The composition of human milk

Over 200 components of human milk have been discovered so far. You’ll find a description of some of them in the section Breast milk: a food like no other.

What influences the composition of milk

The mother’s diet

Drinking a lot of fluids doesn’t increase the amount of milk you produce. While you’re breast-feeding, you’ll naturally be thirstier than usual. Listen to your body—you don’t need to force yourself to drink a lot. However, if you notice your urine is dark or cloudy, it means you’re not drinking enough.

There aren’t any foods that increase milk production. Eat regularly and eat enough. You can also have snacks if you’re hungry.

Some foods can have a slight effect on the taste of the milk you produce, but your baby will adapt. Some studies suggest that it can help babies develop their taste for food if mothers eat a varied diet while breast-feeding.

Most breast-feeding mothers can eat whatever they like, including foods deemed risky during your pregnancy (sushi, deli meats, cheese).

If you think your baby is having a reaction to something you’re eating, read Breast-fed babies and allergies.

If you are a vegan (i.e., you don’t eat any animal products, that is, meat, fish, eggs or milk products) and you are breast-feeding, you should take a Vitamin B12 supplement. Eat foods rich in protein, iron, calcium and Vitamin D. It might be a good idea to consult a nutritionist.


Fish belongs on your menu. However, some fish species absorb pollutants that make their way into breast milk and could harm a baby. To take advantage of the benefits of eating fish while minimizing the risk from contaminants such as mercury, read What’s on the menu? Fish!.

Coffee, tea, chocolate, herbal tea and other drinks

Caffeine passes into breast milk. If you consume a lot of it, it can make your baby nervous and irritable until the caffeine is eliminated from his system. Caffeine is found in coffee, tea, energy drinks, cola-type soft drinks and chocolate.

Energy drinks are not recommended while breast-feeding because they contain other substances that might harm your baby.

Other products (coffee, tea, cola, etc.), may be consumed in moderation, up to two cups or so per day.

Decaffeinated drinks such as cereal-based beverages and herbal tea can be good substitutes for caffeinated beverages.


Any alcohol you do drink goes into your breast milk and into your bloodstream. Depending on your weight, it takes your body two to three hours to eliminate the alcohol from one drink from your blood and milk. Once the alcohol is gone from your bloodstream, there is none in the breast milk for the next feeding.

Even though a breast-feeding baby only receives a tiny share of the alcohol his mother drinks, he eliminates it more slowly than an adult and his system is more sensitive to its effects.

Avoid drinking large quantities of alcohol while breast-feeding. Alcohol can interfere with milk production and reduce the amount of milk your baby drinks. It may also have harmful effects on his motor development and sleeping habits.

Breast-feeding mothers can enjoy the occasional alcoholic beverage. The benefits of breast-feeding outweigh the risks of occasional light alcohol consumption (around two drinks a week or less). This level of consumption has not been shown to harm a nursing baby.

If you do have a drink, you can reduce your baby’s exposure to alcohol in one of these ways:

  • Breast-feed your baby right before having a drink.
  • Or wait 2 to 3 hours per serving of alcohol before nursing again. After waiting, simply nurse normally at the next feeding.

If you have more than one serving, feed your baby milk you expressed in advance (frozen or refrigerated) while the alcohol remains in your system. You may need to express milk to relieve engorgement of your breasts, but this milk should be discarded because it contains more alcohol.

To find out how long it takes for your body to eliminate alcohol according to your weight, visit

If you have questions about alcohol consumption while breast-feeding, talk to your health professional or call the Motherisk Helpline at 1-877-327-4636.

In Canada, one serving or 1 drink = 13.6 g (17 ml) of pure alcohol

1 glass of beer = 341 ml or 12 oz (5% alcohol). 1 glass of wine = 142 ml or 5 oz (12% alcohol). 1 glass of fortified wine = 85 ml or 3 oz (e.g., Porto. 16 -18% alcohol). 1 shooter ou 1 glass of spirits = 43 ml ou 1,5 oz (40% alcohol).

Illustrations: Maurice Gervais

Each serving or glass of an alcoholic beverage takes 2 to 3 hours to be eliminated from your blood and milk.


Tobacco is harmful to your baby when you’re breastfeeding, just as it is during pregnancy.

Tobacco can interfere with milk production. Nicotine from tobacco also passes into breast milk and can cause crying, irritability and insomnia. Try to avoid smoking just before feeding.

Talk to your doctor if you are thinking about using pharmacological aids such as patches or nicotine gum to quit smoking.

Even if you do smoke, breast-feeding provides many benefits for you and your baby, including protecting him from respiratory infections.

Cannabis and other drugs

Drug use and exposure to second-hand drug smoke is not recommended during breast-feeding.

It is not known what effect a nursing mother’s use of marijuana and other cannabis derivatives might have on her baby, but it is a source of concern.

Other drugs, such as amphetamines, cocaine, heroin, LSD and PCP pass into breast milk and are dangerous for your baby.


Most medications pass into breast milk, but in very small amounts. Some medications are a better choice because more is known about their effects on nursing babies.

Many medications may be taken while breast-feeding, including acetaminophen, ibuprofen and most antibiotics.

Decongestants containing pseudoephedrine can reduce milk production. It’s best to ask your pharmacist to recommend another product.

Talk to a health professional before taking any medication or natural health product. Some medications may decrease your milk supply or cause other problems.

It’s very rare to have to stop breast-feeding because of medical treatment. If a health professional advises you to stop breast-feeding because of a medication, here’s what you can do:

  • Say that breast-feeding is important to you and your baby.
  • Ask if there are any medications that can be taken while breast-feeding instead.

Exposure to contaminants

In Québec, environmental pollution is not generally a problem for breast-feeding mothers and babies.

Breast-feeding mothers who come in contact with or breathe in chemical substances contained in household products may pass these substances on in small amounts to their babies through breast milk. This is only a problem in the case of regular and prolonged exposure, such as occurs at work.

In day-to-day life, exposure to the following products on an occasional basis is nothing to worry about:

  • At the hairdresser: hair styling products, dyes and perms
  • At the dentist: local anaesthetic, fillings and root canals
  • In the home: latex paint and varnish, home cleaning products.

If you work in an environment where you are exposed to contaminants like solvents, inks or dyes that may be dangerous to your breast-fed baby, you may be eligible for reassignment or preventative withdrawal (see For a Safe Maternity Experience program). You can also consult your doctor.