Gemma, 26, was suffering from extreme headaches. She had a range of really expensive tests, took loads of pain medication and even got glasses. “I tried everything to make them go away but nothing worked,” she says. “I was in so much pain, it was really debilitating.”
It wasn’t until Gemma saw a nutritionist and gave up caffeine that she noticed a dramatic difference.
"It's always been underestimated just how much food has an influence on health," says GP Dr Hilary Jones.
There's a big difference between having a food intolerance and being allergic to certain foods.
Food allergies affect the body's immune system and, in some situations, can be life-threatening. Food intolerances tend to cause more everyday health problems such as fluid retention, nausea, IBS and migraines.
"When you think of the full range of foods we eat today, with their chemical content and potential to react in our system and cause symptoms, the variety of health-related problems is enormous," says Dr Jones.
A common problem
Certain foods have long been known to cause discomfort. Many people are intolerant to substances such as lactose, while others are allergic to peanuts and cereals containing gluten.
Reasons vary and depend entirely on the person and their genetic make-up - meaning that diagnosis and treatment can be very difficult indeed, according to Lindsey McManus of Allergy UK.
"The variation in the cause of food intolerance from person to person means that there is no one test to identify all types of food intolerance, however there are now tests available on the market that may help identify some of the major causes of symptoms.
While food intolerances can be comparatively easy to live with, allergies are a major problem.
Being allergic to nuts or shellfish can result in an instantaneous and severe reaction. Sufferers can break into a rash, have difficulty breathing, experience swelling of the tongue - and in some cases need to be rushed to hospital.
But symptoms of food intolerances tend to be less specific, obvious and severe.
"As opposed to severe symptoms like respiratory distress, one could suffer from headache, aching joints, bloating, irritable bowel or sinusitis - all fairly non-specific symptoms," explains Dr Jones.
Migraines are one of the most debilitating problems, she adds, as they cause acute headaches, vomiting and visual disturbances.
Director Lee Tomkins of charity Migraine Action says: "We know from our own members that diet and certain foods can be a factor in triggering attacks and exacerbating symptoms for many."
Look at what you eat
Food intolerance sufferers often react to more than one food, which means that identifying the foods which cause the problem can be a long process.
"Symptoms can also take several days to develop, which can make it very difficult to identify the culprit food," says Dr Jones.
Traditionally, sufferers keep a food diary to note every food and drink they consume and how it makes them feel. An expert then assesses the diary according to when symptoms were present in order to establish a pattern.
Also, home IgG (Immunoglobulin G) tests are now available to those on the hunt for an answer to their health woes.
Blood samples taken from finger-prick tests can be sent away and the IgG antibodies analysed against 113 different food antigens.
The results are then used to establish which foods are causing the problems and should be avoided.
However, there is no firm scientific evidence to support the role of IgG testing in the diagnosis of food intolerances.
Registered dietician Gail Pollard, a specialist on allergies, says if there was one foolproof test available she would use it.
"It would be ideal if we had one, but we don't. The gold-standard for diagnosing food intolerances is a good medical history, a good diet history and any dietary elimination of some description and then reintroduction."
Pollard explains that the process of reintroducing food is very important.
"A lot of these alternative tests do not specify that. They unfortunately give the impression that you are intolerant or allergic to these foods and advise generally stopping them, but they don't advise adequately on trial test reintroducing.
So people go away often from a health food shop having some test done, under the impression they are so-called allergic."
She adds: "I had somebody yesterday who'd been told she was allergic to eggs and bananas and had been off them for the past couple of years without any adequate reason, so it needs to be properly monitored by experienced dieticians."
Advice for those worried about having an intolerance
"They need to ensure that there is nothing else that is an issue," says Pollard. “You could miss some other medical diagnosis such as coeliac disease for example."
"Often when people come off wheat as a result of doing a home test, for example, they're better and then they're poorly when they go back on the wheat, so they don't want to eat it again. But that means they can't be tested for coeliac disease and that can be very serious."
Find out more
Recipes, tips on shopping and common pitfalls to avoid can all be found at the website Food Intolerance Awareness, which also has lots of information about common food intolerances and their effect on the body.
With greater awareness about these intolerances, more people should start to feel in better health - even if they have to seek it out for themselves.
"For years the orthodox medical profession has neglected the role of food intolerance in ill health," says Dr Jones.
"If you took your dog or cat to the veterinarian with strange symptoms, one of the first things the vet would ask you is, 'What are you feeding your animal?' Very rarely does a doctor ask a patient with unexplained symptoms what they're eating."
If your doctor doesn't ask you, maybe now's the time to ask yourself.
By Kate Hodal
Find out more on What’s Good For You on LifeStyle YOU.