Milk quality

Should I be worried about the quality of my milk?

Healthy mothers who eat a balanced diet should have no reason to worry about the quality of their milk. There is usually no need to eat specific foods or avoid spices. Mothers should not force themselves to drink liquids but if exercising strenuously, they should make sure they drink enough. Mothers should avoid extreme dieting. Slight changes in breast milk such as those caused by the mother's diet, do not affect the general recommendation to breastfeed.  Milk quality can be affected by high levels of pollutants or a small number of genetic diseases in the mother. Breast milk may be contaminated by pollutants however it is only unsafe for babies in very specific and rare circumstances. 

A) The quality of milk

A mother who is healthy and eats a balanced diet will nearly always produce good milk and colostrum (Jenness 1979; Martin 2016).

Unfortunately, worry about the quality of milk may lead mothers to unnecessarily make significant lifestyle changes, start infant formula, or even wean (Chang 2019). 

One common area of concern is the mother’s diet. There is generally no need for mothers to:

  • Eat or not eat specific foods.
  • Avoid spices.
  • Force themselves to drink more liquids.

Occasionally mothers are told to keep the baby on one breast instead of offering the second side to allow the baby to get the fat present in the hindmilk (Kent 2006). This should not be a concern nor is it a valid way to breastfeed and can result in a reduced milk supply and in breast problems. 

Mothers may also worry about milk fat in expressed breast milk. It is normal for expressed breast milk to separate and the fat (cream) to rise to the top, creating a thin cream layer. Mothers may believe the separation is a sign the milk has gone bad or the cream layer is too thin. Neither is correct. Separation is normal and the cream layer is usually thin. Mothers need only lightly shake the milk to mix the layers before feeding this to the baby. 

Just as the quality of breast milk is nearly always good, most mothers have a normal milk supply and can breastfeed without giving their babies with extra milk. Mothers with a low milk supply will nearly always have milk of normal quality; there is just not enough of it.

Short-term stress does not appear to affect the quality of milk (Palnizky Soffer 2020).

B) Changes in milk quality

Some differences in milk components may be related to the age of the baby and the mother’s diet and health (Keikha 2017). Slight changes in the quality of breast milk do not affect the general recommendation to breastfeed. Mothers with illness should see their health-care providers and optimize their health. 

1) The mother’s diet

Unless the mother is very malnourished, her milk will be able to provide all the necessary nutrients and many benefits for her baby. Mothers should avoid extreme dieting. They should make sure they drink enough liquids, if they are exercising strenuously.

Breast milk fat content and type are variable and can be affected by the mother’s diet, weight, and weight gain during pregnancy but these minor changes do not affect the baby’s rate of growth (Martin 2017).

Drinks sweetened with high-fructose corn syrup as is found in soda pop drinks for example, can increase the amount of fructose in a mother’s milk and may contribute to faster growth of the baby (Berger 2018; Goran 2017).

2) Vitamins and minerals

The breast is very good at maintaining proper levels of vitamins and minerals in milk (Lönnerdal 2007). Rarely, a mother and subsequently her milk may be low in certain vitamins or minerals such as vitamins A, B2, and B12, iodine, zinc, and iron for dietary or health reasons (Allen 2018).

Mothers who are at risk of nutritional or vitamin deficiencies should speak with their health-care providers to prevent, monitor, and treat such problems as these can impact the quality of their milk.

3) The mother’s health

Illness in the mother can cause slight changes in her milk (Amaral 2019):

  • Diabetes (Azulay Chertok 2020; Peila 2020)
  • High blood pressure 
  • Overweight 

There is much evidence that breastfeeding prevents obesity in babies but the nature of breast milk of obese mothers may reduce this effect (Álvarez  2020; Enstad et al. 2020; Saben 2020).

4) Genetic problems

It is very rare for genetic conditions to affect the amount or quality of a mother’s breast milk.

5) Environmental contaminants

Lead, mercury, and other environmental contaminants can be in breast milk. Mothers should minimize their exposure to these. If there is a particular concern, mothers can be tested and treated.

Some types of fish can contribute to increases in mercury levels in the mother’s body and breast milk.

6) Colour changes

Normal breast milk will take on a more bluish appearance over time. On rare occasions, as when mothers are taking certain medications, it can change colour.

Colostrum can occasionally be bloody but breast milk should not have blood present. Mothers who have bloody breast milk should be seen by their health-care providers.

7) Fast rate of growth

A very small number of babies have been reported to grow very quickly while exclusively breastfeeding. One study showed that their rate of growth decreased to normal once solid food was started, suggesting that something in their mother’s milk was causing the rapid growth (Larsson 2018).

The cause of this is unknown but may be related to differences in fats, proteins, unique breast milk sugars (HMOs), or hormones (Baldeón 2019; Galante 2020; Lagström 2020; Pekmez 2019). 


Allen LH, Dror DK. Introduction to Current Knowledge on Micronutrients in Human Milk: Adequacy, Analysis, and Need for Research. Adv Nutr. 2018;9(suppl_1):275S–277S
Amaral YNDVD, Rocha DM, Silva LMLD, et al. Do maternal morbidities change the nutritional composition of human milk? A systematic review. Cien Saude Colet. 2019 Jul 22;24(7):2491-2498

Azulay Chertok IR, Haile ZT, Shuisong N, Kennedy M. Differences in Human Milk Lactose and Citrate Concentrations Based on Gestational Diabetes Status. Breastfeed Med. 2020 Oct 19

Baldeón ME, Zertuche F, Flores N, et al. Free Amino Acid Content in Human Milk is Associated with Infant Gender and Weight Gain during the First Four Months of Lactation. Nutrients. 2019 Sep 17;11(9):2239
Berger PK, Fields DA, Demerath EW, et al. High-Fructose Corn-Syrup-Sweetened Beverage Intake Increases 5-Hour Breast Milk Fructose Concentrations in Lactating Women. Nutrients. 2018 May 24;10(6). pii: E669
Chang PC, Li SF, Yang HY, et al. Factors associated with cessation of exclusive breastfeeding at 1 and 2 months postpartum in Taiwan. Int Breastfeed J. 2019 May 7;14:18

Enstad S, Cheema S, Thomas R, et al. The impact of maternal obesity and breast milk inflammation on developmental programming of infant growth. Eur J Clin Nutr. 2020;10.1038/s41430-020-00720-5

Galante L, Pundir S, Lagström H, et al. Growth Factor Concentrations in Human Milk Are Associated With Infant Weight and BMI From Birth to 5 Years. Front Nutr. 2020 Jul 29;7:110

Goran MI, Martin AA, Alderete TL, et al. Fructose in Breast Milk Is Positively Associated with Infant Body Composition at 6 Months of Age. Nutrients. 2017 Feb 16;9(2). pii: E146

Hamosh M, Bitman J. Human milk in disease: lipid composition. Lipids. 1992 Nov;27(11):848-57 

Jenness R. The composition of human milk. Semin Perinatol. 1979 Jul;3(3):225-39
Keikha M, Bahreynian M, Saleki M, et al. Macro- and Micronutrients of Human Milk Composition: Are They Related to Maternal Diet? A Comprehensive Systematic Review. Breastfeed Med. 2017 Nov;12(9):517-527
Kent JC, Mitoulas LR, Cregan MD, et al. Volume and frequency of breastfeedings and fat content of breast milk throughout the day. Pediatrics. 2006 Mar;117(3):e387-95

Lagström H, Rautava S, Ollila H,et al. Associations between human milk oligosaccharides and growth in infancy and early childhood. Am J Clin Nutr. 2020 Apr 1;111(4):769-778

Larsson MW, Larnkjær A, Christensen SH, et al. Very High Weight Gain During Exclusive Breastfeeding Followed by Slowdown During Complementary Feeding: Two Case Reports. J Hum Lact. 2018 Mar 1:890334418756580
Lönnerdal B. Trace element transport in the mammary gland. Annu Rev Nutr. 2007;27:165-77
Martin CR, Ling PR, Blackburn GL. Review of Infant Feeding: Key Features of Breast Milk and Infant Formula. Nutrients. 2016 May 11;8(5). pii: E279

Palnizky Soffer G, Siri M, Mangel L, et al. Impact of Maternal Anxiety on Human Milk Macronutrients Content: A Prospective Observational Study. Breastfeed Med. 2020 Jun 26

Peila C, Gazzolo D, Bertino E, et al. Influence of Diabetes during Pregnancy on Human Milk Composition. Nutrients. 2020 Jan 9;12(1):185 

Pekmez CT, Larsson MW, Lind MV, et al. Breastmilk Lipids and Oligosaccharides Influence Branched Short Chain Fatty Acid Concentrations in Infants with Excessive Weight Gain. Mol Nutr Food Res. 2019 Dec 4;e1900977

Saben JL, Sims CR, Piccolo BD, et al. Maternal adiposity alters the human milk metabolome: associations between nonglucose monosaccharides and infant adiposity. Am J Clin Nutr. 2020 Nov 11;112(5):1228-1239