The vitamin D listed on the box of your favourite breakfast cereal may actually be disguising a surprising ingredient – sheep’s wool grease.

This grease, known as lanolin, is secreted by woolly animals such as sheep.

Vitamin D is commonly sourced from lanolin, which is extracted from sheep wool and treated before being used in numerous food products. It does not harm the animal.

These include breakfast cereals such as Special K and Milo, as well as infant formula, margarine, milk, cheese and yoghurt.

In fact, it is mandatory for all margarine spreads to add vitamin D for public health reasons, according to Food Standards Australia NZ.

Vitamin D can be derived from either plants or animals, but the packaging of most products does not make the source of these vitamins readily obvious to consumers.

While lanolin might sound off-putting, there is actually a good reason it is in the food we eat.

Why is lanolin in our food?

Nicole Dynan, a dietitian at The Good Nutrition Company, said manufacturers often add vitamins and minerals to products to help us reach our recommended daily intake.

For Vitamin D, it is advised that adults consume 5 to 10 micrograms every day. The actual average intake is about 2 to 3 micrograms.

It may come as a surprise that vitamin D in certain cereals is made from sheep’s wool grease. Photo: Getty

“Very few foods contain significant amounts of vitamin D,” she said.

“Deficiency of vitamin D results in poor bone health and can lead to rickets in young children, causing bowed legs and knock knees and fracture risk in adults.

“Sheep grease, or lanolin, can be a convenient and cost-effective way for manufacturers to obtain vitamin D for product fortification.”

The major function of vitamin D in the body is to help absorb calcium from our diet and keep bones healthy, she said.

This comes both from sun exposure and a limited range of foods such as eggs and fatty fish such as salmon, herring and mackerel. Some mushrooms are also grown in ways that boost their vitamin D content.

Do we need vitamin D added to foods?

The Cancer Council of Australia’s advice is that “regular, incidental” sun exposure is the best source of vitamin D – although also the major cause of skin cancer.

Adding vitamins to food such as cereal helps boost our nutritional intake without risking skin cancer.

Molecular biologist Rebecca LeBard of UNSW said that growing awareness of the dangers of sun damage and tanning has meant that Australians avoid being out in the sun, making low levels of vitamin D an “increasing problem”.

“Consequently, there is an argument for fortifying foods that have a reach across the population, such as cereals,” she said.

The New Daily contacted several companies and manufacturers of products containing vitamin D.

Nestlé confirmed its Milo cereal contained vitamin D sourced from lanolin and Kellogg’s Derek Lau also said some of its Special K products contain vitamin D.

He added that the use of lanolin does not harm the sheep as it comes from the wool as opposed to the animal itself.

Special K Original, Nourish, Oats and Honey, Fruit and Nut, Forest Berries and High Fibre each has vitamin D listed in their ingredients.

The a2 Milk Company said the vitamin D in its infant formula is derived from sheep’s wool lanolin, while Blackmores said its product range generally uses vitamin D primarily derived from lanolin.

Alternatives for vegans

Vegan Australia’s Greg McFarlane advised that vegans or anyone concerned about lanolin should check the labels of any foods containing vitamin D carefully. He said there are vegan alternatives available.

Australia is the third-largest vegan market in the world, according to market research company Euromonitor International.

“Check the labelling and if there is no information, contact the company directly to see where it’s sourced from,” Mr McFarlane said.