What is the fine-grained topic of the following text: If you're concerned about skin cancer or have a deficiency in spite of spending lots of time outside, consider taking a supplement containing at least 2,000 IU of vitamin D. Foods fortified with vitamin D, milk, animal organs such as liver, and fish oil are all high in vitamin D. Only return the topic.
Supplementing Vitamin D for Skin Cancer Prevention and Deficiency Treatment