What is Functional Lactose Overload?
You may have heard the term “functional lactose overload” when referring to fussy, unsettled babies. We’re used to the idea of “lactose intolerance” for adults, but how is this different from functional lactose overload in infants?
Lactose is a “disaccharide”, which means that it is made up of two separate sugar molecules (glucose and galactose - “monosaccharides”) joined together. Lactose needs to be broken into these two individual sugars by the enzyme lactase (produced in the small intestine) to be absorbed and used as energy.
Many adults (and older children) no longer produce adequate amounts of lactase, so any lactose that is eaten (through cows, goat or sheep milk/cheeses) passes through to the large intestine where bacteria digest it and create carbon dioxide as a byproduct, resulting in symptoms such as bloating, pain and diarrhoea.
Lactose is the main sugar in breastmilk and provides approximately 40% of an infant’s caloric needs, so it’s lucky that “lactose intolerance” is extraordinarily rare in infants.
On the other hand, infants with functional lactose overload (FLO) often have impressive weight gain, even though they appear hungry and need to feed frequently. They’re generally unsettled/miserable and have a tight, bloated tummy and explosive stools (which are sometimes frothy). Sometimes parents are told to feed less frequently, which leads to more crying.
FLO occurs when there is a mismatch in breastmilk production and infant milk requirements - or “over-supply”. Infants will fill their stomachs with lactose-rich milk (which is crucial for growth and brain development) but may not get much of the “cream”, or fat, which triggers satiety hormones. This results in hunger and infants that cue often to feed, despite getting adequate volumes (and calories).
The amount of lactose in this milk may then overwhelm the digestive ability of their lactase; this lactose then passes into the large intestine where (you guessed it!) the bacteria have a bit of a party, digesting the lactose and producing carbon dioxide as a byproduct. Carbon dioxide causes distention of the large intestine (pain and bloating) and acts like a laxative to draw water into the bowel, leading to loose, frothy diarrhoea.
Because of this distension, infants are often very unsettled or miserable. There may also be conditioned dialling up at the breast with back arching and fussing, as a vigorous letdown frequently goes hand in hand with an over-abundant milk production. Pain with breastfeeding can occur if the infant is clamping down on the nipple to slow the flow or has a shallow latch. It’s also not uncommon for mastitis to occur in the setting of over-supply.
Treatment, then, is geared around matching milk production with your infant’s requirements. Generally, this means stopping pumping or passive milk collection devices, and managing hyperlactation - this should be done with a skilled lactation professional where possible to reduce the risk of mastitis or hypolactation. Positioning at the breast can also be assessed to help with fussiness at the breast.
If you have an over-supply and suspect your infant may have functional lactose overload, be assured that you are not harming your baby. Your milk is still amazing, as are you. If you need support around milk production or a fussy, unsettled baby, please consider booking an appointment.