The Dietary Fat—Breast Cancer Hypothesis: Is It Really Alive?

To the Editor.—  The recent article by Schatzkin et al¹ presents the opinion that the relationship of dietary fat and breast cancer is direct and causal and can be quantitated. We wish to point out two major flaws in their presentation of data in that article that significantly weaken the position presented.In attempting to show that data from animal experiments support their view, Schatzkin et al state it is indisputable that animals fed a high-fat, high-energy diet ad libitum have a substantially higher incidence of mammary tumors than animals fed a low-fat, energy-restricted diet. Presenting the comparison this way obfuscates the proper question, which is whether the promoting effect of dietary fat on breast cancer is due to some innate quality of fat or to its higher energy content. Animal experiments clearly show that energy restriction significantly inhibits mammary cancer, even when dietary fat is three to five