0:05

Milk. Is such a whole me

0:07

familiar substance? That it might seem

0:09

to ordinary to hold any mysteries.

0:11

Yet in reality, milk and the

0:13

Act of Nursing are extraordinary biological

0:15

innovations the researchers are still trying

0:18

to understand. It's

0:22

well, Known: The breast milk can

0:24

help ensure the health of

0:26

nursing infants, but those benefits

0:28

aren't simply a result of

0:30

milk nutritional content. along with

0:32

being a source of nourishment,

0:34

milk also provides protection against

0:37

germs, stimulates infant development, and

0:39

allows mom and baby to

0:41

have all sorts of chemical

0:43

conversations. Breast milk contains thousands

0:45

of diverse molecules including growth

0:47

factors, hormones, antibodies, and microbes.

0:49

All these work in concert

0:51

to. Provide human babies with what

0:53

they need to grow and develop

0:56

normally. But how exactly I see

0:58

drug ads on? This is the

1:00

joy of why. A podcast

1:02

from Quantum Magazine. Where my

1:04

co jan eleven and I take

1:06

turns exploring some of the biggest

1:08

unanswered questions in math and science.

1:10

Today In this episode will talk

1:12

with molecular biologist Elizabeth Johnson about

1:15

the mysteries of Milk. And how

1:17

we've evolved to be so dependent. On this

1:19

all powerful all natural substance.

1:34

Least. As an assistant professor of

1:36

Molecular Nutrition at Cornell University in

1:38

the division of Nutritional Sciences. And

1:41

a Hughes Medical Institute Freeman

1:43

or About Ski scholar. She.

1:45

Specializes in genomic and metabolomics

1:48

approaches to studying the effects

1:50

of nutrition on the gut

1:52

microbiome. With. Particular interest in

1:54

infant nutrition and the infant

1:57

gut microbiome. Bears. Welcome to

1:59

the joy of Y! Thank you for

2:01

having me Steve My pleasure! I'm very

2:03

happy to see you. I don't think

2:05

it's exactly relevant, but I can't resist

2:07

saying that we're almost next door neighbors

2:09

there's one house in between us. Was

2:11

is my very good friend as well

2:13

as. A steamed colleague of yeah,

2:15

well. I think that the good point

2:17

to make our rights are not that

2:19

disclosures out of the weights. Let me

2:22

just confess I don't know the first

2:24

thing about milk as a scientific subject.

2:26

I was shocked as I was doing

2:28

well research for this show about just

2:30

how many puzzles there are still remaining.

2:32

As a little kid when I would

2:34

come home after school, I'd have milk

2:36

and cookies. maybe have peanut butter and

2:38

jelly. So. From that way of.

2:40

Thinking about it, milk is just another kind

2:43

of food. Let's talk about it first as

2:45

food. What are those fundamental nutritional components of

2:47

milk? The context that you're talking about with

2:49

the same way that I used to think

2:52

about milk. Not that it was food for

2:54

babies, but that it was just food. Something.

2:56

That tasted pretty good. As you get

2:58

older and you. Realize how specialized

3:00

milks can be? especially when you

3:03

may have an infant that needs

3:05

milk and you'd start thinking about

3:07

human milk. That's. When

3:09

you realize there's more to milk,

3:11

then I really thought. About when

3:14

I was having those cookies and

3:16

milk as a kid. What it

3:18

really is. It's composed of things

3:20

that are needed for the nutrition.

3:22

have babies for a short period

3:24

of time, and it's a very

3:27

characteristic trade of all mammals which

3:29

use milk to feed their babies.

3:31

And so when you think about

3:33

what's really in it's there are

3:35

sugars, low carbohydrates, there are sat.

3:38

There. Are pro teams, there are minerals

3:40

and and milk and many other

3:42

mouth there are other factors such

3:44

as I mean factors and other

3:46

cells and nucleic acids and things

3:48

like that that are also not

3:50

just for growth but also for

3:52

the development. During that period it

3:54

time So when you pick up

3:56

a cold glass of milk it

3:58

was really designed. They do a lot

4:01

more than it's doing right now. So

4:03

you have opened the door now to

4:05

this larger role that milk can play.

4:07

that it's much more than a food

4:09

is everything you ever read about in

4:11

your biology textbooks. His ah right enzymes,

4:13

hormones, antibodies, stem cells, Microbes,

4:15

Things that aren't even exactly human?

4:18

Yeah, exactly. And it is a

4:20

great source of nutrition. You're thinking

4:22

about something that's going to allow

4:24

for the most rapid growth and

4:26

development of a human outside of

4:28

the womb rape. But then you

4:30

think there is also this really

4:32

great opportunity here for communications, right?

4:35

A lot of the information that's

4:37

there can be transferred through the

4:39

active just feeding, and this is

4:41

a very important thing that we

4:43

forget about when we think about.

4:45

It as just like the consumer product

4:47

or just something that's for energy needs

4:50

By information here of can you give

4:52

us an example of what kind of

4:54

information is that a two way communication

4:56

or the each talking to each other.

4:58

Yeah there's some evidence that it can

5:01

be two ways. There can be saliva

5:03

information and baby saliva you can imagine

5:05

if there was a virus or other

5:07

particles are they are that may be

5:09

interacting with the memory or at the

5:11

breast. And then

5:14

also whatever gets. Put. Into

5:16

milks through the milk ducts. So

5:18

lactation is the production of milk

5:20

and then the a jackson of

5:22

milk. So whatever the jack did

5:24

in there is something that potentially

5:26

the incentive gonna consume. and then

5:28

the seldom the organs of the

5:30

infant command process. That and some

5:32

of that we can call information.

5:34

They may be small molecules or

5:36

other chemical signals that are really

5:38

important for. Growth. And

5:40

development during that period of time are

5:42

still trying to understand what those are

5:44

because we want to understand. Are.

5:47

They necessary for hell. Saw

5:49

what happens when you don't see some of

5:51

these signals and how do we think about

5:54

feeding babies in the most optimal way with

5:56

this type of information? On.

5:58

Start exploring some of that. For

6:00

example, a to talk about like

6:02

variation from person to person. It.

6:04

Stands to reason that the ingredients

6:07

wouldn't be exactly the same from

6:09

one person to another. Maybe the

6:11

fat content would change or the

6:13

antibodies I get transferred are different.

6:15

but does milk very even more

6:17

than that from person to person

6:19

say over the course of time

6:21

over the course of breastfeeding. Oh,

6:23

most definitely the most famous example

6:25

of. This is classroom. This is the

6:27

first milk which is a very high.

6:29

Protein Dance milk. It looks kind

6:31

of gold of like liquid gold

6:34

and it comes in very small

6:36

amounts and that's in the first

6:38

moments of life. the nutrition that

6:40

baby is getting, but then over

6:42

and the next five to seven

6:45

days there this maturation of milk.

6:47

Where'd you go from this area?

6:49

protein dent substance to a watery,

6:51

more sugary and if milk that

6:53

might be the melt that's going

6:56

to sustain growth across the next.

6:59

Few months and so there's

7:01

this biological process that. Happens

7:03

that is characteristic of lactation and

7:05

the tear point. I

7:07

don't think we even have a grasp

7:10

on how much milk can vary between

7:12

individuals on the day to day, and

7:14

that's something that my lab is trying

7:16

to do. Like if you just look

7:18

at milk. Every single

7:20

day of lactation. Is it very

7:23

similar? Or is it changing? Too

7:25

Many of the life events that

7:27

may happen during the first six

7:29

months of life there been a

7:31

some really amazing. Studies that show

7:33

last diet has an influence

7:35

so. The particular things they get into

7:37

milk can be depended on that, and you

7:40

can imagine that there are some regional. Specificities

7:42

to that's that. Would allow

7:45

for melts of certain populations to

7:47

look more similar than other populations.

7:49

You'll still see variation, not just

7:52

across individuals, but there is individual

7:54

temporal variation throughout the day. There

7:56

is also time of the feed,

7:58

so there is. The for Malkin

8:00

they the hind milk. I don't know

8:03

those terms for male can hind milk.

8:05

Yeah when a baby latches on. That.

8:08

Seed. May last anywhere from five.

8:11

To. Thirty mrs heads

8:13

or even longer and throughout

8:15

the course of that seed

8:17

the macro nutrient. Composition of

8:20

milk contains the milk in the beginning

8:22

of the seed of gonna have a

8:24

different macro nutrient compositions and that's the

8:27

for milk then the high milk which

8:29

com. That be ended of feeds. I

8:31

always call it nature's most interesting bio

8:33

fluid because there's so many complications to

8:35

how we understand it. But if we

8:38

treat those in the right way, we

8:40

actually learn a lot information. Oh, that's

8:42

great. I can't think of what other

8:44

bio fluid could rival it. What complicated

8:47

I suppose, but milk? Maybe the champ.

8:49

Yeah I like to put a word and

8:51

from mel assess assess what is fascinating. About

8:53

melt. In terms of

8:56

understanding. Human. Health is

8:58

that. Everything you need to nourish

9:00

as human baby is in this one

9:02

substance that we can quantify and we

9:04

can look at and we don't have

9:07

the ghastly answers are there and we

9:09

then had the opportunity to decode some

9:11

of those answers as we get better

9:13

at analyzing melt and understanding the right

9:15

questions to ask. But a very different

9:18

than how maybe you and I feed

9:20

ourselves where we're making our own decisions

9:22

and we may be making good decisions

9:24

and bad decisions and those may have

9:27

good or bad consequences on our health.

9:29

But more thinking during infancy and were

9:31

thinking about human milk. The good

9:33

is there. And we just need to

9:35

understand why. So earlier you mentioned about

9:37

the diet. Of the caregiver

9:39

and as a bomb on this I

9:42

said caregiver here to include mother's but

9:44

also what's keep in mind other people:

9:46

wet nurses, breast milk donors, trans people,

9:49

anyone who might be providing milk or.

9:51

You say Caregivers? Relaxing pair when

9:53

you look at family units. There's.

9:55

A lot going on, so it's really

9:57

important to be very inclusive of everything.

10:00

Going on during the day time we

10:02

think about feeding babies and all the

10:04

many people who see baby it. On

10:06

this question of diet. How does the

10:08

diet of the caregiver affect the composition

10:10

of the milk that they produce? I

10:12

think we're still trying to understand exactly

10:14

how that works so you can. Think

10:16

of this on a macro scale.

10:18

In my lab, we focus on

10:21

the fat fraction of milk in

10:23

human milk. It's assassinating. Fraction.

10:26

Of milk. To study because it's really

10:28

responsible for all the calories. It's

10:30

also responsible for a lot of.

10:32

Small. Molecules and chemical signals that

10:34

have not been quantified that are

10:37

extremely important. And so when we

10:39

think about the different types of

10:41

sad that are in milk, they

10:43

can come from many different places.

10:45

They can either be synthesized. In.

10:47

The memory they can come from

10:50

circulation, but the ones that are

10:52

coming from circulation can be directly

10:54

related to what. The. Particular

10:56

mother likes eating parent is actually

10:58

consuming because that can change the

11:00

profile of what structures the fats

11:02

are in milk. Maybe some of

11:04

the most famous would be. Let's

11:06

say if you are eating a

11:08

lot of fatty fish, polyunsaturated fatty

11:10

acid, omega three fatty acids, and

11:12

things like that, you can have different

11:14

profiles of those and melt based

11:16

off of the consumption of those

11:18

nutrients in the diet. So we're

11:20

learning and some people are doing

11:22

extremely. Great work we wanted definitive

11:24

the. We know what you ate, see, know

11:27

that made it into the milk and we

11:29

know that's the thing that's gonna be exposed

11:31

to baby. And I think that when we

11:33

get the tools to keep doing this better

11:35

and better, we can better understand how what

11:38

we eat affects. How we synthesize

11:40

milk. Interesting. I hadn't really

11:42

thought about how it a whole body

11:44

for ducks and effort. It's not just

11:46

the mammary gland you mentioned circulation but

11:48

of course diet. Other things we should

11:50

keep in mind. There a lot of

11:53

factors that go into. Lactation that

11:55

make it hard or easy

11:57

like health as a parent.

11:59

What's going. In times of

12:01

infection or other diseases or

12:03

disorders can also affect what's

12:05

going into milk and. Also,

12:07

were trying to get a better

12:09

idea of not just new transpired

12:11

what if you take tylenol or

12:14

what if you do sir? Another

12:16

thing, there's a lot that we

12:18

are still trying to understand, but

12:20

I. Think what's great about it is

12:22

that we have some the blueprints on

12:24

how to ask those questions and now

12:26

it's just. Asking them So you mentioned

12:28

that much of your work in your

12:30

lab has to do with Sat contents

12:33

and in particular there's a molecule or

12:35

a class of molecules I had never

12:37

heard of until try to prepare myself

12:39

to talk to you about this. Am

12:41

I gonna say right? Single whippets? Yes

12:43

you fit it right over going to

12:45

Ferry and I felt right path. success

12:47

is the purpose of this at. More

12:49

people know about single beds that will

12:51

be great. It has such as kind

12:53

of foreboding name but it's actually a

12:56

class of with ads that are involved

12:58

in many of the process he than

13:00

the body their part of the cellular

13:02

membranes. They can act as structural molecules

13:04

and they can also act as signaling

13:06

molecules. That Woods is cool about single.

13:08

A bid to us is that

13:10

they're in the satisfaction of milk.

13:13

They. Are produced by certain

13:15

beneficial microbe and they're all

13:17

so many signaling. Pathways in

13:19

as as humans that can actually

13:22

accept these. Signal! So we were

13:24

thinking about how diet. Microbiome.

13:27

And host interaction Support health. This

13:30

is actually maybe one of the

13:32

metabolite or chemical signals that may

13:34

give us some of those clues.

13:36

The word itself is a little bit. Off

13:39

putting, an intimidating single leopards. why

13:41

would you call them that? Yeah,

13:43

I think that all came from

13:46

how difficult these limits were to

13:48

study. Originally they got this reputation

13:50

of being gay, elusive sin, and

13:53

a manic like the thanks and

13:55

so that stock even though now

13:57

it's a lot more straightforward to.

14:00

The measure some leave were beds,

14:02

and as more people access the

14:04

ability to measure single a bids,

14:06

they're finding out how really they're

14:08

connected to so many facets of

14:10

our biology. and they're really important

14:12

mechanistically. And a lot of the

14:14

process. His return understand. Once you learn

14:17

about the word, you learn. About single of

14:19

it's you can't get them outta your life. You're going

14:21

to see them everywhere you go. Sell you have to

14:23

let me know if that's true of it. Seems to

14:25

have such a multi. Faceted,

14:27

Or versatile role you said. you can

14:30

use it as building blocks. Like structural

14:32

components, it can be used to communicate

14:34

information can be used for building. You

14:37

mention cell membranes. Cell membranes really important

14:39

for. The cell. And I think

14:41

that you can also say that

14:44

certain structures a single a bids

14:46

can be used as chemical signals

14:48

between cells and between even. Microbes.

14:51

And cells in the body and sell.

14:53

That's what we've. Really been trying to

14:56

think about in the case of

14:58

how do know where something in

15:00

the diet goes. My. Lab

15:02

has really been trying to think about. How

15:04

do we know which nutrients interact

15:07

with the microbiome so that we

15:09

know what are the important microbes

15:11

that are affected by diets and

15:13

then what are the consequences of

15:15

those interaction? So we have these

15:17

microbes that may be taking up

15:20

in transforming. These. Nutrients.

15:22

What? Are they making and how does that

15:24

affect our health and. I think that

15:27

is. Really? Important in

15:29

the infant context because a

15:31

large portion of milk or.

15:34

Molecules. That interact with the

15:36

incense gut microbiome, you have estimates

15:38

that almost ten percent of the

15:40

dry mass. Of human milk is

15:42

for communicating with so that microbiome and

15:44

we're trying to figure out are there

15:47

more molecules that are doing that and

15:49

what are the consequences? When you don't

15:51

have some of those chemical signals that

15:53

are occurring, they must. There's some sort

15:56

of beneficial function you might postulate. Will.

15:59

Be right. After this message. Did.

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16:30

Back. So. If I'm hearing you

16:32

write. The most my easy was

16:34

milk as food. Now are seeing that milk

16:36

is duchess food to build strong teeth and

16:38

bones and stuff like that when I'm hearing

16:41

from you is that these single lip or

16:43

does this an example of the cool kinds

16:45

of molecules in milk? They could be away

16:47

for the mom to talk to these bacteria.

16:50

That. Make up the microbiome. Possibly yeah

16:52

little are trying to figure out and not

16:54

a single a business. Also, look at. And

16:56

maybe some people save it or

16:58

least favorite nutrient cholesterol Things that when

17:00

we consume mostly bids are the interacting

17:03

with the microbiome and how that part

17:05

of. Our health is determined

17:07

by what we eat, and so we're

17:09

really at the stage where we're trying

17:11

to figure out. Who's. Important

17:14

and why they're important in this

17:16

kind of system Cell which bacteria

17:18

are. Significant. For having

17:20

effects on our health and why? What are

17:22

the mechanism? So if I can show you

17:25

something, Are you on a shelf? Me: Something:

17:27

Can I show you something for you? Cause

17:29

I think that what we've been trying to

17:31

do is make it so that you can

17:33

actually see this happening. So what we're looking

17:36

at here is a pitcher. Of.

17:38

The microbiome and the microbiome as

17:40

a collection of microbes and in

17:42

this case this is bacteria. so

17:44

very small thing and this picture.

17:46

Was taken by a microscope that we

17:49

have in the lab and what you

17:51

can see is that there are. Some.

17:53

Microbes that are blue and some

17:55

microbes that are red. And.

17:58

The ones that are read. Or. ones

18:00

that we actually were

18:03

able to introduce a label

18:06

of a nutrient, in this case

18:08

it's cholesterol, and

18:11

this cholesterol was consumed and

18:13

then we can follow that label

18:15

and the label turns

18:17

out red. So any microbe you see

18:20

that is red has taken up

18:22

cholesterol and anyone that's blue has

18:25

no interest in cholesterol at

18:28

that particular time. You're talking about like

18:30

a label in the sense of radioactive

18:32

labeling? The same concept but this is

18:34

fluorescence. So the red is

18:37

a red fluorescence and so that

18:40

for us is important

18:42

because it lets us actually identify

18:44

the microbes that are

18:46

interacting with what you eat versus

18:49

the ones that are not. Very

18:51

cool. I'm not going to mind

18:53

this because so much of biology is about

18:55

seeing things that are hard to see but

18:58

it's been a tremendous help in neurobiology and

19:00

now apparently in nutrition that something that was

19:02

invisible, you with these labeling tricks

19:04

can now track and see what's going on. Yeah,

19:07

it's why they give out the Nobel Prize for

19:09

these things because it helps people like me

19:12

ask the questions that we want to ask.

19:14

It seems really simple but it gives us

19:16

a little clue that we're going in the

19:18

right direction and then we can ask a

19:20

lot of things that may not depend on

19:22

the fluorescence signal but allow us to get

19:24

into some of the chemical pathways that

19:26

are involved in it. Then we have

19:29

machinery where we can physically

19:31

separate them and we can

19:33

identify all the microbes that are

19:35

red. You may

19:37

think that this is trivial but this actually helps

19:39

start the basis of some of the questions that

19:42

we're talking about. Are these

19:44

nutrients important for the microbiome

19:47

if they're being consumed and they are

19:49

being transformed at least they're having some

19:51

sort of effect? Okay, the

19:53

whole thing with the microbiome, maybe it's not so

19:56

new to you but for a lot

19:58

of us out there in the public, we haven't really been thinking

20:00

about the microbiome until I don't know the

20:02

past decade or two or

20:04

something. What's cool about studying

20:06

the microbiome and teaching it

20:09

here at Cornell is that when you walk into

20:11

a class, people believe you when you walk in.

20:13

They're like, microbiome is important. You don't have to

20:15

sell that. My gut health is my whole health.

20:18

When I ask students in the class, how many

20:20

of you have taken a probiotic or how many

20:22

have you done? How many of you have eaten

20:24

a prebiotic? All the hands shoot

20:26

up. And so there's a sense that it's

20:28

very important. But what specifically is

20:30

important? What is it that we

20:33

eat that is actually having these

20:35

effects? And so it lets us know, you

20:38

know, Steve, I don't know. Have you ever

20:40

taken a probiotic? I think I have. I'm

20:42

mostly familiar with it because I often give

20:44

them to my dog Murray. Yes.

20:46

When Murray's taken these probiotics and

20:48

things like that, how

20:50

do we decide which one's the

20:53

one that's beneficial? To give those answers, we

20:55

have to start at the basics of like,

20:57

I don't want to simplify it too much,

20:59

but what are the good

21:02

microbes and what are the contexts

21:04

that they are acting in support

21:06

of health versus not? And

21:08

so if we want to know that

21:10

probiotic that we're taking is

21:12

going to work for us, I think we

21:14

need to know some of these very

21:17

specific interactions on the molecular and biochemical

21:19

level. Now, does it count that I

21:21

eat yogurt? That counts. You

21:23

guys are probiotic, in nutritional

21:25

sciences, we really think about how

21:27

diet and the microbiome are

21:30

very well connected because sometimes you

21:32

can have microbes, but they need

21:34

certain nutrients to survive in the

21:36

gut. And if you don't provide

21:38

that, then there's no point in

21:40

taking that probiotic potentially. And

21:42

then there's also nutrients that you may

21:44

be taking and you may think that

21:47

they have a beneficial effect. But if

21:49

you don't have the microbes that are

21:51

actually acting upon that dietary substance, then

21:54

you're also not going to get that health

21:56

effect. The famous case would be dietary fiber.

21:58

So we do a lot of asking

22:01

who and what did they do, and

22:03

that actually gives us a lot of insight into

22:05

what might be important

22:07

for promoting health when we think

22:09

about diet microbiome interactions. So in

22:11

speaking about fiber, let

22:14

me shift gears slightly to a

22:16

different study that's come out of

22:18

your lab having to do with

22:20

diagnosing infant illness based on their

22:22

poop. If

22:25

I can say it that way. You

22:27

got right to it, Steve. You're a

22:29

parent. You've looked at a few

22:31

diapers in the years, and were they all the

22:33

same looking? No, they were not. And when we

22:36

talk about feeding babies and taking care of babies,

22:38

one of the big things is that they

22:41

don't always tell you what

22:43

they need in the way that you can understand,

22:45

but there's a wealth of information

22:48

in these diapers that are basically

22:50

microbes and metabolites. And

22:52

if we can understand what's

22:55

going on here, then we may have clues into

22:57

how babies' health

23:00

changes in real time. Then maybe

23:02

therapeutics can be more responsive if

23:04

we have more information about what

23:07

a healthy diaper is versus what

23:09

a not so healthy diaper is.

23:11

We all have maybe Google

23:13

is green, okay, what's going on

23:16

here? It's actually one of the

23:18

most popular parent searches out there.

23:22

We think that we can put a little more rigor into

23:24

that because we have the tools

23:27

to actually maybe determine is this

23:29

okay or is this not okay.

23:31

The great thing is that you're never

23:33

at a loss for samples. Our

23:36

group and many other groups around

23:38

the world have really been able

23:40

to start to ask these questions

23:43

about how do we understand infant

23:45

health through the development

23:47

of the microbiome in the first few months

23:49

of life. What exactly

23:51

is the kind of study that you would

23:53

do? So you collect some poop and then

23:55

what would you do to analyze it? We

23:58

can isolate the microbe and then we can use it. use

24:00

DNA sequencing to understand what

24:03

the classification of that microbe is. And

24:05

then we can also look at all of

24:07

the small molecules or chemicals

24:10

that are in there as well.

24:13

So that's maybe a combination of things

24:15

that were digested, things that were

24:17

not digested, intestinal cells.

24:20

We can also measure that and try

24:22

to interpret what that may mean in

24:25

the infant context. One of

24:27

the most famous examples of it is that in

24:29

certain infant liver diseases, they

24:31

stop making bile. And

24:33

so if you can measure bile and it's

24:36

there, then great. And

24:38

if you measure bile and it's not there, that's

24:40

indicative of that. But also the stool turns

24:42

a completely different color when bile's not there.

24:45

But on the day-to-day, there's probably a lot

24:47

of information that we're missing just because we

24:49

haven't been able to decode it yet. All

24:51

right. So it sounds like we

24:53

could spend many shows on the microbiome itself, but

24:55

I wanted to get back to milk because

24:57

there are so many fascinating things to discuss with you

25:00

here. What is a typical amount of

25:02

time to be feeding in that way? When is

25:04

it time to move on to other kinds of

25:06

nutrients? That's a good question because I think it's

25:08

good to orient it. So the

25:11

recommendations by the World Health

25:13

Organization and the CDC would

25:15

be exclusive human milk feeding for

25:17

six months. And then the

25:19

introduction of complementary foods. Different people have different

25:21

ways that they do it, but still having

25:23

milk as the main source of calories for

25:26

the infant for a while. And then the

25:28

introduction of cow's milk potentially at

25:30

one years old. And

25:33

then also the encouragement of any human

25:35

milk feeding if that works for you. So

25:38

there's not really a time that

25:40

you have to cease that necessarily. But

25:42

I think you're about to ask me

25:44

the trillion-dollar question, what are

25:46

the long-term health consequences of

25:49

exposure to human milk versus

25:53

exposure to infant formula? By

25:56

feeding baby milk today, am I starving

25:58

off allergic asthma? asthma in

26:00

five years or are there

26:02

developmental processes that are really time

26:05

dependent, that are very important and

26:08

are those things that can lead

26:10

to lifelong health and

26:12

could we actually determine what

26:15

those are so that they're in every

26:17

single form of infant nutrition? I

26:20

think about this a lot, about what's important even

26:22

as parents you think, geez, if

26:24

I drop them off their head yesterday, was

26:26

that important or was it not or no,

26:28

they looked that off the ground, was that important? What are

26:30

the things that I really need to worry about

26:32

in terms of am I creating the right

26:34

environment for setting them up for success in

26:36

the future? And the answer is

26:39

probably like babies are very robust so we worry

26:41

maybe more than we should. And

26:43

is it too early to answer any of

26:45

these questions about the long term effects? Is

26:47

it the subject too young or do we

26:49

have some clues already? I think

26:51

there's some clues. I mean there are

26:53

epidemiological studies that have correlations

26:56

between feeding mode and

26:58

outcomes or even microbiome composition

27:00

based off of feeding mode and

27:02

outcomes but I think it's

27:04

too early because the studies are extremely

27:07

hard to do. What's really challenging

27:09

about some of the studies is that

27:13

feeding babies is very difficult.

27:16

It's not usually like human milk versus

27:18

formula or this versus that. There are

27:20

different times like you may have gone

27:22

to three months or you may have

27:24

gone to six months or there may

27:26

be exclusive feeding for one month. There's

27:28

so much variation there that we need

27:30

to capture if we want to really

27:32

answer those questions properly and then

27:35

we need to be able to follow

27:37

cohorts very intensely for a long period

27:39

of time to start getting at

27:41

some of those questions. That takes a

27:43

lot of resources. So in a broader

27:46

context than just human milk, what if

27:48

we talk about other kinds of mammalian

27:50

milk? For instance, a lot of us

27:52

are drinking cow's milk all the time

27:55

and how different is it? Does

27:57

the milk of some other animal?

28:00

do jobs that human milk doesn't and vice-versa?

28:02

Yeah, I think that there are some similarities,

28:04

but there are a lot of differences. If

28:06

you think about the function of milk, it's

28:09

to grow a

28:11

baby of that particular species,

28:14

and cows and babies are different sizes,

28:16

and they have different growth trajectories, so you

28:19

can imagine that can be reflected in the

28:21

milk. So when you think about cow's

28:24

milk, more protein-forward

28:26

versus human milk, very

28:28

carbohydrate-forward, there's all

28:31

sorts of different strategies

28:33

for the transfer of

28:35

nutrients in different species of

28:37

animal milk, but cow milk does have a

28:39

lot of the things that are

28:41

the building blocks of human milk, so when

28:43

we think about using cow milk as

28:46

an alternative, it can make a lot

28:48

of sense. So typically, we drink pasteurized

28:50

milk. There are people who don't,

28:52

right? I guess the difference being if it's

28:54

pasteurized, you've killed off all

28:56

or most of the microbes that are going along for

28:58

the ride, you may have still

29:00

some of the nutrients. And there's pasteurized human

29:03

donor milk, so there's

29:05

a whole thought about how do we

29:08

think about donor milk,

29:10

and are those live factors in

29:12

donor milk and also the things

29:14

that may be denatured

29:17

in heat, molecules may change

29:19

their conformation, and different

29:21

types of pasteurization methods, there's

29:24

a lot of really smart people out there

29:27

thinking about what are the consequences of

29:29

this. Another one that I'm sure is on

29:31

the minds of many of our listeners has

29:33

to do with lactose intolerance. I

29:35

read somewhere that the ability of

29:37

adult humans to break down lactose,

29:40

which is, of course, the primary sugar

29:42

in animal milk, that's a

29:44

relatively modern trait, only something like 6,000

29:46

years ago that we started

29:49

to be able to do it. Historically, only

29:51

infants had the enzyme lactase

29:53

that would allow them to digest breast

29:55

milk. So I guess

29:57

my question is, if adults have 10... thousand

30:00

years ago couldn't drink milk at all,

30:02

but now most of us can, with

30:04

a few exceptions. Do

30:06

we have any idea what instigated this

30:09

change? Do we think there's some genetic

30:11

mutation that was favorable and began to

30:13

propagate? Yeah, my understanding is

30:15

that lactase is under neonatal promoter, so

30:17

this is a gene that will be

30:19

expressed during the infancy phase

30:22

and then that shuts off. But then you

30:24

can have a mutation that doesn't shut that

30:26

off and that can allow

30:28

for lactase to be expressed into adulthood.

30:31

Some people have done some really good work about the

30:33

spread of this particular ability

30:36

based off tracing the genetics

30:38

of this particular mutation. Some

30:40

of your microbes can also metabolize

30:42

lactose, bringing it back to the

30:44

gut microbiome. How is that involved

30:47

in lactase persistence and such?

30:49

Interesting. You already touched on this

30:51

a little, but you brought up

30:53

about milk versus formula. Certainly

30:55

many parents or caregivers will

30:57

be thinking about this. Does

30:59

your research give us any

31:02

insight into this important conversation? Yeah,

31:04

I think if you come to my

31:06

lab, Steve, we've analyzed every kind

31:08

of formula that we can get our hands on.

31:11

We talk about infant formula as one thing, but

31:13

there are many different formulations. So

31:15

in our lab, we quantify the milk

31:17

that we get in and we also

31:19

quantify any of the formulas that any

31:21

of the caregivers may be using. And

31:24

you can very clearly see the

31:27

differences in the nutrient profiles between

31:30

the different types of formula and

31:32

also between formula and

31:34

human milk. And really trying to understand

31:36

is there an essential

31:39

set of nutrients that the microbiome needs

31:41

to be exposed to? Anything you feed a

31:43

baby, we'll measure it in the lab. What's

31:46

so hard to talk about the subject is

31:48

that everybody's evaluating. Like I gave this talk

31:50

at the Pew meeting and afterwards people are

31:52

like, what formula? What did I do? I

31:54

called my wife and I told her that

31:56

we're doing it all wrong and I don't

31:58

want that to be the message. I want

32:00

the message to be more that people are

32:03

doing things right and we

32:05

just wanted more information. I know

32:07

that there's important issues at stake

32:09

here for medicine, for population, public

32:12

health, all kinds of things, but just in

32:14

terms of the pleasure of being a scientist,

32:16

what is it that gives you joy in

32:18

your research? Oh wow, so

32:21

many things. Getting to ask the questions

32:23

that we think are interesting and then

32:25

also working with a team of scientists

32:27

that I work with to see

32:30

the creativity and also the resilience

32:32

because these questions are hard. The

32:35

picture that I wanted to show you, the day that

32:37

we got that picture, standing around and looking at the

32:39

computer screen and I'm like, is this it? Is this

32:42

who we think it is? That kind of excitement really

32:44

drives a lot of the hard

32:49

work that goes into what we do.

32:51

That's great. Thank you so much. So

32:53

we've been speaking with Cornell molecular biologist

32:56

Liz Johnson. Thanks again Liz

32:58

for this insightful conversation about milk and

33:00

the microbiome. Thank you so much Steve

33:02

for having me. Including

33:20

Liz's picture of fluorescence labeling in

33:22

the microbiome at qantamagazine.org.

33:27

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