What food item has been linked to acne through population studies?

Dairy has been linked to acne through various population studies, which suggest that the consumption of dairy products may increase the likelihood of developing acne. Research has indicated that dairy can promote the production of insulin-like growth factor 1 (IGF-1), a hormone that is associated with increased sebum production and the development of acne lesions. Additionally, the presence of hormones in milk, even in small quantities, may also contribute to this effect, especially in those who are more sensitive to these dietary components.

In contrast, foods such as spinach, quinoa, and rice have not been shown to have the same association with acne in the scientific literature. These foods are generally considered to be nutritious and may not influence skin health in a negative manner like dairy does in certain individuals. Therefore, the evidence supporting a connection between dairy consumption and acne makes it the correct answer in the context of this question.