What is the question?

• What is the relationship between beverage consumption and growth, size, body composition, and risk of overweight and obesity?

What is the answer to the question?

• Insufficient evidence is available to determine the relationship between consumption of milk during pregnancy and birth weight outcomes.
• Insufficient evidence is available to determine the relationship between consumption of tea during pregnancy and birth weight outcomes.
• Insufficient evidence is available to determine the relationship between consumption of coffee during pregnancy and birth weight outcomes.
• Insufficient evidence is available to determine the relationship between consumption of sugar-sweetened beverages or low- or no-calorie sweetened beverages during pregnancy and birth weight outcomes.
• Insufficient evidence is available to determine the relationship between consumption of water during pregnancy and birth weight outcomes.

Why was this question asked?

• This important public health question was identified by the U.S. Departments of Agriculture (USDA) and Health and Human Services (HHS) to be examined by the 2020 Dietary Guidelines Advisory Committee.

How was this question answered?

• The 2020 Dietary Guidelines Advisory Committee, Beverages and Added Sugars Subcommittee conducted a systematic review to answer this question with support from the Nutrition Evidence Systematic Review (NESR) team.

What is the population of interest? 

• This review examines beverage consumption in women before and during pregnancy and birth weight in their children. 

What evidence was found? 

• This review includes 19 articles.
• These articles did not provide enough evidence to answer the question. They presented inconsistent findings from studies with many limitations.

How up-to-date is this systematic review?

• This review searched for studies from January 2000 to June 2019.

Background

• This important public health question was identified by the U.S. Departments of Agriculture (USDA) and Health and Human Services (HHS) to be examined by the 2020 Dietary Guidelines Advisory Committee.
• The 2020 Dietary Guidelines Advisory Committee, Beverages and Added Sugars Subcommittee conducted a systematic review to answer this question with support from the Nutrition Evidence Systematic Review (NESR) team.
• The goal of this systematic review was to examine the following question: What is the relationship between beverage consumption during pregnancy and birth weight standardized for gestational age and sex?

Conclusion statements and grades

• Insufficient evidence is available to determine the relationship between consumption of milk during pregnancy and birth weight outcomes. (Grade: Grade not assignable)
• Insufficient evidence is available to determine the relationship between consumption of tea during pregnancy and birth weight outcomes. (Grade: Grade not assignable)
• Insufficient evidence is available to determine the relationship between consumption of coffee during pregnancy and birth weight outcomes. (Grade: Grade not assignable)
• Insufficient evidence is available to determine the relationship between consumption of sugar-sweetened beverages or low- or no-calorie sweetened beverages during pregnancy and birth weight outcomes. (Grade: Grade not assignable) 
• Insufficient evidence is available to determine the relationship between consumption of water during pregnancy and birth weight outcomes. (Grade: Grade not assignable)

Methods 

• A literature search was conducted using 4 databases (PubMed, Embase, Cochrane, and CINAHL) to identify articles that evaluated the intervention or exposure of non-alcoholic beverage consumption and the outcomes of growth, size, body composition, and risk of overweight and obesity. A manual search was conducted to identify articles that may not have been included in the electronic databases searched. Articles were screened by two NESR analysts independently for inclusion based on pre-determined criteria. 
• Data extraction and risk of bias assessment were conducted for each included study, and both were checked for accuracy. The Committee qualitatively synthesized the body of evidence to inform development of a conclusion statement(s), and graded the strength of evidence using pre-established criteria for risk of bias, consistency, directness, precision, and generalizability.

Summary of the evidence

• Nineteen studies published between January 2000 and June 2019 met the criteria for inclusion in this systematic review, including 1 RCT and 18 prospective cohort studies (PCS).
• Many studies examined intake of multiple beverages.
• Evidence is summarized below by beverage type.

Dairy milk

• Six studies examined the relationship between dairy milk consumption and birth weight outcomes. The body of evidence included 1 RCT and 5 PCS.
• The search strategy focused on dairy milk, which included commercially available cow’s milk and soy beverages with varying fat and sweetener content. However, no studies examining soy beverages met the inclusion criteria. 
• The body of evidence showed little consistency in the timing of exposure assessment (ranged from first through third trimesters) and the period of intake it represented (ranging from the previous 24 hours to average intake for the first half of pregnancy), which limited comparability across studies.
• Both continuous and categorical birth weight outcomes were examined:
  • Five studies assessed continuous birth weight.
  • Three studies assessed categorical birth weight outcomes.
• The 5 studies examining continuous birth weight found significant associations with milk intake, but in different directions. Four studies suggested greater milk intake was related to higher birth weight, but 1 study found the opposite.
• The 3 studies examining categorical birth weight outcomes had limited consistency in the outcomes measured and in findings:
  • Two of the 3 studies examined risk of SGA; 1 found greater milk intake was associated with lower risk, while the other did not find a significant relationship. One of those studies also evaluated risk of LGA and did not find a relationship with milk intake.
  • One study (the RCT) examined risk of LBW and found milk was related to lower risk.
• Overall, findings were inconsistent in both direction and statistical significance, limiting the ability to draw conclusions.
• This body of evidence had several limitations:
  • SES differed by geographic location, with the 2 studies conducted in Asia enrolling populations with substantially lower SES than did the European and Canadian studies, potentially limiting generalizability of those findings.
  • Two studies, including the RCT, had attrition rates of more than 25 percent, and neither provided information on the potential for selective attrition across intervention or exposure groups.
  • Outcomes examined, definitions used, and adjustment techniques varied across studies.
  • Many studies did not adjust for birth weight for gestational age and sex.
  • All studies failed to adjust for at least one key confounder.

Tea

• Eight PCS examined the relationship between tea consumption and birth weight outcomes. 
• Studies varied in the type of tea examined:
  • Three studies reported on overall tea intake.
  • Three studies reported on caffeinated tea only.
  • Three studies reported on specific types of tea (e.g., green, black, dark, oolong).
• Most studies examined tea intake in early pregnancy.
• Continuous birth weight was examined in 6 studies, and categorical birth weight outcomes were examined in 8.
• The 6 studies examining continuous birth weight reported mixed findings:
  • Three studies found tea intake at the highest amount related to lower birth weight.
  • Three studies found the relationship was not significant.
• The 8 studies examining categorical birth weight reported similarly mixed findings:
  • Of the 7 that examined risk of SGA or IUGR at birth, 3 found greater tea intake was related to higher risk of SGA, while the relationship was non-significant for the remaining 4.
  • Low birth weight (LBW) was examined in 2 studies, and greater risk of LBW was significantly associated with greater tea intake in 1 study and was non-significant in the other.
• This body of evidence had several limitations:
  • The majority of participants were White, well-educated, and higher SES, potentially limiting generalizability. 
  • Three studies examined only caffeinated tea, which may not accurately represent total tea intake and limited the ability to draw independent conclusions about the beverage as compared to caffeine.
  • Outcomes examined and the definitions used varied across studies.
  • Studies inconsistently adjusted birth weight for gestational age and sex.
  • Two studies had attrition rates of more than 20 percent, and neither provided information on the potential for selective attrition across exposure groups. 
  • Seven of the 8 studies failed to adjust for at least one key confounder, most commonly pre-pregnancy body mass index (BMI) and diabetes diagnosis.

Coffee

• Seven PCS examined the relationship between coffee consumption and birth weight outcomes. 
• The timing of exposure assessment showed little consistency (ranging from 5 to 39 weeks gestation).
• Continuous birth weight was examined in 5 studies, and categorical birth weight outcomes were examined in 6.
• The 5 studies examining continuous birth weight reported mixed findings:
  • Three studies found greater coffee intake was related to lower birth weight.
  • Two studies found the relationship was not significant.
• The 6 studies examining categorical birth weight reported similarly mixed findings:
  • Of the 5 that examined risk of SGA or IUGR at birth, 2 found greater coffee intake was related to higher risk of SGA, while the relationship was not significant for the remaining 3.
  • LBW was examined in 3 studies. One found greater coffee intake was related to greater risk of LBW, while the other 2 were not significant.
• This body of evidence had several limitations:
  • The majority of participants were White, well-educated, and higher SES, potentially limiting generalizability. 
  • Three studies examined only caffeinated coffee, which may not accurately represent total coffee intake and limited the ability to draw conclusions about the beverage as compared to caffeine.
  • Outcomes examined and the definitions used varied across studies.
  • Studies inconsistently adjusted birth weight for gestational age and sex
  • Seven of the 8 studies failed to adjust for at least 1 key confounder, most commonly pre-pregnancy BMI and diabetes diagnosis.
  • Two studies had attrition rates of more than 20 percent, and neither provided information on the potential for selective attrition across exposure groups. 

Sugar-sweetened beverages and low- or no-calorie sweetened beverages

• Seven PCS examined the relationship between birth weight outcomes and intake of sugar-sweetened beverages (SSB), low- or no-calorie sweetened beverages (LNCSB), or both:
  • Three studies examined SSB independently. 
  • Two examined LNCSB independently.
  • Two examined combined SSB and LNCSB.
  • Two did not specify whether the exposure represented SSB only or SSB plus LNCSB.
• The 3 studies examining SSB independently:
  • Measured intake across early, mid- and late-pregnancy.
  • Examined both continuous (n=3) and categorical (n=2) birth weight outcomes and were inconsistent in both the direction and statistical significance of their findings.
    • For continuous birth weight, 1 study found a positive relationship, 1 a negative relationship, and the third found no relationship with SSB intake.
    • No categorical outcomes were examined in more than 1 study.
• The 2 studies examining LNCSB independently:
  • Measured intake across early, mid- and late-pregnancy.
  • Examined continuous birth weight and found mixed results. One study showed greater LNCSB intake was related to lower birth weight, while the other did not find a significant association.
• The 2 studies that combined SSB and LNCSB intake looked specifically at caffeinated versions of the beverages:
  • Both examined risk of SGA, with one finding a significant association between greater intake and greater risk of SGA while the other did not report a significant relationship.
  • One study also examined continuous birth weight and found combined caffeinated SSB and LNCSB intake in early and mid-pregnancy was related to lower birth weight, but intake at 30 weeks was not.
• The 2 studies that did not clearly define the exposure variable and may have combined SSB and LNCSB intake defined the exposure as “cola” or “soda” and measured different outcomes.
  • One study found significant associations between greater intake and higher birth weight and higher risk of SGA, while the other found no relationship with intake and risk of IUGR.
• The body of evidence for SSB and LNCSB had several limitations:
  • The number of studies available for each beverage type was very small.
  • The exposure variable is poorly defined in multiple studies.
  • Three studies examined caffeinated versions of these beverages specifically, which may not represent complete intake of the beverage. 
  • The studies showed little consistency in exposure assessment timing, outcome definitions, or direction of findings across studies.
  • Studies inconsistently adjusted birth weight for gestational age and sex.
  • Five studies had attrition rates of more than 20 percent for the full sample and did not include attrition rates by exposure group.

Plain water

• Two PCS assessed the relationship between water intake during pregnancy and birth weight outcomes.
• Exposure definitions made it difficult to determine whether the assessment included plain water intake only or also included water-based beverages, limiting the usefulness of the data.
• Both studies measured continuous birth weight and risk of SGA, and neither found a significant association with plain water intake for either outcome.
• This body of evidence had several limitations:
  • The number of studies available for this beverage type was very small.
  • Exposure definitions lacked clarity to confidently state they include plain water only.
  • Studies inconsistently adjusted birth weight for gestational age and sex.