Nutrition in the first year of life is crucial to an infant's development and lifelong health. An abundance of scientific evidence demonstrates that insufficient or inadequate nutritional support impairs mental and physical growth. Consequently, the risk of developing metabolic and cardiovascular diseases such as obesity, diabetes, and hypertension in childhood – as well as later in life – is likely determined by early feeding and nutritional status.
Breastfeeding provides the biologically superior means to feed an infant. The American Academy of Pediatrics recommends exclusive breastfeeding for the first six months of an infant's life, and then continued breastfeeding while introducing age-appropriate foods until an infant is 12 months old or older. The goal of these recommendations is to supply an infant optimal nutritional support and immunity during critical windows of growth and development.
Breast milk is a species-specific product, containing both nutritional and non-nutritional components that are uniquely tailored to the needs of a human infant. But breast milk is also dynamic, changing in composition during a single feeding, from day to night, and throughout the lactation period in response to a growing infant's requirements.
The primary nutritional components of breast milk – proteins, fats, and carbohydrates – play double- or even triple-duty, providing not only basic nutrients for growth and survival but also serving in critical roles that might be somewhat surprising.
Proteins, for example, support the growth of muscle and other tissues. But they also facilitate the digestion of other nutrients while supplying antimicrobial and immunomodulatory factors that contribute to defense against pathogens. Interestingly, the presence of many of these proteins is regulated by circadian rhythms that are synchronized with the infant's needs.
Fats are the predominant source of energy provided in breast milk, supplying roughly half of its total calories and providing necessary energy for growth. Fats also aid in the maturation of an infant's gastrointestinal and central nervous systems and provide protection from pathogens. Perhaps the best known of the fats in breast milk is docosahexaenoic acid, or DHA, an omega-3 fatty acid that plays critical roles in brain development.
Carbohydrates in breast milk also provide energy for a growing infant, but in a surprising twist, a significant portion of these carbohydrates provide no nutrition at all, existing for the sole purpose of inducing and supporting a healthy population of commensal bacterial in the infant's gut. These unique carbohydrates, called human milk oligosaccharides, or HMOs, play many other roles in infant immunity and, subsequently, survival.
But HMOs are just one aspect of immune function. An infant's immune system is the last of the biological systems to develop, taking months or even years to match that of an adult's capacity for defense. Breast milk contains a multitude of components that work together synergistically to provide a compensatory immune "system" that confers both passive and active immunity.
This surrogate system provides protection against respiratory infections and certain types of cancer in childhood and might even contribute to lifelong immunity. Some of these protective components have demonstrated the capacity to prevent the translocation of infectious pathogens across the gastrointestinal tract, kill or inhibit the growth of pathogenic bacteria (including Escherichia coli), and interfere with postpartum transmission of human immunodeficiency virus, or HIV.
Of course, breast milk also provides a vehicle for delivering harmful substances to an infant. Heavy metals and prescription drugs, especially those used to treat cancer, readily transfer to breast milk and pose considerable threats due to an infant's limited capacity to metabolize drugs. But commonly used "social drugs," such as alcohol, nicotine, caffeine, and cannabis all carry some risk to a breastfed infant, as well. Alcohol, in particular, can have negative effects on a breastfed infant, including altered sleep patterns, decreased milk intake, and impaired motor development, among others.
As one would expect, breastfeeding provides a wide range of benefits to infants, including enhanced neurological development, evidenced by children who were breastfed as infants scoring nearly three points higher on intelligence tests than those who were not breastfed, even after taking maternal intelligence into consideration. In fact, breastfed babies tend to have 20-30 percent higher amounts of white matter in their brains than children who are not breastfed. Breastfeeding also appears to confer a measure of protection against the cardiovascular-related complications associated with pre-term birth.
But breastfeeding benefits mothers, too. Women who breastfeed are more likely to return to their pre-pregnancy weight, typically sooner than women who do not breastfeed. Having excess body fat carries considerable risks, including greater likelihood of developing cardiovascular disease, type 2 diabetes, and cancer. Interestingly, research indicates that women who breastfeed are less likely to develop ovarian or breast cancer. The mechanisms behind the protective effect on the breast, in particular, are not well understood, but some evidence suggests they may be related to breastfeeding's capacity to moderate the deleterious effects of involution, a process that occurs when lactation ends.
Despite breastfeeding’s superiority, breastfeeding rates in the United States are low. Among children born between 2010 and 2013, approximately 80 percent were breastfed initially, but only 20 percent of those children were breastfed exclusively (receiving no formula or other foods) at six months of age Several factors influence whether a woman chooses to breastfeed her infant, including the mother's age, race, ethnicity, education level, socioeconomic status, family structure, and mental status.
But some of the primary contributors to whether a woman continues to breastfeed stem from more personal factors, ranging from sore nipples and plugged ducts to lack of family support and concerns about physical image and sexual intimacy. Working with a lactation consultant during the first few weeks of breastfeeding may be helpful, especially for mothers of preterm infants. If a woman's milk is insufficient to meet the needs of her infant or if she has a health concern that prevents her from breastfeeding, donor milk may be an option for healthy, full-term babies.
In this episode, Dr. Rhonda Patrick describes the production and composition of breast milk and discusses the benefits of breastfeeding to both infant and mother. She also provides practical information for dealing with the challenges associated with breastfeeding.
How breast milk composition changes at night to help the infant sleep. 1
Interview clip with Drs. Erica and Justin Sonnenburg.
Infants who fed formula with milk fat globule membranes and lactoferrin scored higher on cognitive, language, and motor skills tests than infants who received ordinary formula. 1
Lactating women who took 400 milligrams of the omega-3 DHA, had 123% more DHA in their breast milk. 1.
Which vitamins and minerals are robustly passed to the infant through breast milk and others that are poorly transferred.
Breast milk can also contain harmful substances that are transferred to the infant.
Cadmium levels in breast milk are 4 times higher in mothers who smoke. 1
Breastfeeding increases the likelihood of mothers returning back to their pre-pregnancy weight. 3
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Immune protection acquired following exposure to a pathogen. Active immunity can take days or even weeks to develop but can confer long – even lifelong – immunity.
A genus of bacteria known to inhabit the human gut. Bifidobacteria are anaerobic commensal bacteria. They are among the first bacteria to colonize the infant gut and may play critical roles in gut-mediated immune function.
Densely packed communities of microorganisms that live on or in inert surfaces as well as plant and animal tissues. Biofilms are spatially organized into three-dimensional structures and enclosed in a matrix of extracellular material that confers protection to the microbial community they house.
A commonly occurring metal element. Cadmium is used in batteries, alloys, electroplated coatings, solar cells, plastics, and pigments. Cadmium and its related compounds are carcinogenic and target the body’s cardiovascular, renal, gastrointestinal, neurological, reproductive, and respiratory systems. Exposure to cadmium typically occurs via food, cigarettes, second-hand smoke, or emissions from fossil fuels.
A collective term for the various components of Cannabis sativa, also known as marijuana.
The body’s 24-hour cycles of biological, hormonal, and behavioral patterns. Circadian rhythms modulate a wide array of physiological processes, including the body’s production of hormones that regulate sleep, hunger, metabolism, and others, ultimately influencing body weight, performance, and susceptibility to disease. As much as 80 percent of gene expression in mammals is under circadian control, including genes in the brain, liver, and muscle. Consequently, circadian rhythmicity may have profound implications for human healthspan.
A thick, sticky fluid produced during the first stage of lactogenesis, the production of milk. Colostrum is rich in immunomodulatory factors, and its primary role is immunological, rather than nutritional. Relative to a mother's later milk, colostrum is low in lactose, potassium, and calcium and high in sodium, chloride, and magnesium. It is commonly yellow, orange, or white in color.
Bacteria that are beneficial or at least not harmful to the host, in contrast to pathogenic bacteria where the host derives no benefit and is actively harmed from the relationship. Roughly 100 trillion commensal bacteria live in the human gut. The term commensal comes from Latin and literally means “eating at the same table.”
Foods other than breast milk or infant formula introduced to an infant. Complementary foods are typically introduced around the age of six months and include age-appropriate grains, vegetables, fruits, and, eventually, meats.
An omega-3 fatty acid found in the human brain and the meat of fatty fish. DHA plays a key role in the development of eye and nerve tissues, and is essential for normal brain function in humans. DHA may also reduce the risk of Alzheimer’s disease1 and cardiovascular disease, and may be useful in treating certain inflammatory conditions, such as rheumatoid arthritis. Dietary sources of DHA include krill oil and the meat and roe of salmon, flying fish, and pollock.  Patrick, Rhonda P. "Role of phosphatidylcholine-DHA in preventing APOE4-associated Alzheimer’s disease." The FASEB Journal (2018): fj-201801412R.
A collective term for a group of conditions characterized by itchy or inflamed skin with a rash-like appearance. Seven types of eczema have been identified: atopic dermatitis, contact dermatitis, dyshidrotic eczema, nummular eczema, seborrheic dermatitis, and stasis dermatitis.
An organic compound produced during the refining of petroleum products. Ethane is also produced in humans during the peroxidation of lipids. It is measurable in exhaled air and is a marker of oxidative stress.
A molecule composed of carboxylic acid with a long hydrocarbon chain that is either saturated or unsaturated. Fatty acids are important components of cell membranes and are key sources of fuel because they yield large quantities of ATP when metabolized. Most cells can use either glucose or fatty acids for this purpose.
Breast milk that is expressed during the early part of a single feeding session. Foremilk is high in lactose and has a watery consistency.
A class of bacteria commonly present in the lower gastrointestinal and genital tracts of humans. Group-B streptococcus colonization in pregnant women is a major risk factor for neonatal and infant infection.
Breast milk expressed during the latter part of a single feeding session. Hindmilk is high in fat and has a creamy consistency.
Complex, indigestible sugars present in human breast milk. The primary role of HMOs is to serve as prebiotics in the infant's gut. In turn, these beneficial bacteria produce short-chain fatty acids and other substances that prevent the colonization of pathogenic bacteria in the gut. More than 200 HMOs have been identified, and they are the third most abundant factor in breast milk after fat and lactose, averaging 20 to 25 grams per liter in colostrum and 5 to 20 grams per liter in mature milk. The quantity and composition of the HMOs in breastmilk are genetically determined and differ slightly between women.
High blood pressure. Hypertension, defined as a systolic pressure of 130 mm Hg or higher, or a diastolic pressure of 80 mm Hg or higher, is a robust predictor of future incidence of stroke, coronary heart disease, heart attack, heart failure, and cardiovascular-related death. Central to the pathophysiology of hypertension is the loss of arterial compliance, which can have far-reaching effects on multiple organ systems, including the brain and kidneys.
Abnormally low blood glucose. Hypoglycemia can occur due to low glycogen stores, diabetes medications, or other drugs. Maternal alcohol consumption can cause hypoglycemia in breastfed infants. Symptoms of hypoglycemia include confusion, heart palpitations, shakiness, and anxiety.
IL-10, also known as human cytokine synthesis inhibitory factor (CSIF), is an anti-inflammatory cytokine with multiple, pleiotropic, effects in immunoregulation and inflammation. It downregulates the expression of Th1 cytokines, MHC class II antigens, and co-stimulatory molecules on macrophages. It also enhances B cell survival, proliferation, and antibody production. A study in mice has shown that IL-10 is also produced by mast cells, counteracting the inflammatory effect that these cells have at the site of an allergic reaction. IL-10 is capable of inhibiting synthesis of pro-inflammatory cytokines such as IFN-γ, IL-2, IL-3, TNFα and GM-CSF made by cells such as macrophages and Th1 T cells.
A cytokine that plays roles in immune function. IL-12 is produced by cells in the innate immune system. It influences the differentiation of naïve T cells into T-helper 1 cells and modulates allergic inflammation.
A cytokine that plays roles in immune function. IL-4 regulates antibody production, hematopoiesis, and inflammation, and drives T-cell responses. It can exert both pro- and anti-inflammatory properties, depending on the physiological context. IL-4 also plays roles in learning and memory.
A trace mineral that is essential for human health. Iodine is necessary for normal thyroid and immune function.
An essential mineral present in many foods. Iron participates in many physiological functions and is a critical component of hemoglobin. Iron deficiency can cause anemia, fatigue, shortness of breath, and heart arrhythmias.
A whey protein found in milk. Lactalbumin is rich in many essential and conditionally essential amino acids and comprises up to 25 percent of the total protein found in human breast milk. It serves many crucial physiological and immunological functions, and some evidence suggests that lactalbumin exerts antiviral, anti-apoptotic, and anti-tumor properties in humans.
The processes of synthesis and secretion of milk from the mammary glands. Lactation requires both mechanical and hormonal inputs. Nipple stimulation and subsequent milk removal promote the continued release of prolactin and oxytocin. In turn, these hormones drive ongoing production and release of milk (respectively).
An iron-binding protein found in human and bovine milk, as well as other fluids, such as saliva, tears, and nasal secretions. Lactoferrin exerts antiviral and antibacterial properties. Some evidence indicates that lactoferrin may be protective against coronaviruses.
An enzyme found in the tears, saliva, and milk of humans and other mammals. Lysozyme exerts antimicrobial properties via its capacity to destroy the cell walls of certain bacteria. It also demonstrates antiviral activity.
A hormone that regulates the sleep-wake cycle in mammals. Melatonin is produced in the pineal gland of the brain and is involved in the expression of more than 500 genes. The greatest influence on melatonin secretion is light: Generally, melatonin levels are low during the day and high during the night. Interestingly, melatonin levels are elevated in blind people, potentially contributing to their decreased cancer risk.
A collective term for the community of commensal, symbiotic, and pathogenic microorganisms that live in a particular environment. The human body has multiple microbiotas, including those of the gut, skin, and urogenital regions.
A triple-layered structure that surrounds fat globules present in breast milk. The MFGM is interspersed with a variety of proteins, enzymes, and cholesterol that, together, exert bioactive properties that confer many of the antibacterial and anti-inflammatory properties of breast milk. Currently, most infant formulas do not contain MFGM; however, evidence suggests that the bovine form of MFGM exerts similar beneficial effects on human infants when included in infant formula.
A naturally occurring monoglyceride present in breast milk and coconut fat. Monolaurin exerts antiviral and antibacterial properties.
A biological relationship that is mutually beneficial to two living things.
A highly toxic, addictive substance present in the tobacco plant. Nicotine is an alkaloid compound that stimulates the central nervous system by acting an agonist at the nicotinic cholinergic receptors in various regions of the brain. It promotes the release of several neurotransmitters, including acetylcholine, beta-endorphin, dopamine, norepinephrine, serotonin, and ACTH. Nicotine intake can cause peripheral vasoconstriction, tachycardia, and elevated blood pressure. Nicotine in breast milk can interfere with an infant's sleep patterns.
One of four nitrogen-containing molecules that comprise DNA. A nucleotide consists of one of four chemicals, called a “base,” plus one molecule of sugar and one molecule of phosphoric acid. Nucleotides are typically identified by the first letter of their base names: adenine (A), cytosine (C), guanine (G), and thymine (T). They form specific pairs (A with T, and G with C), and their bonds provide the helical structure of the DNA strand.
A type of polyunsaturated fat that is essential for human health. Omega-3 fatty acids influence cell membrane integrity and affect the function of membrane-bound cellular receptors. They participate in pathways involved in the biosynthesis of hormones that regulate blood clotting, contraction and relaxation of artery walls, and inflammation. They have been shown to help prevent heart disease and stroke, may help control lupus, eczema, and rheumatoid arthritis, and may play protective roles in cancer and other conditions. Omega-3 fatty acids include alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). ALA is found mainly in plant oils such as flaxseed, soybean, and canola oils. DHA and EPA are found in fish and other seafood. The human body can convert some ALA into EPA and then to DHA, but the efficiency of the process varies between individuals.
Immune protection acquired from another source, such as antibody transfer across the placenta or in breast milk, or serum from a person who has recovered from an illness and has immunity. Passive immunity gives immediate, but short-lived protection, lasting several weeks to a few months at most.
A hormone released by the pituitary gland. Prolactin promotes milk production in women and regulates behavior, immune function, metabolism, and reproductive health.
An antibody that plays key roles in immunity. Secretory IgA is the most abundant antibody in the mucosal immune system, accounting for nearly 20 percent of serum immunoglobulin. It is crucial in protecting the intestinal epithelium from toxins and pathogenic microorganisms.
Fatty acids that contain fewer than six carbons in their chemical structure. SCFAs are produced by the gut microbiota during the fermentation of dietary fiber. They provide energy to colonic cells and are crucial to gut health. In addition, SCFAs may play roles in the prevention and treatment of metabolic syndrome, inflammatory bowel disorders, and certain types of cancer. Some evidence suggests SCFAs can cross the blood-brain barrier to affect brain function. The principal SCFAs produced in the human gut are acetate, propionate, and butyrate.
Sleep-promoting substances or activities. Somnogenic entities include exercise, meditation, and illness, among others.
A cell that has the potential to develop into different types of cells in the body. Stem cells are undifferentiated, so they cannot do specific functions in the body. Instead, they have the potential to become specialized cells, such as muscle cells, blood cells, and brain cells. As such, they serve as a repair system for the body. Stem cells can divide and renew themselves over a long time. In 2006, scientists reverted somatic cells into stem cells by introducing Oct4, Sox2, Klf4, and cMyc (OSKM), known as Yamanaka factors.
The primary psychoactive substance present in the leaves of the marijuana (cannabis) plant. THC alters the functioning of the hippocampus and orbitofrontal cortex, leading to altered perception and changes in cognition, such as short-term memory impairment. THC’s chemical structure is similar to the brain’s endogenous cannabinoid anandamide, allowing it to bind to anandamide receptors to elicit its effects.
An essential amino acid. Tryptophan plays key roles in the biosynthesis of proteins and is a precursor to several molecules with physiological significance, including melatonin, niacin, and the neurotransmitter serotonin. Inflammation causes tryptophan to be reallocated from serotonin synthesis to that of kynurenine, which then converts to the neurotoxin quinolinic acid, leading to depression. Dietary sources of tryptophan include most protein-based foods, such as meat, beans, or nuts.
A metabolic disorder characterized by high blood sugar and insulin resistance. Type 2 diabetes is a progressive condition and is typically associated with overweight and low physical activity. Common symptoms include increased thirst, frequent urination, unexplained weight loss, increased hunger, fatigue, and impaired healing. Long-term complications from poorly controlled type 2 diabetes include heart disease, stroke, diabetic retinopathy (and subsequent blindness), kidney failure, and diminished peripheral blood flow which may lead to amputations.
The rate at which the body eliminates certain drugs. Zero-order kinetics is independent of drug concentration; rather, it is time-dependent. As such, a constant proportion of a drug is eliminated per unit time. Drugs that follow zero-order elimination kinetics include alcohol, warfarin, and theophylline.
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