Yes, Your Diet Matters While Breastfeeding: The Science Every Breastfeeding Mom Should Know

I’m writing this to clear something up—it's actually one of the main reasons I started this blog in the first place:

Yes, your diet directly impacts the composition of your breast milk.

What you eat—fats, proteins, vitamins, minerals, phytonutrients—all gets broken down, absorbed, and ultimately contributes to the makeup of your milk. It’s not made from pixie dust and wishes (well, maybe a little sunshine... in the form of vitamin D).

Of course, it’s more complex than “you are what you eat.” Breast milk doesn’t contain undigested chunks of spinach or banana. But through digestion, absorption, and transport via your bloodstream, the nutrients you consume are delivered to your mammary glands, where milk is produced. It's biochemistry at work—and it's powerful.

"But I thought breast milk is perfect no matter what?"

You’ve probably heard that breast milk is ideal for babies—even for mothers facing food insecurity. And it is! Breast milk is incredible and continues to be the best nutrition for infants, especially during the first 6 months of life.

But here’s what isn’t talked about enough:

There’s a lot more to the story.

Many health professionals avoid this topic because they don’t want to discourage anyone from breastfeeding. They fear that talking about nutrition might make moms feel like they need a “perfect” diet in order to nurse. I get that. But unfortunately, this approach often ignores the science.

You don’t need a perfect diet. But a better one can make a big difference.

Even if your diet isn’t optimal, breast milk remains the gold standard. But knowing how your nutrient intake affects the quality of your milk - and how certain foods can boost key nutrients - gives you an amazing opportunity to support both your baby’s development and your own postpartum healing.

After all, breastfeeding requires more of several nutrients than pregnancy does. And let’s face it: this might be the most control you’ll ever have over your child’s nutrition.

Nutrition during breastfeeding = support for:

• Your baby’s brain and immune development

• Your postpartum recovery

• Your energy and hormone balance

• Your long-term health and weight goals

  
  

Let me show you why I’ve made it my career goal, as a Dietitian and Lactation Counselor, to prove that #nutritionmatterswhilebreastfeeding.

Breast is best, even if mom's diet is less than optimal. But let me introduce you to a different way of looking at it:

You Can Optimize Your Breast Milk Through Diet!

Let take a look at what the research says:

• Vitamin D: Daily supplementation of a breastfeeding mother’s diet with 6400 IU Vitamin D can fully meet an infant's Vitamin D needs through breast milk alone (1).

  
  

• DHA (Omega-3's): Supplementation with DHA, an omega-3 fatty acid important for brain development in infants, significantly altered the fatty acid composition of the mother’s breast milk (2). Many lactation nutritionists now recommend weekly fish intake or a fish oil supplement to their nursing mothers.

  
  

• Probiotics: In moms with mastitis, those taking probiotics recovered faster and had fewer recurrences than those taking antibiotics (3).

These examples show just how much our diet can support the breastfeeding journey.

But Some Diets Can Negatively Impact Breast Milk, Too

While breast milk is incredibly resilient, some dietary extremes or deficiencies can cause problems:

• A vegan breastfeeding mother's baby developed Vitamin B12 and iron deficiency, leading to developmental delays and organ enlargement (4).

• A non-diabetic mom following a very low carb, high-fat (keto) diet developed ketoacidosis while breastfeeding - a life threatening condition (5).

These aren’t scare tactics. They’re reminders that breastfeeding requires intentional nourishment—for both mom and baby.

Nutrients That Depend on Your Diet

Some nutrients in breast milk are heavily influenced by maternal intake, including:

• Selenium and Iodine: Both are critical for thyroid function for mom and baby and a deficiency can lead to developmental delays in babies. Needs are even higher during lactation than pregnancy (6).

  • Food sources: Brazil nuts, seafood, dairy, seaweed, supplements and iodized salt

    
    

• Vitamins A, D, E, K, Choline, and B Vitamins: These all influence milk concentration and play key roles in brain development, metabolism, and immune support.

  
  

• Probiotic Foods: Support gut health and reduce breast infections like mastitis. All too often, mom stops breastfeeding due to the pain or because her milk production dwindles. Could taking a daily probiotic or eating foods such as Tempeh, Sauerkraut and probiotic yogurts lead to a quicker recovery, or even prevent such infections?

  
  

• Fat Profile of Breast Milk: The fatty acid profile of your milk also varies based on your diet. Consuming cold-water fish like salmon or sardines at least once a week can boost your baby’s intake of brain-supportive fats like DHA. Concerned about mercury? Choosing the right types and portions of fish can keep exposure minimal while maximizing benefits

“Milk is successfully produced by mothers regardless of their nutritional status. Nevertheless, the concentrations of some nutrients, specifically vitamins A, D, B1, B2, B3, B6, and B12, fatty acids, and iodine, in human milk depend on or are influenced by maternal diet.” – Valentine et al.

Nutrients That Do NOT Influence Breast Milk

There are also those nutrients in breast milk which are not influenced by the mother’s diet.

Examples are Calcium, Iron, Zinc, Copper and Folate. To protect the infant from a deficiency (or overload!), these nutrients are filtered through an active transport mechanism into the mother’s milk, where other factors, such as stage of lactation, determine its content.

This does not mean these nutrients aren’t important in a breastfeeding mother’s diet! The opposite is the case: While baby may be protected from a deficiency or overload, you may not be. This is why supporting your own nutrition while breastfeeding is so important.

The Bottom Line:

You don’t need to eat perfectly to breastfeed successfully. That burger or slice of pizza won’t turn your milk into “junk food.”

But by improving your diet—even just a little—you can:

• Enhance the nutrient profile of your milk

• Support your baby’s development

• Reduce your risk of depletion and long-term health issues

• Feel better, heal faster, and thrive in motherhood

  
  

The benefits of nourishing your body during this time are long-lasting—and may even pass on to future generations.

Let’s stop ignoring the science. Let’s empower moms with knowledge—not guilt.

Share this article if you believe moms deserve to know how powerful their diet truly is while breastfeeding.

About the Author

This article was written by Marina Lane, a Registered Dietitian and Certified Lactation Counselor with a passion for helping moms nourish themselves and their babies. As a mother of two who were both breastfed until age 3, Marina combines professional expertise with personal experience to provide evidence-based advice and support to breastfeeding moms. With her background in nutrition and lactation, she offers practical, science-backed insights to help you navigate your breastfeeding journey with confidence.