Wednesday, April 14, 2010

A "Natural" Age of Weaning

How old is too old to be breastfed?

Many obstetricians tell their patients that there is no benefit to breastfeeding after 6 months. They say breast milk is no longer nutritious after 6 months, or provides no immunological benefits, or that a nursing toddler will be socially mal-adjusted.

A typical response to a mother who is nursing her toddler is "eww gross" and "if he/she is old enough to ask for it, he/she is too old to nurse." 

There are numerous studies that show that all of this is wrong, that breast milk is just as nutritious as it always has been after 6 months, that the longer a child nurses the longer they benefit nutritionally, and are sick less often, are smart, and well-adjusted socially. Mothers also benefit from extended breastfeeding. 

So what is a good age to wean?
  • The World Health Organization suggests that moms nurse up until two years and beyond.
  • The American Academy of Pediatrics recommends 12 months "and thereafter if mutually desired."
  • The American Academy of Family Physicians says, “Breastfeeding beyond the first year offers considerable benefits to both mother and child, and should continue as long as mutually desired. If the child is younger than two years of age, the child is at increased risk of illness if weaned.”

Even with these recommendations to nurse far past infancy, you may feel a societal pressure not to nurse your child past a certain age. You may feel that our culture just doesn't accept it, and make a decision about when to wean based on cultural norms.

But beyond recommendations and societal norms, what is a natural age to wean?

Well, what if we were to use some Biological Anthropology and take a look at our closely related primate brethren?

Anthropologist Kathy Dettwyler compared primate biology and behavior, particularly gorillas and chimpanzees (who share 98% of our genes) with human biology and behavior to try to come up with what a "natural" weaning age, outside of cultural rules, might be. 

She writes:

It has been common for pediatricians to claim that length of gestation is approximately equal to length of nursing in many species, suggesting a weaning age of 9 months for humans. However, this relationship turns out to be affected by how large the adult animals are -- the larger the adults, the longer the length of breastfeeding relative to gestation. For chimpanzees and gorillas, the two primates closest in size to humans and also the most closely genetically related, the relationship is 6 to 1. That is to say, they nurse their offspring for SIX times the length of gestation (actually 6.1 for chimps and 6.4 for gorillas, with humans mid-way in size between these two). In humans, that would be: 4.5 years of nursing (six times the 9 months of gestation).

It has been common for pediatricians to claim that most mammals wean their offspring when they have tripled their birth weight, suggesting a weaning age of 1 year in humans. Again though, this is affected by body weight, with larger mammals nursing their offspring until they have quadrupled their birth weight. In humans, quadrupling of birth weight occurs between 2.5 and 3.5 years, usually.

Her conclusion: the natural age of weaning for humans would be somewhere between 2.5 to 7 years.

She notes in her commentary that though the first six months are probably the most important in terms of the baby's nutrition and development, that doesn't mean you shouldn't continue to nurse beyond this time if you and the baby would like to. I like this quote:
It would be like saying, "Well Mabel, we don't get very much income from that oil well anymore. Used to get $56 a month in royalties, now we're lucky if we get $25 a year. Guess we should tell that oil company just to keep their durn money." And Mabel says, in return "Good grief, Clyde, don't be ridiculous. That check still buys $25 worth of food. Where has your mind gone to now?"

Of course, one must base her decision on when to cease breastfeeding on whatever variables she likes, and this comparison to primates, while fascinating, may have no basis on a woman's actual choice. It is good to know, however. I'm sure that societal pressures will play a much larger role in a woman's "choice."


  1. My oldest son self-weaned at 4yrs old (he's currently 8yrs old), my baby is still nursing of course.

    I always find it odd when people think breastmilk somehow is "self aware" and can "turn off" nutrients and such because a baby is a year old. It's not HAL for crying out loud lol.

  2. really fascinating information, thank you! remind me again, breastmilk continues to be produced during another pregnancy? I wonder how it changes over the course of (a second) pregnancy/childbirth

  3. @Sarah HAL? Lol what a reference!

    @Ren Then I will write a post on it! Thank you for your request :)

    I just read the chapter in my breastfeeding book on how breast milk changes... throughout the day, over several months, after a year, etc!

  4. ohhh, sweet, I'm excited to read it! :)

  5. What a fantastic read. I'm expecting my first in June and this further inspires me to breastfeed and to do so loud, proud, and as long as mutually desirable.


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