ORIGINAL ARTICLE Breast feeding in infancy and arterial endothelial function later in life. The Cardiovascular Risk in Young Finns Study MJ Ja ¨rvisalo 1,2,3 , N Hutri-Ka ¨ho ¨nen 4 , M Juonala 2,3 , V Mikkila ¨ 5 , L Ra ¨sa ¨nen 5 , T Lehtima ¨ki 6 , J Viikari 2 and OT Raitakari 1 1 Department of Clinical Physiology, University of Turku, Turku, Finland; 2 Department of Medicine, University of Turku, Turku, Finland; 3 Research Centre of Applied and Preventive Cardiovascular Medicine, University of Turku, Turku, Finland; 4 Department of Pediatrics, Tampere University Hospital and the Medical School, Tampere, Finland; 5 Division of Nutrition, University of Helsinki, Helsinki, Finland and 6 Department of Clinical Chemistry, Tampere University Hospital and the Medical School, Tampere, Finland Background/Objectives: Breast feeding in infancy may be associated with reduced cardiovascular morbidity in adulthood. We examined the association between breast feeding in infancy and arterial function and structure in adulthood in a population- based cohort of Finnish adults. Subjects/Methods: Noninvasive ultrasound was used to measure brachial artery flow-mediated dilatation (FMD), carotid artery intima-media thickness (IMT) and carotid artery compliance (CAC) in 1667 young adults participating in the Cardiovascular Risk in Young Finns Study with data on early nutrition. Results: Maximal FMD was higher in breast-fed men compared to formula-fed men (7.2 ± 4.0 vs 5.9 ± 3.4%, P ¼ 0.029) while no differences were seen between breast-fed and formula-fed women (8.9±4.5 vs 8.8±5.0%, P ¼ 0.84). In men, the multivariable correlates of FMD included the group variable for breast feeding (P ¼ 0.014), birth weight (P ¼ 0.043), waist circumference (Po0.001) and baseline brachial artery diameter (Po0.001). In women, the multivariable correlates of FMD were birth weight (P ¼ 0.02), waist circumference (Po0.001) and brachial artery baseline diameter (Po0.001). Breast feeding was not significantly associated with IMT or CAC in multivariable models. Conclusions: Adult men who have been breast fed have better brachial endothelial function compared to men who have been formula fed. European Journal of Clinical Nutrition advance online publication, 20 February 2008; doi:10.1038/ejcn.2008.17 Keywords: arteries; atherosclerosis; breast feeding; risk factors; ultrasound Introduction Breast feeding in infancy has been associated with reduced cardiovascular risk in adulthood. Observational studies have associated breast feeding with lower blood pressure (Martin et al., 2004) and favourable serum lipid profile (Ravelli et al., 2000), and with a decreased risk for obesity (Gillman et al., 2001), impaired glucose tolerance (Pettitt et al., 1997) and cardiovascular disease (Fall et al., 1992). Moreover, Singhal et al. (2004) demonstrated in a randomized controlled setting that breast milk in comparison to formula feeding leads to a favourable cardiovascular disease risk factor status later in life. Brachial artery flow-mediated dilatation (FMD) is a marker of arterial endothelial function that can be measured noninvasively by ultrasound. The FMD response reflects nitric oxide release from vascular wall endothelial cells (Mullen et al., 2001). Normal endothelial function is recognized as an important atheroprotective factor that inhibits atherogenesis by favouring vasodilatation over vasoconstriction, and by regulating leukocyte-endothelial cell interactions, smooth-muscle cell proliferation and thrombocyte aggregation (Raitakari and Celermajer, 2000). Endothelial dysfunction is an early event in athero- genesis that precedes the development of morphological Received 18 December 2007; accepted 20 January 2008 Correspondence: Professor OT Raitakari, Department of Clinical Physiology, Turku University Hospital, Kiinamyllynkatu 4-8, FIN-20520 Turku, Finland. E-mail: olli.raitakari@utu.fi European Journal of Clinical Nutrition (2008), 1–6 & 2008 Nature Publishing Group All rights reserved 0954-3007/08 $30.00 www.nature.com/ejcn