National Science Popularization Day | Let’s run, nutrition labels – reveal the brand names of food nutrients

Ice cream, biscuits, potato chips, pudding, chocolate, candied fruit... When we enter the supermarket, a wide variety of food rushes into our eyes, attracting the attention of foodies of all sizes.

When children reach out to the shelves, how can you, as a parent, correctly identify the nutritional content of food? This requires us to tear off the "brand name" of the food - the nutrition label.

Food nutrition labeling refers to marking the nutritional ingredients and displaying nutritional information on the outer packaging of food.

Today, we will introduce the "three-step" method for identifying nutrition labels, teaching you to develop a "keen eye" and uncover the brand names of food nutritional ingredients.

Step 1: First impression, know what you are doing

The first step after getting food is to find the information on the food packaging and quickly browse the product name, production date, storage conditions, method of consumption, shelf life, quality certification, net content, etc., to have a general understanding of it. With this information, we can confirm whether the food under the various packaging is what we want, and avoid buying expired or near-expiry products.

Some foods have claims such as "high calcium", "high protein", "low fat", "suitable for the elderly", "suitable for infants and young children", etc., which show their characteristics in a prominent position. We can also choose the products that suit us according to these tips. It should be noted that these claims such as "high, low, rich" only represent the comparison results of the product with general products of the same type, which is a relative concept. As a food, it has no effect of treating or preventing diseases. Everyone should choose wisely.

Figure 1: A brand of low-fat milk. “Low-fat” is a relative concept. Compared with regular milk, it has a lower fat content.

Step 2: Calculate accurately and be confident

The nutritional information table can be said to be the most important information on the nutrition label. If we want to clearly understand the nutritional content of food, we must calculate based on the nutritional information table.

First of all, we cannot talk about nutrition without considering dosage, and confirming the net content is essential. Most products label the nutritional content in units of 100g or 100ml, but it should be noted that some foods define the weight of a serving of food by themselves, and the corresponding table shows the nutritional content of a serving of food.

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Figure 2: The amount of a “portion” defined in the nutrition information table of different foods varies

As shown below, this is the nutrition label of a certain brand of biscuits. Each box has a net weight of 90g, with a total of 12 pieces. The average weight of each biscuit is 90÷12=7.5g. The nutrition information table indicates the corresponding content of each biscuit. Let's take this biscuit as an example to explain the calculation process.

Figure 3: Part of the nutrition label of a certain brand of biscuits

Calculation steps:

1. After confirming the nutritional content of a serving of food, we can roughly imagine the amount consumed each time. For example, if we eat two cookies each time, that is two servings. Then, the amount consumed each time is the nutritional content of one serving of food shown on the label × 2 servings.

2. Nutritional content of each serving of biscuits (2 pieces):

Energy: 166 kJ × 2 = 332 kJ

Converted to the international unit kcal is approximately 332kJ÷4=83kcal (1kJ≈4.184kcal)

Protein: 0.4g x 2 = 0.8g

Fat: 2.1g x 2 = 4.2g

Carbohydrates: 4.8 g x 2 = 9.6 g

According to calculations, each consumption of biscuits provides 83kcal of energy, 0.8g of protein, 4.2g of fat, and 9.6g of carbohydrates.

What do these numbers mean for our daily intake?

Here we need to pay attention to the NRV% on the right side of the nutrition information table - the nutrient reference value on the food label.

Energy and nutrients per serving/nutrients per serving for a daily intake of 2000 kcal × 100% = NRV%

Generally speaking, NRV%≤5% is low; 10%≤NRV %≤19% is relatively high; and NRV%≥20% is very high.

Figure 4: Part of the nutrition label of a certain brand of biscuits

3. The nutritional content of each serving of biscuits (2 pieces) accounts for the total daily intake (based on the amount of nutrients that a 2000kcal food intake should contain):

Energy: 2%×2=4%

Protein: 1% x 2 = 2%

Fat: 4%×2=8%

Carbohydrates: 2% x 2 = 4%

Sodium: 0%

It has been calculated that each consumption of these biscuits (2 pieces) accounts for 4% of the total daily energy, 2% of protein, 8% of fat, 4% of carbohydrates and 0% of sodium.

Based on the above calculations, if two pieces of the biscuits are consumed each time, the energy intake for the whole day is less than 5%, which is a low proportion and has little impact on the whole day's energy intake. It can be eaten as a snack. And the sodium content of the snack is low. However, if the biscuits contain a relatively high proportion of fat, if the consumption is large, we should be wary of excessive energy intake and fat intake.

Step 3: Pay attention to details and make the right decisions

To make the right decision, the following details cannot be ignored.

1. Many children have food allergies, so we need to pay attention to the "allergy information" label. If the food contains foods that cause children to be allergic, such as milk, seafood, nuts, eggs, wheat bran, etc., you should avoid buying it.

Figure 5: Allergen information/allergenic substances

2. The content of the ingredient list is also worth noting. Generally speaking, the order of appearance in the ingredient list is arranged from most to least. In addition, you should pay attention to the use of some ingredients. Common ingredients that need to be vigilant are as follows:

Added sugar: There are many "zero sucrose" and "sugar-free" foods on the market now, but this does not necessarily mean that there is no added sugar. Maltose, glucose, honey, fructose syrup, concentrated fruit juice, etc. in the ingredient list are still sources of sugar.

Trans fatty acids: Trans fatty acids are also "bad guys" that are harmful to health, so when we buy food, if trans fatty acids appear in the ingredient list, we should avoid buying them. It should be noted that trans fatty acids also have "disguises", shortening, margarine, artificial butter, non-dairy creamer, hydrogenated vegetable oil, etc. are also ingredients containing trans fatty acids.

With the "three-step" method, I believe everyone has a clear understanding of nutrition labels. In the upcoming food shopping campaign, you can easily tear off the "brand" of food nutrition labels and bring health and happiness home!

Project source: Shanghai Science and Technology Commission Science Popularization Project Funding (Project No.: 21DZ2301800)

Author: Xu Kaijie Niu Yang | Department of Clinical Nutrition, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine