To interpret a dietary dataset, calculate only what the table supports, then write a conclusion that stays inside the data. The skill is arithmetic, unit care and careful wording. It is not advice about what any person should eat.
This lesson belongs to human nutrition and digestion. It uses the terms from distinguishing assimilation from absorption only lightly, so you can do it at any point in the topic.
How should you read a nutrient table?
Start with the title and units. Most food tables give values per 100 g, but a question may talk about a portion. Scale first, compare second.
- Scale to a portion: value per 100 g × (portion mass ÷ 100).
- Add up a meal: scale each food, then add each nutrient separately.
- Share of a total: part ÷ total × 100.
- Compare foods fairly: use the same mass or the same portion for each.
Worked example
All values below are invented for practice and are not real food data. Per 100 g:
| Food | Energy (kJ) | Protein (g) | Fibre (g) |
|---|---|---|---|
| P | 540 | 2.5 | 0.4 |
| Q | 620 | 20 | 0 |
| R | 140 | 2 | 3 |
A model meal has 200 g of P, 100 g of Q and 150 g of R. Find the totals and the share of protein from Q.
Step 1, scale factors: P = 2, Q = 1, R = 1.5.
Step 2, energy: P 540 × 2 = 1080; Q 620 × 1 = 620; R 140 × 1.5 = 210. Total 1080 + 620 + 210 = 1910 kJ.
Step 3, protein: P 2.5 × 2 = 5; Q 20; R 2 × 1.5 = 3. Total 5 + 20 + 3 = 28 g.
Step 4, fibre: P 0.4 × 2 = 0.8; Q 0; R 3 × 1.5 = 4.5. Total 0.8 + 0 + 4.5 = 5.3 g.
Step 5, share of protein from Q: 20 ÷ 28 × 100 = 71.4%, so about 71%.
Step 6, conclusion: in this model meal, food Q supplies most of the protein and R supplies most of the fibre. The table says nothing about whether the meal suits any particular person.
The mistake to watch for
A common slip is to use the per 100 g values as if they were the amounts eaten, or to turn a pattern into advice.
Mistaken answer: “Meal energy is 540 + 620 + 140 = 1300 kJ, so this is a healthy meal for students.”
The values were not scaled to the portions, and “healthy for students” is a claim the table cannot support.
The correction is to scale first and describe only what the data show: “In this model meal, total energy is 1910 kJ.” Keep the words in this data in your conclusion.
Check yourself
Try these without a calculator if you can, then open each answer. The data are the invented table above.
1. How much fibre is in a 150 g portion of food R alone?
Show answer
Factor = 150 ÷ 100 = 1.5. Fibre = 3 × 1.5 = 4.5 g.
2. How much energy does 1 g of food Q provide?
Show answer
620 kJ per 100 g, so 620 ÷ 100 = 6.2 kJ per gram.
3. An invented survey finds that students who ate more fibre also reported fewer colds. A classmate writes, “Fibre prevents colds.” Rewrite the conclusion so the data support it.
Show answer
“In this survey, higher fibre intake was linked to fewer reported colds.” A survey shows an association. It cannot show that fibre was the cause, because other factors such as sleep or activity may differ.
Where this leads next
Practise scaling and cautious wording in the human nutrition and digestion practice set. The mistake log and retest queue can hold arithmetic slips separately from wording slips.
For questions about your own diet or health, speak to a doctor or registered dietitian. If you would like help with data questions in general, online one-to-one Biology tuition can work through your own answers. The probability tree and counting board and inheritance model board are separate tools for modelling tasks in other topics.