A diet high in sugar during adulthood is associated with weight gain, and has also been linked to risk of type 2 diabetes, fatty liver disease, and heart disease.
New research shows that when consumed by moms during the breastfeeding period, a high sugar diet can also impact developmental outcomes during infancy.
Michael I. Goran, PhD, Program Director for Diabetes and Obesity at Children’s Hospital Los Angeles, has studied how sugar can impact family health.
His previous research has shown that moms who consume sugary beverages and juices in the months after giving birth are at risk for weight gain, and may also expose their newborns to these added sugars through breast milk.
A new study published in The American Journal of Clinical Nutrition reveals that consuming these beverages during the breastfeeding period may also lead to poorer cognitive development in children nearly two years later.
The participants were 88 mothers who reported sugary beverages and juices consumed per day during the first month of breastfeeding. Their children were assessed using the Bayley-III Scales of Infant Development at 2 years old.
Moms who reported greater consumption of sugary beverages and juices had children with poorer cognitive development scores.
The researchers speculated that added sugar from the mom’s diet was passed to their infant through breast milk, and this exposure could conceivably interfere with brain development.
“Breastfeeding can have so many benefits,” says Dr. Goran, “but we’re seeing that breast milk is influenced by what moms eat and drink even more than we realized.”
He says that limiting added sugars, found in beverages such as soft drinks, may have benefits not only for moms, but also for babies. “Moms may not realize that what they eat and drink during breastfeeding may influence their infant’s development down the road, but that’s what our results indicate.”
“Ultimately, we want babies to receive the best quality nutrition,” says Paige K. Berger, PhD, RD, Postdoctoral Research Fellow and first author of the study.
“Our findings may be used to guide future nutrition recommendations for moms during breastfeeding, to better ensure that babies are getting the right building blocks for cognitive development.”
Funding: The study was funded by the Eunice Kennedy Shriver National Institute of Child Health & Human Development (K99 HD098288), the National Institute of Diabetes and Digestive and Kidney Diseases (R012DK110793), and the National Center for Advancing Translational Science (UL1TR001855 and UL1TR000130). This work was also funded by the Gerber Foundation (15PN-013).
Added sugar is an established risk factor for obesity as well as related metabolic diseases including type 2 diabetes, cardiovascular disease and non-alcoholic fatty liver [1,2,3,4,5].
Fructose appears to be at least partially responsible for this detrimental relationship, as fructose metabolism is unregulated [6,7] and fructose has been linked to greater adiposity and metabolic disturbances compared to other sugars that appear to be especially important during critical periods of growth and development [8].
While many studies have examined the impact of fructose and other sugars on body weight in childhood, few studies have examined the impact of early exposures to these sugars during infancy [9,10].
One of the most direct routes by which infants may be exposed to fructose and other sugars is through breastfeeding. During the first six months of life, many infants obtain their nourishment predominately if not exclusively from breast milk, which contains a variety of macronutrients and other relevant factors (e.g., cytokines, appetite hormones) [11,12,13].
While this exclusive breastfeeding period would appear to preclude any access to fructose exposure in early-life, studies have shown that the composition of breast milk is shaped by the maternal diet [14,15].
Therefore, breast milk may contain varying levels of maternal dietary macronutrients that have the potential to contribute to childhood obesity and future metabolic disease risk [16,17,18,19]. For instance, in infants born to mothers diagnosed with gestational diabetes (GDM), consuming greater volumes of ‘diabetic’ milk in the first week of life has been found to be associated with a 2-fold increased risk of being overweight at age 2 [20].
This effect is attributed, in part, to the higher levels of glucose and insulin observed in the breast milk of mothers with GDM [21,22]. Breast milk concentrations of glucose and insulin have also been found to positively predict adiposity in infants born to non-diabetic mothers [12].
Recent research suggests that even non-nutritive carbohydrates found in breast milk (i.e., human milk oligosaccharides) have the potential to contribute to infant growth and body composition in infancy [23]. Together, these studies highlight the need to better understand the composition of breast milk and whether macronutrient composition affects infant growth and development.
The first aim of this study was to determine whether fructose was detectable in human breast milk. The second aim was to examine if fructose in breast milk was associated with infant weight and body composition at six months of age. We tested this hypothesis within a cohort of 25 mother-infant pairs where infants were exclusively breastfed, analyzing relationships between breast milk sugar composition and infant growth and body composition. To our knowledge, this study is the first to examine the associations between breast milk fructose and infant body composition.
Discussion
The detrimental effects of fructose are well documented in children and adults, but no study that we are aware of has examined whether fructose is detectable in human breast milk, and whether this might be associated with growth and body composition, particularly adiposity in infancy.
These associations were observed even though the level of fructose in breast milk was extremely low (7 μg/mL), approximately 1/30th the level of glucose.
Despite this very low concentration, fructose levels in breastmilk appeared to be biologically relevant. Each 1-μg/mL higher fructose was associated with a 257 g higher body weight, 170 g higher lean mass, 131 g higher fat mass, and 5 g higher bone mineral content at six months of age in our sample.
These effects remained significant even after accounting for covariates known to impact infant growth, such as sex, baseline weight, and maternal BMI prior to pregnancy and were not apparent for glucose levels in breastmilk.
In this small proof of concept study, we observed that fructose was significantly associated with higher body weight, and that this effect was distributed across all components of body composition (i.e., fat mass, lean mass, and bone mass). It is important to note that these observed associations do not necessarily imply causation.
Further work is needed to examine the possibility that even these very small amounts of fructose can affect musculoskeletal development as well as adipose tissue development in infancy and early life, which is a rapid growth period where significant changes in muscular and skeletal growth are occurring.
Indeed, although evidence investigating age-related changes are generally lacking in this area, our results are consistent with a recent paper which found that a high fructose diet led to increased skeletal density and increased length in adolescent rats [25].
Further research is needed examining the effects of fructose in early life, including at low doses, in order to draw more causative conclusions about the specific impact of fructose on infant adiposity and tissue development.
Since human milk does not naturally contain fructose [26], our findings highlight maternal intake of fructose-containing products, such as sugar sweetened beverages, as a targetable intervention for reducing exposure to fructose in early life. While previous studies have shown that fructose can be transmitted in utero through the placenta [27,28], our findings extend this literature by identifying breast milk as a potential route of fructose transmission in the postnatal period.
Assuming 800 mL daily intake of breast milk, the concentration we observed in our sample would represent approximately 5 mg/day fructose consumption—an amount roughly equal to 1 mg per kg of body weight for a one-month old infant. We recognize that this amount of fructose is very low and far outside the range where fructose is currently known to have physiological effects. Although very small, this concentration could have meaningful effects in developing infants.
For example, fructose may be obesogenic in low concentrations in infants where there can be increased susceptibility to chemicals in the environment, including those delivered indirectly as a result of maternal transmission [29,30,31]. There is some evidence that fructose may induce obesogenic effects at very low levels of concentration similar to what we have detected in human breastmilk.
For example, in a dose-response study, fructose was shown to increase adipogenesis and induce gene expression in cultured pre-adipocytes, with effects seen at levels as low as 55 µM [32].
This concentration is equivalent to 10 µg/mL, which is only slightly above the concentrations in breast milk that we observed. Of particular significance, even the lowest fructose concentration (10 µg/mL) led to a highly significant and four-fold increase in GluT4 expression in pre-adipocytes, a marker of adipogenesis [32].
Collectively, this study supports the idea that even very low levels of fructose could potentially prime pre-adipocytes towards an adipogenic fate.
Unlike glucose, the metabolism of fructose in unregulated by the liver and affects brain development [8]. Studies have shown that increased levels of fructose can contribute to liver fat, resulting in insulin resistance as well as alterations in insulin and glucose metabolism.
However, the dose-response of these effects are completely unknown in infants. The first year of life is a critical developmental period, where even small levels of fructose may have detrimental effects on infant metabolism.
In addition, it is possible that the very low levels of fructose reported here are indicating “basal” levels, and higher levels of fructose might be delivered via breast milk to the infant when the mother is consuming sugars during the time of feeding. It is also possible that the detected fructose levels are serving as a proxy measure for some other factor affecting infant growth.
More studies are needed to examine the pharmacokinetics of fructose transmission through breast milk in response to maternal consumption. Unfortunately, dietary data were not collected as part of this study; thus, it is not possible to formally determine whether mothers’ habitual consumption of fructose was positively associated with the level of fructose detected in their breast milk.
Future studies examining the relationship between maternal diet and breast milk sugar concentrations will be important for informing guidelines for monitoring sugar and fructose intake during the lactation period, and for determining how the Western diet typically affects breast milk composition and infant growth.
Previous studies have shown that higher breast milk glucose concentrations were associated with greater adiposity in infants [12,20]. In the current study, breast milk glucose levels were not related to infant measures of adiposity. It is possible that this discrepancy may be explained by different study designs, or interactions with maternal factors that were not present in our cohort (i.e., gestational diabetes).
Ultimately, more studies are needed to determine whether the effects of breast milk sugars are robust and replicable across a variety of infant cohorts and future studies should consider the potential effects of both fructose and glucose in breast milk.
Limitations of the present study include the small sample size in this proof-of-concept study, limited length of follow-up (six months of age), and a lack of dietary intake data that could help explain the relationship between fructose and breast milk sugar composition.
Although women were instructed to exclusively breastfeed, it is possible that food introduction may have occurred in some infants during the study period and contributed to growth and body composition, particularly if infants were given access to fructose-containing food products. Indeed, a recent study which evaluated the sugar content of commercial infant and toddler food products found that between 30% and 50% of snacks, desserts, and juices/drinks targeted at infants contain at least one added sugar, with high fructose corn syrup being present in 2%–4% of these items [33].
Many of these items contain sugars in amounts that differ from nutrition labels and often in excess of recommended daily levels [34]. Together, these findings indicate that it is highly likely that infants are exposed to fructose in the first few months of life (e.g., during breastfeeding and/or weaning when complementary foods are introduced to the diet), highlighting the need for further research into the effects of these sugars on child development.
Another potential limitation is that we have limited metabolic variables in the mothers. Although we did exclude mothers with type 1 or 2 diabetes based on standard clinical criteria, we were unable to assess prediabetes in this sample. Therefore, it may be possible that mothers with prediabetes had increased levels of insulin and sugars in breast milk. However, breast milk levels of insulin and glucose were not associated with infant growth and body composition.
reference link : https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5331577/
