“Anti-inflammatory Diet for Depression” Depression affects more than
150 million people worldwide, making it a leading cause of
losing healthy years of life as a result of disability. In fact by 2020, depression
may be the second leading cause of healthy years of life lost,
second only to heart disease. Why is depression so common? Well, it is said “Nothing in
biology makes sense except in the light of evolution,” but why would be
evolve to get depressed? Depression poses a baffling
evolutionary puzzle. It has such negative effects, but
remains so common and heritable, meaning a big chunk of risk is
passed down through our genes, so there must be some
kind of adaptive benefit. Otherwise, presumably, it would have
been naturally selected against. Maybe, depression is an evolutionary
strategy for defense against infection. Infection has been the
leading cause of mortality throughout human history. The average life
expectancy was 25, and it was not uncommon
for half our kids to die. With such stark capabilities,
infection has been a critical and potent driving force
in natural selection. When we become infected, there
is a surge of inflammation as our body mounts a counterattack,
and then what happens? We feel lousy. We feel sick,
we get weak, tired, slow, and sleepy. We don’t see anyone;
we don’t want to do anything; all we want to do is sleep. It’s like we’re depressed— and that’s great for
fighting infection. Not only does that help us
conserve energy so we can put up a good fight,
but reduces social contact, we’re not running around
infecting everyone. It’s the same reason we evolved
to think poop doesn’t smell good, or decaying flesh. That keeps us safe
from infection. In fact, we see this phenomenon
with other social animals like honeybees
and mole rats who feel impelled to crawl off
and die alone when they get sick, which reduces the risk
to the rest of the community. The relationship between mental
health and inflammation was first noted in 1887,
for which the only psychiatrist to ever win the award
got a Nobel Prize. But what evidence have we
accumulated in the century since that inflammation
causes depression? Well, people who are depressed
have raised inflammatory markers such as C-reactive protein. Inflammatory illnesses are associated
with greater rates of major depression. Indeed, that’s what’s found in
a variety of inflammatory conditions including more benign
inflammatory conditions, like as asthma
and allergies, and that’s important,
suggesting the mood symptoms are not simply ‘feeling bad
about having a terrible disease’ but may be directly tied
to the inflammation. Most powerfully, you can
actually induce depression by inducing inflammation,
like when we give interferon for certain cancers or
chronic infections— up to 50% go on to suffer
major depression. Even just giving a vaccine
can cause enough inflammation to trigger
depressive symptoms. Taken together, these studies
are strongly suggestive of inflammation being a causative
factor of mood symptoms. So can an anti-inflammatory diet
help prevent depression? We didn’t know… until about 43,000 women without
depression were followed, along with their diets,
for about a dozen years to see who became depressed,
and it was those who at a more inflammatory dietary pattern, characterized by more soda,
refined grains and meat, suggesting that chronic inflammation
may underlie the association between diet
and depression. Normally, we think of omega-3’s
as anti-inflammatory, but they found fish to
be pro-inflammatory, associated with increased C-reactive protein
levels consistent with recent findings that omega-3’s don’t seem to help
with either depression or inflammation. The most anti-inflammatory
diet is plant-based, which can cut C-Reactive Protein
levels by 30% within two weeks. Perhaps because of the anti-
inflammatory properties of antioxidants. I’ve talked about this before,
but never explained WHY antioxidants are
anti-inflammatory. Oxidative damage caused by
free radicals may cause an autoimmune response in the body
by changing the chemical structures of otherwise ubiquitous molecules
to generate new structures that the body
attacks as foreign. For example, when LDL
cholesterol gets oxidized, our body creates antibodies
against it and attacks it. And so clinical depression can be
accompanied by increased oxidative stress and the autoimmune inflammatory
responses it creates. Free radicals lead to
auto-immune inflammation. Where else does inflammation
come from in our diet? Endotoxins. It’s worth reviewing how
the endotoxins in animal products can cause a burst of inflammation
within hours of consumption. What does it
do to our mood? If you inject endotoxin into people,
within a few hours, inflammation shoots up, and so does feelings
of depression, as well as feelings of social
disconnection from people. Although previous research has
demonstrated that inflammatory activity contributes to
depressive symptoms, no work in humans has examined
the effect of experimentally induced inflammation
on anhedonia— a key diagnostic
feature of depression, as well as anhedonia, the lack
of reaction to pleasurable stimuli— this is an an important
symptom of depression. No work has been done
that is…. until now. Within hours of endotoxin
hitting their bloodstream, these experimental subjects not only
started to feel depressed, but they had significant
reductions in activity in the reward center
of the brain. They were less excited
about winning money playing video games,
for example in the study. But by eliminating animal products,
and eating antioxidant rich diets, we may be able to
prevent or treat depression.