Decreased severity of ovarian cancer and increased survival in hens fed a flaxseed-enriched diet for 1 year

Abstract

Objective: With the exception of the laying hen, no other animal model of spontaneous ovarian surface epithelial cancer replicates the human disease. Flaxseed is the richest vegetable source of omega-3 fatty acids, which are chemopreventive in breast cancer and may be important in other cancers. The objective of this study was to determine if a flaxseed-enriched diet had a chemopreventive effect on ovarian cancer in the laying hen.

Methods: White Leghorn hens were fed with 10% flaxseed-enriched or standard diet for 1 year. The incidence and severity of ovarian cancer were determined by gross pathology and histology in the two groups. General health markers were also measured. Eggs were collected and analyzed by gas chromatography to determine omega-3 fatty acid levels.

Results: A significant reduction in late stage ovarian tumors was detected in the flaxseed-fed hens. Incidence rates of ovarian cancer were not significantly different between the two groups. The results indicate that a flaxseed diet increases overall survival in the laying hen. Flaxseed-fed hens' eggs incorporated significantly more omega-3 fatty acids compared to control hens.

Conclusions: These findings show that 10% flaxseed supplementation for 1 year in the laying hen results in a significant reduction in the severity of ovarian cancer, but no change in the incidence of the disease. Hens fed flaxseed had overall better health and reduced mortality. These findings may provide the basis for a clinical trial that evaluates the efficacy of flaxseed as a chemosuppressant of ovarian cancer in women.

Figure 1

Flaxseed fed hens lay eggs with higher OM-3FA content. Eggs were collected from control and flaxseed fed hens at time of necropsy after 12 months on the diet. There was no difference in the number of eggs laid between the groups. 6 egg yolks from each group were measured for total OM-3FA content by gas chromatography. Yolk was separated from the rest of the egg and diluted with a phosphate buffered saline solution. Lipids were extracted with hexane and measured by a gas chromatograph. Fatty acids were determined from their retention time and quantified by integration of area under peak after normalization to 17:0 and 22:2 standards. Eggs from flaxseed fed hens contained significantly more OM-3FA compared to control fed hens (P<0.007).

Figure 2

Flaxseed suppresses the severity of ovarian cancer in the laying hen. Hens were fed a diet enriched with 10% flaxseed or a control diet for 1 year. After 1 year, the hens were euthanized, necropsied, and examined for the presence of ovarian cancer. There was no significant difference in incidence rates between the two groups (A). There was a reduction in the severity of the disease in hens fed flaxseed (B). Hens fed flaxseed had more ovarian tumors in stage T1/T2, when the tumor was still confined to the ovary (P<0.05). Hens on the control diet had more late stage tumors (T3/T4), where the cancer had spread to other organs (P<0.05).

Figure 3

Egg laying frequency is unaffected by the addition of flaxseed to the diet. Eggs were collected and counted weekly over the 1 year study from the two groups. There were no significant differences in the numbers of eggs laid in the flaxseed fed group compared to the control group. Egg laying frequency in both groups appeared to slow in the last quarter of the study, but this change was not significant.

Figure 4

Flaxseed fed hens maintain a steady weight compared to control hens over a 12 month study. At 6 months, 20 hens from each group were randomly selected to be euthanized and necropsied. All hens were weighed before necropsy. At the 12 month time point, the remaining hens were weighed and necropsied. At the 6 month time point, the flaxseed fed hens weighed significantly less than the control diet hens (P<0.05). By 12 months, the control fed hens weight had significantly decreased (P<0.001), while the weight of the flaxseed fed hens remained stable.

Figure 5

Flaxseed increased survival rates over a year-long study. At the beginning of the study there were 194 hens in the control diet group and 193 hens in the flaxseed diet group. At the 6 and 9 month time points, 20 hens from each group were randomly selected to ensure that the treatment was effective. By the end of the study, only 79 hens from the control group were alive out of the 154 remaining compared to 111 hens out of 153 hens from the flaxseed group (P<0.0001), indicating that flaxseed reduces mortality. Mortality rates include all natural causes of death over the total study.