A diet high in sugar contributes significantly to depression, anxiety, and stress. Learn how sugar affects the brain and what you can do about it.
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We are born hardwired to like things that taste sweet.
Preferring sweets is a survival mechanism that humans have developed to protect us from eating toxic foods.
But if you’re feeling stressed out, anxious, or depressed, this inborn preference works against you.
You may crave sweets and find that eating them makes you feel better. Temporarily.
Sugar-rich foods and foods that are mostly refined carbohydrates are anything but better in the long run.
There’s a complicated relationship between sugar, your brain, and mental health.
Let’s look at how sugar and other sweeteners affect your brain and fuel both depression and anxiety.
Understanding Sugar’s Role in the Brain
Table sugar is pure white crystalline sucrose usually extracted from sugar cane or sugar beets.
It is intensively processed, has no nutritive value, and in many ways is more like a drug than a food.
To understand how sucrose impacts you and your mood, we need to take a look at its two components, glucose and fructose.
While glucose and fructose are structurally very similar, they behave differently in the body.
Glucose — The Brain’s Main Energy Source
Glucose is a simple sugar molecule that’s a building block of mainly plant-based complex carbohydrates such as those found in whole grains, legumes, fruits, and vegetables.
It is essential to life.
It circulates in your blood and provides energy to all of your cells especially your brain cells which use a disproportionate amount of energy. (1)
Since brain cells can’t store energy, they need a steady supply of glucose.
While your liver can break down stored fat to produce ketones to feed the brain in a pinch, most brains run on glucose most of the time.
Why Added Fructose Is a Problem
Fructose is another simple sugar naturally found in fruit and sweet vegetables like carrots, beets, and yams. (2)
Virtually every cell in the body can metabolize glucose for energy, but only liver cells can handle fructose. (3)
Refined sugars like white sugar, high fructose corn syrup, and even “healthy” sweeteners like honey and maple syrup are roughly half glucose and half fructose.
The fructose found in fruit and vegetables is easily handled by the body, but a diet high in added fructose from concentrated sweeteners raises blood fructose levels — and this is a health disaster.
It increases the risk of obesity and type 2 diabetes. (6)
And it contributes to chronic inflammation, an underlying cause of a wide range of psychiatric and neurodegenerative disorders. (7)
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The Link Between Sugar and Depression
You may turn to sugar when you’re feeling blue.
Here’s what research shows regarding the link between sugar and depression:
- A study across six countries found a “highly significant” correlation between sugar consumption and the rate of depression. (10)
- Frequent consumption of fast food and commercial baked goods can increase the risk of depression up to 38%. (11)
- Both sugar-sweetened and artificially-sweetened drinks increase the chances of developing depression. (12)
And most significantly is the Women’s Health Initiative Dietary Modification Trial.
This huge 20+ year project followed the dietary habits of over 48,000 women. (13)
One finding of this study was that sugar and processed grains increase the risk of depression, while fruits and vegetables decrease the risk. (14)
One surprise of this study was that no health benefits were found by following a low-fat diet. (15)
It did not lower participants’ risks for heart disease or cancer, nor did it help them maintain a normal weight.
This is important to know because the healthy fats missing from the foods in low-fat diets are critical to brain health and function.
How Sugar Can Cause Depression
It’s not fully understood how sugar contributes to depression, but here are the three most widely accepted theories.
Sugar Causes a Serotonin Crash
Serotonin is a major neurotransmitter known as the “happiness molecule” for the important role it plays in maintaining a positive mood.
Sugar and other processed carbs beckon when you’re feeling blue because they give you a serotonin boost. (16)
But this lift is short-lived, lasting only an hour or two before your serotonin level crashes and you feel even worse.
A smarter long-term strategy for increasing serotonin is to regularly eat healthy carbohydrates.
But you can eat carbs on their own without protein to increase serotonin naturally.
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Sugar Increases Brain Inflammation
The medical consensus is that depression is caused by a lack of two neurotransmitters, mainly serotonin and sometimes dopamine.
However, another promising theory is emerging — the “cytokine model of depression.” (19)
The foundation of this theory is that brain inflammation is the root cause of depression.
Cytokines are immune system messengers that regulate inflammation.
Inflammatory cytokines have been linked to: (20)
- Alzheimer’s disease
- bipolar disorder
- brain fog
- lack of focus
- memory loss
Currently, the most widely-used antidepressants are selective serotonin reuptake inhibitors (SSRIs) which are thought to work by increasing serotonin levels.
But now there’s evidence that SSRIs are anti-inflammatory.
SSRIs don’t always work but when they do, it may be for the wrong reason.
It’s possible that their anti-inflammatory property is responsible for their antidepressant effect. (21)
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Sugar Suppresses BDNF, a Natural Antidepressant
Brain-derived neurotrophic factor (BDNF) is a protein critical for brain health.
BDNF stimulates the formation of new brain cells and protects the brain from neurodegenerative diseases. (22)
It also acts as a natural antidepressant. (23)
- Alzheimer’s disease
- anxiety disorders
- obsessive-compulsive disorder
- post-traumatic stress disorder
The Link Between Sugar and Anxiety
Just as you may eat sugar to lighten your mood when you’re blue, you may also eat it to relax when you are feeling stressed or anxious.
In the short term, stress can depress appetite, but chronic stress increases appetite by raising levels of stress hormones and the hunger hormone ghrelin. (29)
Stress also affects food preferences, making you crave sugar, fat or both.
That’s why no one craves a big bowl of broccoli when they’re stressed out!
Here’s how sugar affects blood sugar levels, contributing to anxiety.
The Blood Sugar Roller Coaster
Foods with a high glycemic index like sugar, high fructose corn syrup, or wheat cause blood sugar levels to spike.
Your body responds by making insulin which causes your blood sugar to drop.
Low blood sugar then causes your adrenal glands to release the stress hormones cortisol, norepinephrine, and epinephrine. (30)
This gets your liver to release stored sugar to bring your blood sugar level back to normal.
But these hormones, the same ones released when you are in fight-or-flight stress mode, also ramp up anxiety and can even trigger panic attacks. (31)
The Hypoglycemia-Anxiety Connection
There’s evidence that eating sugar can induce anxiety independently of hypoglycemia, but hypoglycemia is undoubtedly a major physical cause of stress and anxiety. (32)
Hypoglycemia occurs when your blood sugar level drops too low.
The symptoms of anxiety and hypoglycemia are so similar that doctors have been misdiagnosing hypoglycemia as anxiety for decades. (33)
Common symptoms of both include mood swings, brain fog, nervousness, restlessness, irritability, inability to concentrate, and crying spells.
A low blood sugar attack can leave you feeling jittery, sweating, heart pounding, and confused — very much like an anxiety attack.
If you suspect your anxiety is related to hypoglycemia, it’s critical that you limit your intake of all refined carbohydrates and sugar, and eat protein, healthy fats, and complex carbohydrates instead.
This is also an excellent time to examine your caffeine intake, since there are over a dozen different ways caffeine contributes to anxiety.
Caffeine and sugar often go hand-in-hand in soft drinks, lattes, and energy drinks.
Also, consider taking a magnesium supplement.
This mineral can help you relax and stabilize your blood sugar level if you have hypoglycemia. (36)
Sugar Substitutes Are No Better for Depression and Anxiety
You might be thinking of trading in sugar for an artificial sweetener, but that comes with its own drawbacks.
Over 10,000 complaints of aspartame side effects have been reported to the FDA (US Food and Drug Administration). (37)
You used to be able to find a list of the reported aspartame side effects on the FDA’s website, but this information has been taken down.
However, you can find many of these reported side effects listed on the Centers for Disease Control and Prevention website, in this article on Harvard’s digital library, and in this Journal of the Diabetic Association of India article.
Mental health conditions reported to be aggravated by aspartame include anxiety, depression, attention disorders, Alzheimer’s, and Parkinson’s.
One major study on over 250,000 soda drinkers found that drinking soft drinks sweetened with aspartame, saccharin, or Splenda increased the likelihood of depression by 30%. (38)
Reported neurological side effects linked to sucralose include: (39)
- blurred vision
- mental confusion
- panic attacks
How Artificial Sweeteners Harm Your “Second Brain”
One of the latest, and most unexpected, findings about artificial sweeteners is the effect they have on your gut bacteria, collectively known as your microbiome.
A dysfunctional microbiome can be a root cause of anxiety and depression and many other brain-related disorders. (40)
Artificial sweeteners change your microbiome which can have a profound impact on your brain, mood, and mental health.
The intestines are now considered a “second brain” or “backup brain” since they contain over 100 million neurons.
Gut bacteria are responsible for making over 30 neurotransmitters including serotonin, GABA, dopamine, and acetylcholine. (41)
This gut-brain connection is a relatively recent discovery that we’ll be hearing a lot more about in the future.
There’s an entire class of probiotics called psychobiotics that specifically bestow mental health benefits.
In fact, this exciting new discovery is being called “the new frontier” in mental health treatment.
Numerous studies support that taking the right probiotics can alleviate symptoms of stress, anxiety, and depression. (42)
Quitting Sugar: What To Do Next
If you suspect that sugar is fueling your anxiety or depression, you might want to eliminate it from your diet to see if you notice any improvements in symptoms.
This is not easy since sugar is hidden in most processed foods and goes by over 60 different names on food labels.
And if you’ve ever tried to quit eating sugar, you may have found that sugar cravings can be strong.
In fact, sugar meets most of the criteria of an addictive substance!
Sugar’s Role in Anxiety and Depression: Take the Next Step
We are hardwired to love sweet foods.
But to the detriment of our mental health, the modern diet contains an overabundance of sugar and refined carbohydrates.
The glucose and fructose found in whole plant foods are not hazardous to your health.
But the evidence is clear — refined sugars significantly contribute to depression and anxiety via several mechanisms.
The solution is simple, but not easy.
Replace processed foods and refined sugars with whole foods that don’t contain added sweeteners.
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