Issue Date: May 2021 | PDF for this issue.
Vaccinating While Lactating: COVID-19 Vaccines Are Safe and Provide Immune Benefits to Mother and Infant
- Breastfeeding mothers were excluded from clinical trials for COVID-19 vaccine safety and have been advised to discuss their options for vaccination with their health care provider.
- The Centers for Disease Control and Prevention, the Academy of Breastfeeding Medicine, and the American College of Obstetricians and Gynecologists all have official statements supporting the safety of vaccinating lactating mothers.
- The ingredients from COVID-19 vaccines are highly unlikely to pass into human milk and even if they were to do so, pose little risk to breastfed infants.
- New research demonstrating vaccine-derived SARS-CoV-2 antibodies in milk shows that vaccination can also benefit infants.
Less than a year from the first recorded SARS-CoV-2 infection in the U.S., the Food and Drug Administration (FDA) authorized the emergency use of three COVID-19 vaccines. Usually a decade long endeavor, the global pandemic that has claimed over three million lives necessitated a rapid and all- hands-on-deck approach to vaccine development and delivery. Even with the accelerated pace, the vaccine trials made sure to include a diverse group of adults across multiple races, ethnicities, and age groups to ensure vaccine safety and efficacy for all recipients. What this diverse group did not include, however, were breastfeeding mothers. Without any clinical data to guide their vaccination decision, what’s a mother to do?
COVID-19 vaccines may be new, but vaccination during lactation is not. Combining what is known about the ingredients in each of the vaccines with decades of research on vaccine safety during lactation indicates that breastfeeding mothers can receive a COVID-19 vaccine. And mothers might not be the only ones who benefit from getting the vaccine. A pair of new studies [1, 2] identified vaccine-generated SARS-CoV-2 antibodies in milk that could potentially protect infants from COVID-19 infection.
If breastfeeding mothers were hoping for clear COVID-19 vaccine guidance from a national health authority, they were out of luck. In the UK, health agencies initially advised against breastfeeding mothers receiving the COVID-19 vaccine but then back-pedaled and included them in the eligible group. In the U.S., the FDA was not able to make a recommendation either way and instead advised breastfeeding mothers to discuss getting one of the three authorized vaccines with their health care provider. These conflicting recommendations coupled with the absence of a definitive statement on safety undoubtedly created apprehension, even among mothers who were themselves medical professionals.
“Some of the first women to reach out to me with questions about the vaccine were doctors and nurses working on COVID-19 floors,” says Rachel O’Brien, M.A., an international board-certified lactation consultant (IBCLC) in the Boston area. “They knew that they had to get the vaccine, they just needed me to tell them whether or not they needed to stop breastfeeding after they got it.”
O’Brien responded to these medical workers the same way she would to any mother reaching out to her with a concern about the safety of a medication, food, or vaccine: with an educated response. The document she created refers her patients to statements on vaccine safety from the Centers for Disease Control and Prevention (CDC) , the Academy of Breastfeeding Medicine (ABF) , and the American College of Obstetricians and Gynecologists (ACOG) .
The CDC and both professional societies converged on the recommendation that it is safe for lactating mothers to receive any of the three COVID-19 vaccines currently authorized for use in the U.S. [3-5]. They specifically addressed two common and important concerns: (1) can the vaccine give the mother or the baby COVID-19? and (2) can any parts of the vaccine pass from mother to infant in milk and cause issues?
The COVID-19 vaccines stimulate the immune system to make antibodies specific to SARS-CoV-2 by introducing the body to the spike proteins found on the outside of the virus. The spike proteins are used to attach the virus to cells in a host’s body but contain no viral RNA. As a result, they can stimulate an immune response specific to SARS-CoV-2 but do not result in a COVID-19 infection. None of the three vaccines currently authorized for use in the U.S. contain live or infectious virus. In fact, none of them contain the SARS-CoV-2 virus at all. This is important because no non-live virus vaccine has ever been reported to cause issues to infants from human milk .
Two vaccines (Moderna and Pfizer-BioNTech) use a messenger RNA (mRNA) sequence that codes for the spike protein delivered by lipid (aka fat) molecules and one vaccine (Johnson and Johnson/Janssen) uses a DNA sequence for the spike protein delivered by a modified adenovirus (a type of virus that causes a cold). This virus is able to enter cells but can’t make copies of itself once inside. After injection, the lipid particles or modified virus are taken up by muscle cells in the arm, which then use either mRNA or DNA to manufacture spike proteins.
It is unlikely that the lipid nanoparticles used to deliver the mRNA or the mRNA fragment that codes for the spike protein would enter the bloodstream and eventually reach breast tissue, and even more unlikely that they would make their way into milk [4, 6]. But should these unlikely events happen, there is no evidence that either would cause issues or have any biological effects for the nursing infant [4, 6]. Free mRNA degrades rapidly, and vaccine lipid nanoparticles would be destroyed by the infant’s gastrointestinal tract . The adenovirus vector in the Johnson and Johnson/Janssen vaccine is equally unlikely to pass from muscle cells to the maternal bloodstream and then to milk, and also poses no risk to infants should this occur because it lacks the ability to replicate [4-6].
Kailey Littleton, a pediatrician and IBCLC from West Virginia, says she has been sharing this information from the ABF statement  with her patients, who include health care workers, teachers, and breastfeeding mothers who want to be prepared when their eligibility for vaccination arrives.
“I think it helps them when I go through all of the steps that would need to happen for the vaccine to get from the mother’s arm to the baby,” Littleton explains. “I think there is this idea that anything that goes into the mother’s body, goes into the milk. By explaining why this isn’t the case, they feel more comfortable about the vaccine.”
Immunity for Mothers and Infants
It might also make mothers feel more comfortable getting vaccinated if they were informed that it could result in protection for their infants. Several studies identified neutralizing antibodies directed at SARS- CoV-2 in the milk of mothers that tested positive for COVID-19 and now two new studies [1, 2] report that COVID-19 vaccination also produces an immunological response in human milk.
These studies used a similar research design and collected blood and milk samples from lactating mothers (n=31 , n=23 ) at the time of the first mRNA-based vaccine dose (baseline), at the time of the second dose, and either two to six weeks  or four weeks  following the second dose. Unfortunately, they didn’t look for the same types of antibodies in milk, which makes it difficult to draw a direct comparison of their results.
The study led by researchers at Massachusetts General Hospital  looked at three types of immunoglobulins (Ig) in milk: IgM, IgG, and IgA. All three increased from baseline to the second dose . But the dominant milk antibody response two weeks post-second vaccine was IgG. This contrasts with milk antibody profiles from COVID-19-positive mothers that were predominantly IgA. The study authors suggest the difference could be related to the intramuscular injection of the vaccine, which boosts systemic immunity, compared with a natural infection that boosts humoral immunity .
In contrast, the study from the University of California, San Francisco, [2, available as a pre-print] measured only milk IgA. The authors report that levels of milk SARS-CoV-2 IgA were similar between vaccinated mothers and those that had previously been infected with COVID-19 .
The take home message of these studies should not be their conflicting results but that both identified an immune response in milk that could potentially protect infants from COVID-19 infection. Both milk-derived IgA and IgG play critical roles in neonatal and infant immunity against viruses. Future research will be needed to better quantify the milk immune response after vaccination and determine what role each plays in infant protection from SARS-CoV-2.
Risks, Benefits, and Support
Vaccination programs are part of public health but getting vaccinated still remains a personal choice. Everyone must weigh the benefits of getting the vaccine against the risks of contracting COVID-19, and breastfeeding mothers have additional concerns to consider before making their vaccination decision: What is the risk to their infant if they get vaccinated? What is the risk to their infant if they decide to stop nursing? Will the vaccine influence their milk supply? What are the risks if they wait to get vaccinated? How could the vaccine protect their infant against the virus?
Both ABF  and ACOG  emphasize the importance of shared decision making between breastfeeding mothers and their health care provider, be it their primary care physician, child’s pediatrician, OBGYN, or lactation consultant. And many mothers are following this advice.
“I feel like breastfeeding moms are relying a lot on their doctors to guide them through this decision compared with other vaccines,” says Tricia Rambur, an OBGYN in San Diego. “The vaccines are new and there is a feeling that there is not enough information. But I try to share with my patients that the [professional] organizations have done enough to make it clear that the vaccines are safe.”
But access to a health care provider is not a luxury shared by all lactating mothers. ACOG’s official statement about vaccinating pregnant and breastfeeding mothers explicitly states that discussion with a healthcare provider should not be a requirement to receive a COVID-19 vaccine because it could act as a barrier to vaccination. As a result, the World Health Organization  recommends that because the vaccines pose little biological or clinical risk to the mother or breastfeeding child, they should be offered to breastfeeding mothers as they would be to any adult.
- Gray KJ, Bordt EA, Atyeo C, Deriso E, Akinwunmi B, Young N, Baez AM, Shook LL, Cvrk D, James K, De Guzman R, Brigida S, Diouf K, Goldfarb I, Bebell LM, Yonker LM, Fasano A, Rabi A, Elovitz MA, Alter G, Edlow AG. 2021. COVID-19 vaccine response in pregnant and lactating women: a cohort study. American Journal of Obstetrics and Gynecology doi: https://doi.org/10.1016/j.ajog.2021.02.023.
- CDC Statement: https://www.cdc.gov/breastfeeding/breastfeeding-special-circumstances/vaccinations-medications-drugs/vaccinations.html
- Academy of Breastfeeding Medicine Statement: https://www.bfmed.org/abm-statement-considerations-for-covid-19-vaccination-in-lactation
- American College of Obstetricians and Gynecologist Statement: https://www.acog.org/clinical/clinical-guidance/practice-advisory/articles/2020/12/vaccinating- pregnant-and-lactating-patients-against-covid-19
- Drugs and Lactation Database (LactMed) [Internet]. Bethesda (MD): National Library of Medicine (US); 2006-. COVID-19 vaccines. [Updated 2021 Mar 17]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK565969/
- Golan Y, Prahl M, Cassidy A, Wu AHB, Jigmeddagva U, Lin CY, Gonzalez VJ, Basilio E, Warrier L, Buarpung S, Asiodu IV, Ahituv N, Flaherman VJ, Gaw SL. 2021. Immune response during lactation after anti-SARS-CoV2 mRNA vaccine. doi: https://doi.org/10.1101/2021.03.09.21253241
- World Health Organization, Jan 8, 2021. Interim recommendations for use of the Pfizer-BioNTech COVID-19 vaccine, BNT162b2, under Emergency Use Listing. WHO/2019-nCoV/vaccines/SAGE_recommendation/BNT162b2/2021.1
- The new Dietary Guidelines are organized by age group, including Birth-24 months, Children and Adolescents, Adults, Pregnant and Lactating Women, and Older Adults.
- Ninety percent of Americans are not reaching their recommended intake of dairy. To mitigate this, the guidelines recommend drinking low-fat milk or fortified soy beverages and integrating yogurt into breakfasts and snacks.
- To meet your nutritional needs without consuming too many calories, focus on eating nutrient-dense foods. Avoid eating too many added sugars, sodium, or saturated fats.
- Infants should be fed exclusively human milk or infant formula for the first 6 months of life. At around 1 year, dairy can be incorporated into their diets.
The U.S. government recently released its 2020-2025 Dietary Guidelines for Americans (DGA), designed to help policymakers and health professionals advise everyday Americans on how to consume a balanced and nutritious diet. New to this edition are recommendations for the tiniest Americans, from Birth to 24 months. This latest edition is also organized by age group for the first time, as well as includes recommendations for pregnant and lactating women. As ever, dairy remains a key food group to consume for all age groups, as it is a unique source of quality proteins, vitamins, and minerals.
Diet is undoubtedly a key component of health and wellness, and with 74% of American adults overweight or obese and 60% having diet-related chronic diseases , the guidelines are imperative in helping people maintain a healthy lifestyle. Eating right can also reduce the risk of diet-related conditions such as cardiovascular disease, cancer, and diabetes, and while diet has an undisputed role in prevention of these conditions, the suggested dietary patterns are not meant as a treatment.
A Failing Grade
The DGA are evidence-based recommendations jointly published every five years by the U.S. Departments of Agriculture (USDA) and Health and Human Services (HHS) and have been in publication since 1980. Despite this, the average American is still getting a failing grade on their dietary report card. According to the Healthy Eating Index (HEI), a measure out of 100 that indicates how close a diet adheres to these guidelines, the average American adult has a score of only 59 . This score also hasn’t budged much in the past few years.
Surprisingly, nearly 90% of the US population are not meeting their recommended intake for dairy or fortified soy. To counter this, the guidelines suggest drinking low-fat milk or fortified soy beverages with their meals, or incorporating yogurt into breakfasts and snacks. Other food groups that have low scores overall were whole grains at 98% and vegetables at around 90%.
The New Guidelines
Many of the recommendations in the latest version echo guidelines past, with suggestions to eat more vegetables and whole grains and to cut back on added sodium, sugars, saturated fats, and alcohol. But the authors of the latest 149-page dietary guidelines have organized their recommendations through four overarching principles:
- Follow a healthy dietary pattern at every life stage.
- Customize and enjoy nutrient-dense food and beverage choices to reflect personal preferences, cultural traditions, and budgetary considerations.
- Focus on meeting food group needs with nutrient-dense foods and beverages, and stay within calorie limits.
- Limit foods and beverages higher in added sugars, saturated fat, and sodium, and limit alcoholic beverages .
The new guidelines are also structured to be inclusive and cater to a diversity of diet choices, whether they be influenced by personal preferences, cultural traditions, or budgetary considerations. Rather than give a single specific dietary pattern, the guidelines are meant to be a customizable, adaptable framework.
In sum, adults on a 2,000 calorie diet should be consuming 2.5 cups of vegetables, 2 cups of fruit, 6 ounces of grains, 3 cups of dairy, 5.5 ounces of protein, and 27 grams of oils per day . These portions should ideally be met through whole, nutrient-dense foods and beverages, with little added sugars and salt.
Make Every Bite Count
In addition to conducting systematic reviews and analyzing the latest in health and nutritional studies, the recommendations in the DGA are made through a process called dietary pattern modelling. This analysis involves changing the amounts or types of foods in a dietary pattern to see how those changes would affect meeting nutritional needs. This type of modelling highlighted the importance of choosing nutrient-rich foods. These foods are rich in vitamins, minerals, fibers, and proteins and consuming them can help people reach their daily nutritional requirements without going overboard on the caloric budget. Adults are advised to limit added sugars to less than 10% of calories per day to reach their nutritional requirements without consuming too many calories .
The dietary pattern modeling also found that children under the age of two should not be eating foods with added sugars because their high nutritional but low caloric needs leave no space in the diet for added sugars. Now, this doesn’t mean that toddlers can never enjoy a cookie, but the overall dietary pattern should be free of added sugars.
The dietary pattern modelling also places dairy and fortified soy as a highly recommended food group to consume. Dairy is a rich source of healthy proteins seldom found in other foods and contains a suite of nutrients such as calcium, vitamin B12, vitamin D (if fortified), potassium, phosphorus, and zinc.
To help Americans improve their dietary patterns, helpful tips on how to replace low-nutrient foods with healthier alternatives are littered throughout the DGA. For example, rather than eating applesauce, consumers can opt for a whole apple, as the peel contains fiber and important micronutrients, whereas processed foods often contain a bevy of added sugars and less fiber. Another alternative is consuming low-fat yogurt with fresh fruit rather than a fruity, full-fat yogurt with added sugar.
Consumers serious about eating right can also try MyPlate, a suite of customizable digital tools and online resources to help implement their dietary goals. Users can input their weight, height, activity level, and nutritional goals, and the service provides meal plans, progress tracking, and resources such as recipes and budgetary cheat sheets.
New Age Groups
Perhaps the biggest shift from previous guidelines is an organization based around age groups. Previous guidelines only had recommendations from two years onward, but the Agricultural Act of 2014 (aka the “Farm Bill”) mandated that the 2020-2025 edition and all editions thereafter include recommendations for infants, young toddlers, and pregnant and lactating women.
The guidelines recommend that infants from birth to 6 months be fed exclusively human milk or infant formula, and at around 12 months cow’s milk and other dairy can be introduced to the baby’s diet. For young infants, it’s not recommended to replace human milk with cow’s milk because the two have very different nutritional properties; human milk is much higher in lactose and oligosaccharides, the latter of which are beneficial for gut bacteria, whereas cow’s milk contains an excess of protein that may be difficult for the infant to digest. After 1 year, toddlers can be fed dairy as a rich source of calcium, vitamin D, potassium, and protein–critical nutrients for children’s growth.
Dietary recommendations for pregnant and lactating women resemble those for non-pregnant women of the same age group but with an added caloric budget dependent on the stage of the pregnancy or lactation. Pregnant and lactating women also tend to score higher on the Healthy Eating Index at 63 and 62, respectively, but pregnancy also ushers a more urgent need for nutrients such as folate/folic acid, iron, iodine, and vitamin D . Because meeting these nutritional requirements may be difficult for some women, many health experts recommend taking a prenatal vitamin. In sum, the guidelines encourage Americans to enjoy a nutrient-dense dietary pattern, low in added sugars, salts, and saturated fats, and catered to personal preferences and age group. With 90% of American adults not reaching their recommended dairy intake, incorporating low-fat milk and yogurt into the diet becomes an essential part of a healthy lifestyle.
1. U.S. Department of Health and Human Services and U.S. Department of Agriculture. 2020-2025 Dietary Guidelines for Americans. 9th Edition. March 2020. Available at: https://www.dietaryguidelines.gov/sites/default/files/2020-12/Dietary_Guidelines_for_Americans_2020-2025.pdf
Breastfeeding May Offer Long-term Advantages to Children’s Neurodevelopment Compared with Feeding Expressed Milk
- Human milk consumption is known to provide several benefits for children, but it’s unclear if the mode of feeding makes a difference.
- A new study examines some of the long-term effects of feeding expressed milk versus breastfeeding on 6-year-old children.
- The study finds that feeding at the breast may offer clinically meaningful advantages to children’s working memory compared with feeding expressed milk.
- The researchers suggest that breastfeeding may offer some long-term advantages to children’s neurodevelopment compared with expressed milk feeding, although larger follow-up studies are required to clarify these results.
Could how you eat something matter as much as what you eat? At least when it comes to human milk, the answer is still unclear.
Human milk is known to provide several benefits to children. Studies have shown that exclusive breastfeeding and breastfeeding for a longer duration are associated with enhanced cognitive development of children, improved behavioral outcomes related to attention and hyperactivity, and benefits to food-related behaviors such as less food fussiness [1-9]. But researchers still don’t know whether feeding at the breast might confer some advantages over feeding expressed milk.
In the United States, more than 85% of infants fed human milk are fed expressed milk at least sometimes . “Pumping and feeding expressed milk has become extremely common over the past couple of decades in the U.S. and other countries, yet information about whether expressed milk is as beneficial for infants is lacking,” says Dr. Sarah Keim of the Ohio State University.
In a longitudinal study of U.S. mothers and children up to age 6, Keim and her colleagues examined associations between mode of feeding human milk and long-term effects on neurodevelopment and behavior . “We built a cohort of mothers and children with funding from the Ohio State University and the U.S. Centers for Disease Control and Prevention to learn more about the differences between expressed milk feeding and feeding at the breast,” says Keim. “The main challenge with a study like this is encouraging a high response rate among participants after many years,” she says.
The researchers were particularly interested in looking at the effects of breastfeeding versus feeding expressed milk on higher-level cognitive abilities that are predictive of school success, usually grouped under the umbrella-term “executive function” . They also examined long-term outcomes on global cognitive development and eating behaviors.
The researchers found that the mode of feeding human milk may be important to the development of executive function. Among 285 participants included in the analysis, feeding at the breast for longer periods of time was associated with clinically-meaningful advantages in working memory ability—a component of executive function—at 6 years of age. Each additional month of exclusive feeding at the breast decreased the risk of a working memory score compatible with an attention deficit hyperactivity disorder (ADHD) diagnosis by 22%.
However, the mode of human milk feeding did not show any association with global cognitive ability, and only weak associations were observed with eating behaviors. Feeding human milk was associated with increased food enjoyment, and longer exclusive feeding at the breast was associated with a small increase in emotional overeating and food fussiness.
The results suggest that the mode of feeding human milk may be important to the development of executive function. “Expressed milk feeding may not offer all the benefits of feeding at the breast for optimal neurodevelopment,” says Keim.
Executive function develops rapidly during the preschool years. The brain regions involved in executive function require several nutrients that are enriched in human milk, suggesting a potential mechanism by which milk intake could influence their development [1,2,6,13-16]. The researchers suggest that feeding at the breast may also offer infants greater maternal bonding opportunities compared with expressed milk feeding, which could play a role in development of early executive function [17,18].
The researchers note the need for follow-up studies to tease apart how the mode of feeding of human milk influences neurodevelopment. “Larger and more detailed studies are needed,” says Keim. These could include larger prospective studies that incorporate multiple complementary measures of child cognition, including objective laboratory assessments. “We are planning to follow up these results with future, more detailed studies,” says Keim.
The study concludes that feeding at the breast may offer advantages to some aspects of executive function, such as working memory, that expressed milk may not. “It’s difficult to shift clinical recommendations without stronger evidence, but other studies have started to show that expressed milk feeding may be less optimal than feeding at the breast for other child health outcomes as well,” says Keim. “It seems that if there is a choice available, feeding at the breast may be preferred over feeding expressed milk,” she says.
1. Anderson JW, Johnstone BM, Remley DT. Breast-feeding and cognitive development: a meta-analysis. Am J Clin Nutr. 1999 Oct;70(4):525-35.
2. Kramer MS, Aboud F, Mironova E, Vanilovich I, Platt RW, Matush L, Igumnov S, Fombonne E, Bogdanovich N, Ducruet T, Collet JP, Chalmers B, Hodnett E, Davidovsky S, Skugarevsky O, Trofimovich O, Kozlova L, Shapiro S; Promotion of Breastfeeding Intervention Trial (PROBIT) Study Group. Breastfeeding and child cognitive development: new evidence from a large randomized trial. Arch Gen Psychiatry. 2008 May;65(5):578-84.
3. Belfort MB, Rifas-Shiman SL, Kleinman KP, Guthrie LB, Bellinger DC, Taveras EM, Gillman MW, Oken E. Infant feeding and childhood cognition at ages 3 and 7 years: Effects of breastfeeding duration and exclusivity. JAMA Pediatr. 2013 Sep;167(9):836-44.
4. Bernard JY, De Agostini M, Forhan A, Alfaiate T, Bonet M, Champion V, Kaminski M, de Lauzon-Guillain B, Charles MA, Heude B; EDEN Mother-Child Cohort Study Group. Breastfeeding duration and cognitive development at 2 and 3 years of age in the EDEN mother-child cohort. J Pediatr. 2013 Jul;163(1):36-42.e1.
5. Victora CG, Horta BL, Loret de Mola C, Quevedo L, Pinheiro RT, Gigante DP, Gonçalves H, Barros FC. Association between breastfeeding and intelligence, educational attainment, and income at 30 years of age: a prospective birth cohort study from Brazil. Lancet Glob Health. 2015 Apr;3(4):e199-205.
6. Groen-Blokhuis MM, Franić S, van Beijsterveldt CE, de Geus E, Bartels M, Davies GE, Ehli EA, Xiao X, Scheet PA, Althoff R, Hudziak JJ, Middeldorp CM, Boomsma DI. A prospective study of the effects of breastfeeding and FADS2 polymorphisms on cognition and hyperactivity/attention problems. Am J Med Genet B Neuropsychiatr Genet. 2013 Jul;162B(5):457-65.
7. Hayatbakhsh MR, O’Callaghan MJ, Bor W, Williams GM, Najman JM. Association of breastfeeding and adolescents’ psychopathology: a large prospective study. Breastfeed Med. 2012 Dec;7(6):480-6.
8. Boswell N, Byrne R, Davies PSW. Eating behavior traits associated with demographic variables and implications for obesity outcomes in early childhood. Appetite. 2018 Jan 1;120:482-90.
9. Brown A, Lee M. Breastfeeding during the first year promotes satiety responsiveness in children aged 18-24 months. Pediatr Obes. 2012 Oct;7(5):382-90.
10. Labiner-Wolfe J, Fein SB, Shealy KR, Wang C. Prevalence of breast milk expression and associated factors. Pediatrics. 2008 Oct;122 Suppl 2:S63-8.
11. Keim SA, Sullivan JA, Sheppard K, Smith K, Ingol T, Boone KM, Malloy-McCoy A, Oza-Frank R. Feeding infants at the breast or feeding expressed human milk: long-term cognitive, executive function, and eating behavior outcomes at age 6 years. J Pediatr. 2021 Feb 13:S0022-3476(21)00138-4.
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14. Doom JR, Georgieff MK. Striking while the iron is hot: Understanding the biological and neurodevelopmental effects of iron deficiency to optimize intervention in early childhood. Curr Pediatr Rep. 2014 Dec 1;2(4):291-98.
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- Bladder cancer is the ninth most common cancer globally, and the most expensive malignancy to treat.
- One consortium of studies has found that people who eat more than a couple of servings of yogurt per week, on average, are less likely to develop bladder cancer than people who do not eat yogurt.
- Another analysis of many different studies reports that milk consumption is associated with lower odds of bladder cancer.
Bladder cancer is a difficult condition to treat. It can hit anyone at any age but is more likely to afflict men than women, and smokers more than non-smokers. It is certainly costly for individuals. For health-system managers, tasked with trying to save as many years of life as possible with finite resources, it has the notorious title of the most expensive malignancy to treat from diagnosis to death . Identifying preventative measures, especially cheap ones, can therefore bring benefits beyond reducing bladder cancer rates, as they may free up resources for treatments of other diseases. Over the years, whether dairy products are preventative of bladder cancer has been debated. However, recently, one study that pooled evidence from many other studies found that yogurt consumption is associated with lower bladder cancer risk . A second recent analysis, also combining data from many previous studies, concludes that consuming more milk is linked to lower bladder cancer rates .
Dairy, especially low-fat dairy, such as milk and various fermented milk products, is thought to protect against a number of diseases, including several cancers. For example, milk and yogurt consumption is associated with lower rates of cardiovascular disease around the world, and yogurt fermented with certain types of bacteria may act as a therapeutic against arthritis and additional autoimmune diseases. When it comes to cancer, eating and drinking fermented milk products has been linked to reduced odds of developing colorectal and esophageal cancers , as well as premenopausal breast cancers .
Researchers seeking to establish broad tendencies between diet and disease are faced with a complex array of available data, collected as part of studies that were designed differently. For them, an especially important task is deciding exactly which studies are of sufficient quality and comparability to be included in a larger assessment. One of the two recent papers about bladder cancer risk and dairy, published in the European Journal of Clinical Nutrition, included 13 cohort studies from countries spread across Europe and North America. All of these were coordinated under the same umbrella international consortium, called BLEND (BLadder cancer Epidemiology and Nutritional Determinants) . Crucially, to avoid recall bias, which can occur in nutrition studies when study participants are asked to remember what they ate in the past, these were all prospective studies. The second recent paper started with a literature search and then excluded 180 of 202 studies initially identified because they did not meet strict criteria, such as providing sufficient data . This paper was published in the journal, Nutrition and Cancer.
In the analysis of the BLEND data, the research team of Anke Wesselius and Merab Acham, of Maastricht University in The Netherlands, first converted all of the food-intake data from different cohort studies into weekly consumption totals, from which daily averages could be calculated. They were able to separately analyze liquid milk intake from other forms of dairy, including cheese, ice cream, cream and yogurt. Of the 3,590 bladder cancer cases in the 13 BLEND studies, three-quarters occurred in men, and 71% occurred in smokers. These studies included 593,637 people who did not develop bladder cancer. Comparing dairy consumption patterns of people who had developed bladder cancer with those who did not revealed only one statistically significant finding: bladder-cancer-free individuals were more likely to be yogurt-eaters. Indeed, when the researchers looked within the at-risk groups—comparing with men separately to among women, and with smokers separately to among non-smokers—the same pattern was evident: individuals who ate yogurt were less likely to develop the disease.
The BLEND analysis did not, however, pick up a dose-dependent response. In other words, the data did not suggest that the more yogurt you eat, the less likely you are to get bladder cancer. Instead, the study found that participants who ate more than an average of 25 grams of yogurt per day—that is, roughly a couple of servings per week—had a 15% lower chance of developing bladder cancer compared with participants who did not eat yogurt. Among the studies pooled together under the BLEND consortium, almost all had individually identified this association. Moreover, a double-blind randomized control trial conducted in Japan pointed to a particular bacterial strain in yogurt, called Lactobacillus casei, providing a protective effect .
The second recent paper combined and compared studies from four continents. Bringing together all of the data from 18 studies led the research group that authored this paper to conclude that consuming milk specifically—as opposed to dairy products in general—is associated with a 26% reduction in bladder cancer risk. Curiously, when the researchers, based out of Sun Yat-Sen University, in HuiZhou, China, compared different world regions, they found a stronger protective effect in Asian studies than in studies conducted in Europe and North America. This finding could be linked to the fact that people in Asia tend to consume less dairy overall, and hence, among those who do include milk in their diets, the results are statistically cleaner.
There is no straightforward conclusion as to why milk and yogurt could reduce the risk of developing bladder cancer. Like many cancers, bladder cancer’s development involves many complex steps. One idea is that vitamin B2 (riboflavin), found in high levels in both milk and yogurt, is the component conferring protection. It is excreted in urine, and so logically comes into contact with the bladder epithelium. Another proposal as to why yogurt appears to be protective is that fermentation, while reducing sugar content, increases the amount of antioxidative phenolic compounds in yogurt. These compounds quench free radicals that promote cellular mutations.
Whatever the mechanisms responsible for the apparent protective effects, these findings are heartening, especially to individuals most at risk. As well as being hugely expensive to treat, bladder cancer is the ninth most common cancer globally. As such, doctors may wish to consider recommending a yogurt every few days, and a splash of milk in one’s tea.
1. Acham M., Wesselius A., van Osch F. H., Yu E. Y., van den Brandt P. A., White E., Adami H. O., Weiderpass E., Brinkman M., Giles G. G., Milne R. L. & Zeegers M. P. Intake of Milk and Other Dairy Products and the Risk of Bladder Cancer: A Pooled Analysis of 13 Cohort Studies. Eur J Clin Nutr., 74:28-35 (2020).
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