Research has
linked sweetened beverages — both sugar- and artificially-sweetened
beverages — with an increased risk of depression, the highest risk being
associated with diet fruit drinks and diet soda
Another study
found adolescents who had elevated levels of sodium and low levels of
potassium in their urine — two factors indicative of a diet high in junk
food and processed food — had more frequent symptoms of depression
A 2019 study
found dietary intervention can effectively treat depression in young
adults. Those who ate a Mediterranean-style diet reported a significant
reduction in depression symptoms after 21 days
A recent
meta-analysis also concluded that “Dietary interventions hold promise as
a novel intervention for reducing symptoms of depression across the
population”
As a general
guideline, eating a whole food diet can go a long way toward lowering
your inflammation level and thus your risk of depression. A cornerstone
of a healthy diet is limiting sugar of all kinds, ideally below 25 grams
a day
Foods have an immense impact on your
body and your brain, and eating whole foods as described in my nutrition
plan is a good way to simultaneously support your mental and physical
health. Avoiding sugar and artificial sweeteners is in my view, based on
the evidence, a crucial aspect of preventing and/or treating
depression.
Both contribute to chronic inflammation and can wreak
havoc with your brain function. Recent research also shows how swapping
processed junk food for a healthier diet can significantly improve
depression symptoms, which really shouldn’t come as a great surprise.
The Sugar Trap
Research1,2 published in 2014 linked sweetened beverages — both sugar- and artificially-sweetened beverages — with an increased risk of depression.
Those who drank more than four cans or glasses of soda had a 30% higher
risk of depression compared to those who did not consume sweetened
beverages of any kind.
Interestingly, fruit juices were even more hazardous. The same amount
of sweetened fruit drinks (four glasses) was associated with a 38%
higher risk of depression.
Overall, artificially sweetened so-called “diet” drinks were
associated with the highest risks of depression, compared to beverages
sweetened with sugar or high-fructose corn syrup. More specifically, compared to those who did not drink sweetened beverages:
Those who drank primarily diet soda were 31% more likely to suffer
with depression, whereas regular soda was associated with a 22%
increased risk
Those who drank primarily diet fruit drinks had a 51% higher risk
for depression, while consuming regular fruit drinks was associated with
a more modest 8% increased risk
Drinking primarily diet iced tea was associated with a 25% increased
risk for depression, whereas those who drank regular sweetened iced tea
actually had a 6% reduced risk
Similarly, recent research3 detailed in “The Link Between Fast Food and Teenage Depression”
found adolescents who had elevated levels of sodium and low levels of
potassium in their urine — two factors indicative of a diet high in junk
food and processed food — had more frequent symptoms of depression.
According to the authors,4
“Given the substantial brain development that occurs during
adolescence, individuals in this developmental period may be
particularly vulnerable to the effects of diet on the neural mechanisms
underlying emotion regulation and depression.”
Why Sugar Takes a Toll on Mental Health
There are at least four potential mechanisms through which refined sugar intake could exert a toxic effect on mental health:
Sugar (particularly fructose) and grains contribute to insulin and
leptin resistance and impaired signaling, which play a significant role
in your mental health
Sugar suppresses activity of a key growth hormone called brain
derived neurotrophic factor (BDNF), which promotes healthy brain
neurons. BDNF levels are critically low in both depression and
schizophrenia, which animal models suggest might actually be causative
Sugar consumption also triggers a cascade of chemical reactions in
your body that promote chronic inflammation. In the long term,
inflammation disrupts the normal functioning of your immune system,
which is linked to a greater risk of depression5
Sugar impairs the microbiome and its influence on the modulation of
stress response, immune function, neurotransmission and neurogenesis
In 2004, British psychiatric researcher Malcolm Peet published a provocative cross-cultural analysis6
of the relationship between diet and mental illness. His primary
finding was a strong link between high sugar consumption and the risk of
both depression and schizophrenia. According to Peet:
“A higher national dietary intake of refined sugar and dairy
products predicted a worse 2-year outcome of schizophrenia. A high
national prevalence of depression was predicted by a low dietary intake
of fish and seafood.
The dietary predictors of ... prevalence of depression are
similar to those that predict illnesses such as coronary heart disease
and diabetes, which are more common in people with mental health
problems and in which nutritional approaches are widely recommended.”
One of the key predictors of heart disease and diabetes
is in fact chronic inflammation which, as Peet mentions, is also
associated with poor mental health. Sugar is a primary driver of chronic
inflammation in your body, so consuming excessive amounts of sugar can
truly set off an avalanche of negative health events — both mental and
physical.
Three-Week Dietary Intervention Lifts Depression
Most recently, a study7,8,9
published in the October 2019 issue of PLOS ONE said to be the first of
its kind, found dietary intervention can effectively treat depression
in young adults. The researchers enrolled 101 individuals aged 17 to 35,
whose stress and depression scores indicated moderate to high levels of
depression.
Participants were divided into two groups. One received dietary
intervention while the other (controls) received no intervention.
Dietary instructions were provided to the treatment group by a
registered dietician via a 13-minute video, which could be revisited at
will.
The dietary recommendations were based on the 2003 Australian Guide
to Healthy Eating protocol “with additional recommendations to increase
concordance with Mediterranean-style diets … and diet components (e.g.,
omega-3 fatty acids, cinnamon, turmeric) that have beneficial effects on
neurological function.”10 More specifically, the treatment group was instructed to eat:
Five servings of vegetables per day
Two to three servings of fruit per day
Three servings of wholegrain cereal per day
Three servings of protein (such as lean meat, poultry, eggs or legumes) per day
Three servings of unsweetened dairy per day
Three servings of fish per week
3 tablespoons of nuts and seeds per day
2 tablespoons of olive oil per day
1 teaspoon of turmeric and cinnamon on most days
Refined carbohydrates, sugar, processed meats and soft drinks were to be avoided as much as possible. According to the authors:11
“There is strong epidemiological evidence that poor diet is
associated with depression. The reverse has also been shown, namely that
eating a healthy diet rich in fruit, vegetables, fish and lean meat, is
associated with reduced risk of depression …
There was good compliance with the diet intervention
recommendations assessed using self-report and spectrophotometry. The
Diet group had significantly lower self-reported depression symptoms
than the Control Group …
Reduced DASS-21 depression subscale scores were maintained on
follow up phone call 3 months later. These results are the first to show
that young adults with elevated depression symptoms can engage in and
adhere to a diet intervention, and that this can reduce symptoms of
depression.”
The first graph below illustrates the difference in primary
depression scores (based on Centre for Epidemiological Studies
Depression Scale or CESD-R) between the two groups. The second graph
illustrates the difference between the two groups based on DASS-21
depression subscale scores. Source: PLOS ONE October 9, 2019, Figure 212Source: PLOS One October 9, 2019, Figure 313
The researchers also report that the dietary intervention resulted in
lower levels of anger. In the Discussion section of the paper, the
authors make the following observations:14
“The results of this RCT provide support for improving diet as a
useful adjunct treatment to reduce depressive symptoms … One of the most
interesting findings is the fact that diet change was feasible in this
population.
As the participants were young adults and university
undergraduate students, we anticipated several potential barriers such
as the perceived cost of the diet, the time demands of preparing food
and/or reliance on others for food preparation (particularly if they
lived at home).
Additionally, the participants were recruited based on
self-reported symptoms of depression. We anticipated that the symptoms
of depression, including low energy, reduced motivation and apathy,
would present as barriers to eating well.
Despite these factors, there was a significant increase in the
recommended foods and decrease in processed foods for the diet change
group but not the habitual diet group.
Furthermore, within the diet change group, increase in
recommended foods was associated with spectrophotometer readings. This
provides objective evidence to support the participants’ self-reported
compliance with the diet …
Even in the general population, adherence to diet advice is
typically very poor, with over 80% of Australians reporting that they do
not comply with dietary recommendations.
As a result, there is substantial nihilism regarding the ability
to change people’s diets. The current study simply provided a brief
13-minute video, paper resources and minimal phone support.
The fact that this relatively low-cost intervention can result in
a population of young adults adhering to diet recommendations is very
promising. Furthermore, it is important to consider that participants in
the current study did not need to adhere strictly to the diet
recommendations to derive benefit.”
Other Studies Support Dietary Intervention for Mental Health
Another recent paper found similar results. The meta-analysis,15
published in the April 2019 issue of Psychosomatic Medicine, looked at
16 randomized controlled trials with outcome data — based on a variety
of depression scores — for 45,826 participants ranging in age from 21 to
85. Interventions ranged from 10 days to three years.
While all but one examined nonclinical depression, dietary
interventions were still found to significantly reduce symptoms of
depression. Interestingly, women appeared to reap the greatest benefits,
not only for depression but also anxiety.
According to the authors, “Dietary interventions hold promise as a
novel intervention for reducing symptoms of depression across the
population.”
Interestingly, studies specifying the involvement of a nutritional
professional had significantly better results than those in which the
dietary advice was delivered without a professional’s involvement.
However, as shown in the featured PLOS ONE study, this doesn’t
necessarily have to be a complicated affair. There, participants simply
viewed a video in which a dietician gave the instructions.
Mechanisms of Action
In the Implications and Recommendations section of the Psychosomatic
Medicine meta-analysis, the authors point out a number of possible
mechanisms of action allowing depressed patients to benefit from
nutritional intervention:16
“… diet may act via several pathways that are implicated in
mental health. These include pathways related to oxidative stress,
inflammation, and mitochondrial dysfunction, which are disrupted in
people with mental disorders.
Gut microbiota dysbiosis has also been implicated because of
emerging research demonstrating involvement of the microbiome in the
modulation of stress response, immune function, neurotransmission, and
neurogenesis. A healthy diet typically contains a wide variety of
bioactive compounds that can beneficially interact with these pathways.
For example, vegetables and fruits contain, in addition to
beneficial vitamins, minerals and fiber, a high concentration of various
polyphenols that seem to be associated with reduced rates of depression
… potentially because of their anti-inflammatory, neuroprotective, and
prebiotic properties.
Furthermore, vitamins (e.g., B vitamins), fatty acids (e.g.,
omega 3 fatty acids), minerals (e.g., zinc, magnesium), and fiber (e.g.,
resistant starch) as well as other bioactive components (e.g.,
probiotics), which are typically abundant in healthy dietary patterns,
may also be protective from mental illness.
Along with increasing the intake of beneficial nutrients, dietary
interventions may also impact on mental well-being by reducing the
consumption of unhealthy food associated with increased risk for
depression, such as processed meats, refined carbohydrates, and other
inflammatory foods.
Unhealthy diets are also high in other compounds that may
negatively affect these pathways. For example, elements commonly found
in processed foods such as saturated fatty acids, artificial sweeteners,
and emulsifiers may alter the gut microbiome, which may activate
inflammatory pathways.”
Nutritional Advice for Mental Health
Keeping inflammation in check is an important part of any effective
mental health treatment plan. If you’re gluten sensitive, you will need
to remove all gluten from your diet. A food sensitivity test can help
ascertain this. Reducing lectins may also be a good idea.
As a general guideline, eating a whole food diet as described in my optimal nutrition plan
can go a long way toward lowering your inflammation level. A
cornerstone of a healthy diet is limiting sugar of all kinds, ideally to
no more than 25 grams a day.
In one study,17
men consuming more than 67 grams of sugar per day were 23% more likely
to develop anxiety or depression over the course of five years than
those whose sugar consumption was less than 39.5 grams per day. Certain
nutritional deficiencies are also notorious contributors to depression,
especially:
• Marine-based omega-3 fats —Omega-3 fats have been shown to improve major depressive disorder,18 so make sure you're getting enough omega-3s in your diet, either from wild Alaskan salmon, sardines, herring, mackerel and anchovies, or a high-quality supplement.
I recommend getting an omega-3 index test to make sure you’re getting enough. Ideally, you want your omega-3 index to be 8% or higher. • B vitamins (including B1, B2, B3, B6, B9 and B12) — Low dietary folate can raise your risk of depression by as much as 304%.19,20 A 2017 study21,22
showing the importance of vitamin deficiencies in depression involved
suicidal teens. Most turned out to be deficient in cerebral folate and
all of them showed improvement after treatment with folinic acid. • Magnesium — Magnesium
supplements have been shown to improve mild-to-moderate depression in
adults, with beneficial effects occurring within two weeks of treatment.23 • Vitamin D — Studies have shown vitamin D deficiency can predispose you to depression and that depression can respond favorably to optimizing your vitamin D stores,24 ideally by getting sensible sun exposure.
A double-blind randomized trial25
published in 2008 concluded that supplementing with high doses of
vitamin D “seems to ameliorate [depression] symptoms indicating a
possible causal relationship.” Research26 published in 2014 also linked low vitamin D levels with an increased risk for suicide.
The 2017 paper “Depression and Vitamin D Deficiency: Causality,
Assessment and Clinical Practice Implications,” published in the journal
of Neuropsychiatry, notes:27
“The Third National Health and Nutrition Examination Survey,
which enrolled a sample of 7,970 non-institutionalized U.S. residents
age 15 to 39, confirmed that people with serum vitamin D ≤50 nmol/L [20
ng/mL] are at a significantly higher risk of showing depression than
individuals whose serum levels of vitamin D are greater or equal to 75
nmol/L [30 ng/mL] …
A … large cohort study28
showed an association between low vitamin D levels and both presence
and severity of depression, this suggesting the possibility that
hypovitaminosis D indicates an underlying biological susceptibility for
depression.”
For optimal health, make sure your vitamin D level is between 60 and 80 ng/mL year-round. Ideally, get a vitamin D test at least twice a year to monitor your level.
A number of herbs and supplements can also be used in lieu of drugs
to reduce symptoms of anxiety and depression, including the following:
St. John’s Wort (Hypericum perforatum) — This
medicinal plant has a long historical use for depression, and is thought
to work similarly to antidepressants, raising brain chemicals
associated with mood such as serotonin, dopamine and noradrenaline.29
S-Adenosyl methionine (SAMe) — SAMe is an amino
acid derivative that occurs naturally in all cells. It plays a role in
many biological reactions by transferring its methyl group to DNA,
proteins, phospholipids and biogenic amines. Several scientific studies
indicate that SAMe may be useful in the treatment of depression.
5-Hydroxytryptophan (5-HTP) — 5-HTP is another
natural alternative to traditional antidepressants. When your body sets
about manufacturing serotonin, it first makes 5-HTP. Taking 5-HTP as a
supplement may raise serotonin levels. Evidence suggests 5-HTP
outperforms a placebo when it comes to alleviating depression,30 which is more than can be said about antidepressants.
XingPiJieYu — This Chinese herb, available from
doctors of traditional Chinese medicine, has been found to reduce the
effects of “chronic, unpredictable stress,” thereby lowering your risk
of depression.31
Other Helpful Treatment Options
Evidence clearly shows antidepressants are not an ideal choice for
most people with depression. For more information about this, see “What Does the ‘Best Evidence’ Say About Antidepressants?”
In it, I also review a number of other treatment suggestions, such as phototherapy, cognitive behavioral therapy, the Emotional Freedom Techniques and the importance of limiting your electromagnetic field exposure.
Aside from diet, which I believe is foundational, the depression
treatment with the most solid scientific backing is exercise. I
discussed some of the mechanisms behind this effect in “How Exercise Treats Depression.”
I also review the evidence against antidepressants and provide a list
of studies detailing the effectiveness of exercise for depression in “The Depression Pill Epidemic.”
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