If causality is assumed, we estimate that risk of colorectal cancer in the U.S. population could be reduced about 31% (50,000 cases annually) by an average increase in fiber intake from food sources of about 13 g/d, corresponding to an average increase of about 70%.

The relationship between energy intake, selected nutrients and colorectal cancer was investigated in the population of Majorca, a Spanish island in the Mediterranean basin. A population-based case-control study using food frequency questionnaires was conducted during the period 1984-1988 and included 286 cases of colorectal cancer, 295 population controls and 203 hospital controls. Food composition tables and ad-hoc estimates of portion sizes were used to derive intake estimates of 29 nutrients and of total calories. Relative risks were calculated for quartiles of consumption of each specific nutrient after adjustment for total calorie intake. Colorectal cancer was found associated with dietary intake of total calories (RRs = 1.0, 1.6, 1.6, 2.6) and cholesterol (RRs = 1.0, 0.9, 1.7, 1.7) and a protective effect was associated with the intake of fibre from legumes (pulses) and folic acid. The associations and the trends were statistically significant. Among the main energy-supplying nutrients, after adjustment for calories from other sources, increased risks were found for protein (RRs = 1.0, 1.1, 1.7, 2.5), notably animal protein, and carbohydrates (RRs = 1.0, 1.5, 1.4, 2.2), whereas no effects were found for increased consumption of lipids or saturated fats.

A population-based case-control study was conducted between July 1984 and February 1988 in the Spanish island of Majorca; 286 incident colorectal cancer cases, 295 population controls and 203 hospital controls were interviewed using a food frequency questionnaire. In a multivariate analysis, an increased risk of colon cancer was found for high consumption of fresh meats (RR = 2.87) while a high consumption of cruciferous vegetables afforded protection (RR = 0.48). For rectal cancer an increased risk was associated with dairy products (RR = 3.08) while a protection was afforded by consumption of cruciferae (RR = 0.50). For colorectal cancer, the cereal food group also showed an increase in risk (RR = 1.92). When cases were compared to hospital controls, the effects of cruciferae in colon and rectum and those of dairy products in rectal cancer remained. The magnitude of the RR estimates was decreased for most comparisons, although in general terms the direction of the associations was the same. In addition, univariate analyses of food groups also suggested significant increases in risk of colorectal cancer for increasing consumption of cereals, potatoes, pastry, eggs and number of meals per day. An indication was found of a reduction in risk for consumers of coffee. An analysis based on risk scores was also conducted and a 4-fold increase in the risk of colorectal cancer and a highly significant statistical trend was found for high consumption of fresh meat, dairy products and cereals combined with low consumption of cruciferae.

Two forest soils rich in organic matter but differing in texture (sandy loam and silty loam) were heated under controlled laboratory conditions in order to examine the consequences of the heating effect that accompanies the passage of a fire on the physical properties of soil. Three samples of both soils were heated for 30 min in a muffle furnace at temperatures of 25, 170, 220, 380 and 460°C. At each temperature, the following parameters were determined: dry aggregate size distribution, water aggregate stability, total porosity, pore size distribution, water repellency and hydraulic conductivity. Heating the soils at 170 and 220°C caused no significant changes in aggregate size distribution or total porosity but increased water aggregate stability and the volume of pores 0.2–30 μm. Also, increased water repellency and strongly decreased the hydraulic conductivity. All parameters underwent much more dramatic changes at 380 and 460°C that can be ascribed to the combustion of organic matter. At such temperatures, water repellency was destroyed and the low hydraulic conductivity can be attributed to the aggregate breakdown observed under dry and wet conditions.

At three adjacent sites in steeply sloping woodland in Galicia (NW Spain), surface runoff and associated erosion under simulated rainfall (64 mm h 1 ) were measured on five occasions between June 1998 and July 1999. Two of the three sites had recently been deforested and topsoil added, and one of these two had been sown with grass, which was germinating at the onset of the study. Deforestation greatly increased runoff and erosion rates, and the recovery of plant cover reduced erosion. All three soils were very hydrophobic due to high levels of poorly humified organic matter, which led to higher runoff rates than expected, especially during dry periods. However, great structural stability prevented there being a significant correlation between runoff rate and soil erosion.