TABLE 3.

Recommendations for data, testing, and biospecimens to study human milk as a system-within-a-system.

Type of Data	External Ecologies	Internal Ecologies
		Lactating Parent	Infant or Child
Environmental and biological sample collections	Environmental samples •Water, •Soil •House dust •etc.	•Human milk •Blood •Saliva •Oral and nasal swabs •Skin swabs, including nipple and areola •Hair •Feces •Urine •Vaginal swabs	•Blood •Saliva •Oral and nasal swabs •Skin swabs •Hair •Feces •Urine
Physiological measurements or testing or observations		•Height •Weight •Body composition •Milk production •Brain structure and functional MRI •Endocrine, immune, and intestinal function (see Table 4) •Biopsychosocial interactions between parent and child, particularly during feeding	•Length or height •Weight •Body composition •Milk intake and mode of feeding •Brain structure and functional MRI •Cognitive function (tested) •Endocrine, immune, and intestinal function (see Table 4) •Biopsychosocial interactions between parent and child, particularly during feeding
Medical records, questionnaires, and surveys	•Social determinants of health∗ •Geography •Religion •Culture •Employment type •Sanitation •Stress • Xenobiotic exposure - environmental contaminants, - therapeutic or recreational drugs, - cigarette smoke - other toxins	•Race and ethnicity •Sex •Health history and current status •Medications and supplements •Breastfeeding duration and exclusivity •Sleep patterns •Weight status: prepregnancy, gestational weight gain, recent weight gain or weight loss •Parity •Pregnancy complications •Breast surgery (reduction or augmentation) •Lactation history •Timing of initiation of lactation •Executive function •Physical activity	•Race and ethnicity •Sex •Health history and current status •Medications and supplements •Breastfeeding duration and exclusivity •Sleep patterns •Gestational age •Singleton or multiple birth •Infant formula use and type •Dietary intake (human milk, infant formula, complementary feedings) •Cognitive function (parent reported)

MRI, magnetic resonance imaging.

^∗Social determinants of health are conditions in the places where people live, learn, work, and play that affect a wide range of health and quality-of life-risks and outcomes (https://www.cdc.gov/socialdeterminants/index.htm).