Karen Reid, a nutritionist for the English Institute of Sport, answers the last set of questions on London Marathon preparation.

Charlie, 26, Bristol
Is eating during the marathon possible and is it recommended?

I often feel really hungry towards the end of a long run.

Karen says:
Eating during a marathon is certainly possible and provides a useful top-up on fuel towards the latter stages of the race.

Baked beans are also a good source of carbs

However, it may not suit all individuals to take solid food so I would emphasise that you must try this out beforehand during training.

The best choices might be jelly sweets, a white bread honey sandwich or scotch pancakes.

Naomi, 19, Bournemouth
I know that bananas are a really good energy source, but when I eat them I get stomach cramps.

Can you recommend an alternative for the Marathon?

Karen says:
Bananas can be a little slow to digest - especially if they are still fairly green and starchy.

Why not try scotch pancakes, jelly sweets, or a white bread honey sandwich.

Zac, 17, Scunthorpe
My girlfriend says that I should eat baked beans the night before the race. Is this a good idea?

Karen says:
Eating plenty of foods high in carbs the night before the race is most definitely a good plan to build up your glycogen reserves.

So pile on the pasta, rice potatoes, cous cous, bread, or noodles, with your meal. Baked beans are also a good source of carbs.

And so long as you feel comfortable eating them before a race - go ahead.

Just a word of caution though. They are very high in fibre and are filling and bulky and may cause a little flatulence!

Martha, 22, Kent
I keep hearing about electrolytes being good for distance running. What are they and where can I get them?!

Karen says:

I would suggest you include salty foods or add salt to your meals the night before the race

Electrolytes generally refer to the salts we lose in sweat.

The most important electrolyte which we need to replace is salt or sodium which is present in salty foods such as bacon, ham, cheese, tinned soups, as well as bread and cereals.

Adding extra salt to food when exercising in hot weather is a good idea for sports people to replace the higher losses they experience.

If the body's sodium levels become depleted muscle cramps, and, in extreme cases, a condition called hyponatraemia can develop which requires urgent medical attention to correct the body's salt balance.

Sports drinks contain some sodium and you can also purchase electrolyte replacement drinks such as dioralyte which you can add to water.

As far as the marathon is concerned I would suggest you include salty foods or add salt to your meals the night before the race, and use a sports drink during the race.

You may also wish to carry a sachet of dioralyte in case you experience cramps. If you do not use a sports drink, you can add a small pinch of salt to squash instead.

Winston, 22, Cornwall
It's my niece's birthday on Wednesday and we're taking her to a burger bar.

I'm running the Marathon on Sunday (aiming for a sub four-hour time) and have a strict diet in place.

But this night out might force me to break it! Is it okay to indulge in a burger and chips three days before the race?

Karen says:
Burger and chips is not an ideal choice for preparing for a marathon, although it has been known for athletes to have them as a well earned treat after an event.

McDonalds do a number of other healthier options such as chicken in a bun, bagels and salads - so I would recommend you choose one of those.

Or two chicken sandwiches would be a better option than burger and fries - they are lower in fat and provide a better balance of carbs to protein.

Milkshakes do provide a lot of useful carbs - approximately 90gms in a large serving - so you could indulge in one of those as part of your carbo-loading strategy.