Carbohydrate Intake and Depression – Q&A

Question: I’m a 45 year old female. I currently weigh 221lbs. I’ve lost 30lbs in the last three months. My protein intake is roughly 120 to 130 grams per day.  I’m limiting my carb intake to 180 to 200 grams a day. I suffer from life long depression and I find that when I limit by carb intake I slowly slide into a depressed state after two or three months (it’s happening to me now). My sleep is disturbed, I develop anxiety I’m bitchy as hell and I’m dragging ass.  Is there a correlation between carb intake and production of neurotransmitters? If so, how can I eliminate the effect lower levels of carbs is having on me? Any information is greatly appreciated.

Answer: Dieting in general tends to lower serotonin in the brain and this can cause depression in susceptible people.  Interestingly, this effect seems to be more likely to occur in women than men (women being more susceptible to depression in general).  In my experience, low carbohydrate/higher proteins diets tend to be even worse in this regards for reasons I’ll explain now.

First and foremost, nutrient intake per se affects the production of neurotransmitters with the effects being both direct and indirect.

In a very direct way, specific amino acids are the precursors for specific neurotransmitters in the brain.  Tryptophan is a precursor for serotonin in the brain and the amino acid tyrosine (as well as phenylalanine which converts into tyrosine in the body) is the precursor for dopamine (and subsequently adrenaline/noradrenaline).

As an extreme example of this, researchers will sometimes use something called acute tryptophan depletion (accomplished by providing an amino acid solution containing all of the amino acids except tryptophan) to drastically lower brain levels of serotonin.  This is used to test various things but, among other things, it tends to cause acute depression in those who are susceptible.   However, this is a pretty extreme type of intervention, decreasing blood tryptophan levels massively (by about 80%); in dieting, tryptophan levels only drop by about 10%.

As usual, it gets more complicated.  The different amino acids have different transporters in the body and some amino acids use the same transporter; this means that different amino acid can compete for transport.

Specifically relevant to this topic is the fact that both the branched chain amino acids (BCAAS), tyrosine and phenylalanine and tryptophan all use a transporter called the Large Neutral Amino Acid (LNAA) transporter.  Again, this means that they compete for transport, meaning that levels of the different amino acids can affect the transport of the other. Which means that the relative amounts of the different amino acids will impact on how much is getting into a specific tissue in the body; in this case the brain.

If there is a large amount of tryptophan relative to the other LNAA, there will be greater serotonin production in the brain; if there is less tryptophan relative to the other LNAA, there will be less tryptophan transport into the brain and impaired serotonin production.

This brings us to one potential problem with higher protein intakes per se: most dietary proteins contain a lot more LNAA than they do tryptophan.  One exception is a derivative of whey called alpha-lactalbumin which has the highest tryptophan content of any dietary protein; recent studies have found that consumption of this protein can increase the ratio of tryptophan to the LNAA in the bloodstream, increasing brain serotonin synthesis.  For comparison, while most dietary proteins may ony contain about 2 grams of tryptophan per 100 grams, alpha-lactalbumin contains nearly 5 grams of tryptophan per 100 grams.

As well, there is an interaction with the carbohydrate intake of the diet.  Diets very high in carbohydrates and low in protein are known to raise plasma tryptophan and serotonin levels (which is probably why such diets make some people sleepy and dopey).  It’s worth mentioning that unless dietary protein is taken to exceedingly low levels (below 5% of total calories), the real-world impact of high-carbohydrates and low-protein isn’t that massive in terms of its effect on serotonin levels in the brain.

However this may explain why some people who are prone to depression tend to crave low-protein/high-carbohydrate foods at certain times (stress, seasonal affective disorder), they are trying to self-medicate themselves and improve serotonin levels.

In any case, let me explain why carbohydrates can impact on all of this since this will help clear up why lowering carbohydrates can cause problems.

The reason is this, the uptake of some of the LNAA (especially the branched chain amino acids) are insulin sensitive; for example, when insulin levels go up, blood levels of the BCAA go down.  This shifts the tryptophan:LNAA ratio towards tryptophan such that more gets transported into the brain, potentially increasing serotonin production.

The corollary to that is that when carbohydrates are reduced (and high quality dietary protein is increased), there is the potential for serotonin levels to be reduced. Between the increased intake of LNAA from most high-quality proteins, decreased clearance of them due to reduced insulin levels and the overall effect of dieting in general on plasma tryptophan levels, this all adds up to problems for people at risk for depression.

Which is a long way of answering your question with a resounding yes.

Both dieting in general and low carbohydrate/higher protein diets in specific can cause issues with depression in susceptible people.  I do find it a bit surprising that what I consider fairly moderate intakes of both protein and carbohydrates are causing you to experience this but some of it may depend on the depths of depression you experienced (e.g. your genetic susceptibility).

It may also explain why it takes a good 2-3 months for your symptoms to show up, a very low carbohydrate (e.g. 100 grams per day or less) and/or higher protein diet would probably cause things to go south that much faster.

Ok, so that’s what’s going on, what are the solutions?  I wouldn’t tend to generally recommend lowering dietary protein and increasing carbohydrates (higher protein diets having a number of benefits in terms of weight and fat loss) but, depending on the specifics of your situation (e.g. training, etc.) that might be one option.

Assuming it isn’t, here are some things to consider:

1. Add the protein I mentioned above, alpha-lactalbumin to your daily protein intake.  High in tryptophan, it will help support serotonin synthesis.  Consuming some near bedtime might help with sleep, taking it at other times throughout the day may help with overall mood.  In this context, I’d note that having a relatively higher carb/lower protein meal at dinner time may help with some of the sleep issues.

2. Consider supplementing with 5-hydroxytryptophan.  5-HTP is another precursor to serotonin in the brain that many have used to deal with depression and sleep problems. Doses seem to vary significantly but 50-100 mg taken up to three times daily may be worth considering to keep serotonin levels from falling while dieting.

3. Given that your symptoms only show up after 2-3 months of dieting, I’d strongly suggest taking a full diet break (discussed in detail in A Guide to Flexible Dieting) between periods of active dieting.  Basically, perhaps every 2 months, take 2 weeks to raise calories and carbohydrates to restore brain serotonin levels back to normal. Then you can enter another phase of active dieting, stopping before the depression really sets in to take another full diet break.  I think you get the idea.

I hope that helps and good luck.

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