Are all processed foods bad for health?

Health promotion messages today often advised the public to reduce consumption of processed foods. For example, in the Singapore Health Promotion Board’s “My Healthy Plate”, the public is advised to limit intake of processed foods that are high in sugar or salt [1]. However, what constitutes processed foods and are they necessarily bad for health? This is a question that we shall explore here.

Avoiding Trans Fat

Highly processed foods commonly found in supermarket these days.

Diversity of processed foods

When we mentioned about processed foods, many people may think of cookies, sweets, canned foods, or carbonated drinks. They are right to think so. However, processed foods actually cover a much wider spectrum of foods we consume today.


Definition:

“Food processing is any deliberate change in a food that occurs before it’s available for us to eat”

[2].


Hence, any form of food preservation, such as freezing or drying, or preparation such as dehusking, milling, or even cooking is considered food processing.  As such, processed foods can be placed on a continuum ranging from minimally processed items to more complex preparations that combine many ingredients [2]. As such, not all processed foods are equal in their nutritional profile.

In order to understand the health impact of processed foods available on the market, we shall divide foods into a few groups based on the latest international classifications [3][4].

Nova Food Processing Classification

Group 1 – Unprocessed and minimally processed foods

This group includes all the basic food items such as fruits, vegetables, legumes, meats, fish, grains, milk, etc. Some processes may still be involved in order to better preserve them or making them more available and safer to consume. For example, freshly harvested apple may be washed, waxed and boxed; grains require milling to remove the husks and brans, etc. Nonetheless, most of the processing involved is physical in nature, and the foods are not altered. Furthermore, no additional substance in introduced.

Group 2 – Processed culinary or food ingredients

bake-599521_1920These are ingredients extracted or purified from the minimally processed foods, or items obtain from nature. The primary purpose of this group is to be used in cooking, or for further processing. This group covers items such as flour, oils, fats, salt, sugar, sauces, noodles, tofu etc. More complex physical and chemical processes such as pressure, milling, refining, hydrogenation and hydrolysis, and use of enzymes and additives may be used. For example, soy sauce is produced from the fermentation of soybeans through a series of processing.

Group 3.1 – Processed food products

homemade-pickles-700037_1920This is the first type of processed foods that is ready to be consumed. They are manufactured items made from minimally processed foods with the addition of substances such as oil, sugar, salt, or preservation. The final products are still recognisable as a version of the original food. Examples include canned or bottled vegetables preserved in salts, canned fruits preserved in syrups, salted nuts, ham, and bacon. Traditional foods such as salted fish, smoked duck, fermented bean curd, tempeh, plain yogurt, etc. also belong to this group.

Group 3.2 – Ultra-processed products

frozen-food-1336013_1920Food items in this group are the inventions of modern food processing technologies. They are formulated foods made mostly or even entirely, from substances derived from foods and contain little or no whole foods. They are highly durable, convenient, accessible, nice-to-eat, and can be quite addictive! Notable examples include chips, instant noodles, ice-cream, sweets, French fries, fast food burgers, frozen pizzas, cookies, breakfast cereals, cakes, soft drinks, colas, 3-in-1 instant coffees etc. They are typically not recognisable from the original whole food, and contain a lot of processed ingredients and chemical additives, such as preservatives; stabilizers, emulsifiers, solvents, binders, etc.

Processed foods: The good, bad, and ugly

With the understanding of the different types of processed foods, we can now analyse their potential impacts to health.

The good

Natto mixed

The fermentation process significantly increase the health benefits of soy beans in Japanese Natto

Food processing is unavoidable and necessary in today’s urbanised society. Historically, without the ability to process foods to make them last longer, more digestible, and safer to consume, human society could never progress beyond hunter-gather’s way of life. Here are some food processing methods that are highly beneficial [5]:

  • Milling – helps to turn the otherwise indigestible grains into staple foods for the world’s population. The removal of the outer husks and brans makes the starches and phytochemicals in grains bioavailable to human’s digestive tract.
  • Heat processing – helps to sterile foods, killing harmful microorganism that can otherwise spoil the foods. The bioavailability of certain nutrients, such as lycopene, is further enhanced under heat.
  • Fermenting – helps to preserve, enhance the taste and digestibility, and improve the nutritional value of certain foods. For instance, probiotic culture in yogurt helps to improve digestive health.
  • Enzymatic extraction – helps to separate oils from plant parts such as rice bran or grated coconut flesh. This process produce oil at low heat and does not change the chemical structures of the fatty acids within the oils. Some healthy oil, such as flaxseed oil which is rich in omega-3 fatty acids, can be produced with enzymatic extraction efficiently [6].
  • Freezing – helps to prevent spoilage and loss of nutrients for a long time [7]. This helps to improve accessibility and availability of healthier foods, in the form of frozen fruits and vegetables, for urban poor, and thus ensure food security [8].

Therefore, the processing applies to food products in Group 1 and 2 can be beneficial to improve the shelf life of the products and some of them can be health promoting.

The bad

When the processing goes beyond making the foods last longer and more digestible, and seek to enhance the taste and appeal while lowering the cost of processing, the nutritional values of the foods can become compromised. A classic example is the polishing process that turned brown rice into white rice. Although the polishing improves the aroma and change texture of the rice to be more palatable, it also significantly depletes the nutritional value of the rice: about 80% of vitamin E, 75% of phytochemicals. 60% of dietary fibres, 50% of fats, 16% of protein are lost [9]. Thus, highly polished white rice becomes refined carbohydrate that is highly starchy. The polishing process significantly increase the glycaemic index of white rice comparing to brown rice, which can be detrimental to health. Research has shown that higher consumption of white rice is linked higher risk of not only type 2 diabetes [10], but also cardiovascular diseases [11].

Artificial food colouring is linked to the hyperactivity in kids. (Photo credit: Larry Jacobsen/Flickr)

Artificial food colouring is linked to the hyperactivity in kids. (Photo credit: Larry Jacobsen/Flickr)

The additives in processed foods can pose significant health risk to the body. Here are some potentially harmful food additives:

  • Salt and sugar are common additives to most processed foods. In fact, many food items in Group 3 contain high amount of either salt or sugar. Frequent consumption can lead to hypertension, cardiovascular disease and type 2 diabetes [12].
  • Monosodium glutamate (MSG), a commonly used flavour enhancer in processed foods, can cause many side-effects including headache and dizziness [13]. Long-term consumption of MSG can also lead to weight gain [14].
  • Artificial food colours have also been recognised as a public health risk. The latest evidence suggested that the artificial colouring in food can affect children’s behaviours, making them more aggravated even in children without attention-deficit/hyperactivity disorder [15].
  • Sulphites, commonly added in processed foods as a preservative and an antioxidant, can induce non-specific allergic effects in sensitive individuals, ranging from dermatitis, urticaria, flushing, hypotension, abdominal pain and diarrhoea, to life-threatening anaphylactic and asthmatic reactions [16].
  • Nitrites and nitrates are used in curing meat are powerful carcinogens, i.e. they are substances that can cause cancer [17].

The fact is, many commonly used chemical additives including dyes, colour fixatives, preservatives, antioxidants, fungicides, and sweeteners are found to be DNA-damaging in an experimental animal model [18]. They can all potentially cause cancer in human!

The ugly

There is an increasing trend of ultra-processed food consumption globally. Data from 79 high- and middle-income countries show that ultra-processed products dominate the food supplies of high-income countries, and that their consumption is now rapidly increasing in middle-income countries [21]. An analysis of 2013 survey data on packaged supermarket food and non-alcoholic beverages in New Zealand found that 83% of them were classified as ultra-processed foods [19].  It is estimated that about 40% to 75% of the energy and nutrients consumed in developed countries comes from ultra-processed foods [22]. In USA, 89.7% of the energy intake from added sugars of the population comes from ultra-processed foods [23].

obesity-993126_1280

Obesity is a global health concern aggravated by over consumption of ultra-processed foods

Ultra-processed foods (Group 3.2) have the worst nutritional profile when compared to processed food products (Group 3.1) and minimally-processed foods (Group 1) [19]. A meal consists of mainly of the ultra-processed foods far exceeds the upper limits recommended for added sugar intake, sodium intake and energy density, it is close to the upper limit for saturated fat intake, and it is clearly insufficient in fibre [20]. There is a strong link between unhealthy diet and the risk of obesity, diabetes, cardiovascular diseases, and cancers that plague the world. Therefore, the over consumption of ultra-processed products is a major public health concern worldwide. Public education on a healthy diet to reduce this dietary trend is imperative.

Healthy food choices

A healthy meal from whole foods

A healthy meal from whole foods

A healthy diet should consist of:

  • A majority of unprocessed and minimally processed foods (Group 1) should be fresh fruits and vegetables, whole grains, lean proteins, nuts, and legumes.
  • Meals should be prepared with a selection of natural culinary ingredients from Group 2 emphasising on the use of good fats (e.g. olive oils), no added sugar, low in sodium, and no chemical additives.
  • Ready-to-consume food products (Group 3) can be used to supplement the diet but in small amount only. Their selection should be discreet. Ultra-processed food items from Group 3.2 should be minimised.

It is important to learn to read the food labels on each product on the supermarket shelves to make smart choices. (See my previous post on “Read food labels in 3 easy steps”)

Conclusion

Processed foods cover a wide spectrum that can be classified into four main groups: minimally processed, processed culinary or food ingredients, processed food products, and ultra-processed foods. Basic processing such as milling, heat processing, freezing, fermenting, etc. make foods last longer, more digestible, safer to consume, and can be health promoting. Nevertheless, excessive processing can deplete the nutritional values of the foods and food additives such as added sugar, salt, MSG, artificial food colours, preservatives, etc. can be health damaging.

Ultra-processed foods have the worst nutritional profile when compared to processed food products and minimally-processed foods. The increase in consumption of ultra-processed foods is a worrying global trend that increases the risk of obesity, diabetes, cardiovascular diseases, and cancers in the general population. A healthy diet should consist mainly of unprocessed and minimally processed foods prepared with healthy natural culinary ingredients. Choices of ready-to-consume food products should be minimised and their selection should be discreet. Processed foods are not necessarily bad; it is important to read the labels before you buy!

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References

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