Ratios and Indexes

P:S Ratio

This is a comparison of polyunsaturated fat and saturated fat. The formula to calculate the ratio is:

polyunsaturated fat (g) / saturated fat (g).

If there is more polyunsaturated than saturated, the ratio will be large, such as 1.38:1. This is usually rounded up to 1.4:1. If there is more saturated than polyunsaturated, the ratio will be small, such as 0.3:1. There are various interpretations of what the correct ratio should be. Generally speaking, there should be more polyunsaturated than saturated-i.e. the ratio should be slightly greater than 1:1.

Potassium:Sodium Ratio

Sodium and potassium are minerals that are kept in a precise balance in the body. The ratio of potassium to sodium intake may be helpful in evaluating this balance.

The formula to calculate the ratio is:

potassium (mg) / sodium (mg).

The general recommendation is that the ratio be maintained either at 1:1 or with a slight preference for potassium.

Cholesterol Saturated Fat Index (CSI)

This index is indicative of the cholesterol and saturated fat content of a diet and is a useful figure for comparing diets and intakes.

CSI = [1.01 x saturated fat (g)] + [0.05 x cholesterol (mg)]

Generally, the lower the CSI value, the better. The Dietary Guidelines for Americans 2000, recommend that fat intake not exceed 30 percent of the total Calorie intake, with saturated fat less than 10 percent of total Calories and cholesterol intake less than 300 mg/day.

Research suggests that a CSI value of approximately 16 for women and 22 for men correlates with reduced blood lipids and lower cholesterol. Some of the variance relates to differences in body size and general food intake needs between the sexes. As food intake increases, the CSI value correspondingly increases.