What is the question?

• The question is: What is the relationship between shorter versus longer durations of exclusive human milk feeding and cardiovascular disease outcomes in offspring?

What is the answer to the question?

• Limited evidence suggests that there is no association between the duration of exclusive human milk feeding and blood pressure in childhood or metabolic syndrome at 11.5 years of age. Most of the evidence comes from just one non-US sample assessed using a strong study design. 
  
  There was insufficient evidence to determine the relationship of shorter versus longer durations of exclusive human milk feeding with endpoint CVD outcomes, blood pressure in adolescence or adulthood, blood lipids, and metabolic syndrome at ages other than 11.5 years.

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

What is the population of interest? 

• The population of interest was generally healthy infants and toddlers (ages 0-24 months) who were in studies examining cardiovascular disease outcomes from childhood through adulthood (ages 2 years and up).

What evidence was found? 

• This review includes 6 articles. 
• These articles compared infants fed human milk exclusively for shorter durations with infants fed human milk exclusively for longer durations. 
• These articles examined available evidence related to cardiovascular disease outcomes in offspring from childhood through adulthood, including blood lipids, blood pressure, arterial stiffness, metabolic syndrome, cardiovascular disease, and cardiovascular disease-related mortality. 
• A single study that used a strong study design examined blood pressure and metabolic syndrome in children and one additional study provided supporting evidence about blood pressure in children. 
  • Children who were fed human milk exclusively for shorter durations and children who were fed human milk exclusively for longer durations do not seem to have different blood pressure levels or risk of metabolic syndrome.
• There are limitations in the evidence as follows:
  • There were not a lot of studies. 
  • Most of the evidence came from a single study that was outside of the U.S., and the risk of cardiovascular disease in the U.S. may be higher than it is in the populations with available evidence.

How up-to-date is this systematic review? 

• This review includes literature from 01/1980 to 03/2016.

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 shorter versus longer durations of exclusive human milk feeding and cardiovascular disease outcomes in offspring?
• This systematic review examines comparisons of infants who were fed human milk exclusively for shorter durations with infants who were fed human milk exclusively for longer durations. 
• Exclusive human milk feeding was defined as feeding human milk alone and not in combination with infant formula and/or complementary foods or beverages such as cow’s milk. This definition is inclusive of the World Health Organization definitions of exclusive and predominant breastfeeding, which permit limited quantities of (a) drops or syrups containing vitamins, minerals, or medicines, (b) water and water-based drinks such as sweetened water and teas, (c) fruit juice, (d) oral rehydration salts solution, and (e) ritual fluids . Human milk was defined as mother’s own milk provided at the breast (i.e., nursing) or expressed and fed fresh or after refrigeration or freezing. Donor milk (e.g., banked milk) was not examined in this review. 
• This systematic review examines available evidence related to cardiovascular disease outcomes in offspring from childhood through adulthood, including blood lipids, blood pressure, arterial stiffness, metabolic syndrome, cardiovascular disease, and cardiovascular disease-related mortality.

Conclusion Statement and Grade

• Limited evidence suggests that there is no association between the duration of exclusive human milk feeding and blood pressure in childhood or metabolic syndrome at 11.5 years of age. Most of the evidence comes from just one non-US sample assessed using a strong study design. 
  
  There was insufficient evidence to determine the relationship of shorter versus longer durations of exclusive human milk feeding with endpoint CVD outcomes, blood pressure in adolescence or adulthood, blood lipids, and metabolic syndrome at ages other than 11.5 years.
  
  Grade: Limited – blood pressure in childhood, metabolic syndrome at age 11.5 years; Grade Not Assignable – cardiovascular disease, cardiovascular disease-related mortality, blood lipids, blood pressure in adolescence or adulthood, arterial stiffness, metabolic syndrome at ages other than 11.5 years

Methods 

• The systematic review was conducted by a team of staff from the Nutrition Evidence Systematic Review in collaboration with a Technical Expert Collaborative.
• A single literature search was conducted to identify literature for several related systematic reviews that examined infant milk-feeding practices and different outcomes. The search was conducted in CINAHL, Cochrane, Embase, and PubMed, and used a search date range of January 1980 to March 2016. A manual search was done to identify articles that may not have been included in the electronic databases searched. 
• Articles were screened independently by 2 NESR analysts to determine which articles met predetermined criteria for inclusion.
• Data from the included article were extracted, risks of bias were assessed, and both were checked for accuracy. 
• 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 

• Six articles met the inclusion criteria for this systematic review, including 4 with evidence about blood pressure, 2 with evidence about blood lipids, and 1 with evidence about metabolic syndrome (1 article included evidence about both blood pressure and metabolic syndrome).
• Evidence about the lack of an association between shorter versus longer durations of exclusive human milk feeding and blood pressure in childhood and metabolic syndrome at 11.5 years of age was limited. Most of the evidence came from the Promotion of Breastfeeding Intervention Trial, which used a strong design to examine blood pressure and metabolic syndrome in children in Belarus. One additional study from Brazil provided supporting evidence about childhood blood pressure. The ability to draw stronger conclusions is primarily restricted by the limited number of studies and the lack of evidence from the U.S. where the risk of cardiovascular disease may be higher. 
• Evidence related to other cardiovascular disease outcomes was scant.