Food supplements and breastfeeding: which are compatible, and why your nutritional needs increase

1. Fatigue in the first few months has several causes, with lack of sleep at the top of the list. Nutrition may help with this, particularly by adjusting your evening meals and making sure you get enough magnesium. Several nutrients deserve particular attention during breastfeeding, and some are difficult to get enough of through diet alone.
2. The nutritional demands of breastfeeding come on top of stores already drawn on during pregnancy and childbirth.
3. Some nutrients depend on your diet: the amount in your milk follows what you eat. Others depend on your stores: the amount in your milk remains stable while your stores decrease. The reasons for taking a supplement differ in each case.
4. A multivitamin formulated for the postpartum period may be compatible with breastfeeding. Three types of product should, however, be avoided: appetite suppressants, hair supplements with very high doses of vitamin A, and essential oils taken orally.

Breastfeeding increases energy expenditure. It also increases your need for micronutrients: vitamins and minerals needed in small amounts.

These needs come on top of two earlier stages that have already drawn on your stores:

Pregnancy drew on your stores. Foetal development draws in part on the mother’s stores, particularly of iron and vitamin B9, also called methylated folate (5-mthf).

Childbirth caused blood loss. These losses are gradually replenished. ANSES sets the iron reference intake for breastfeeding women at 16 mg per day, the highest value it specifies for adult women (1).

Breastfeeding adds to your daily energy expenditure. The recommended increase in energy intake during breastfeeding is approximately 500 kcal per day (2). Some of your nutrients also pass into your milk each day.

These three factors add up, which may explain why you feel tired despite eating well: a shortfall may already be present before the first breastfeed. Two nutrients are of particular concern in the French population. In 2019, more than 70 % of French adults had an insufficient vitamin D intake, with 6,5 % having a deficiency. ANSES also reports that vitamin B9 intake is insufficient (3).

A balanced diet remains the foundation, but it does not always meet every nutritional need.

Nutrients do not all behave in the same way during breastfeeding. Scientific literature distinguishes two groups (4) (5).

Nutrients that depend on your diet. For these nutrients, the amount in your milk follows your intake: eating less of them quickly reduces the amount found in your milk, while an improvement in your nutritional status increases it.

Nutrients that depend on your stores. For these nutrients, the amount in your milk varies little with your intake. The amount passed on remains stable, even when your diet does not provide enough. Instead, your own stores decrease, so supplementation benefits you first and foremost.

In practical terms, if you eat little fish this week, your milk will contain less DHA. If your iron intake is low, your milk will contain the same amount of iron, but your own stores will have fallen.

There is a limit to this stability: if your intake remains insufficient for a long period, your stores gradually become depleted (5).

There are therefore two distinct reasons to consider supplementation: for the first group, the question is how much is passed on to your baby. For the second, it is about your own stores.

Iodine is used to produce thyroid hormones, which regulate metabolism and contribute to the development of the infant’s brain. ANSES considers 200 µg per day an adequate intake for pregnant or breastfeeding women, compared with 150 µg for adults (1). The iodine content of your milk follows your recent intake (4). Iodine is found in seafood, dairy products, eggs and iodised salt.

DHA is an omega-3 fatty acid involved in the development of the brain and retina. The fatty acid profile of breast milk reflects the mother’s diet over the preceding days (4) (6). DHA itself is found in oily fish: sardines, mackerel, herring and salmon. Rapeseed and walnut oils provide another omega-3, alpha-linolenic acid, which the body can convert into DHA, but the conversion rate is very low and varies from person to person. French PNNS dietary guidelines recommend two portions of fish a week, including one portion of oily fish.

Vitamin B12 contributes to the formation of red blood cells and the functioning of the nervous system. It is found only in animal products, and its concentration in milk is correlated with the mother’s nutritional status (5). A vegan or strict vegetarian diet without supplementation increases the risk of low levels.

Vitamin D helps with calcium absorption and the mineralisation of bones and teeth. It belongs to this first group, but France has chosen a different approach for babies: rather than relying on maternal supplementation to increase the amount in breast milk, vitamin D is prescribed directly to infants. It remains useful for you, given that dietary intake is insufficient across the population (3).

Iron carries oxygen in the blood. The iron content of breast milk varies little with the mother’s intake (5). Insufficient intake therefore lowers your stores rather than the iron content of your milk: a mother with low iron levels continues to pass on the same amounts. It is worth noting that breast milk is naturally low in iron, and a baby’s iron stores are built up mainly during pregnancy. This is why iron-rich foods are important from the start of introducing solid foods. For mothers, iron is the nutrient most often implicated in persistent fatigue after giving birth, and its levels can be checked with a blood test.

Vitamin B9, or methylated folate (5-mthf), plays a part in cell renewal and the formation of red blood cells. It is the exception among the B vitamins: levels of the others depend on what you eat, whereas B9 behaves like iron or zinc, with its concentration in milk little affected by maternal intake (5). Pregnancy has already drawn on these stores, and ANSES reports that some people in France do not get enough B9 from their diet (3). So it is your own levels that are at stake, not the B9 content of your milk.

Magnesium plays a part in muscle and nervous system function and contributes to the reduction of tiredness and fatigue. Its level in milk is also independent of maternal intake (7). Supplementation is therefore about meeting your own needs.

Zinc contributes to the normal function of the immune system, wound healing and the maintenance of normal hair and nails, three common concerns in the months after giving birth. The same principle applies to your stores (5).

What your milk contains, nutrient by nutrient

What may be related to nutrition

Fatigue that persists and does not ease with rest may be associated with low iron levels, with or without anaemia, or low levels of vitamin B12, vitamin B9 or vitamin D. Insufficient iodine intake can also affect thyroid function, which plays a part in how fatigued you feel.

These factors have one useful thing in common: they can be measured. A blood test can show where you stand rather than leaving you to guess, so supplementation can be adjusted to your results.

What does not fall into this category

A food supplement cannot make up for a lack of sleep. Broken nights over several months cause real fatigue that no vitamin can undo.

The mental load, returning to work and isolation can have a similar effect. Two medical conditions should also be ruled out when fatigue is pronounced: postpartum thyroiditis and postpartum depression. Both can be treated, but not through nutrition.

Compatible with breastfeeding

A multivitamin formulated for the postpartum period and dosed within regulatory limits is compatible with breastfeeding. The same applies to vitamin D, DHA, magnesium, vitamin B12 and zinc at usual doses.

For iodine, there is a specific guideline: the recommended maximum is 200 µg when the supplement is intended specifically for pregnant or breastfeeding women (11).

What to seek advice about

Iron comes first: it is worth having your levels checked before taking it, as unnecessary supplementation can cause digestive side effects without any benefit. The same applies to iodine if you are being treated for a thyroid condition, and to plant extracts with no safety data for this period, particularly those intended for weight loss or that are highly concentrated. In general, pregnant and breastfeeding women are advised to consult a healthcare professional before taking any supplements (11): speak to your midwife or doctor.

What to avoid during this period

Appetite suppressants and weight-loss products. They often contain stimulating ingredients for which there are no safety data during breastfeeding. Severe dietary restriction is also considered unfavourable for lactation (12).

High-dose vitamin A hair supplements. Unlike B vitamins, which are water-soluble and whose excess is excreted in urine, vitamin A is fat-soluble: it is stored in the liver and accumulates with repeated doses. A safety limit of 3000 µg per day has been set at European level, compared with a dietary reference value of 650 µg per day for women (11). Some hair supplements contain high amounts, and taking several products together can bring you close to this limit. Vitamin A intake also depends on what you eat, and a high maternal intake is reflected in breast milk.

Essential oils taken orally, whose components pass into breast milk and for which safety data during breastfeeding are insufficient. Finally, be cautious with products bought outside the European Union, where labelling and dosages may not meet the same requirements for this period.