Schloss I, Kidd M S, Tichelaar H Y, Young G O, O'Keefe S J
Gastro-intestinal Clinic, University of Cape Town.
S Afr Med J. 1997 Feb;87(2):152-8.
To examine the relative roles of dietary fibre, anti-oxidant vitamins and fish oils in the relatively low incidence of colon cancer in coloured West Coast fishermen.
Dietary intake survey, based on food frequency questionnaire and household surveys. Blood sampling for vitamin and fatty acid concentrations.
Isolated West Coast fishing villages (sample population) and urban Cape Town inhabitants (controls).
101 male and female West Coast fishermen over the age of 40 years, and 99 age- and sex-matched urban whites.
Dietary analysis by 'Foodfinder' technique, and nutrient blood levels. Statistical analysis using SASR program version 6.
An analysis of the number of recorded cases of colorectal cancer over a period of 5 years leading up to the study confirmed a lower rate of colorectal cancer in the West Coast fishermen than in the Cape Town population: fishermen 6 cases/120000, urban whites 677/2 million. A significantly higher proportion of fishermen were smokers, had hypertension and gave a history of previous tuberculosis infections. Vitamin supplementation was noted in one-third of whites but in no fishermen. The results of the dietary analysis (mean (SD)) demonstrated that fishermen consumed less fibre (9.9 (4.7) g/d v. 17.4 (7.2) g/d; P < 0.01) and less fruit and vegetables (190 g/d v. 365 g/d; P < 0.001), with a lower intake of vitamin C, thiamin, riboflavin, vitamin B6 and folate. Sodium intake was higher in fishermen, whereas intakes of potassium, magnesium, calcium, iron, zinc and copper were lower. In addition, the daily intake of omega-3 fatty acids (fish oils), docosahexaenoic acid (C22:6) and eicosapentaenoic acid (C20:5) in the West Coast population was considerably higher (0.71 (0.51) g/d v. 0.14 (0.09) g/d; P < 0.0001 and 0.37 (0.3) g/d v. 0.05 (0.05) g/d; P < 0.0001, respectively) than in the urban population owing to their higher intake of fish (110 g v. 30 g/d; P < 0.001). Plasma fatty acids correlated positively with these dietary intake figures, showing fishermen to have higher levels of circulating omega-3 fatty acids, C20:5 (3.9 (1.8)% v. 0.66 (0.29)%; P < 0.001) and C22:6 (5.6 (1.8) v. 2.9 (0.08)%; P < 0.001) and lower levels of omega-6 fatty acids, C18:2 and C20:3 (29.7 (4.7)% v. 33.5 (5.6)%; P < 0.05 and 0.85 (0.48)% v. 1.5 (0.47)%; P < 0.001, respectively) compared with the urban group.
The low incidence of colorectal carcinoma in West Coast fishermen might be explained by the protective effects of fish (omega-3) oils, but not by other "protective' dietary items such as fibre, anti-oxidant vitamins or calcium. The high incidence of hypertension may be related to a higher sodium intake, accompanying high consumption of salted fish, or to the higher prevalence of tobacco smoking.
研究膳食纤维、抗氧化维生素和鱼油在西海岸有色人种渔民结肠癌发病率相对较低中所起的作用。
基于食物频率问卷和家庭调查的膳食摄入量调查。采集血液样本检测维生素和脂肪酸浓度。
西海岸偏远渔村（样本人群）和开普敦城市居民（对照组）。
101名年龄在40岁以上的西海岸男女渔民，以及99名年龄和性别匹配的城市白人。
采用“食物查找器”技术进行膳食分析以及检测血液中的营养物质水平。使用SASR程序版本6进行统计分析。
对研究前5年记录的结直肠癌病例数进行分析，证实西海岸渔民的结直肠癌发病率低于开普敦人群：渔民为6例/120000人，城市白人为677例/200万人。渔民中吸烟者、高血压患者以及有既往结核感染史的比例显著更高。三分之一的白人补充维生素，但渔民中无人补充。膳食分析结果（均值（标准差））表明，渔民摄入的纤维较少（9.9（4.7）克/天对17.4（7.2）克/天；P<0.01），水果和蔬菜摄入量也较少（190克/天对365克/天；P<0.001），维生素C、硫胺素、核黄素、维生素B6和叶酸的摄入量较低。渔民的钠摄入量较高，而钾、镁、钙、铁、锌和铜的摄入量较低。此外，西海岸人群中ω-3脂肪酸（鱼油）、二十二碳六烯酸（C22:6）和二十碳五烯酸（C20:5）的每日摄入量显著高于城市人群（分别为0.71（0.51）克/天对0.14（0.09）克/天；P<0.0001和0.37（0.3）克/天对0.05（0.05）克/天；P<0.0001），因为他们摄入的鱼类较多（110克对30克/天；P<0.001）。血浆脂肪酸与这些膳食摄入量数据呈正相关，表明渔民循环中的ω-3脂肪酸、C20:5（3.9（1.8）%对0.66（0.29）%；P<0.001）和C22:6（5.6（1.8）对2.9（0.08）%；P<0.001）水平较高，而ω-6脂肪酸、C18:2和C20:3水平较低（分别为29.7（4.7）%对33.5（5.6）%；P<0.05和0.85（0.48）%对1.5（0.47）%；P<0.001），与城市组相比。
西海岸渔民结直肠癌发病率低可能是由于鱼类（ω-3）油的保护作用，但不是由于其他“保护性”膳食成分，如纤维、抗氧化维生素或钙。高血压发病率高可能与钠摄入量较高有关，这与咸鱼的高消费量有关，或者与吸烟率较高有关。
