Experiences in applying “The Biodeterminist’s Guide to Parenting”

I’m post­ing this be­cause LessWrong was very in­fluen­tial on how I viewed par­ent­ing, par­tic­u­larly the em­pha­sis on helping one’s brain work bet­ter. In this con­text, cre­at­ing and in­fluenc­ing an­other per­son’s brain is an awe­some re­spon­si­bil­ity.

It turned out to be a lot more anx­iety-pro­vok­ing than I ex­pected. I don’t think that’s nec­es­sar­ily a bad thing, as the pos­si­bil­ity of screw­ing up some­one’s brain should make a par­ent anx­ious, but it’s some­thing to be aware of. I’ve heard some blithe “Ra­tional par­ent­ing could be a very high-im­pact ac­tivity!” state­ments from child­less LWers who may be in­ter­ested to hear some ex­pe­riences in ac­tu­ally ap­ply­ing that.

One thing that re­ally scared me about try­ing to raise a child with the healthiest-pos­si­ble brain and body was the pos­si­bil­ity that I might not love her if she turned out to not be smart. 15 months in, I’m no longer wor­ried. Evolu­tion has been very suc­cess­ful at pro­duc­ing par­ents and chil­dren that love each other de­spite their flaws, and our fam­ily is no ex­cep­tion. Our daugh­ter Lily seems to be do­ing fine, but if she turns out to have dis­abil­ities or other prob­lems, I’m con­fi­dent that we’ll roll with the punches.

Cross-posted from The Whole Sky.

Be­fore I got preg­nant, I read Scott Alexan­der’s ex­cel­lent Biode­ter­minist’s Guide to Par­ent­ing and was so ex­cited to have this knowl­edge. I thought how lucky my child would be to have par­ents who knew and cared about how to pro­tect her from things that would dam­age her brain.

Real life, of course, got more com­pli­cated. It’s one thing to in­tend to avoid neu­ro­tox­ins, but an­other to ar­rive at the grand­par­ents’ house and find they’ve just had ant poi­son sprayed. What do you do then?

Here are some trade­offs Jeff and I have made be­tween things that are good for chil­dren in one way but bad in an­other, or things that are good for chil­dren but re­ally difficult or ex­pen­sive.

Germs and parasites

The hy­giene hy­poth­e­sis states that lack of ex­po­sure to germs and par­a­sites in­creases risk of auto-im­mune dis­ease. Our pe­di­a­tri­cian recom­mended let­ting Lily play­ing in the dirt for this rea­son.

While ex­po­sure to an­i­mal dan­der and pol­lu­tion in­crease asthma later in life, it seems that be­ing ex­posed to these in the first year of life ac­tu­ally pro­tects against asthma. Ap­par­ently if you’re go­ing to live in a house with roaches, you should do it in the first year or not at all.

Ex­cept some stuff in dirt is ac­tu­ally bad for you.

Scott writes:

Par­a­site-in­fest­ed­ness of an area cor­re­lates with na­tional IQ at about r = −0.82. The same is true of US states, with a slightly re­duced cor­re­la­tion co­effi­cient of −0.67 (p<0.0001). . . . When an area elimi­nates par­a­sites (like the US did for malaria and hook­worm in the early 1900s) the IQ for the area goes up at about the right time.

Liv­ing with cats as a child seems to in­crease risk of schizophre­nia, ap­par­ently via tox­o­plas­mo­sis. But in or­der to catch tox­o­plas­mo­sis from a cat, you have to eat its fe­ces dur­ing the two weeks af­ter it first be­comes in­fected (which it’s most likely to do by eat­ing birds or ro­dents car­ry­ing the dis­ease). This makes me guess that most kids get it through tast­ing a hand­ful of cat lit­ter, dirt from the yard, or sand from the sand­box rather than sim­ply through cat own­er­ship. We live with in­door cats who don’t seem to be mousers, so I’m not con­cerned about them giv­ing any­one tox­o­plas­mo­sis. If we build Lily a sand­box, we’ll keep it cov­ered when not in use.

The ev­i­dence is mixed about whether in­fec­tions like colds dur­ing the first year of life in­crease or de­crease your risk of asthma later. After the new­born pe­riod, we de­faulted to be­ing pretty ca­sual about germ ex­po­sure.

Tox­ins in buildings

Our ex­pe­riences with lead (and les­sons learned about how to re­duce risk). Our ex­pe­riences with mer­cury.

In some ar­eas, it’s not that fea­si­ble to live in a house with zero lead. We live in Bos­ton, where 87% of the hous­ing was built be­fore lead paint was banned. Even in a new build­ing, we’d need to go far out of town be­fore reach­ing soil that wasn’t near where a lead-painted build­ing had been.

It is pos­si­ble to do some ren­o­va­tions with­out ex­pos­ing kids to lead. Jeff re­cently did some de­mo­li­tion of walls with lead paint, very care­fully sealed off and cleaned up, while Lily and I spent the day el­se­where. After­wards her lead level was no higher than it had been.

But Jeff got se­ri­ous lead poi­son­ing as a tod­dler while his par­ents did ma­jor ren­o­va­tions on their old house. If I didn’t think I could keep the child away from the dust, I wouldn’t ren­o­vate.

Re­cently a house across the street from us was gut­ted, with work­ers throw­ing de­bris out the win­dows and cre­at­ing big plumes of dust (pre­sum­ably lead-laden) that blew all down the street. Later I re­al­ized I should have called city build­ing in­spec­tion ser­vices, which would have at least made them carry the de­bris into the dump­ster in­stead of throw­ing it from the sec­ond story.

Floor var­nish re­leases formalde­hyde and other nas­ties as it cures. We kept Lily out of the house for a few weeks af­ter Jeff re­did the floors. We found it worth­while to pay rent at our pre­vi­ous house in or­der to not have to live in the new house while this kind of work was hap­pen­ing.

Pres­sure-treated wood was treated with ar­senic and chromium un­til around 2004 in the US. It of­ten has a green­ish tint, though it may not be ob­vi­ous af­ter fad­ing or stain­ing. Play­ing on play­sets or decks made of such wood in­creases chil­dren’s can­cer risk. It should not be used for fur­ni­ture (I thought this would be ob­vi­ous, but ap­par­ently it wasn’t to some of my handy­man rel­a­tives).

I found it difficult to know how to deal with fresh paint and other fumes in my build­ing at work while I was preg­nant. Women of re­pro­duc­tive age have a height­ened sense of smell, and many preg­nant women have height­ened aver­sion to smells, so you can liter­ally smell things some of your cowork­ers can’t (or don’t mind). The most crit­i­cal pe­riod of de­vel­op­ment is dur­ing the first trimester, when most women aren’t tel­ling the world they’re preg­nant (be­cause it’s also the time when a mis­car­riage is most likely, and if you do lose the preg­nancy you might not want to have to tell ev­ery­one). Dur­ing that pe­riod, I found it difficult to ex­plain why I was con­cerned about the fumes from the roofing ad­he­sive be­ing used in our build­ing. I didn’t want to seem like a princess who thought she was too good to work in con­di­tions that ev­ery­body else found ac­cept­able. (After I told them I was preg­nant, my cowork­ers were very un­der­stand­ing about such things.)


Recom­men­da­tions usu­ally fo­cus on what you should eat dur­ing preg­nancy, but ob­vi­ously chil­dren’s brain de­vel­op­ment doesn’t stop there. I’ve opted to take pre­cau­tions with the food Lily and I eat for as long as I’m nurs­ing her.

Claims that pes­ti­cide resi­dues are poi­son­ing chil­dren scare me, al­though most sci­en­tists seem to think the pa­per cited is overblown. Other sources say the lev­els of pes­ti­cides in con­ven­tion­ally grown pro­duce are fine. We buy or­ganic pro­duce at home but eat what­ever we’re served el­se­where.

I would love to see a study with fam­i­lies ran­domly se­lected to re­ceive or­ganic pro­duce for the first 8 years of the kids’ lives, then look­ing at IQ and hy­per­ac­tivity. But no one’s go­ing to do that study be­cause of how ex­pen­sive 8 years of or­ganic pro­duce would be.
The Biode­ter­minist’s Guide doesn’t men­tion PCBs in the sec­tion on fish, but fish (par­tic­u­larly farmed salmon) are a ma­jor source of these pol­lu­tants. They don’t seem to be as bad as mer­cury, but are neu­ro­toxic. Un­for­tu­nately their half-life in the body is around 14 years, so if you have even a vague idea of get­ting preg­nant ever in your life you shouldn’t be eat­ing much farmed salmon (or At­lantic/​farmed salmon, bluefish, wild striped bass, white and At­lantic croaker, black­back or win­ter flounder, sum­mer flounder, or blue crab).

I had the best in­ten­tions of eat­ing lots of the right kind of high-omega-3, low-pol­lu­tant fish dur­ing and af­ter preg­nancy. Un­for­tu­nately, fish was the only food I de­vel­oped an aver­sion to. Now that Lily is eat­ing food on her own, we tried sev­eral sources of omega-3 and found that kip­pered her­ring was the only suc­cess. Les­son: it’s hard to pre­dict what foods kids will eat, so keep try­ing.
Postscript, 2016: Based on this re­view, we’ve been giv­ing her a fish-oil sup­ple­ment which she loves (“More fishy pill!”)

In terms of has­sle, I un­der­es­ti­mated how long I would be “eat­ing for two” in the sense that any­thing I put in my body ends up in my child’s body. Count­ing pre-preg­nancy (be­cause mer­cury has a half-life of around 50 days in the body, so sushi you eat be­fore get­ting preg­nant could still af­fect your child), preg­nancy, breast­feed­ing, and pre­sum­ing a sec­ond preg­nancy, I’ll prob­a­bly spend about 5 solid years feed­ing an­other per­son via my body, some­times two chil­dren at once. That’s a long time in which you have to con­sider the effect of ev­ery med­i­ca­tion, ev­ery cup of coffee, ev­ery glass of wine on your child. There are hardly any med­i­ca­tions con­sid­ered com­pletely safe dur­ing preg­nancy and lac­ta­tion—most things are in Cat­e­gory C, mean­ing there’s some ev­i­dence from an­i­mal tri­als that they may be bad for hu­man chil­dren.


Too much fluoride is bad for chil­dren’s brains. The CDC re­cently recom­mended low­er­ing fluoride lev­els in mu­ni­ci­pal wa­ter (though ap­par­ently be­cause of con­cerns about tooth dis­col­ora­tion more than neu­ro­tox­i­c­ity). Around the same time, the Amer­i­can Den­tal As­so­ci­a­tion be­gan recom­mend­ing the use of fluoride tooth­paste as soon as ba­bies have teeth, rather than wait­ing un­til they can rinse and spit.

Cav­i­ties are ac­tu­ally a se­ri­ous prob­lem even in baby teeth, be­cause of the pain and pos­si­ble in­fec­tion they cause chil­dren. Pul­ling them messes up the al­ign­ment of adult teeth. Drilling on chil­dren too young to hold still re­quires full anes­the­sia, which is dan­ger­ous it­self.

But Lily isn’t par­tic­u­larly at risk for cav­i­ties. 20% of chil­dren get a cav­ity by age six, and they are dis­pro­por­tionately poor, Afri­can-Amer­i­can, and par­tic­u­larly Mex­i­can-Amer­i­can chil­dren (pre­sum­ably be­cause of differ­ent diet and less abil­ity to af­ford den­tists). 75% of cav­i­ties in chil­dren un­der 5 oc­cur in 8% of the pop­u­la­tion.

We de­cided to have Lily brush with­out tooth­paste, avoid juice and other sug­ary drinks, and see the den­tist reg­u­larly. We also use a $20 wa­ter filter that re­moves fluoride (we ver­ified with lab tests; I recom­mend the Maine state lab if you need this kind of thing). Fluoride ba­si­cally doesn’t pass into breast­milk, but I used it while I was preg­nant and will use it when the kids start drink­ing wa­ter in­stead of mostly milk.

Home pesticides

One of the most com­monly ap­plied in­sec­ti­cides makes kids less smart. This isn’t too sur­pris­ing, given that it kills in­sects by dis­abling their ner­vous sys­tem. But it’s not some­thing you can ob­serve on a small scale, so it’s not sur­pris­ing that the ex­ter­mi­na­tor I talked to brushed off my ques­tions with “I’ve never heard of a prob­lem!”

If you get car­pen­ter ants in your house, you ba­si­cally have to choose be­tween poi­son­ing them or let­ting them struc­turally dam­age the house. We’ve only seen a few so far, but if the prob­lem pro­gresses, we plan to:

1) re­move any rot­ting wood in the yard where they could be nesting

2) have the per­ime­ter of the build­ing sprayed

3) place gel bait in ar­eas kids can’t access

4) only then spray poi­son in­side the house.

If we have mice we’ll plan to use me­chan­i­cal traps rather than poi­son.

Flame retardants

Since the 1970s, Cal­ifor­nia re­quired a high de­gree of flame-re­sis­tance from fur­ni­ture. This ba­si­cally meant that US man­u­fac­tur­ers sprayed flame re­tar­dant chem­i­cals on any­thing made of polyurethane foam, such as so­fas, rug pads, nurs­ing pillows, and baby mat­tresses.

The law re­cently changed, due to grow­ing ac­knowl­edge­ment that the car­cino­genic and neu­ro­toxic chem­i­cals were more dan­ger­ous than the fires they were sup­posed to be pre­vent­ing. Even fire­fighters op­posed the use of the flame re­tar­dants, be­cause when peo­ple die in fires it’s usu­ally from smoke in­hala­tion rather than burns, and fire­fighters don’t want to breathe the smoke from your toxic sofa (which will even­tu­ally catch fire even with the flame re­tar­dants).

We’ve opted to use fur­ni­ture from com­pa­nies that have stopped us­ing flame re­tar­dants (like Ikea and oth­ers listed here). Ap­par­ently fu­tons are okay if they’re stuffed with cot­ton rather than foam. We also have some pre-1970s fur­ni­ture that tested clean for flame re­tar­dants. You can get foam sam­ples tested for free.

The main ve­hi­cle for chil­dren in­gest­ing the flame re­tar­dants is that it set­tles into dust on the floor, and chil­dren crawl around in the dust. If you don’t want to get rid of your fur­ni­ture, fre­quent damp-mop­ping would prob­a­bly help.

The stan­dards for mat­tresses are so stringent that the chem­i­cal sprays aren’t gen­er­ally used, and in­stead most mat­tresses are wrapped in a flame-re­sis­tant bar­rier which ap­par­ently isn’t toxic. I con­tacted the com­pa­nies that made our mat­tresses, and they’re fine.

Rat­ings for chem­i­cal safety of chil­dren’s car seats here.

Thoughts on IQ

A lot of peo­ple, when I start talk­ing like this, say things like “Well, I lived in a house with lead paint/​played with mer­cury/​etc. and I’m still al­ive.” And yes, I played with mer­cury as a child, and Jeff is still one of the smartest peo­ple I know even af­ter get­ting acute lead poi­son­ing as a child.

But I do won­der if my mind would work a lit­tle bet­ter with­out the mer­cury ex­po­sure, and if Jeff would have had an eas­ier time in school with­out the hy­per­ac­tivity (a symp­tom of lead ex­po­sure). Given the choice be­tween a brain that works a lit­tle bet­ter and one that works a lit­tle worse, who wouldn’t choose the one that works bet­ter?

We’ll never know how an in­di­vi­d­ual’s ner­vous sys­tem might have been differ­ent with a differ­ent child­hood. But we can see pop­u­la­tion-level effects. The En­vi­ron­men­tal Pro­tec­tion Agency, for ex­am­ple, is fine with calcu­lat­ing the ex­pected benefit of mak­ing coal plants stop re­leas­ing mer­cury by look­ing at the ex­pected gains in terms of chil­dren’s IQ and in­creased earn­ings.

Scott writes:

A 15 to 20 point rise in IQ, which is a lit­tle more than you get from sup­ple­ment­ing io­dine in an io­dine-defi­cient re­gion, is as­so­ci­ated with half the chance of liv­ing in poverty, go­ing to prison, or be­ing on welfare, and with only one-fifth the chance of drop­ping out of high-school (“as­so­ci­ated with” does not mean “causes”).

Salkever con­cludes that for each lost IQ point, males ex­pe­rience a 1.93% de­crease in life­time earn­ings and fe­males ex­pe­rience a 3.23% de­crease. If Lily would earn about what I do, sav­ing her one IQ point would save her $1600 a year or $64000 over her ca­reer. (And that’s not count­ing the other benefits she and oth­ers will reap from her hav­ing a bet­ter-func­tion­ing mind!) I use that for per­spec­tive when mak­ing de­ci­sions. $64000 would buy a lot of the posh pre­na­tal vi­tam­ins that ac­tu­ally con­tain io­dine, or or­ganic food, or al­ter­nate hous­ing while we’re fix­ing up the new house.


There are times when Jeff and I pri­ori­tize so­cial re­la­tion­ships over pro­tect­ing Lily from ev­ery­thing that might harm her phys­i­cal de­vel­op­ment. It’s awk­ward to re­fuse to go to some­one’s house be­cause of the chem­i­cals they use, or to re­fuse to eat food we’re offered. So­cial in­ter­ac­tions are good for chil­dren’s de­vel­op­ment, and we value those as well as phys­i­cal safety. And there are times when I’ve had to stop be­ing so care­ful be­cause I was get­ting par­a­lyzed by anx­iety (liter­ally perched in the rocker with the baby try­ing not to touch any­thing af­ter my in-laws scraped lead paint off the out­side of the house).

But we also pri­ori­tize neu­rolog­i­cal de­vel­op­ment more than most par­ents, and we hope that will have good out­comes for Lily.