type:Article

日本では, 大腸癌の罹患率が増加しており, その原因として食生活の西洋化による脂肪摂取量の増加が示唆されている。そこで, 本研究では, 食事指導で脂肪摂取量を減らすことにより大腸癌の発生を予防できるか否かを検討した。大阪府立成人病センターで行われた大腸癌予防のための「無作為割付臨床試験」の参加者で, 多発性大腸腫瘍患者367名を解析の対象とした。食事調査は平日連続3日間食事記録法を用い, その結果をもとに脂肪エネルギー比率が全摂取エネルギーの18～22%になるように指導した。参加時の食事調査は1993年6月から1998年4月に実施し, 4年目の大腸内視鏡検査は2002年2月に終了した。脂肪エネルギー比率が18～22%の範囲の人は, 試験参加時に比べ3ヶ月目では有意に増えた。3ヶ月目の脂肪エネルギー比率が18～22%の群に対して, 22%以上の群で4年目の大腸腫瘍発生の相対危険度は有意に低くなった (RR:0.68, 95%CI:0.55-0.85)。脂肪エネルギー比率を5群に分けた結果では, 脂肪エネルギー比率が最も低い (<18.4%)群に対して, 脂肪エネルギー比率が24.1～27.2%の群が最もリスクが低くなった (RR:0.56, 95%CI:0.40-0.79)。リノール酸は摂取量が増えるにつれ, 相対危険度は低くなった。大腸腫瘍発生を予防するには, 脂肪エネルギー比率は24%～27%が望ましく, リノール酸が不足すると大腸腫瘍の発生が促進される可能性が示された。

The incidence of colon cancer is rapidly increasing in Japan. This trend has been attributed to the high-fat diet resulting from westernization of the dietary lifestyle among the Japanese people. To examine whether the dietary instruction on the restriction of fat intake suppresses the development of colorectal tumors, we performed the following dietary intervention. The subjects were 367 men and women aged 40 to 65 years who underwent surgical removal of two or more colorectal tumors (adenomas and/or early cancers), which were diagnosed histologically. They were recruited to participate in a randomized clinical study at Osaka Medical Center for Cancer and Cardiovascular diseases. The first dietary survey was conducted from June 1993 to April 1998. Colonoscopy in the 4 years after the first survey ended in February 2002. The core purpose of the dietary instruction was to restrict the fat intake so that the energy from fats constituted 18 to 22% of the total energy intake. The subjects were asked to record, on a diet record form, the contents of their meals during the 3 days before consultation, and nutritionists calculated, from these records, the total energy intake and the intake of fats and oils. The subjects having a fat energy ratio in the range of 18-22% increased significantly 3 months after dietary survey as compared with the results in the first dietary survey. The relative risk of developing one tumor decreased significantly in the group whose fat energy ratio in the 3rd month was more than 22% as compared with the group with a ratio of 18-22% (RR: 0.68, 95% CI: 0.55-0.85). When the subjects were divided into five groups according to their fat energy ratio, the risk was the lowest in the group whose the fat energy ratio was 24.1-27.2% as compared to the group with the lowest fat energy ratio (<18.4%) (RR:0.56, 95%CI:0.40-0.79). As the intake quantity of linoleic acid increased , the relative risk became low. The results of our present study suggest that adjusting the fat intake so that the energy from fat constitutes 24-27% of the total energy intake suppresses the development of colorectal tumors. Our survey also suggests that the lack of linoleic acid may promote the development of colorectal tumors.