Our previous work identified that across a wide range of species optimal ratios of macronutrients exist and that protein intake is a critical determinant of total energy intake [ 14 15 ]. Animal models confirm that the ratio of dietary P:C impacts on aging and disease, with indirect evidence from human models suggesting the P:C ratio is a primary determinant of health [ 16 ]. We have demonstrated a link between maternal dietary ratio of protein to non-protein energy to variations in offspring body composition [ 15 ]. In human pregnancy, maternal macronutrient profile was associated with fetal adiposity and fat distribution [ 14 ]. Here we have examined the link between maternal macronutrient ratios and childhood blood pressure trajectory. We hypothesized that after adjustment for potential confounders and growth indices, child systolic BP up to age four years would be associated with maternal pregnancy macronutrient intake and protein-to-carbohydrate (P:C) ratio.

The escalation in prevalence of maternal and child obesity increases the public health significance of determining the extent to which maternal diet can predict offspring BP [ 10 ]. In healthy weight pregnant women exposed to a variety of dietary and/or supplement regimes there was minimal impact on offspring BP, compared to women who experienced lifestyle and nutritional limitations similar to conditions in World War II [ 12 13 ]. However, much stronger associations have been reported on later BP when birthweight and/or accelerated postnatal growth were considered, or adjustment for current body weight [ 13 ]. This highlights the inter-relationships between childhood growth, current body weight and cardiovascular control.

Variations in maternal diet during pregnancy may lead to elevated offspring risk in adulthood for hypertension and obesity. Both human and animal studies provide compelling evidence suggesting a link between maternal nutritional status and offspring cardiovascular function [ 5 ]. Animal studies provide indisputable evidence that maternal protein restriction or a global reduction in dietary intake during pregnancy can influence offspring cardiovascular function [ 5 8 ]. Studies have mainly focused on interventions in pregnant rodents, although several dietary intervention studies in pregnant sheep suggest commonality among species [ 5 ]. Raised blood pressure has frequently been reported in offspring of nutritionally deprived animals and those fed a low protein-to-carbohydrate (P:C) ratio diet during pregnancy [ 5 9 ]. Prenatal exposure to protein restriction or dietary global restriction in animal models has produced offspring with abnormalities in vascular function in isolated resistance arteries [ 5 ]. However in recent cross-sectional studies of children born in developed countries, associations between changes in diet during pregnancy with childhood BP have been small, or negligible [ 10 ]. A recent Finnish study found systolic BP in four year old children was positively associated with maternal pregnancy carbohydrate and fat intakes [ 11 ]. The same group also reported a U-shaped relationship between both maternal carbohydrate and monounsaturated fat intakes and infant BP at six months [ 12 ].

The worldwide burden of cardiovascular disease (CVD) has substantially increased, to cause an estimated 17.3 million deaths in 2008 [ 1 ]. It is forecast that by 2030, more than 23 million people will die annually from CVDs [ 2 ]. Elevated blood pressure (BP) and childhood adiposity are independent predictors of adult hypertension and CVD [ 3 ]. Both obesity and hypertension are increasingly prevalent in the pediatric population, with 42 million children under five estimated to be overweight in 2013 and 2% to 5% of children considered hypertensive globally [ 2 ]. There is strong evidence across diverse populations for tracking of BP from childhood into adulthood [ 4 ]. Even short periods of hypertension in childhood increases the adult risk of hypertension [ 1 ]. Thus early prevention of elevated BP is an important global public health goal.

In preliminary univariate analyses, maternal age, pre-pregnancy weight, education, parity, smoking status, weight gained during pregnancy, preterm delivery, marital status, ethnicity and child gender were not significant predictors for childhood systolic or diastolic BP (< 0.2) and did not remain in multivariate models (data not shown). Analyses were conducted using: (i) unadjusted data; (ii) data adjusted for maternal energy intake and child birthweight; and (iii) data adjusted for maternal energy intake, birthweight and child BMI-score. All analyses were repeated with and without women who reported diabetes or hypertension during pregnancy. The main findings did not change with the exclusion of women who reported diabetes (= 8) or hypertension (= 10) during pregnancy, thus analyses were not adjusted for these conditions. To address potential dietary misreporting, the pregnancy energy cut-off values recommended by Meltzer(2008) [ 24 ] were applied, by excluding those who reported daily energy intakes <4.5 or >20.0 MJ/day [ 24 ].

Details of the data collection have been described elsewhere [ 20 ]. Demographic and social data were collected during the first study visit using questions modeled on those in the Women’s Health Australia, Australian Longitudinal Study on Women’s Health survey. Pre-pregnancy weight was self-reported at either the first antenatal clinic visit at 14 weeks gestation or at the first study visit. Dietary data during pregnancy were collected between 18 to 24 weeks and again at 36 to 40 weeks gestation using a validated 74-item food frequency questionnaire (FFQ), the Dietary Questionnaire for Epidemiological Studies. This tool was previously validated against weighed-food records in young women [ 21 ]. The FFQ includes food and beverage data but does not ask about vitamin or mineral supplement use. The dietary intake reference period was the previous three months. Therefore, dietary data collected between 18 to 24 weeks and 36 to 40 weeks gestation referred to a reference period of 6 to 24 weeks gestation (early pregnancy) and 24 to 40 weeks gestation (late pregnancy), respectively. Positive moderate to strong pairwise correlations have been previously reported between all dietary variables in early and late pregnancy (0.46 << 0.78;< 0.001) [ 14 ]. Therefore, maternal dietary intakes during pregnancy were expressed as the mean of intakes during early and late pregnancy.

The characteristics of the WATCH cohort have been reported previously [ 19 20 ]. The WATCH study contained a higher proportion of women with post-school qualifications and socioeconomic advantage, but a similar proportion of overweight/obese and of indigenous ethnicity as the Australian population [ 14 20 ]. Significant differences were also previously found between women with available dietary data (= 156) and women without dietary data (= 23). Women without dietary data were less likely to be married or in a de facto relationship (= 0.03) and more likely to be of socio-economic disadvantage (= 0.04) and to have had a preterm delivery (= 0.001) [ 14 ].

The sample is from the Women and Their Children’s Health (WATCH) study (= 179). WATCH is a prospective, longitudinal cohort investigating whether maternal nutrition is an important predictor of offspring outcomes including growth, body composition and childhood cognition [ 17 ]. The WATCH study was initiated in July 2006 in Newcastle, Australia. Pregnant participants were recruited from the antenatal clinic at the John Hunter Hospital from July 2006 to June 2008. A consent rate of 61% was achieved for pregnant women who were approached [ 18 ]. No exclusion criteria were used during recruitment. Women attended study visits during pregnancy at 19, 24, 30, and 36 weeks of gestation. Postnatal follow-up of women and their children occurred at 3-month intervals during the first year after birth and annually thereafter, until age 4 years.

Figure 1. Effects of maternal macronutrient intake during pregnancy on child mean systolic blood pressure up to four years. Plotted onto arrays of maternal dietary macronutrient composition points are fitted surfaces for the response variable (child mean systolic blood pressure). The isolines for the child mean systolic blood pressure rise in elevation from dark blue to dark red. A maternal diet with a P:C ratio of 0.29 corresponded with a child systolic BP of 104.5, compared with a systolic BP of 97.5 for a P:C ratio of 0.9. Child systolic BP was greatest at low proportions of dietary protein (<16% of energy) and high carbohydrate (>40% of energy) intakes.

Figure 1. Effects of maternal macronutrient intake during pregnancy on child mean systolic blood pressure up to four years. Plotted onto arrays of maternal dietary macronutrient composition points are fitted surfaces for the response variable (child mean systolic blood pressure). The isolines for the child mean systolic blood pressure rise in elevation from dark blue to dark red. A maternal diet with a P:C ratio of 0.29 corresponded with a child systolic BP of 104.5, compared with a systolic BP of 97.5 for a P:C ratio of 0.9. Child systolic BP was greatest at low proportions of dietary protein (<16% of energy) and high carbohydrate (>40% of energy) intakes.

The association between maternal P:C ratio during pregnancy and child mean systolic BP up to 4 years is presented in Figure 1 . The surface plot highlighted that mean child systolic BP remained constant with changing proportions of dietary fat, but was influenced by the P:C ratio of maternal diet during pregnancy. A maternal diet with a P:C ratio of 0.29 corresponded with a child systolic BP of 104.5, compared with a systolic BP of 97.5 for a P:C ratio of 0.9. Child systolic BP was greatest at low proportions of dietary protein (<16% of energy) and high carbohydrate (>40% of energy) intakes.

Maternal dietary composition during pregnancy is summarized in Table 3 . Results of the mixed-model regression analyses examining relationships between pregnancy diet and child systolic BP up to age 4 years are summarized in Table 4 . The components of maternal diet associated with child systolic BP included: PUFA (% of energy), specifically-6 fatty acids (% of energy), and the P:C ratio ( Table 4 ). Median (25p, 75p) P:C ratio was 0.43 (0.38, 0.48). Therefore, for each 0.1 unit decrease in the P:C ratio during pregnancy, child systolic BP increased by 1.41 mmHg ( Table 4 ). Similar findings were observed in the comparison of energy-adjusted values ( Table 4 ). In subgroup analyses, maternal smoking status did not have a significant effect on childhood systolic BP (data not shown). There were no relationships between maternal pregnancy diet and child diastolic BP up to 4 years.

4. Discussion

This is the first prospective study to longitudinally examine the relationship between maternal diet during pregnancy and the trajectories of child BP up to four years. Results indicate that lower P:C ratios in maternal diet are associated with increased child systolic BP up to four years of age. Childhood systolic BP was also positively associated with maternal intake of PUFA and n -6 fatty acids, despite remaining constant with changing total fat intake.

i.e. , below the 90th percentile) [ Strong evidence supports the tracking of BP from childhood to adult life [ 4 ]. Women who gave birth during the Dutch famine in 1944–1945 illustrate that offspring BP as young adults was inversely associated with the P:C ratio of the average ration during the third trimester, but not associated with any absolute measure of intake [ 26 ]. This suggests that long-term health may be linked more strongly to the macronutrient ratio of maternal diet as opposed to absolute intakes. This study is the first to confirm similar findings in children. Mean childhood BP measures were within normal ranges (, below the 90th percentile) [ 27 ]. However, mean systolic BP and diastolic BP measures within this study were significantly higher than those reported by other contemporary birth cohorts [ 11 13 ]. The most likely explanation for these higher values is that BP was only measured on one occasion at each time point rather than an average of the two or three values used in other studies. The P:C ratio may further influence non-energy providing micronutrients that may affect childhood BP. Intervention studies have shown that a modest increase in dietary protein (5.3% of energy) with a corresponding reduction in carbohydrate subsequently decreased sodium intake (25mmol/day) in adults, in conjunction with a reduction in blood pressure [ 28 ]. Macronutrient ratios may influence offspring health and disease [ 16 ]. Future research is required to include the P:C ratio when evaluating the influence of maternal macronutrient composition during pregnancy on offspring health outcomes, and consider its impact on micronutrient intakes.

8, 1 - and β 1 - Na+/K+ ATPase and renal tubular bumetanide-sensitive and thiazidesensitive sodium co-transporters [ While potential molecular mechanisms related to our findings are poorly understood, animal models provide important mechanistic insights and suggest that nutritional deprivation or excess during pregnancy may stimulate epigenetic processes [ 5 13 ]. These events lead to both acute changes in offspring tissue structure and organ development, and permanent alterations in gene expression through DNA and histone methylation or histone acetylation [ 29 30 ], with subsequent cardio-metabolic consequences [ 5 ]. Rodent and sheep models support findings in the current study and provide strong evidence of a relationship between maternal protein intake during pregnancy and offspring cardiovascular function [ 6 31 ]. Offspring of nutritionally deprived animals commonly display elevated BP, while offspring exposed to protein or energy restriction during pregnancy show abnormal vascular function in isolated resistance arteries [ 32 ]. Additional consequences include increased sympathetic outflow [ 6 ], possibly due to altered interactions between the aberrant central signaling pathways in the renin-angiotensin system and sympathetic efferent activity [ 32 ]. While others have suggested mechanistic changes in renal sodium transport, including altered mRNA expression of α- and β- Na/KATPase and renal tubular bumetanide-sensitive and thiazidesensitive sodium co-transporters [ 5 ]. However, evidence for associations between maternal diet during pregnancy and offspring cardiovascular function in human cohorts, while valuable, is indirect. Causality cannot be inferred from this study because of its observational nature and the possibility of residual confounding cannot be excluded. Therefore, the effect of variations in maternal macronutrient composition requires further investigation using (i) animal model interventions; (ii) observational studies using statistical approaches such as propensity score analysis, to address residual confounding; or (iii) opportunistic examination within interventions targeting maternal nutrition to improve pregnancy dietary intake.

Compelling arguments have emerged from animal models of dietary balance (specifically the ratio of dietary P:C) regarding nutritional targets for optimal health and ageing [ 16 ]. The balance of macronutrients, rather than the absolute intake of a single nutrient, is a key determinant of lifespan [ 16 ]. In insect and mouse models, diets with decreased P:C were associated with increased lifespan and improved cardio-metabolic outcomes in later life [ 16 ]. These data are supported indirectly by a systematic review showing increased mortality in human studies associated with low carbohydrate diets [ 16 ], and a recent study showing increased mortality and cancer in humans on high protein diets [ 16 ]. Both high and low P:C diets have benefits and risks [ 33 ], which highlights an important role for macronutrient balance in optimizing the relationship between diet and disease risk. Recent evidence indicates that the interaction of a dominant protein appetite with weaker carbohydrate and fat appetites is a primary driver of total energy intake in mice and humans (termed “protein leverage”) [ 15 ]. The findings suggest that pregnant women may be driven to achieve a “target” percentage protein intake, as the median percentage of energy from protein throughout pregnancy within our sample was stable at 19% [ 14 ]. This potentially dominant appetite for protein during pregnancy may significantly influence the development of offspring BP in early childhood and thus play an important role in the development of pediatric and adult hypertension. Coupled with a severe decrease in P:C ratio being related to a greater tendency to store excess body fat and increased risk of decreased longevity associated with obesity [ 15 ], maternal macronutrient ratio may further increase the risk of elevated blood pressure through its influence on offspring adiposity [ 14 ]. Research investigating protein leverage during pregnancy, including the role of macronutrient balance (maternal prenatal and offspring postnatal diet) in the development of offspring blood pressure up until adulthood, and secondary outcomes such as increased adiposity, are required before pregnancy dietary recommendation to optimize childhood blood pressure can be formulated.

n -3 and n -6) have differential health effects, with n -6 PUFAs and PUFA ratios generating scientific debate regarding their role in human physiological processes [ n -6 intakes surround the notion that inflammation plays a key role in CVD mechanisms [ n -6 linoleic acid (LA) in place of SFA showed no cardiovascular benefit and actually increased the risk of death from all causes, coronary heart disease and CVD [ n -6 PUFAs to cardiovascular pathogenesis is based on a diet-induced increase in the production of bioactive oxidized LA metabolites [ n -6 LA facilitate this oxidation, leading to oxidized LA metabolite mediated atherosclerotic progression and increased cardiovascular mortality [ n -6 fatty acids intakes during pregnancy, despite BP remaining constant with changing maternal total fat intake and being altered with P:C ratio. The influence of maternal diet on child BP may also be secondary to its influence on maternal BP during pregnancy. A higher maternal BP during pregnancy could reflect the mother’s own fetal experience, which consequently influences the intrauterine environment she provides for her children. Further research to elucidate the role of n -6 fatty acids in cardiovascular disease mechanisms, particularly maternal and child blood pressure, is warranted. The role of maternal pregnancy PUFA intakes with development and regulation of child BP remains unclear. It is known that dietary PUFA intakes play a role in BP regulation and have usually been associated with beneficial effects [ 34 ]. However, emerging evidence suggests that PUFA classes (-3 and-6) have differential health effects, with-6 PUFAs and PUFA ratios generating scientific debate regarding their role in human physiological processes [ 34 ]. Both classes of fatty acids have been shown to reduce BP in adult rats and hypertensive subjects [ 35 36 ]. However, significant reductions in BP in normotensive subjects have not been shown, nor have beneficial effects of PUFA on CVD risk markers been reported universally [ 36 ]. Arguments for reduced-6 intakes surround the notion that inflammation plays a key role in CVD mechanisms [ 36 ]. Recent evidence from the Sydney Diet Heart Study reported that in men aged 30 to 59 years, substituting dietary-6 linoleic acid (LA) in place of SFA showed no cardiovascular benefit and actually increased the risk of death from all causes, coronary heart disease and CVD [ 37 ]. The proposed mechanistic model linking-6 PUFAs to cardiovascular pathogenesis is based on a diet-induced increase in the production of bioactive oxidized LA metabolites [ 37 ]. Oxidized LA metabolites are the most abundant oxidized fatty acids in oxidized low-density lipoprotein molecules. Ramsden and colleagues hypothesize that oxidative stress combined with diets high in-6 LA facilitate this oxidation, leading to oxidized LA metabolite mediated atherosclerotic progression and increased cardiovascular mortality [ 37 ]. Increased circulating oxidized low-density lipoprotein has been reported in hypertensive men [ 38 ] and women with pre-eclampsia [ 39 ]. Limited research has been conducted in pregnancy. There is a lack of population-based research examining the relationship between maternal pregnancy PUFA intake and offspring BP. Results in the current study support a positive relationship between trajectory of childhood systolic BP up to age four years and maternal PUFA and-6 fatty acids intakes during pregnancy, despite BP remaining constant with changing maternal total fat intake and being altered with P:C ratio. The influence of maternal diet on child BP may also be secondary to its influence on maternal BP during pregnancy. A higher maternal BP during pregnancy could reflect the mother’s own fetal experience, which consequently influences the intrauterine environment she provides for her children. Further research to elucidate the role of-6 fatty acids in cardiovascular disease mechanisms, particularly maternal and child blood pressure, is warranted.