It’s the first thing we reach for in the fridge when we stumble into the kitchen for a morning cuppa.

Most of us probably won’t give it a second thought – but the colour of the plastic cap on your milk bottle could make a big difference to your health. And it’s not what you might think…

[Read more: The surprising health benefits of goat’s milk]

Whole milk vs skimmed

Research from America found that people who drink whole milk (with the blue lid) have a lower risk of diabetes than those who don’t.

The 15-year-long study by Tufts University looked at 3,333 people aged between 30 and 75. The researchers found that people with high levels of three different by-products of full-fat dairy in their bodies had a 46% lower risk of diabetes mellitus than those who had low levels of dairy fat.

Dr Dariush Mozaffarian, whose findings were published in the journal Circulation, told Time:  “I think these findings, together with those from other studies do call for a change in the policy of recommending only low-fat dairy products. There is no prospective human evidence that people who eat low-fat dairy do better than people who eat whole-fat dairy.”

[Read more: 13 things you didn’t know about diabetes]

A big fat surprise

In recent years, we’ve all been led to believe we should cut down on fat to reduce our calorie intakes (and waistlines), but studies have found that when we cut out fat from our diet, we tend to bulk up on other calorific foods, including carbs and sugar, which can give us a much higher risk of diabetes in the long run.

In another study, published in the American Journal of Clinical Nutrition, researchers looked at the link between full and low-fat dairy and obesity in women. They found, strangely, that those who ate the most high-fat dairy products actually lowered their risk of being obese or overweight by 8%.

[Read more: 5 reasons why World Milk Day is good for your health]

Isn’t semi-skimmed OK?

Current health guidelines recommend children from the age of one drink whole milk and, over the age of two, gradually move to semi-skimmed milk as a drink to cut down on saturated fat, as long as they’re eating a balanced diet and growing well.

But although it’s lower in fat and calories, semi-skimmed milk also has lower levels of fat-soluble vitamins, including A and E, than whole milk, so children and grown-ups might be missing out on nutrition by optiNew advice says whole milk might be better for us than skimmed – we asked the experts to find out.ng for the green-topped milk.

Dr Mozaffarian says: “We should be telling people to eat a variety of dairy and remove the recommendation about fat content.”