Currently, most of Kellogg's cereals that are fortified with Vitamin D3 come from lanolin, which is found in sheep's wool and therefore not considered vegan.
The switch would 'extensively' expand the amount of vegan-friendly cereals available. However, some of Kellogg's products also use other animal ingredients such as gelatine - which has caused outrage on social media in the past.
An online petition created by Herbivore Club requesting Kellogg's to opt for a plant-derived source of Vitamin D3 has exceeded 500 signatures - with one supporter saying there is 'no need' to use lanolin.
An 'ever-growing vegan market'
Vegan charity Animal Aid, who has also pressured the company to ditch animal-derived Vitamin D3, said: "This simple swap does nothing to alter the taste or quality of the product, but it does open it up to a huge and ever-growing vegan market."
The company does, however, sell vegan products as part of its plant-based range W.K Kellogg's - all of which aren't fortified with Vitamin D.
"We recognize that consumers' tastes are changing and that people want more choice at breakfast, such as organic and vegan, so these are areas we will continue to explore," Kellogg's state on its website.
You can sign the petition here