How Fructose makes us Unhappy.

By June 1, 2011Sugar

We don’t know what causes depression and we certainly don’t know how to cure it. But some interesting new research suggests that there may be a very strong link between depression and what we shove in our gobs.

Depression is a catch-all diagnosis for a spectrum of illness affecting our mood. The spectrum covers everything from a mild bout of feeling down through to the most severe Major Depressive Disorder.

We can become depressed because things aren’t going well. If having your cat run over doesn’t alter your mood (one way or the other depending on how you feel about cats I guess) then you were probably built by aliens. But the science suggests how long we stay depressed has more to do with biochemistry than the state of Fluffy’s road-safety skills.

Food makes us happy (I know, you’re shocked at this revelation). Even seeing food improves our mood. This is because the anticipation of a feed, fires up the hormones responsible for how we feel.

The sight (or smell) of food gives us a squirt of the pleasure hormone, dopamine. Dopamine focuses our attention, makes us think more clearly and helps us move faster and more effectively. It’s an important signal to our body that we are in for something good and we need to pay attention. And that was probably pretty handy in times gone by (when dinner was on the hoof rather than in the burger box).

Once we actually start eating, serotonin kicks in. The serotonin makes us feel happier and less stressed. We relax, our mood improves (Fluffy will still be road kill, but we’ll feel better about it) and our minds can turn to less important things than eating (such as sex – the anticipation of which will give us another dopamine hit and the aftermath of which will give us a nice relaxing serotonin hit). While the cliché that the way to a man’s heart is through his stomach may be the G-rated version – it is largely accurate.

Researchers have known for a long time that severe depression is strongly associated with an inability to properly absorb serotonin in the brain. No (or low) serotonin absorption makes it much harder for us to come back from unhappiness. And this can translate into anxiety and depression if it’s sustained for long enough.

The primary anti-depressant drugs available in Australia (Cipramil, Luvox, Prozac, Lovan, Aropax and Zoloft) all work by targeting the serotonin system. They give the brain more time to absorb the serotonin. Some other drugs (Ecstasy, Amphetamines and LSD) work by enhancing the amount of serotonin we produce (but you might find it tricky to get a prescription for them).

If all is well with our hormone system then severe depression should be an extremely rare disease. But it’s not. Most studies suggest that one in ten of us is suffering some form of depression at any given time. So it won’t come as too much of a surprise to discover that one in every 30 GP consultations in Australia is now about depression.

Depression is a major chronic health problem and it is getting much worse at a very rapid rate. Something is messing with our serotonin system and the evidence is starting to mount that the something is fructose.

Fructose is the only carbohydrate which produces a significant spike in our cortisol levels. Cortisol is our stress hormone. It’s terribly handy for confrontations with unexpected bears (for example) because it ramps up dopamine (to focus the mind and sharpen the movements). It also rapidly increases the amount of dopamine we can absorb. But it does so at the expense of our ability to absorb serotonin.

We like dopamine. It is our reward drug. Frequent hits of fructose mean frequent hits of dopamine. This leads inevitably to fructose addiction and that is exactly the mechanism used by other man-made opiods (like nicotine and cocaine). The trouble is that it seems the upregulating of dopamine at the expense of serotonin can become hard-wired if we allow it to go on for long enough. And once we’re addicted, we cant help but let it go on for long enough.

We don’t run into that many bears on a daily basis (well, I don’t). Fructose was once about as common as a bear encounter, but is now embedded in almost every processed food we buy. And it has an addictive quality as powerful as nicotine (so it isn’t exactly going to harm sales now is it?).

We are now on a constant drip of fructose. That means we are on a constant cortisol (and therefore dopamine) high. This in turn continuously impairs our ability to absorb serotonin, the one substance that can turn our mood around.

Fluffy will still become a bumper sticker if he chooses an inopportune moment to cross the freeway and that will probably be a downer. But the science is suggesting that how quickly (or if) we bounce back from that may depend (to a large extent) on how much fructose we are eating.

In an environment of non-stop fructose infusion, the wonder is not that one in ten of us is depressed, it’s that nine in ten of us aren’t (yet).

Image courtesy of David Castillo Dominici /

Join the discussion 16 Comments

  • Janelle says:

    Serotonin Seekers is an easy to read little book available online

  • Cassiel says:

    Thanks so much for this article, David! I’ve just recently come across your blog (via Eve Schaub’s ‘year of no sugar’, actually) but I’m so glad I did. (And I will be picking up your book very soon!)

    Earlier this year, I cut sugar (and most processed carbs) out of my diet, and the health benefits I’ve had as a result have been astounding. Long-term health problems I could never have imagined were caused by sugar have been cleared up permanently.

    I’ve also suffered from major depression for almost all of my adult life, and a great deal of my teen years — and I was also a sugar junkie for most of that time. This article just brings home to me, once again, that sugar has likely been ruining my life in so many unexpected ways for a lot, lot longer than I realise! And lately I’ve definitely been a heck of a lot more positive and capable of getting through the bad days than I used to be before I cut out the sugar — and that change really did occur directly after I cut out the sugar, and enough so that it has been very noticable. Hard to ignore!

    I wish I could come listen to your talk! However Aussie though I am, I live in Japan so it’s a bit of a trip. 😛 I hope it goes great and you open a lot of people’s eyes, though!

  • Freda says:

    Terrific article David, how true it seems for me, since giving up sugar, even though only three months ago, I find my mood has been a lot lighter.
    Thank you……….and you’re a bloody good writer, by the way.

  • Diana Hunt says:

    Another great and crystal clear article. Thanks David for bringing this material to light, you’re saving lives.

  • Kylie says:

    Wow!!! Such a great article!! I will certainly help spread the word to our members at Fitness Matters as our intention is to create a happy and healthy world and this information us such a crucial link to happiness!!! Thank you!! Xo

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  • nads says:

    I was so not surprised by this possible link. Working in the health system, with older people as I do, I see so many people who have the whole combo – obesity, diabetes, heart disease, depression. For a long time I’ve thought that bad food must be the cause of depression as well.

  • obakesan says:

    thanks for the research work David. I only found this blog from Steve Austins show. As a long ago trained biochemist and now something else I will be following with interest.

  • daisy says:

    Hi David, how interesting and supportive your blog is. I’ve managed to get the blindingly obvious sugar out of my diet without too much confusion.But what I am puzzled by is the second ingredient listed in the stock-in-a-box that i use – glucose. Is glucose bad for me too, please?

  • Pat says:

    A lot of processed foods here in Canada (and I expect as well in Oz) have glucose-fructose added. It is pretty hard to avoid it, unless one avoids processed food. THAT is something we should be doing, and eating more foods in their natural states.
    When you refer to fructose, I am assuming that you are referring to the processed form? I’d hate to think that fresh fruit could be an issue. Would you mind clarifying this?

  • Daisy – glucose is fine. Almost all carbohydrates (except fructose) are ultimately converted to glucose by our body anyway.


  • Pat – fresh fruit is fine as long as we eat all of it (that is, don’t juice it) and have no more than two pieces a day (adults, one for kids).


  • Moving Girl says:

    David, I have only just started to go sugar free and one of the interesting things that I have noticed is that within days my handwriting has become much smaller and tidier, so something is going on in my brain. Any thoughts on this.

  • David. So glad you are absorbed by your topic. It is great to have someone who actually knows and cares about this stuff.

    Can you take it to the next level and consider a) the endocrine system; b) fructose malabsorption and the breath tests; and c) getting relabelling laws through in Australia?


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