Karen Reid, a nutritionist for the English Institute of Sport, answers your latest questions about preparing for the London Marathon.

Karen will be answering your questions every week in the build-up to the race, so keep them coming!

Graeme, 34
What is the best way to avoid hitting the wall and what carbs should I eat during the race? I was thinking of some type of dried fruit.

Karen says:
Topping up with carbs in a liquid form such as a sports drink is the most convenient form and delivers fluid and electrolytes at the same time.

Additional carbs in a compact form can be taken such as jelly sweets, dolly mixtures or glucose tablets - these are easy to carry, readily digested and absorbed quickly. Best to start taking carbs early in the race and top up little and often to spare muscle glycogen and avoid the decline in blood sugar levels.

Spencer, 31, Faversham
The training is going well but I'm not sure what food I should be avoiding and what I should be eating a lot of? Could you help? Thanks!

Karen says:
Generally, increasing carbs to support the higher training volumes and ensure good recovery is most critical. Sometimes it can be difficult for people to eat enough starchy carbs, as these are more bulky and filling - so increasing sugary foods and drinks which supply "quick carbs" in a more compact form can be really useful addition to a runner's diet.

So extra carbs (both starchy and compact sugary carbs) added into a balanced diet (2-3 servings of protein, 5 or more servings of fruit and veg, and 2-3 servings of dairy foods) is the way forward. Controlling intake of fatty foods can be helpful if you need to reduce body fat.

Steve, 32 Cork
Is it ok to run a marathon if you are a vegetarian? What's the best way for a veggie to eat for the marathon?

Karen says:
It is perfectly okay for you to run a marathon and in fact a number of elite athletes are vegetarian.

Just ensure that you include a good quality protein food at each meal along with your carbs to ensure muscle repair and regeneration after training. Also, plenty of foods which are a good source of iron, such as eggs, fortified breakfast cereals, dark green vegetables and wheatgerm each day.

Julian, 35, London
I'm training for an Ultra Marathon, 56 miles, and anticipate that it will take 10 hours to complete. I usually eat pasta the day before, and porridge on the morning of standard marathons, but expect ultra marathons to be a bit different - are they?

Karen says:
They certainly are and you will obviously be running for a much longer duration, and require a lot more fuel than a standard marathon demands. The ability to take on board fluids and food during these longer races is critical to delaying fatigue. Practise eating light snacks such as sandwiches, cereal bars, cake, dried fruit, and jelly sweets during training.