Principles of Food Nutrient Selection

1The principles of nutrient selection

1. Variety. No single food supplies every nutrient (except breast milk, for a baby's first six months). Choose foods from all the groups every day: energy foods, body-building foods and protective foods.
2. Nutrient density. Nutrient density is the amount of useful nutrients a food gives compared with its energy. A cup of milk gives protein, calcium and vitamins along with its energy; a cup of soda gives energy from sugar and almost nothing else. Foods like soda and sweets are called "empty calorie" foods. Choose nutrient-dense foods first.
3. Combining foods so nutrients work together. Grains with legumes improve protein quality; vitamin C with beans or leaves helps iron absorption; a little fat with orange and green vegetables helps vitamin A absorption.
4. The needs of the person. Age, sex, body size, activity, pregnancy and illness change what a person needs. A growing teenager needs more protein, calcium and iron; a builder needs more energy than an office worker.
5. Freshness and quality. Fresh fruit and vegetables keep more vitamins. Choose firm, bright produce and whole foods over processed ones: whole-grain flour over refined, fresh fruit over sweetened fruit drinks.
6. Season and local availability. Foods in season, such as avocados, mangoes or fresh beans after harvest, are cheaper, fresher and richer in vitamins than foods out of season or transported from far away.
7. Cost per nutrient, not cost per kilogram. The cheapest food per kilogram is not always the cheapest way to get a nutrient, and the most expensive is not always the best. Compare the cost of the nutrient you need (see the worked example).
8. Safety and storage. Buy only what can be stored safely until it is used, and reject damaged or spoiled food.
9. Culture, religion and preference. Food that the family will not eat is wasted, however nutritious. Respect religious rules, such as not eating pork, and find another food that gives the same nutrients.

2Using a food label

• The ingredients list is written in order of weight, the largest first. If sugar is near the start, the food is mostly sugar.
• The nutrition table usually gives values per 100 g (or per 100 ml), which lets you compare two products fairly, and sometimes per serving.
• Look for more protein, fibre, vitamins and minerals, and less sugar, salt (sodium) and saturated fat.
• Check the date and that the salt is "iodised".

Worked example 1: the cost of protein

Task: Using the example prices below (prices vary by season and market), find the cost of 10 g of protein from each food, and rank them from cheapest to most expensive.

Ranking: beans (53 Frw) → groundnuts (100 Frw) → milk (188 Frw) → eggs (333 Frw).

Interpretation: beans give protein at about one-sixth of the cost of eggs, so they should be the family's main protein food. But the cheapest is not the whole story: milk and eggs give high-biological-value protein, milk gives calcium, and both give vitamin B12, which beans lack. A sensible choice is beans every day, with milk or an egg for the youngest children and a pregnant mother when the budget allows.

Worked example 2: choosing between two porridge flours

Task: Two porridge flours cost the same. Which should a mother choose for her family's breakfast? Give reasons.

Solution: Choose Flour A. It has more protein (12 g against 7 g), and its grain and soya complement each other. It has six times as much fibre, from the whole grains. Flour B lists sugar second, so sugar is its second-largest ingredient, and it has 15 g of sugar per 100 g against 2 g. Flour A is the more nutrient-dense choice at the same price.

Practice