Introduction

The inclusion of processed food in our diets has for many years been commonplace. In the United States research has shown that more than 60% of the daily diet[1] comes from highly processed foods. In European countries, the figure is also quite high, particularly in The United Kingdom where 50% of household foods are highly processed, and also in Germany where highly processed foods comprise up to 46% daily intake[2]. It should be noted that some European countries, like Italy and Portugal, consume much less at only 15% highly processed foods.

Is the inclusion of these high levels of processed food in the modern diet a significant problem to our overall health? Should we remove all processed foods and turn to a natural, unadulterated, real food diet? Would that resolve our modern health crisis? Human beings seem to love contrasting information as a means of creating a powerful statement or highlighting a concern. Contrasting creates an apparent black and white scenario, associating facts that are usually unfairly compared. This is often the case in relation to food and diet, where the common sharing of opposing, contrasting positions is used to create shock value and fear. Food and dietary intake are rarely black and white. They are usually varying shades of grey. Let’s investigate this important contrast further.

What is processed food?

Food processing has been defined as ‘any method used to turn fresh foods into food products’[3]. Even this basic definition would indicate that food processing occurs at home in our own kitchens with even the most naturally produced, raw, whole foods. Processing food is an everyday requirement for turning basic ingredients into an enjoyable meal or snack. However, there is a difference between home-prepared food and industrial food preparation.

The general public appears to correctly understand that there is a sliding scale with regards to industrial food processing, and it appears there is a prevailing belief that the more processed our food is the lower its nutritional value upon consumption[4]. The following table defines a range of the most common food processing methods and the primary purpose of applying each within an industrial setting.

The purpose of food processing

As strange as it may sound there are some genuine and appropriate reasons for allowing foods to go through factory processing. It really is not all bad. The primary purposes of food processing can be summed up in this shortlist:

1. Increase palatability, digestibility, appearance, taste or smell
2. Preserve or improve the nutritional value
3. Improve food safety by reducing harmful organisms
4. Food preservation and maintain food qualities
5. Extend shelf life and lengthen food transportation options

Perhaps one of the most important reasons listed above is the need for food producers to extend shelf life and to preserve foods in a safe and edible state. By ensuring that this happens effectively food companies can increase their sales and reduce their food wastage, simply due to slower food spoilage providing a greater window of time for transportation and for a consumer to purchase it. It also means that food lasts longer in the consumer’s cupboards after purchase and can contribute to their nutritional needs over days, weeks or months depending on the recommended storage length.

However, this desirable benefit of longer shelf life is constantly being weighed up against the current negative perception of nutritional damage and the inclusion of undesirable food additives in processed foods. This is the healthy consumer’s modern dilemma! But is it as simple as minimising processed food, and eating more unprocessed, whole foods to guarantee better nutritional sufficiency? It certainly sounds good in principle, but does this mentality stack up under closer investigation?

Nutritional value of processed foods

Scientific research on the impact of processed food on its nutrient density has been very well established. Therefore, it stands to reason that modern Western diets would be nutritionally depleted as a result of such high intake of ultra-processed foods. A recent population-wide study confirms the impact that high consumption of processed foods has on the overall nutritional density of the diet[5]. The study established that the average dietary content of protein, fibre, vitamins A, C, D, and E, zinc, potassium, phosphorus, magnesium, and calcium in the US diet decreased significantly as the energy contribution from ultra-processed foods increased. Unfortunately, they also noted that total carbohydrate intake, added refined sugar, and saturated fat in the diet increased as a direct effect of more processed food consumption. These specifically add more nutritionally depleted calories to the diet, increasing the risk of obesity.

In addition to establishing the nutritional deficiency of a highly processed foods diet, another recent study[6] clearly showed the powerful impact that a processed foods diet can have upon appetite, food intake, and the resulting likelihood for weight gain. The meals presented to the subjects during the study period were matched for calories, energy density, macronutrients, sugar, sodium and fibre. However, they were instructed to eat as much or as little as they wished during each 2-week period of the crossover trial. As it turned out, energy intake was greater by an average of 508 kcals per day during the period when subjects ate the highly processed food diet in comparison to when the same subjects ate the whole, unprocessed food diet. Weight gain also changed in direct association with the dietary variation and the energy intake changes. It appears that eating nutritionally poor, processed food increased the biological drive to consume more calories in the search for the missing nutrients, despite there being an abundance of energy consumed.

Processed food categorisation

It is important to note that the studies explained above were carried out on a category known as ultra-processed foods. This opens the question as to the nutritional impact of lesser methods of food processing and how do we categorise these. The University of Sao Paulo in Brazil created a categorisation system based on the level of processing of different foods, known as the NOVA food classification system[7]. The table below outlines how processed foods can be successfully categorised using this recognised system.

Nutrient comparisons of NOVA foods

To help highlight the point about the level of food processing and the nutritional content of food, please refer to the randomly selected examples below to see how much of a difference food processing makes to the nutritional value of food. The comparisons include group 1, 2, 3 and 4 foods from the NOVA food categories described above.  It is important to note that the following food and nutrient analyses may not be representative of all foods that fall within a specific NOVA processed food category, they are just examples for illustrative purposes.

Colour key in nutritional tables:

Green highlighted row: Higher nutritional content

Grey highlighted row: same nutritional content

Defending against nutritional decline

The examples above show that processed food categories 2, 3 and 4, show a significant reduction in the nutritional value of the food product when compared to a similar, unprocessed option. Category 1, minimally processed food, did show a reduction in nutritional value compared to the unprocessed option, but it was only minor, and the resulting food product still delivered a substantial nutritional punch.

It is likely that other processed foods may show greater or lesser nutritional reductions within each NOVA category compared to the examples shown above. Just because a food has undergone industrial processing does not mean that the food should be completely discounted in terms of its nutritional contribution. We must acknowledge that ultra-processed foods do still provide a level of nutritional value to somewhat justify their inclusion in modern diets, although in most cases, nutrient levels are substantially diminished compared to a similar unprocessed or minimally processed parent food. So, there is usually a preferred or better option to consume to help promote human health than ultra-processed foods.

To finish up this discussion, here are 3 important takeaway messages:

1. Basic food processing helps to increase shelf life, reduces food spoilage, and helps to increase the range and availability of many foods.
2. Minimally processed foods still offer some of the benefits of food processing, while still retaining a significant proportion of the original nutritional value of the food.
3. Ultra-processed foods should, ideally, be reduced and avoided where possible due to the significant reduction in nutritional value, the increased calorie density, and the increased presence of non-nutritive food additives.

A side note on food additives

It is important to note that processed and ultra-processed foods are more likely to contain both artificial and/or natural food additives, and other food-like ingredients to deliver the manufacturers intended taste, texture, smell, colour etc.[8] It is fair to say that food additives have received a lot of negative attention over the years. Perhaps, as a result of the more technical naming associated with additives, and a lack of understanding regarding their purpose in processed food, they tend to be poorly understood.

Over-simplified anecdotes have been re-iterated around the internet, such as, ‘If you can’t pronounce the ingredient, then don’t eat it’. Such phrases are generally unhelpful and have likely caused an over-reaction against food additives. If food experts and nutritionists are really honest about the science, the vast range of food additives (over 300 additives and 2500 flavouring agents)[9] are regulated very tightly, are utilised in very small levels, and have been deemed to be safe for human consumption within the current allowable limits. There is a small range of food additives that have come under more intense scientific scrutiny due to some negative reactions recorded within the literature, and in some cases, these are supported by reports of negative effects from the general public too.

If you are interested in digging a little deeper into the more concerning additives, then here are a few suggestions that may be worth a little more investigation.

• Artificial colours: Hyperactivity in children is a potential side-effect for the following food colours – E102, E104, E110, E122, E124, & E129
• Preservatives: Sulfites, nitrates and nitrites for curing meats are considered to be mildly carcinogenic
• Artificial sweeteners: Aspartame and saccharin have a checkered scientific history as potential carcinogens – there are cleaner alternatives e.g. Stevia
• Flavour enhancers: Some people have demonstrated high allergic sensitivity to monosodium glutamate

Learn more on the subject of nutrition by studying our online Nutrition for Health and Fitness Certificate.

Enjoy more interesting reads, but visiting the NFE blog archive.

References

[1] https://academic.oup.com/ajcn/article/101/6/1251/4626878

[2] https://www.cambridge.org/core/journals/public-health-nutrition/article/household-availability-of-ultraprocessed-foods-and-obesity-in-nineteen-european-countries/D63EF7095E8EFE72BD825AFC2F331149

[3] https://www.eufic.org/en/food-production/article/processed-food-qa?gclid=Cj0KCQiAkePyBRCEARIsAMy5SctnbX9qpQ0os3j4-Y33a94yn2pZEMQccPNLPmUPCivDZ_ymzof2edkaAvLyEALw_wcB

[4] https://www.eufic.org/en/collaboration/article/eufic-forum-n-7-understanding-perceptions-of-processed-food-among-uk-consum

[5] https://www.ncbi.nlm.nih.gov/pubmed/28193285

[6] https://www.ncbi.nlm.nih.gov/pubmed/31105044

[7] https://educhange.com/wp-content/uploads/2018/09/NOVA-Classification-Reference-Sheet.pdf

[8] https://www.eufic.org/en/whats-in-food/article/food-additives

[9] https://www.tandfonline.com/doi/pdf/10.3402/fnr.v44i0.1778