I can eat cheese like it's going out of fashion - whereas one of my pals can't even look at a cheese triangle without getting gassy!
The reason for these different reactions to dairy products is predominantly genetic, and is a good example of how genetic variations can affect the way we process different foods.
What happens if I am lactose intolerant?
Dairy products contain a naturally occurring sugar called lactose, which is broken down in the body by an enzyme called lactase. Due to the wonderment of nature that is the human body, there is a specific gene that is encoded to produce this lactase enzyme.
NOT so clever however, is the fact that some people have a variant of this gene that doesn’t produce enough of the necessary enzyme and so they can’t effectively digest the lactose in dairy products like milk and cheese.
For these people, lactose passes through the intestines undigested. When this occurs, gut bacteria in the intestines ferment the undigested lactose, which produces gas. It is this gas that leads to the bloating, discomfort and sometimes diarrhea associated with lactose intolerance.
Luckily for me (as I have a soft spot for cheese…), I have what is known as the TT genotype which produces plenty of lactose digesting lactase. My friend has the CC genotype which is the variant that produces the least lactase, hence her issues with dairy.
Sometimes you can ‘train’ your body to produce more lactase by gradually introducing lactose into your diet. Also fermented dairy products like kefir or yoghurt tend to be better tolerated by those with lactose intolerance as they contain much lower levels of lactose.
Unsurprisingly, research shows that those who avoid dairy products are at greater risk of inadequate calcium and vitamin D intake than those who can tolerate dairy products. If you follow a dairy free diet, you can still get enough calcium and vitamin D from the diet through fortified milk alternatives (check the labels) or small oily fish (with their skeletons intact) like sardines (try tinned sardines mashed up on toast) and whitebait.