Salty taste acceptance by infants and young children is related to birth weight: longitudinal analysis of infants within the normal birth weight range

Accumbal μ-opioid receptors and salt taste-elicited hedonic responses in a rodent model of prenatal adversity, and their correlates using human functional genomics

Prenatal adversity is associated with behavioral obesogenic features such as preference for palatable foods. Salt appetite may play a role in the development of adiposity and its consequences in individuals exposed to prenatal adversity, and sodium consumption involves individual differences in accumbal µ-opioid receptors function. We investigated the hedonic responses to salt and the levels of µ-opioid receptors and tyrosine hydroxylase in the nucleus accumbens (Nacc) of pups from an animal model of prenatal dietary restriction. In children, we evaluated the interaction between fetal growth and the genetic background associated with the accumbal µ-opioid receptor gene (OPRM1) expression on sodium consumption during a snack test. Sprague-Dawley dams were randomly allocated from pregnancy day 10 to receive an ad libitum (Adlib) or a 50% restricted (FR) diet. The pups' hedonic responses to a salt solution (NaCl 2%) or water were evaluated on the first day of life. FR and Adlib pups differ in their hedonic responses to salt, and there were decreased levels of accumbal µ-opioid and p-µ-opioid receptors in FR pups. In humans, a test meal and genotyping from buccal epithelial cells were performed in 270 children (38 intrauterine growth restricted-IUGR) at 4 years old from a Canadian prospective cohort (MAVAN). The OPRM1 genetic score predicted the sodium intake in IUGR children, but not in controls. The identification of mechanisms involved in the brain response to prenatal adversity and its consequences in behavioral phenotypes and risk for chronic diseases later in life is important for preventive and therapeutic purposes.

Sodium Intake Tracked from Infancy and Salt Taste Preference during Adolescence: Follow-up of a Randomized Controlled Field Trial in Brazil

Background

Effective interventions to promote healthy sodium intakes require understanding factors driving liking for salt taste.

Objectives

To examine effects of an early feeding intervention among low-income mothers on their children's energy and sodium intake and salt taste preferences at 12 years; and to identify age-related changes in dietary sodium sources.

Methods

Secondary analyses were conducted on dietary intake and taste preference data collected from children in a longitudinal trial (NCT00629629). Mothers randomized to the intervention group received counseling on healthy eating practices for 1 year postpartum; the control group received no counseling. Two-day dietary recalls were obtained at 1 year (intervention end) and at 4-, 8-, and 12-year follow-up visits, from which foods were categorized as unprocessed, processed, or ultra-processed. At the 12-year visit, children's most preferred concentration of salt was measured using a validated, forced-choice, paired-comparison tracking method, and pubertal stage was self-assessed.

Results

The intervention group had reduced energy intake compared with controls in all food categories at 1 year (P = 0.04) but not at the other time points. Sodium intake from processed foods increased from 4 to 12 years and from ultra-processed foods from 1 to 4; intake from unprocessed foods decreased from 1 to 8 year (all P < 0.01). At 12 years, children in early stages of puberty (Tanner stages 1-3; P = 0.04) or in the ≥75th percentile of sodium intake (P < 0.01) preferred significantly higher concentrations of salt than the other children.

Conclusions

Both dietary intake of sodium and early puberty were associated with preferences for higher salt concentrations. Childhood and adolescence are important periods for understanding how experience and growth shape diet by changing salt taste.

Clinical Trial Registration

This manuscript reports secondary analysis of data collected in trial NCT00629629 (2001-3) and follow-up [https://clinicaltrials.gov/ct2/show/NCT00629629?term=NCT00629629&draw=2&rank=1].

Salt need needs investigation

Expensive and extensive studies on the epidemiology of excessive Na intake and its pathology have been conducted over four decades. The resultant consensus that dietary Na is toxic, as well as the contention that it is less so, ignores the root cause of the attractiveness of salted food. The extant hypotheses are that most Na is infiltrated into our bodies via heavily salted industrialised food without our knowledge and that mere exposure early in life determines lifelong intake. However, these hypotheses are poorly evidenced and are meagre explanations for the comparable salt intake of people worldwide despite their markedly different diets. The love of salt begins at birth for some, vacillates in infancy, climaxes during adolescent growth, settles into separate patterns for men and women in adulthood and, with age, fades for some and persists for others. Salt adds flavour to food. It sustains and protects humans in exertion, may modulate their mood and contributes to their ailments. It may have as yet unknown benefits that may promote its delectability, and it generates controversy. An understanding of the predilection for salt should allow a more evidence-based and effective reduction of the health risks associated with Na surfeit and deficiency. The purpose of this brief review is to show the need for research into the determinants of salt intake by summarising the little we know.

Birth weight is associated with dietary factors at the age of 6-8 years: the Physical Activity and Nutrition in Children (PANIC) study

OBJECTIVE

Low and high birth weight have been associated with increased risk of type 2 diabetes and CVD. Diet could partly mediate this association, e.g. by intra-uterine programming of unhealthy food preferences. We examined the association of birth weight with diet in Finnish children.

DESIGN

Birth weight standard deviation score (SDS) was calculated using national birth register data and Finnish references. Dietary factors were assessed using 4 d food records. Diet quality was defined by the Finnish Children Healthy Eating Index (FCHEI).

SETTING

The Physical Activity and Nutrition in Children (PANIC) study.

SUBJECTS

Singleton, full-term children (179 girls, 188 boys) aged 6-8 years.

RESULTS

Birth weight was inversely associated (standardized regression coefficient β; 95 % CI) with FCHEI (-0·15; -0·28, -0·03) in all children and in boys (-0·27; -0·45, -0·09) but not in girls (-0·01; -0·21, 0·18) after adjusting for potential confounders (P=0·044 for interaction). Moreover, higher birth weight was associated with lower fruit and berries consumption (-0·13; -0·25, 0·00), higher energy intake (0·17; 0·05, 0·29), higher sucrose intake (0·19; 0·06, 0·32) and lower fibre intake (-0·14; -0·26, -0·01). These associations were statistically non-significant after correction for multiple testing. Children with birth weight >1 SDS had higher sucrose intake (mean; 95 % CI) as a percentage of energy intake (14·3 E%; 12·6, 16·0 E%) than children with birth weight of -1 to 1 SDS (12·8 E%; 11·6, 14·0 E%) or <-1 SDS (12·4 E%; 10·8, 13·9 E%; P=0·036).

CONCLUSIONS

Higher birth weight may be associated with unhealthy diet in childhood.

Infants' and Children's Salt Taste Perception and Liking: A Review

Sodium is an essential nutrient for the human body. It is widely used as sodium chloride (table salt) in (processed) foods and overconsumed by both children and adults, placing them at risk for adverse health effects such as high blood pressure and cardiovascular diseases. The current review focusses on the development of salt taste sensitivity and preferences, and its association with food intake. Three -to- four month old infants are able to detect and prefer sodium chloride solutions over plain water, which is thought to be a biological unlearned response. Liking for water with sodium chloride mostly decreases when infants enter early childhood, but liking for sodium chloride in appropriate food contexts such as soup and snack foods remains high. The increased acceptance and preference of sodium chloride rich foods coincides with infants' exposure to salty foods, and is therefore thought to be mostly a learned response. Children prefer higher salt concentrations than adults, but seem to be equally sensitive to salt taste. The addition of salt to foods increases children's consumption of those foods. However, children's liking for salt taste as such does not seem to correlate with children's consumption of salty foods. Decreasing the exposure to salty tasting foods during early infancy is recommended. Salt plays an important role in children's liking for a variety of foods. It is, however, questionable if children's liking for salt per se influences the intake of salty foods.

High salt intake as a multifaceted cardiovascular disease: new support from cellular and molecular evidence

Scientists worldwide have disseminated the idea that increased dietary salt increases blood pressure. Currently, salt intake in the general population is ten times higher than that consumed in the past and at least two times higher than the current recommendation. Indeed, a salt-rich diet increases cardiovascular morbidity and mortality. For a long time, however, the deleterious effects associated with high salt consumption were only related to the effect of salt on blood pressure. Currently, several other effects have been reported. In some cases, the deleterious effects of high salt consumption are independently associated with other common risk factors. In this article, we gather data on the effects of increased salt intake on the cardiovascular system, from infancy to adulthood, to describe the route by which increased salt intake leads to cardiovascular diseases. We have reviewed the cellular and molecular mechanisms through which a high intake of salt acts on the cardiovascular system to lead to the progressive failure of a healthy heart.

Dietary behaviors of adults born prematurely may explain future risk for cardiovascular disease

Being born prematurely associates with greater cardiovascular disease (CVD) risk in adulthood. Less understood are the unique and joint associations of dietary patterns and behaviors to this elevated risk among adults who are born prematurely. We aimed to model the associations between term status, dietary and lifestyle behaviors with CVD risk factors while accounting for the longitudinal effects of family protection, and medical or environmental risks. In wave-VIII of a longitudinal study, 23-year olds born prematurely (PT-adults, n = 129) and full term (FT-adults, n = 38) survey-reported liking for foods/beverages and activities, constructed into indexes of dietary quality and sensation-seeking, dietary restraint and physical activity. Measured CVD risk factors included fasting serum lipids and glucose, blood pressure and adiposity. In bivariate relationships, PT-adults reported lower dietary quality (including less affinity for protein-rich foods and higher affinity for sweets), less liking for sensation-seeking foods/activities, and less restrained eating than did FT-adults. In comparison to nationally-representative values and the FT-adults, PT-adults showed greater level of CVD risk factors for blood pressure and serum lipids. In structural equation modeling, dietary quality completely mediated the association between term status and HDL-cholesterol (higher quality, lower HDL-cholesterol) yet joined term status to explain variability in systolic blood pressure (PT-adults with lowest dietary quality had highest blood pressures). Through lower dietary quality, being born prematurely was indirectly linked to higher cholesterol/HDL, higher LDL/HDL and elevated waist/hip ratios. The relationship between dietary quality and CVD risk was strongest for PT-adults who had developed greater cumulative medical risk. Protective environments failed to attenuate relationships between dietary quality and elevated CVD risk among PT-adults. In summary, less healthy dietary behaviors contribute to elevated CVD risk among young adults who are born prematurely.

Ontogeny of taste preferences: basic biology and implications for health

Health initiatives address childhood obesity in part by encouraging good nutrition early in life. This review highlights the science that shows that children naturally prefer higher levels of sweet and salty tastes and reject lower levels of bitter tastes than do adults. Thus, their basic biology does not predispose them to favor the recommended low-sugar, low-sodium, vegetable-rich diets and makes them especially vulnerable to our current food environment of foods high in salt and refined sugars. The good news is that sensory experiences, beginning early in life, can shape preferences. Mothers who consume diets rich in healthy foods can get children off to a good start because flavors are transmitted from the maternal diet to amniotic fluid and mother's milk, and breastfed infants are more accepting of these flavors. In contrast, infants fed formula learn to prefer its unique flavor profile and may have more difficulty initially accepting flavors not found in formula, such as those of fruit and vegetables. Regardless of early feeding mode, infants can learn through repeated exposure and dietary variety if caregivers focus on the child's willingness to consume a food and not just the facial expressions made during feeding. In addition, providing complementary foods low in salt and sugars may help protect the developing child from excess intake later in life. Early-life experiences with healthy tastes and flavors may go a long way toward promoting healthy eating, which could have a significant impact in addressing the many chronic illnesses associated with poor food choice.

Genetic and environmental influences on sodium intake determined by using half-day urine samples: the Healthy Twin Study

BACKGROUND

Salt is essential in our diet, but excess intake is a well-established risk factor for hypertension. The presence and importance of genetic contributions to salt intake, however, are not well understood.

OBJECTIVE

The aim of this study was to examine whether a genetic predisposition and an environmental influence exist for sodium intake and salt habit.

DESIGN

In a twin-family cohort, half-day urine samples from 1204 individuals (133 pairs of monozygotic twins, 29 pairs of dizygotic twins, and 880 singletons) were collected to assess 24-h sodium intakes. Daily total sodium intake, sodium density per calorie (Na-D), and salt habit questions were analyzed with adjustment for other epidemiologic characteristics. We calculated heritability (h2) and intraclass correlations to examine the genetic and shared environmental contributions to total sodium intake traits.

RESULTS

The average sodium intake was 208.4 ± 107.0 mmol/d. Men had a higher absolute sodium intake (242.6 ± 117.4 mmol/d), but Na-D did not differ by sex. Moderate genetic influences existed (h2 = 0.31-0.34) for sodium intake and Na-D. We also found that sharing current residence rather than being a family member explained 22% of the variance in Na-D.

CONCLUSION

Our findings suggest that both genetic predisposition and shared environment contribute to sodium intakes and salt habits alike.

Facial soft tissue dynamics before and after primary lip repair

Objectives :  (1) To collect three-dimensional, dynamic facial images from two groups of infants: one group born with cleft lip and palate slated to have a primary lip repair and a second, age-matched, noncleft control group. (2) To develop analyses to determine differences in facial movement between infants with cleft lip with or without palate (CL±P) and noncleft control infants and to determine changes in facial movement before and after primary lip repair. Design :  Longitudinal, prospective case-control study. Setting :  Facial Animation Laboratory at the University of North Carolina School of Dentistry. Participants :  Two groups of infants: one group with unrepaired CL±P slated to have primary lip repair (n = 15) and a second group of age-matched, noncleft controls (n = 15). Interventions :  Movement testing before and 4 months after primary lip repair in infants with CL±P and at similar time points in noncleft infants. Main Outcome Measures :  Seven measures of facial movement. Results :  The range of facial movements increased by 17% for all infants during the 4-month period. Compared with the noncleft group (1) infants with unilateral CL±P had 50% less nasolabial movement, and this difference did not change due to the lip repair; and (2) infants with unilateral or bilateral CL±P had 58% and 118% greater lateral upper lip movement, respectively, and 3.67 and 3.56 times greater asymmetry of movement, respectively, before lip repair. The procedure almost entirely removed the hypermobility and decreased the asymmetry. Conclusions :  Primary surgical lip repair decreased hypermobility and improved asymmetry of upper lip movement.

Does salt intake in the first two years of life affect the development of cardiovascular disorders in adulthood?

Excess salt intake impacts on blood pressure (BP) and the pathogenetic mechanisms of atherosclerosis predisposing to stroke and other cardiovascular disorders. The influence of salt starts early in life. Two randomized controlled trials in newborn infants suggest a direct association between dietary sodium intake and BP since the first few months of life. Newborn infants display aversion to the salt taste to develop a "preference" for salt only at age 2-3 years, in part in relation to post-natal events: this preference might be associated with later development of hypertension. The amount of sodium to be retained by an infant for proper physiological growth is largely covered by breast feeding (or low sodium formula milk) in the first six months, and later on by the gradual implementation of complementary feeding, without the need for any added salt upon food preparation. Given the lack of dose-dependence data, reference nutrient intakes (RNI) or adequate intakes (AI) for sodium have been established by national health institutions in various countries. The U.K. RNI was set at 242 mg a day for infants 0-6 months with gradual increase to 0.5 g up until age 3. The U.S. AI is somewhat lower for age 0-6 months but larger for age 1-3 years. According to a recent report, the average sodium intake in U.S. children is close to the AI up to age 2 years, to become progressively greater exceeding the Institute of Medicine recommendation later on.

The development of salty taste acceptance is related to dietary experience in human infants: a prospective study

BACKGROUND

Sodium intake is related to hypertension and other diseases, but little is known about the early development of salty taste acceptance.

OBJECTIVE

The prospective study asked whether dietary experience with foods containing sodium is associated with development of infant salty taste preference.

DESIGN

Infants (n = 61) were tested at 2 and 6 mo to assess their response to 0.17 and 0.34 mol NaCl/L in water. Intake tests consisted of randomized double-blind 120-s exposure to salt solutions and water. Acceptance, calculated as solution intake relative to water, was examined as a function of exposure to starchy table food-a significant source of sodium. Dietary exposure (yes or no) was defined by maternal report. As a control, similar comparisons were based on exposure to fruit table food. A subset of 26 subjects returned at 36-48 mo for assessment of salty taste hedonics and preference.

RESULTS

Dietary experience was related to salt acceptance, with only those infants previously exposed to starchy table foods (n = 26) preferring the salty solutions at 6 mo (P = 0.007). Fruit exposure was not associated with sodium chloride acceptance. Infants eating starchy table foods at 6 mo were more likely to lick salt from the surface of foods at preschool age (P = 0.007) and tended to be more likely to eat plain salt (P = 0.08).

CONCLUSIONS

The findings suggest an influential role of early dietary experience in shaping salty taste responses of infants and young children.

Evaluation of the Monell forced-choice, paired-comparison tracking procedure for determining sweet taste preferences across the lifespan

Lack of methodology to assess taste in children limits its measurement in research studies that include pediatric populations. We used the Monell 2-series, forced-choice tracking method to measure sucrose preferences of a racially/ethnically diverse sample (n = 949) of children, adolescents, and adults. Reliability was assessed by comparing the results of the first series with the second series. Validity was assessed by relating participants' sucrose preferences to their preferences for foods varying in sweetness. The task required, on average, 7 presentations of aqueous sucrose solution pairs. Children and adolescents preferred more concentrated sweetness than adults (P < 0.001). Black children/adolescents preferred a more concentrated sucrose solution than did White children/adolescents even when gender, parental education level, and family income were used as covariates. Data from a single series were sufficient to detect age-related differences but insufficient to detect racial/ethnic differences in sweet preferences. Level of sweetness preferred significantly correlated with the sugar content of favorite cereals (P < 0.001) and beverages (P < 0.02). This method is brief and has evidence of reliability and external validity. Although a single series will yield useful information about age-related differences in taste preferences, the 2-series version should be considered when differences in race/ethnicity are of interest.

Early flavor learning and its impact on later feeding behavior

In this review, we first outline the role and mechanisms of the chemical senses (taste, smell, and chemical irritation) in the perception of the flavor of a food or beverage. We then describe research findings, much of them from our laboratories, on the ontogeny of flavor perception and the interacting roles of innate responses and learning in the establishment of flavor preference of infants and children. Broadly, taste (sweet, sour, salty, bitter, umami, or savory) preferences have a strong innate component. Sweet, umami, and salty substances are innately preferred, whereas bitter and many sour substances are innately rejected. Nevertheless, these innate tendencies can be modified by pre- and postnatal experiences. Volatile components of flavor, detected by the olfactory system, are strongly influenced by early exposure and learning beginning in utero and continuing during early milk (breast milk or formula) feedings. These experiences set the stage for later food choices and are important in establishing life-long food habits. As many of the diseases plaguing developed and developing societies involve excess consumption of some foods, an understanding of factors that determine choice and ingestion, particularly an understanding of the early factors, is important in designing strategies to enhance the health of the infant, child, and adult.

Biobehavior of the human love of salt

We are beginning to understand why humans ingest so much salt. Here we address three issues: The first is whether our salt appetite is similar to that in animals, which we understand well. Our analysis suggests that this is doubtful, because of important differences between human and animal love of salt. The second issue then becomes how our predilection for salt is determined, for which we have a partial description, resting on development, conditioning, habit, and dietary culture. The last issue is the source of individual variation in salt avidity. We have partial answers to that too in the effects of perinatal sodium loss, sodium loss teaching us to seek salt, and gender. Other possibilities are suggested. From animal sodium appetite we humans may retain the lifelong enhancement of salt intake due to perinatal sodium loss, and a predisposition to learn the benefits of salt when in dire need. Nevertheless, human salt intake does not fit the biological model of a regulated sodium appetite. Indeed this archetypal 'wisdom of the body' fails us in all that has to do with behavioral regulation of this most basic need.

[Nutrient intakes in 2005 by non-breast fed French children of less than 36 months]

BACKGROUND

Knowledge of the nutritional consumption of very young children is of main interest, but little is known about the dietary status of French infants and toddlers.

OBJECTIVE

To assess energy and nutrient intake and the adequacy of diet of French infants and toddlers.

DESIGN AND SETTING

A national cross-sectional survey was conducted in France from January to March 2005, using proportionate quota sampling based on the age of the children, the occupation of the mother, and the family socioeconomic category.

SUBJECTS

Seven-hundred and six children were allocated to 11 age subgroups ranging from one to three months to 31-36 months. Totally or partially breastfed infants were excluded. ANALYSES PERFORMED: Individual consecutive 3-day weight food records were converted into energy intake and intake of 24 nutrients according to food composition databases recently updated for 1260 standard foods and all the formulae and specific baby foods manufactured and marketed in France in 2005.

RESULTS

Mean daily energy intake in 2005 was above the estimated average requirement up to seven months of age, but was lower after one year. Protein, fat, and carbohydrate intakes were adequate, while calcium, magnesium, phosphorus and B group vitamins were above the recommended dietary allowances for all 11 subgroups. However, for toddlers over 12 months of age, some may have had an inadequate intake of alpha-linolenic acid, vitamin E, vitamin C, iron and zinc, whereas mean sodium intake was above the adequate intake for all age subgroups.

CONCLUSIONS

The diet of French infants was adequate for a large proportion of children and satisfied most of their nutritional requirements. However, the intake of iron and alpha-linolenic acid in particular needs to be improved for some French toddlers.