in the first place

Explanation: This is correct because “stop you getting it in the first place” echoes the speaker’s earlier statement about “preventing you getting” a disease. Also, the conjunction “whereas” signals a contrast between the first and second half of the sentence. The first half of the sentence talks about using antioxidants after one has the disease, whereas the second half of the sentence talks about using antioxidants before one gets the disease.

Transcript

Robyn Guymer:

My PhD student, Elaine Chong, did what was called a meta-analysis where you analyze the literature very carefully, to see what evidence there is to suggest that what we eat, particularly in terms of antioxidants, prevents you getting macular degeneration.

Norman Swan: Because ophthalmologists have been using antioxidants quite a lot.

Robyn Guymer: That's right. There have been studies looking at whether antioxidant supplements slow the progression once you have the disease, whereas this study was looking at trying to stop you getting it (in the first place).