A Low Carb Diet Improves Brain Power

The link between carbohydrate intake and poorer performance

I don’t shoot many target tournaments these days (I prefer the other disciplines). Normally just my own club’s indoor and outdoor championships. But in an attempt to entice more of my local club’s archers to shoot target tournaments, I recently allowed myself to be coerced into going with them. It was an education in more ways than one.

As someone who is interested in sports nutrition, I have this tendency to wander around at lunchtime and see what archers are eating and drinking. I also note what sorts of things they eat and drink intermittently during the tournament. What I saw has prompted me to write this article.

In my article on breakfasts (The Glade, Summer 1999), I compared high-carbohydrate breakfasts – cereal, toast and marmalade – with the English cooked breakfast, which is high in protein and fat, to show that cooked breakfasts were far better for archers’ and other athletes’ performance. For those who missed the article, in it I showed how high-carbohydrate breakfasts increased insulin output and lowered blood glucose levels thus reducing the amount of energy available; and how high-protein breakfasts on the other hand, tended to keep blood glucose levels high all through the day, allowing more energy for archers, thus increasing their stamina. I recommended that archers should start the day, just as I would recommend everyone should start the day, with a cooked breakfast.

But there is another reason why low-carbohydrate meals, not just for breakfast but throughout the day, are better for both archers and others.

The food you eat has a wide range of effects on your body systems. So it seems logical to assume that diet may affect the brain and, in turn, behavior and emotions. There is evidence that food can affect brain chemistry. Carbohydrates are generally thought of as being good sources of energy (despite the fact that, weight for weight, they contain the least amount of energy). As all carbohydrates – sugars and starches – are converted immediately into glucose which the body can use for energy, eating them looks like a good idea. It is probably the reason that athletes are told by their coaches and dieticians that it is a good idea for them drink a goodly supply of carbohydrate rich, sugary drinks throughout a tournament. Food and drinks manufacturers, always ready to make a swift buck, have seen this as an opportunity to provide a range of what are laughingly called “isotonic drinks”. These are little more than sugared water which do nothing for performance (although they do wonders for the manufacturers’ profits). And while these do raise blood glucose levels in the short-term they are not a good idea as they have subtle, but nonetheless important, adverse effects.

What are the effects?

Are you feeling tired or depressed? You’ve all seen the adverts on TV for pick-me-ups perhaps in the late afternoon: eat a biscuit, chocolate bar or other source of sugar. These adverts rely on people’s belief that a resulting increase in blood glucose levels will give you a mental boost, that it will make you feel good and make you more alert. Unfortunately, that doesn’t seem to be the case.

There have been many studies of the effects of these different meal patterns and different foods. Some tested and measured subjective things such as fatigue, vigour, anger, hostility, confusion, anxiety and depression. In all of these tests, those who ate carbohydrate meals reported worse scores in all classes except anxiety, where there was no difference. In other, objective tests of alertness, auditory and visual reaction times, and vigilance, carbohydrate eaters again came off worse.

There is certainly evidence that the taking of sugar or other carbohydrate foods has the ability to improve your mood. The role that glucose is known to play in supplying the cells of the body with energy, has led to the assumption that an enhanced supply of metabolic energy is associated with feeling subjectively more alert and energetic. But in fact, much of the evidence is that consuming carbohydrate has a hypnotic effect. In other words, it makes you feel good by making you more relaxed and sleepy, rather than more alert. This is the reason why many dieticians recommend a carbohydrate meal in the evening – it helps you sleep.

Which is the last thing you need if you are driving, trying to get a job done efficiently, or taking part in a tournament.

Serotonin and tryptophan

To understand why this happens, you need to know a bit about how the brain works.

The brain is a vast network of nerves among which messages are sent. The biochemical messengers – chemicals involved in the transmission of nerve impulses between nerve cells of the brain – are called neurotransmitters. There are about forty of them. Among these is one called serotonin, which plays a crucial role in controlling states of consciousness and mood, particularly promoting sleepiness and relaxation.

The body manufactures these neurotransmitters from amino acids it gets from the food we eat. Amino acids are the building blocks of proteins. Tryptophan, an amino acid found in protein derived from meat, milk and eggs, is the precursor of serotonin. Serotonin levels in the brain are increased by eating pure tryptophan. However, when a protein meal is eaten, tryptophan must compete with all other amino acids for entry into the brain. But tryptophan is relatively scarce in protein foods in comparison with other amino acids. As a result only a small amount makes it into the brain to be converted into serotonin.

Carbohydrates

Carbohydrates don’t contain any tryptophan. You might assume, therefore, that eating sugar will have no effect on serotonin production. In fact the opposite is true. Meals rich in carbohydrates and low in protein, increase serotonin levels.

After consumption of a carbohydrate-rich meal, the insulin secreted, as well as storing excess blood glucose away as fat, also facilitates the passage of most amino acids into muscles, which causes a lowering of blood levels of those amino acids. But as it doesn’t have this effect on tryptophan, this process increases the ratio of tryptophan to the other amino acids. When there is high blood tryptophan in relation to other amino acids, that tryptophan is released, enters the brain at a rapid rate and converted to serotonin.

A review of research results indicates that people become tired not long after a carbohydrate rich meal (remember the Chinese meal syndrome – where an hour after having one you feel like another?), which is what you would expect if carbohydrates do in fact increase brain serotonin. What has confused researchers is that obese, premenstrual and depressed subjects usually report a temporary lifting of mood and reduction in depression after a carbohydrate-rich meal. Researchers are still not sure if this is because serotonin levels do not increase under these conditions or if serotonin is released but some factor in these three cases causes the serotonin to be mood elevating rather than relaxing.

I came across these suggestions from a nutritionist on raising serotonin levels with foods:

If you are having trouble falling asleep, try a small snack of carbohydrate rich food. Warm milk may work for the psychological comfort, but also because milk contains a moderate amount of carbohydrate in the form of lactose (milk sugar).

If you tend to have only carbohydrate (i.e. plain bagel) before class and you often fall asleep during class, try adding some protein by putting some hard cheese (cheddar, American, Swiss, etc.) or peanut butter on the bagel. Or have a yogurt or cottage cheese instead.

These suggestions are good advice for those conditions. Serotonin is a relaxant, it helps you sleep. So carbohydrate is the last thing you should eat if you have a job to be done, a class to attend (let’s face it, some of those are sleep-making enough without adding serotonin), or a target to hit 150 times (I’ve included sighters).

What it all boils down to is that carbohydrate meals have exactly the opposite effect from what you might expect. Carbohydrate meals make you relaxed, sleepy and slow your reaction times; protein meals make you feel awake, alert and quick-thinking – the qualities archers and other athletes need. So, if you want to win, stay off the sweets, sweet drinks, cereal breakfasts and make sure that your sandwiches at lunchtime are stuffed with cheese, meat, egg or fish.

Last updated 2 June 2003