We are the paradoxical ape.
Bipedal, naked, large brain,
long the master of fire, tools, and language.
But still trying to understand ourselves.
Aware that death is inevitable,
yet filled with optimism.
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We hand down knowledge.
We empathize and deceive.
We shape the future from
our shared understanding of the past.
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I'm going to talk today about how to
feed 10 billion people.
Much of what I'll be describing,
is the result of a commission that I co-chaired with
Johan Rockstrom from the Resilience Central in Stockholm.
This was funded by the Wellcome Trust,
which allowed us to bring together
35 scientists from 17 different countries,
and that brought together expertise from
many different disciplines that were
clearly needed to take on this challenge.
The challenge was great.
How can we feed what will be about
9.8 billion people in 2050,
a diet that is both healthy and sustainable?
Already today, we're not where we should be.
About two billion people around
the world lack key micronutrients,
many millions of children are stunted and
over 2 billion adults are overweight or obese.
The obesity epidemic is probably
the most conspicuous indicator of
what's happening on the nutrition side.
We have, today, about 42 percent of Americans are obese,
whereas back in 1970, this was only about 10 percent,
huge increase over time.
But it's not just the United States
that it's experiencing this obesity,
this is the prevalence of
overweight and obesity around the world.
As you can see on the top that
these are the affluent countries and
there's been a steady increase going back here from 1980.
But if we look at low-income countries at the bottom,
these are actually increasing in
prevalence at an even greater rate.
There is projected to be a convergence down the road.
This is really a global problem.
But, of course, we can't just look at the averages.
There are huge disparities
within countries as well as between countries.
This is showing life expectancy in the United States,
in the middle are the white population,
and the overall population average, and what's
happened during the pandemic, and you
can see even before the pandemic,
there was a decline in life expectancy in all groups.
But there were huge differences in
life expectancy of men and now
the African American population
is lost about three years of
life expectancy projected compared
to the white population,
the gaps have increased even further.
This is happening in many countries,
but it's not universal and that's important.
Because that means that declines in
life expectancy are not inevitable.
These are data from the upper income countries
and you can see at the bottom,
the United States has been
lagging in life expectancy quite
awhile while it's been steadily going up in Japan,
both in men and in women.
On the environmental side,
the challenges are, perhaps even, greater.
We've seen increases in
global average temperatures from year-to-year,
and what's really troublesome
here's not that there are just increases,
but there's acceleration and we're reaching
a point where we're entering vicious circles,
whereas world gets warmer,
that releases more methane gas from a permafrost from
the Arctic Ocean that's speeds up
warming and this cycle is going faster and faster.
Against that background,
our commission faced very serious challenge
and how to address this
was something we thought about for awhile.
Ultimately, we broke this down into four steps.
First of all, defining a healthy reference diet
using the best available evidence
from all kinds of studies.
Then we defined planetary boundaries using
environmental systems or in
particular like the greenhouse gas,
crop land use, water use,
nitrogen and phosphorus fertilizer
application, and looking at extinction rates.
Then we used the global food systems modeling framework,
to analyze whether what we identified as
a healthy diet could be
produced within planetary boundaries.
Finally, we looked at
strategies to stay within those boundaries.
I'm going to use protein sources as an example,
since I can't, within this time limit,
look at all of the major food groups.
But protein sources are particularly
important because our choices among them,
have great implications for both health and nutrition,
and climate change as well.
If we look at D, for example, the ratio of
polyunsaturated and saturated fat is extremely low.
Poultry has quite a bit more polyunsaturated fat,
salmon more, but if we really
want higher ratios of polyunsaturated,
desaturated fat, we need to go to
plant protein sources like
nuts, soy products and lentils.
We know that ratio is important because it
reduces blood cholesterol if we have a higher P/S ratio.
Our colleagues in Germany
took this a step further and looked at
the relationship between
various protein sources and food groups,
and cardiovascular risk factors.
This is a summary of
66 randomized trials with risk factors and outcomes.
These included our blood lipids,
indicators of glucose, homeostasis,
blood pressure, and inflammatory factors.
Then from the effects of
each food group by all of these risk factors,
they created the risk score, and then ranked the foods.
The best foods were nuts, followed by legumes,
whole grains, fish, fruits and
vegetables, refined grains, stem,
red meat being lower,
these are less healthy foods now,
eggs, dairy, and sugar-sweetened beverages
which have no nutritional value.
Another kind of study we
used was long-term follow-up studies,
and our group has been conducting these kinds
of cohort studies back since the 1970s.
The first was the Nurses Health Study,
in which we enrolled 121,000
women and track diet since 1980.
Then, identifying incident cases
of cardiovascular disease, cancer,
and other outcomes and we were able to control
for many potential confounding variables like smoking,
physical activity, and medication use,
and family history.
That result, women so we enrolled about
52,000 men and similar studies starting in 1986,
then another 116,000 women in 1989.
Again, tracking diet over time,
risk factors, and incidences of all major diseases.
I would point out this is the work of many individuals.
It's a very multi-disciplinary set of projects.
These are data looking at, again,
major protein sources here in relation to total mortality.
We've combined cohort, so this is
over 130,000 people followed for
several decades and among them
about 33,000 died during this period.
We had a lot of statistical power.
All of these foods are compared to dairy foods
and it's really important to have a specific comparison.
The worst, not surprisingly, was processed meat and eggs,
and then unprocessed red meat.
Fish and poultry were pretty similar to dairy.
But if we really wanted to go to low mortality,
that meant emphasizing plant protein sources like nuts,
legumes, and swipe products.
I'm very consistent with what we saw.
Looking at the shorter term
randomized controlled trials with
risk factors is an outcome.
Together, that evidence creates
a very strong body of evidence to support
shifting to a more plant-based diet for health reasons.
But it's not just important to have this ranking.
We really need to look at
those response relationships to identify what
would be an optimal amount of intake of each food group.
Here, we used
the combination of over 200,000 men and women,
among whom 13,000 developed
incident type II diabetes
during the several decades of follow-up.
Even by just going from the first to second quintile,
we saw a significant increase,
small but statistically significant increase
in risk of type II diabetes.
The overall relationship was quite linear.
We didn't want to recommend this increments,
so we somewhat, arbitrarily took
the midpoint of this first increments.
This corresponded to about one serving
of red meat per week.
After going through all of the major food groups,
we put the data together and came
up with what we call the healthy reference diet.
Run through some of these numbers quickly.
This meant that there was quite a flexible amount of
whole grains that were possible.
But what's really important is it to be
whole grains, not refined grains.
Potatoes have a less advantageous health profile,
so it kept that number pretty low.
About five servings of fruits and vegetables per day.
Dairy is pretty interesting because
there are health benefits.
We specified a range from 0-500.
All the animals source proteins have a
possibility of zero because we
know a vegan diet can be healthy.
But we found this is about two glasses of milk
per day that's 500 grams per day.
If we had the whole world
go to two servings of dairy a day,
we couldn't stay within planetary boundaries,
so we use the midpoint of that range
about one serving of dairy a day.
I already mentioned that red meat
would be about one serving per week.
Poultry, better from a health perspective,
so about two servings per week.
Eggs, about two eggs per week.
Fish twice a week, which does have
some positive health benefits
because of the omega-3 fatty acids.
But mostly emphasizing plant protein sources like beans,
lentils, peas, soy, and nuts. Fat intake.
If it's healthy fats, mostly unsaturated fats, quite a
bit of flexibility about that.
We kept up with
sugar-sweetened beverages and other sources
of added sugar low, which would mean about 5 percent
of energy from sugar or less.
Even if we go to one serving per day,
we would be over that limit.
That's a lot of numbers pretty quickly,
but it does boil down to something actually pretty simple
when it comes to protein sources, one plus one.
Most people can't get that,
meaning about one serving dairy day if you'd like
it and about one serving whether protein sources per day,
some combination of fish, poultry, eggs, or red meat.
This has been called a flexitarian
diet and could be that you are vegan.
This is the maximum amount,
but it does provide a lot of variety for people who
would like to have some animal sources
of protein in their diet.
That would, of course, be on a base
of nut, soy, beans, fruits,
vegetables, whole grains, and plant oils.
Is this realistic?
As it turns out it's actually very similar to
the traditional Mediterranean diet that
Greek men were consuming in the 1960s when they
had the highest life expectancy in the world.
The amount of red meat plus poultry,
35 grams per day in Crete.
In the 60s our reference diet came out to be
43 grams of protein per day, so very similar.
But these fruits can be put together in diets that are
very consistent with traditional diets
from most places around the world.
This happens to be a Vietnamese diet that
encompasses this combination of fruits,
vegetables, some whole grains,
and mostly plant protein sources.
But if you wanted some animal source proteins,
some fish or other sources in moderation would be fine.
Where do we stand today?
If we look around the world,
our vertical line here
represents the targets that I described.
But there's incredible heterogeneity
if we look across regions.
North America, for example,
is way over the reference amount for red meat.
But sub-Saharan Africa is way
over the reference diet in terms of starch or vegetables.
This is mainly due to poverty diets where
these vegetables provide most of
the calories in the diet
that's otherwise quite unbalanced.
What's really important though,
I said most regions of the world
are short in terms of fish,
vegetables, fruits, legumes, whole grains, and nuts.
Moving toward a healthy diet doesn't
mean just reducing unharmful things.
It means increasing health-promoting aspects of diet.
We did some analyses using
three different modeling systems to see
how much mortality would change if everyone shifted to
the healthy targets that we described.
Basically, they all showed similarly that we
would prevent about 3 million premature deaths per year,
or about 19-24 percent
of total mortality by the whole world,
shifting to those healthy diets.
On the environmental side, we also looked at a summary
of data life-cycle analysis specifically here.
For example, looking at
how much greenhouse gas per serving would be
produced for each serving of different food groups,
red meat and, I think, not surprisingly,
was the worst, and soy and
legumes were the best protein sources along with nuts.
But the difference is huge, red meat is
about 140 times greater amount
of greenhouse gas production
compared to these plant protein sources.
Pork, chicken, fish, dairy, eggs,
quite a bit less greenhouse gas promoting than red meat,
but still, these are about 30-40 times the amount of
greenhouse gas per serving
compared to plant protein sources.
Fruits, vegetables, cereals all have
quite low environmental footprints
with respect to greenhouse gas emissions.
Putting this all together,
looking at greenhouse gas emissions,
we found that the planetary boundaries
that were defined suggests that we
could produce about five gigatons
per year of greenhouse gas emissions
from the food systems, but by 2010, we were
already a little bit over that number.
If we continued on the business as
usual track that we're on now today,
with more population being added,
about 2.5 billion people by 2050, and
more meat consumption, we'd be
about double the sustainable amount
of greenhouse gas emissions.
But if we adopted the target numbers that I described,
we'd be back just about at the planetary boundaries.
If we improve production methods and reduced waste,
we would be under the limits
for greenhouse gas emissions,
which is where we would like to be, of course.
We went through this for
the other indicators of sustainability.
I won't go through those numbers now.
But the point being that we not only need
to shift to this dietary targets, but also incorporate
better agricultural production methods
and substantially reduce
food waste if we're going to remain within stable
limits for these other indicators of sustainability.
To put this in the even bigger picture of
the IPCC pathway to
staying under two degrees centigrade increase,
we, of course, need to fundamentally eliminate
fossil fuel emissions now used by industry by
energy production, buildings, transportation.
The food sector looks small
here in comparison to these other sectors,
but if we continue on
our business as usual path and we reduce
fossil fuel emissions, we'll still not be able to stay
within the Paris Climate Agreement that limits.
We're also counting under agriculture and
food systems to have negative emissions,
in other words, carbon sequestration in
ways that we don't yet really quite know how to do.
To conclude, feeding 10 billion people
a healthy diet within safe
planetary boundaries is possible,
and that will improve the health and
well-being of billions of people.
This could allow us to pass on
to our children a viable planet.
Thank you.