What is the question?

• The question is: What is the relationship between maternal diet during lactation on flavor transfer to breast milk, children's behavioral response, and dietary intake?

What is the answer to the question?

• Moderate evidence indicates that flavor volatiles originating from the maternal diet during lactation transmit to and flavor breast milk in a time-dependent manner as determined by chemical and sensory measures. Evidence indicates flavor transfer to human breast milk occurs after lactating mothers ingest alcohol, anise, caraway, carrots, eucalyptus, garlic, and mint flavors. 
• Moderate evidence also indicates that infants can detect diet-transmitted flavors in mother’s milk as evidenced by differential response to flavors they have previously been exposed to through their mother’s milk when compared with infants who did not have previous exposure.  Differential infant behavioral response was found: 1) within hours of a single maternal ingestion of flavor (alcohol, garlic, vanilla); 2) within days after their lactating mothers ingested a flavor (garlic, carrot juice) repeatedly (daily for 3 or 7 days); and 3) several months after their lactating mothers ingested the flavor (variety of vegetable juices including carrot) during 1 to 4 months postpartum. 
• No conclusion can be drawn to describe the relationship between maternal diet during lactation and toddler dietary intake, since there was no research identified to answer this question.

Why was this question asked? 

• This important public health question was identified and prioritized as part of the U.S. Department of Agriculture and Department of Health and Human Services Pregnancy and Birth to 24 Months Project.

How was this question answered? 

• A team of staff from the Nutrition Evidence Systematic Review conducted a systematic review in collaboration with a group of experts called a Technical Expert Collaborative.

What is the population of interest? 

• Generally healthy lactating women and their healthy infants and toddlers who were ages 0-24 months. The children's food acceptability and dietary intake was examined through the lifespan.

What evidence was found? 

• This systematic review included 15 controlled trials which examined the relationship between maternal diet during lactation, breast milk flavor, and/or infant response to a flavor. 
• The flavor of a food is a complex combination of tastes (sweet, sour, salty, bitter, umami), textures, and volatile odors which travel to the olfactory receptors when foods or liquids are in the mouth and when odor volatiles are inhaled through the nose.
• The foods, beverages, or supplements ingested by lactating mothers investigated in this review include: alcohol; garlic extract; raw garlic; carrot juice; vegetable juices including carrot, celery, beet, and mixed vegetable;  fennel-anise-caraway tea; vanilla extract; fish oil supplements, d-carvone supplement; trans-anethole supplement (associated with anise, licorice, fennel flavors); and 1,8-cineole (associated with eucalyptus flavor).
• Ten studies analyzed breast milk samples, via chemical or sensory analysis methods, to determine whether there were time-dependent changes in the flavor of breast milk after when compared to before maternal flavor ingestion.
  • Eight of ten studies provide evidence that flavor volatiles found in alcohol, anise, caraway, carrots, eucalyptus, garlic, and mint originating from the maternal diet during lactation, transfer and flavor breast milk. Transmission of flavor from fish oil supplements, fennel-anise-caraway tea and 3-methylbutyl acetate was not demonstrated, which may have been due to limitations in experimental design.
    • Volatile levels or changes in the perceived odor of the breast milk were evident 30 minutes to 1 hour after alcohol ingestion and 2 to 3 hours after ingestion of raw garlic or encapsulated garlic extract, carrot juice or capsules containing caraway, mint and anise flavor and dissipated over the following 3 to 8 hours.   
    • When both chemical and sensory analyses were conducted, there was concordance in the findings; when a change in the flavor volatile concentration was detected by chemical analysis, a change in the flavor of the breast milk was also detected by sensory evaluation analysis. 
• Ten studies evaluated the infants’ behavioral responses, which was assessed 1 of 3 ways: a) during breastfeeding, within hours of a single maternal ingestion of flavor; b) within days after their lactating mothers’ ingested the flavor repeatedly for 3 or 7 days; or c) several months after their lactating mothers ingested the flavor for 1 to 3 months.
  • Evidence from 5 studies displayed that infants could detect a flavor change as evidenced by differential behavioral response 1 to 3 hours after mothers ingested the flavor.
  • Evidence from 2 of 3 studies on repeated maternal ingestion of flavor and infant response days after maternal ingestion of the flavor found that repeated ingestion of carrot juice or garlic by lactating mothers impacted their infant’s acceptance of similarly flavored breast milk or cereal days later when compared to a non-exposed control group. 
  • Two studies revealed that repeated ingestion of carrot and other vegetable juices by lactating mothers during the first 2 to 4 months of lactation modifies their infants’ acceptance of carrot flavored cereal several months later.
• Evidence indicates that the timing may be more important than duration of exposure. 

How up-to-date is this systematic review? 

• This review includes literature from 01/1980 to 06/2017

Background

• This systematic review was conducted as part of the U.S. Department of Agriculture and Department of Health and Human Services Pregnancy and Birth to 24 Months Project.
• The goal of this systematic review was to examine the following question: what is the relationship between maternal diet during lactation on flavor transfer to breast milk, children's behavioral response, and dietary intake?
• The flavor of a food is a complex combination of tastes (sweet, sour, salty, bitter, umami), textures, and volatile odors which travel to the olfactory receptors when foods or liquids are in the mouth and when odor volatiles are inhaled through the nose.

Conclusion Statement and Grade

• Moderate evidence indicates that flavor volatiles originating from the maternal diet during lactation transmit to and flavor breast milk in a time-dependent manner as determined by chemical and sensory measures. Evidence indicates flavor transfer to human breast milk occurs after lactating mothers ingest alcohol, anise, caraway, carrots, eucalyptus, garlic, and mint flavors. Grade: Moderate
• Moderate evidence also indicates that infants can detect diet-transmitted flavors in mother’s milk as evidenced by differential response to flavors they have previously been exposed to through their mother’s milk when compared with infants who did not have previous exposure.  Differential infant behavioral response was found: 1) within hours of a single maternal ingestion of flavor (alcohol, garlic, vanilla); 2) within days after their lactating mothers ingested a flavor (garlic, carrot juice) repeatedly (daily for 3 or 7 days); and 3) several months after their lactating mothers ingested the flavor (variety of vegetable juices including carrot) during 1 to 4 months postpartum. Grade: Moderate
• No conclusion can be drawn to describe the relationship between maternal diet during lactation and toddler dietary intake, since there was no research identified to answer this question. Grade: Grade Not Assignable

Methods 

• The systematic review was conducted by a team of staff from the Nutrition Evidence Systematic Review in collaboration with a Technical Expert Collaborative.
• Literature searches were conducted using 10 databases to identify studies that evaluated the relationship among maternal diet during lactation, breast milk flavor; and children’s food acceptability and overall dietary intake. A manual search was conducted to identify articles that may not have been included in the electronic databases searched. Articles were screened by two authors independently for inclusion based on pre-determined criteria.
• Data from each included article were extracted, risks of bias were assessed, and both were checked for accuracy. The body of evidence was qualitatively synthesized, a conclusion statement was developed, and the strength of the evidence (grade) was assessed using pre-established criteria including evaluation of the internal validity/risk of bias, adequacy, consistency, impact, and generalizability of available evidence.

Summary of Evidence

• This systematic review included 15 controlled trials, which examined the relationship between maternal diet during lactation, breast milk flavor, and/or infant response to a flavor (odor or food stimulus). 
• The foods, beverages, or supplements ingested by lactating mothers investigated in this review include: alcohol; garlic extract; raw garlic; carrot juice; vegetable juices including carrot, celery, beet, and mixed vegetable;  fennel-anise-caraway tea; vanilla extract; fish oil supplements, d-carvone supplement; trans-anethole supplement (associated with anise, licorice, fennel flavors); and 1,8-cineole (associated with eucalyptus flavor).
• Ten studies analyzed breast milk samples, via chemical or sensory analysis methods, to determine whether there were time-dependent changes in the flavor of breast milk after when compared to before maternal flavor ingestion.
  • Eight of ten studies provide evidence that flavor volatiles found in alcohol, anise, caraway, carrots, eucalyptus, garlic, and mint originating from the maternal diet during lactation, transfer and flavor breast milk. Transmission of flavor from fish oil supplements, fennel-anise-caraway tea and 3-methylbutyl acetate was not demonstrated, which may have been due to limitations in experimental design.
    • Volatile levels or changes in the perceived odor of the breast milk were evident 30 minutes to 1 hour after alcohol ingestion and 2 to 3 hours after ingestion of raw garlic or encapsulated garlic extract, carrot juice or capsules containing caraway, mint and anise flavor and dissipated over the following 3 to 8 hours.   
    • When both chemical and sensory analyses were conducted, there was concordance in the findings; when a change in the flavor volatile concentration was detected by chemical analysis, a change in the flavor of the breast milk was also detected by sensory evaluation analysis. 
• Ten studies evaluated the infants’ behavioral responses, which was assessed 1 of 3 ways: a) during breastfeeding, within hours of a single maternal ingestion of flavor; b) within days after their lactating mothers’ ingested the flavor repeatedly for 3 or 7 days; or c) several months after their lactating mothers ingested the flavor for 1 to 3 months.
  • Evidence from 5 studies displayed that infants could detect a flavor change as evidenced by differential behavioral response 1 to 3 hours after mothers ingested the flavor.
  • Evidence from 2 of 3 studies on repeated maternal ingestion of flavor and infant response days after maternal ingestion of the flavor found that repeated ingestion of carrot juice or garlic by lactating mothers impacted their infant’s acceptance of similarly flavored breast milk or cereal days later when compared to a non-exposed control group. 
  • Two studies revealed that repeated ingestion of carrot and other vegetable juices by lactating mothers during the first 2 to 4 months of lactation modifies their infants’ acceptance of carrot flavored cereal several months later.
• Evidence indicates that the timing may be more important than duration of exposure.