Worldwide esophageal cancer is the fifth most common cause of cancer death. Some populations in Asia and South Africa have high rates of esophageal cancer, which could be caused by high intake of N-nitroso compounds and seasonal variations in fresh fruit and vegetable consumption. The consumption of fruit and vegetables has been linked to lower risk of cancer, including esophageal cancer. Black berries containing high levels of phytochemicals, such as egallic acid
, which may inhibit carcinogenesis. Previous studies have shown that egallic acid inhibits carcinogenesis induced by various classes of carcinogens.
The aim of this study to investigate the chemoprotective activity of the intake of black raspberry against esophageal cancer in rats, after treatment with the chemical carcinogen, n-nitrosomethylbenzylamine. In the first experiment (anti-initiation study) the rats were first fed with diets, containing 5 or 10% dried black raspberry, followed by a treatment with the nitrosamine, N-nitrosomethylbenzylamine. The researchers found that the intake of raspberry reduced the esophageal tumor multiplicity by almost 50%, reduced DNA adducts by up to 80 and significantly inhibited adduct formation. In another test (post-initiation study) the rats with first treated with the carcinogen and then received 5 or 10% dried black raspberry. Also in this test, the black raspberry inhibited esophageal tumor progression. After 35 weeks, the tumor incidence and tumor multiplicity decreased significantly. The researchers also observed that the diet with 5% dried raspberry was more effective in reducing DNA damage than the diet with 10% dried raspberry.
The study concluded that the dietary administration of black raspberry has chemopreventive effect on initiation and progression of esophageal cancer. It should be noted that the quantities of 5 to 10% black raspberry in the diet are quite high but could be achievable.
Source: Kresty LA, Morse MA, Morgan C, Carlton PS, Lu J, Gupta A, Blackwood M and Stoner GD. Chemoprevention of esophageal tumorigenesis by dietary administration of lyophilized black raspberries.. Cancer Research. 2001 August 15;61(16):6112-9