Zoe Bastion is an assistant content producer at the BBC. She has had primary lactose intolerance formost of her life.
"I can't digest any dairy products at all, and have had problems with them most of my life. When I eat dairy food I suffer from diarrhoea, usually within a few hours. I avoid milk in coffee and don't eat yoghurt or hard cheese either. Soft cheese affects me really badly, as does any milk at all. If I eat a lot of cheese I get very bad stomach cramps, which unfortunately don't make it any easier to give up: cheese is one of my favourite foods. Every now and then I'm tempted to eat an enormous pizza and always suffer the consequences.
"I wasn't diagnosed until I was about 26. I had realised something was up for years, but didn't really think about it. Even as a child I'd get wind within a few minutes of eating blue cheese, and would get a tickly cough every time I had hot milk at night. I never liked custard made with milk I always had the water-based one.
"When my doctor told me what it was, it took me about a year to give up milk and dairy properly. Cheese, chocolate milk, bread, potatoes and bananas were my staple diet. I went to see a nutritionist when my doctor told me to cut out dairy foods because, as a vegetarian, I wasn't sure what was left for me to eat. I didn't want to start eating meat and fish again, but Iwould have done if I thought my health would suffer.
"Following my nutritionist's advice, I have been eating a healthy, balanced diet ever since. I eat lots of beans, pulses, tofu, vegetables, fruit, Marmite and soya milk, which is enriched with calcium and B12. I'm a good cook because I've had to experiment, so I don't get bored with my food. I have a packed lunch most days, although the canteenat workis enormous and there's always a lot of choice for vegans.
"Eating out is easy, especially in London. I love Thai, Chinese and Indian food. And if you do go anywhere that doesn't cater for veggies or vegans, there's always chips!"
Lactose intolerance is a common digestive problem where the body is unable to digest lactose, a type of sugar mainly found in milk and dairy products.
Lactose intolerance is usually caused by your body not producing enough lactase - an enzyme (protein that causes a chemical reaction to occur) that digests lactose.
It's important to visit your GP if you think you or your child may have lactose intolerance, as the symptoms can be similar to other conditions.
There's no cure for lactose intolerance, but most people are able to control their symptoms by making changes to their diet.
Zoe Bastion is an assistant content producer at the BBC. She has had primary lactose intolerance for most of her life.
Gary Alexander is a writer and author who lives in London. He suffered from secondary lactose intolerance for several months after a severe bout of gastroenteritis.