The benchmark carbohydrate consumption for a marathon distance race is anywhere between 30 and 60g of carbohydrate per hour, plus at least 250ml of fluids per 15 minutes. This can be achieved using 1 L of sports drink per hour (without gel) or 500ml of sports drink plus 500ml of water with 1 - 2 gels per hour.

You don't necessarily need to eat anything else (as in solid food) and need not have any food before the race either. If you want to try going without breakfast, just replace it with sports drink. To give you an idea of quantities, 500ml of sports drink equates to two slices of toast or a bowl of cereal. As long as you are taking in the right amount of fluid and carbohydrate, and have eaten well in the days leading up to a race, you don't HAVE to eat if your gut is more suited to the fluid and gel combination. Some people do find they get hungry if they do not eat, but for others this is not an issue in a race.  

'Runners trots' especially during intensive exercise sessions is not uncommon, so don't feel you are the only one. It can be caused at high intensity by your gut's nervous system reacting to lactate, and this can occur if you are moving to higher intensity. If this is the cause then you will adapt with time and without dietary modification.

Alternately, you may suffer from osmotic type diarrhoea, which means the fluid balance between your gut and bloodstream is out of balance, resulting in fluid being drawn back into the gut. This can be overcome by:

1. Making sure you are well hydrated before running and even sipping on diluted sports drink before running

2. Using water as main fluid with just a touch of sports drink, until you body can cope with more. Start with 50ml of dilute sports drink and 150ml of water instead of 200ml of 50% sports drink.

3. Avoid sports drinks that are high in fructose, opt for those containing sucrose or glucose as fructose can exacerbate diarrhoea, as does fruit juice or fruit.

If it is diet related, it may be less a result of what you eat immediately before training and more a general condition. Do you experience any diarrhoea / constipation at other times? If you do suffer from irritable bowel type symptoms, this can be exacerbated in training. You would need the assistance of an Accredited Practicing Dietitian to get you on track if this is the case.

Yes, to a large extent a high carbohydrate evening meal does help, as your glycogen stores will be fairly well stocked up in muscles and liver, and without burning much carbohydrate overnight, this will help the following morning.

Regarding protein after a hard training session or race, it is mainly carbohydrate ingestion immediately after exercise that refuels muscles and feeds the immune system (they call this period the glycogen window - as in window of opportunity to replenish stores), but the next full meal (say within 2 hours) should contain a combination of carbohydrate and protein.

The amount of protein at this time should probably be about 30 - 40% of you total daily protein intake (from lean meat or equiv. or dairy). If you need exact figures we are aiming for 0.3 to 0.4 grams of protein per kilogram of your body weight at that meal. Most meats contain about 20 grams of protein per 100g.

Carrying even 1kg less over 42.2 kilometres helps, so if you have the capacity to reduce weight slightly in the month before, it will help, as long as you are not compromising your nutrition status. With 8 weeks to go, you could probably aim for six or seven weeks of lighter eating and then one week 'normal' before the event. Start by cutting back about 20% on portion size of protein serves and carbohydratess at each meal.

Yes, I know that feeling too! It may be associated with lactic acid accumulation and/or the fact that during extreme exertion the blood supply to the stomach area is basically shut down as blood flow is diverted to major muscle groups.

Unfortunately, I do not know of a simple solution, but do know that regular sessions (at least once weekly) where you get above threshold do help your tolerance for this type of running, and hence symptoms gradually ease. The only reason this symptom is not more common is probably that many runners do not push to that point!

A couple of things that the symptoms could relate to include:

1. Low blood glucose - your body may not be yet adjusting well to pumping out more glucose to fuel the higher intensity exercise. Try to arrange a blood glucose test (maybe at a local pharmacy). If you reading is under 4mmol/L, it may be contributing. In this case you need to have some sports drink immediately post exercise. As your fitness and exercise tolerance increase, the symptoms should resolve. If not, seek further medical tests on blood glucose and insulin levels in the blood.

2. Other possible causes maybe low blood pressure after exertion, especially if you are dehydrated and blood volume decreases. Again, check this out by having a doctor or nurse or trainer test BP immediately post exercise and follow up with doctor if required.

3. It may be related to iron status, have you had iron studies done to exclude this as a cause? If not, get some blood tests completed and ensure that you obtain a copy of the results so that you have a reference point. If you are low in iron, or any other vitamins or minerals, make an appointment with a sports dietitian for some nutrition advice, or contact me for an on-line nutrition assessment.

My view is that the cramps are caused by changing the fluid balance of the gut by having a hit of carbohydrate once the body is mildly dehydrated, so from that stance they would all react the same. However, I think that any sports drinks or gels that contain more fructose than glucose can affect some people with bloating and cramp. Other ingredients that vary between gels include:

Sodium content - will determine the ability to retain fluid in the body, so if you sweat profusely the higher sodium brand would be better.

Carbohydrate content and type - remember you are aiming for about 40 - 50 grams of carbohydrate per hour of a race, so that equates to about 2 regular sized gels. Most gels contain glucose polymers that are gradually absorbed. If you suffer from any form of irritable bowel condition, be wary of gels that contain fructose or high fructose corn syrup. These could potentially cause gut pain and osmotic diarrhoea, yuck!

Caffeine  - is useful late in a run/race to promote fat utilisation as a fuel. Again, this is specific to race conditions rather than training.

You definitely need to be well hydrated or drink water when you have a gel. If not, you will get bad cramps or abdominal pain. Usually people suck on the gel tube then drink water. For 20 grams of carbohydrate you need around 300ml of water.

You only need to use gels in training in the few weeks or month before your major race unless you are training over very long duration (2.5 to 3 hours). Recent sports nutrition evidence suggests that runners "train low, race high" when it comes to carbohydrate. That means you should train on water alone for runs of up to 2 hours, or longer if you have sufficiently adapted. Only introduce carbohydrate in the form of gels or sports drinks when you find that it is affecting training performance substantially.

You can "train" your body to adapt to lower carbohydrate ingestion and to switch to a fat burning metabolism quite effectively. However, if you have been relying on carbohydrate in training, it will take some time to get used to training without them. Gradually decrease the amount used and the frequency of use until you are just using them when absolutely necessary.

Sports drinks are useful in that unlike the gels and water, the ratio of fluid and carbohydrate is pre-determined and they also contain a good balance of electrolytes. Brand really depends on personal preference. I suggest one that is most palatable to you. Again, only use these sparingly in training and to 'practice' for races, not extensively during training.

As a rule of thumb, you need to drink water during any run over one hour and most runs that are over 2 hours. Some people use gels for all runs, even those under an hour. This is unnecessary and in fact can be detrimental in that it does not allow your body to practice using fats as a fuel, a factor that can become vital during a marathon.

I suggest consuming about 500 ml of water per hour in training for runs over an hour and about 20 - 30 grams of carbohydrate (gel or other) for runs over two hours - if needed. That is, if you find that you are unable to maintain your estimated run duration or intensity, you may need some carbohydrate or extra fluid (more likely). If you run on fine over longer runs with supplements, then only use them when you need to practice race conditions in the final few weeks before your major event. 

Also, bear in mind that your nutrition needs for training vary from session to session depending on the goal of the session. For example, for a high intensity interval type session, being well hydrated in advance (say 2 litres in previous 24 hours, plus adequate carbohydrate (5 grams per kilo of bodyweight per day) are vital as it is hard to complete this type of session without adequate fuel and fluid, and it is hard to replace once the session has commenced.  For longer runs with a goal of aerobic conditioning and fat burning adaptation, it may be desirable to become carb depleted for adaptation purposes (as described above).