To compare foods from a nutrition table, put both on the same basis: per 100 g or per serving, never one of each. Then read the nutrient you were asked about.
This lesson is part of nutrition and digestion in SPM Biology. The roles of nutrients link to explaining absorption and assimilation.
What is the basis check?
Before any comparison, find the column heading: per 100 g or per serving. Then find the serving size in grams, since it decides the conversion.
Write the basis beside every value you quote. A number without its basis cannot be compared.
Worked example: two fictional cereals
An original table, per 100 g:
| Food | Carbohydrate (g) | Protein (g) | Fat (g) | Energy (kJ) | Serving (g) |
|---|---|---|---|---|---|
| Cereal X | 60 | 10 | 5 | 1 500 | 40 |
| Cereal Y | 70 | 6 | 2 | 1 450 | 30 |
Compare per 100 g. Cereal X has more protein (10 g against 6 g). Cereal Y has more carbohydrate (70 g against 60 g).
Convert to a serving. For X, 40 g is 0.4 of 100 g. Protein per serving is 10 × 0.4 = 4 g, and energy is 1 500 × 0.4 = 600 kJ.
For Y, 30 g is 0.3 of 100 g. Protein per serving is 6 × 0.3 = 1.8 g, and energy is 1 450 × 0.3 = 435 kJ.
The mistake that gives the wrong comparison
A student compares 10 g (X, per 100 g) with 1.8 g (Y, per serving) and concludes that X has more than five times the protein. The two values are on different bases.
On the same basis, per 100 g it is 10 g against 6 g, and per serving it is 4 g against 1.8 g. Both comparisons say X has more protein, but the size of the difference is not the same.
How do I link a value to a biological role?
Protein supports growth and repair, carbohydrate is a source of energy, and fat is an energy store and part of cell membranes. A curriculum question may ask you to link the highest value to the nutrient’s role.
Quote the value and the role together: “Cereal X has 10 g protein per 100 g, which is needed for growth and repair”.
A self-check question
Using the table, find the carbohydrate in one serving of each cereal. Which gives more carbohydrate per serving?
Answer
X: 60 × 0.4 = 24 g. Y: 70 × 0.3 = 21 g. So one serving of Cereal X gives more carbohydrate, even though Y has more per 100 g. The serving size reversed the order, which is why the basis matters.
The graph evidence comparison lab and the biological data interpretation trainer offer more table practice. Then try the practice set.
If table questions keep going wrong at the conversion, SPM Biology one-to-one tuition lets a teacher work fresh tables with you.