Dr. Budwig developed the diet based on the hypothesis that cancer is caused by reduced uptake of oxygen by cell membranes in the absence of omega-3 fatty acids (O3FAs) such as linolenic acid ⁽⁷⁾. While metabolic changes such as increased aerobic glycolysis and fatty acid synthesis occur in cancerous cells, ⁽⁸⁾ the role of O3FAs in the pathogenesis or cancer treatment is still under investigation ⁽²⁾. Polyunsaturated O3FAs in flaxseed oil have been shown to decrease levels of proinflammatory cytokines, TNF-alpha, and IL-1 beta ⁽⁹⁾. O3FAs also demonstrated antineoplastic properties by increasing intracellular ROS and decreasing protumorigenic prostaglandins ⁽²⁾. Flax oil supplements increased total phospholipid fatty acid content in erythrocytes  ⁽¹⁰⁾, but the implication of this finding in cancer treatment is unknown. Flaxseed supplements also inhibited in vitro proliferation of human prostate ⁽¹¹⁾ and breast cancer growth by downregulating growth factors and increasing p53 expression ⁽¹²⁾. Whole flaxseed contains lignans, phytoestrogens that may also have antineoplastic properties and exert hormonal effects ⁽¹³⁾.

Budwig believed that combining cottage cheese and flaxseed oil improved availability of essential fatty acids through the plasma membrane, thereby improving aerobic cellular respiration ⁽¹⁾. The effect of cottage cheese consumption on the bioavailability of O3FAs has not been studied. Processed fats, saturated fats, animal fats, processed foods, and sugar are prohibited in the Budwig diet because they are thought to interfere with oxygen uptake and cellular respiration. Epidemiological studies show that people who consume lactovegetarian diets have lower incidence of gastrointestinal cancer compared with non-vegetarians ^(14) (15), although these studies indicate association rather than causation.

Greater tumor regression was reported in mice treated with trastuzumab therapy plus flax oil compared with those treated with trastuzumab alone ⁽¹⁶⁾.