Why sleepiness is not always caused by a lack of sleep

I came across this story earlier this week. It concerns a study presented at a Associated Professional Sleep Societies in Minneapolis in the US. The details are somewhat sketchy from the report, but here’s what I think the researchers did and what their findings were.

262 teenagers with an average age of 17 were rated on measures of daytime sleepiness, depression and cravings for carbohydrate.

The main reported finding was that the more sleepy individuals were, the more the craved carbohydrate, and the greater the risk of them being depressed was.

In the report I link to, there is comment from one of the authors in which he refers to ‘sleep deprivation’ as an important factor. Yet, there is no mention that sleep per se was assessed. I don’t know what precisely has gone here, but I have a feeling that in the author’s mind, daytime sleepiness is a proxy for sleep deprivation. If that’s the case, then I think this is an over-simplistic view, because there’s lots of things that can cause people to be sleepy that have nothing directly to do with sleep deprivation.

The number one offender that I have on my own personal list is blood sugar imbalance, and specifically episodes of low blood sugar (hypoglycaemia). This problem, clinically, is very common, which is one of the reasons I mention it quite often in my writing and lectures.

Here’s the thing, when individuals drop their blood sugar level, not only can they feel sleepy, but they can crave carbohydrate too. Oh, and seeing as brain function generally depends on a good supply of sugar (glucose), we won’t be too surprised to learn that low blood sugar can cause problems with mood, including low mood and depression.

In other words, the one thing that could explain the constellation of sleepiness, carb cravings and depression may not be sleep deprivation, but blood sugar imbalance.

However, could there be a link between blood sugar imbalance and poor sleep? The answer to that question in my view is an unequivocal ‘yes’.

One of the effects of low blood sugar is to cause the body to attempt to top up blood sugar levels internally, through the release of sugar from the liver. To do this, the body can ramp up activity in the so-called ‘sympathetic nervous system’, which plays an integral part in the stress response. The body can also release stress hormones such as adrenaline (epinephrine) that simulate sugar release too.

An activated stress response ain’t so good for sleep. At the very best it will impair the depth of sleep and our ability to feel truly rested. Worse than that, though, is its habit of waking people up at about 3.30 – 4.00 am and then not letting them get back to sleep again until about half an hour before their alarm goes off.

I’ve found in practice that rectifying blood sugar imbalance with a ‘primal’, relatively low-carb diet does wonders for improving energy and mood. And within a couple of weeks, it will have usually sorted out any craving for the carbohydrate-rich foods that usually are the cause of the problem in the first place.

9 Responses to Why sleepiness is not always caused by a lack of sleep

  1. Antje 24 June 2011 at 10:11 am #

    Dr Briffa, I am experimenting since 4 weeks with a primal diet. Try to survive on 100g carbs a day and still go to the sportschool 3 times a week.
    At times i feel i have very little energy, fysical strength. My moods though are getting stabilised.

    It takes quite some time for my body to adapt at my age (58, slim, fit) i suppose.

    My questions to you:

    What is in your opinion “relatively low carb”?

    If i eat low carb where does my brain get its glucose from?

    Thank you,

  2. blackdog 24 June 2011 at 1:19 pm #

    Antge, your brain and any glucose dependent organs get their glucose via a process called gluconeogenesis. This is where glucose is reformed from the building blocks within the body, to feed the brain when blood sugar is low, of stored fats and amino acids from protein. Thus you can live without carbohydrate, but not fats or protein.
    It’s quite complicated but is the process we all use to ‘smooth’ out our nutritional intake, unless of course we are a Type 2 Diabetic.
    As a low carber myself, I generally try to limit intake to 50 grammes but cerainly 100 grammes max. But, I try to ensure all of these are NOT from wheat or grains. My wife as a Diabetic usually trys to eliminate all carbs, but that is rarely possible so 20 grammes is about the usual load over two to three meals. Atkins suggests 20 grammes as the maximum in the first 2 weeks to stimulate ketogenesis which is the body using fat as its main source of energy.

  3. david manovitch 24 June 2011 at 5:40 pm #

    Low blood sugar, stimulates the CNS via the sympathetic nervous system and adrenaline release. It is activating and thus does not make people sleepy.(I would think again on this one Dr. B!) The biological purpose of this is to cause the animal to seek out food and to be vigilant regarding this goal.
    Low blood sugar does induce anxiety via the mechanisms mentioned above, and I suspect that chronic violent swings in blood glucose may well induce depression via the hormonal systems effect on the CNS.

    You are quite right to suggest that sleep deprivation is not the only cause of daytime sleepiness. Excessive cabohydrate consumption is a factor, particularly the polysaccharide type. Also adolescent depression is often associated with hypersomolence, and this phenomenon is found also in young adults, sometimes with increased appetite. So in this study, depression may have been the cause of the sleepiness, which may have been caused by a high sugar junk food diet amongst other things.

    Other causes are narcolepsy, sleep apnoea and serious organic illness, but these are not common, and the last two fortunately are rare in adolescence.

  4. Catherine Gladwin 25 June 2011 at 11:58 pm #

    David, actually in the case of hypoglycaemics (I’m one – and I’m a Nutrition Consultant) it’s true that low blood sugar does make one sleepy – brain dead and sleepy in extreme cases. I agree with Dr. B’s document. But the worst really is when the low blood sugar leads to eating carbs which within a short while results in a worse low and the only way to deal with it is to sleep. As a teenager it’s what I did most days after getting home from school until after a few years I decided it couldn’t be normal and investigated what it could be. It’s only your first paragraph that I mean to reply to – I fully agree with the rest of your interesting post!

  5. John Briffa 26 June 2011 at 12:28 am #

    David Manovitch

    You’re right about hypoglycaemic activating the stress response (though, if you read the post, I had already written about that).

    Re the sleepiness with hypoglycamia, this is actually very common in practice. If you treat patients (don’t know if you do), it’s worth looking out for and managing as it can make a big difference to people’s energy, wellbeing and mood.

  6. gregory barton 27 June 2011 at 6:13 am #

    I used to take a nap after lunch. After cutting carbs the postprandial drowsiness diminished to a few yawns. I would have thought that after lunch I would not have been hypoglycemic, rather, high in insulin.

  7. Penny Vinden 3 July 2011 at 11:23 am #

    I knew it! I’ve been found to have elevated fasting blood sugar levels in the morning (at the bottom edge of the type II diabetes level) – but no one has connected it with the fact that I also wake up early (after 5-6 hours sleep)with what is sort of like a hot flash/flush (but not really – I’m 58 and know what they are like!) and find it difficult to go back to sleep. Waking up with all engines revving and often being unable to get back to sleep leaves me chronically sleep-deprived, which by the sounds of it just exacerbates the problem. It sounds as if I need to go seriously low-carb. I find that salads a nd meat for lunch just don’t seem to get me through the afternoon…even with a handful of nuts to hold me over till dinner. Does anyone have a suggestion for lunches?

  8. Angelyne 14 September 2011 at 11:01 pm #

    Hi Dr Briffa,

    I’ve been listening to all your podcast, in a massive Dr Briffa podcast fest. Very much enjoying them.

    I’ve been trying to get my husband to eat low-carb for a while, and have started to see some degree of success. The one thing I can’t make him budge on, is his alcohol consumption. All I have managed to do is get him to drop beer. He still drinks wine and a few whiskeys in the evening. I don’t think he’s an alcoholic, just Scottish 🙂 He rarely drinks to excess, but strongly resist my suggestion that he only drink (moderately) on the weekends.

    Do you think this is a blood sugar issue ? He has all the classic symptoms of metabolic syndrome, the beer gut and the high blood pressure. I’m afraid that the drinking is damaging his liver and that it will sabotage his weight-loss. Considering his excess weight, he most certainly has a fatty liver.

    He also usually gets up at least once a night, so I’m wondering if the situation is due to blood sugar, as you described it in your podcast.

    Also, do you think it would be a good idea to make him take some milk thistle ?

  9. Lisa Thomas 27 October 2011 at 5:56 pm #

    Thanks a lot Dr Biffa, really appreciate your articles and support they give me.

    Do you think taking 5-HTP will have any bad effect on overall health as I continuously come across 5-HTP as good sleep aid, not sure if should be using it.

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