Is there a problem in owning stock in a company that sells non-kosher food (i.e. Sara Lee inc.)?
According to many authorities, it is permitted to own stock in companies that sell non-kosher food.
Rav Yitzchak Isaav Ha-Levi Ittinger (Shut Maharia Vol. 2, sec. 54, 124), a prominent nineteenth century halachic authority, rules that shareholding does not constitute halachic ownership, which relieves any concern over a prohibition. See Shut Cheishev Ha’ephod (Vol. 1, sec. 62), who writes that the Rov of Tchebin also cited this ruling, and see also Shut Maharam Shik (sec. 158) and Shut Melamed Leho’il (91).
According to the Igros Moshe, it is permitted to own stock in the company provided that the said ownership will not bequeath the shareholder significant decision-making power in company affairs. It is worthy to be stringent for this opinion.
Some are more stringent in this matter (see Minchas Yitzchak 3:1), but one can certainly rely on the lenient authorities.
For a lengthy appraisal of the matter, please see our article on the subject here.
Best wishes and kind regards.