Nutritional properties of soybean oil

Commodity soybean oil is composed of 61% polyunsaturated fatty acids, 25% monounsaturated fatty acid and 15% saturated fatty acids. The essential fatty acids linoleic (18 2, n-6) and a-linolenic (18 3, n-3) acids account for 89 and 11 % of the total essential fatty acids from this source. The n-6 acid content in soybean oil is slightly lower than that in com and sunflower oils, but it is more than double that in canola oil. Soybean and canola are the only two common plant oils that have a considerable amount of the n-3 linolenic acid. 

The physiological effects of vegetable oil are based on their fatty acid composition. Current US dietary guidelines recommend that diets contain less than 30% calories from fat, of which less than 10% is from saturated fat, 10-15% from monounsaturated acid, and 10% from polyunsaturated acids. The primary concerns with fatty acid consumption relate to two chronic diseases—coronary heart disease (CHD) and cancer. Research has shown that high levels of dietary saturated fatty acids are related to increased CHD and that dietary modification can lower plasma cholesterol. Consequent changes in cholesterol level can be predicted by the following relationship (Hegsted et al. 1993). 

The amount of total fat consumed, rather than the specific type of fat, has been positively associated with cancer risk (Dupont et al. 1990). However, animal studies suggested that linoleic acid promotes carcinogenesis under special circumstances (Sundram et al. 1989 Dupont et al. 1990), and that linolenic acid has a potential anticarcinogenic effect (Fritsche and Johnson 1988). Involvement of linolenic acid in carcinogenesis has not been found in humans. The amount of fat and its unsaturation significantly influence normal immune response and expression of inflammatory diseases (Connor 2000). 

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