* Intentional solutions*
13·5 (0·9)† 2·0 (0·3)†
11·1 (0·9)‡ 1·0 (0·3)‡
13·9 (0·7)† 2·0 (0·3)†
*Mean (SE); †p>0·05; ‡p<0·05.
Demographic characteristics and problem-solving scores on entire problem in formula-fed and breastfed groups
1703