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French Fries are unhealthy

Learn why French Fries can harm your health

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First published: 06.Dec.2023

Overview: French fries are the worst food

French fries from fast food restaurants are Ultra-processed foods that contain not only potato, oil and salt; they are industrialized items that undergo processing before they reach the kitchen (washed, scrubbed, sliced, coated with chemical-containing ingredients, pre-fried and frozen), then they are fried again in vats containing a blend of oils that are recycled and filtered through synthetic absorbents.

In this article we will tell you all about ultra-processed French Fries, the ingredients they contain, the benefits of a home fried potato and more.

In this Article (Index)

a bowl with French fries
French fries: ultra-processed food

French fries

Potatoes are an ancient food crop native to America, where they were probably fried in lard by the Amerindians. The Spaniards brought them to Europe in the mid 1500s and the first European fried potatoes were cooked in Spain where you can still find them there as "patatas bravas".

Potatoes became a staple meal for the European masses and they were cooked in many ways. Deep frying was a typical Mediterranean cuisine cooking method and the French cooks fried potatoes this way.

The Americans adopted this cooking method to produce "French fried potatoes", that is, potatoes fried in the French style, or "French fries". The British on the other side of the Atlantic call them "chips."

French fries are potatoes that are cut into thin and even sized strips, dried and deep fried till they are crisp yet not browned on the outside, and cooked yet tender inside.

Fast Food French Fries

French Fries, as sold by fast food restaurants are Ultra-processed foods. They are quite different from home fried potatoes that only have three ingredients: fresh potatoes, cooking oil and salt. Two of them unprocessed or minimally processed foods (the oil and the potatoes).

French Fries used by fast food restaurants have many more ingredients, a few of them are chemicals compounds, the potatoes have been industrialized (machine-sorted, peeled, washed, cut, coated with processed ingredients, pre-fried, and frozen) before they reached the restaurant's kitchen where they are further processed by frying in a blend of different oils that are recycled and filtered using man-made adsorbing chemicals.

Fried potatoes are linked to a higher death risk

A study by Veronese et al. (2017) (1) investigated whether eating potatoes was associated with a higher risk of premature death, and they found that for Americans, eating fried potatoes increased the risk.

They analyzed data of 4,440 subjects followed over eight years in the Osteoarthritis Initiative cohort study and found that those whoe ate more potatoes didn't show an increased risk of death, but "participants who consumed fried potatoes 2–3 times⁄wk... and 3 or more times⁄wk were at an increased risk of mortality. The consumption of unfried potatoes was not associated with an increased mortality risk."

The frequent consumption of fried potatoes appears to be associated with an increased mortality risk...
overall potato consumption was not associated with a higher risk of death in a cohort of North American men and women. On the contrary, frequent consumption of fried potatoes significantly increased overall mortality risk. Veronese et al. (2017) (1)

Eating fried potatoes more than twice a week more than doubled the risk of premature death.
But why? Added salt and high amounts of fat, including trans fat are known to increase heart disease and risk of death. Fried potatoes are linked to obesity, hypertension and diabetes, all of which promote cardiovascular disease. Also, those who eat fried potatoes also tend to have other unhealthy habits regarding food: they eat more ultra-processed foods and this entails health risks.

But this effect wasn't noted by an epidemiologic study conducted in Sweden, so the authors suggest that additional research is necessary "to understand whether a higher consumption of fried potatoes is associated with higher CVD and cancer mortality due to higher intakes of trans fatty acids, oxidized lipids, acrolein, acrylamide, furan, and glycidamide." (1)

What is in a Fast Food French Fry?

McDonald's French Fries (2) ingredients list is: "Potatoes, Vegetable Oil (canola Oil, Corn Oil, Soybean Oil, Hydrogenated Soybean Oil, Natural Beef Flavor [wheat And Milk Derivatives]*), Dextrose, Sodium Acid Pyrophosphate (maintain Color), Salt.
*natural Beef Flavor Contains Hydrolyzed Wheat And Hydrolyzed Milk As Starting Ingredients.
Contains: Wheat, Milk.

In case you don't know, hydrogenated soybean oil is a trans fat; an oil that has been treated with a chemical catalyzer to make it more stable by breaking double bonds in the "natural" oil molecules and adding hydrogen atoms there. Hydrogenated soybean oil contains almost 40% "artificial" fatty acids that were not present in the original soybean oil (3).

McDonalds fries
French fries, packed with many ingredients. Source

Why are there so many ingredients?

As mentioned further up, French fries made at home have three ingredients: oil, potatoes and salt. But ultra processed fries have many more ingredients and some of them are patented: "sodium acid pyrophosphate (SAPP) to minimize product discoloration [and] dextrose to facilitate uniform color development during frying."

Starches are added to reduce the amount of oil absorbed by the potato during frying, improving the appearance and texture of the product, and extending the holding time of the fries (the amount of time they remain crisp after they were fried). McDonald's frozen fries are pre-fried (parcooked or partially cooked) by the company's suppliers.

Dextrose used to coat the potatoes is a sugar (glucose) with a high glycemic index value, meaning it is absorbed very quickly and spikes your blood sugar levels.

The Natural Beef Flavor was added because in the past, until the 1990s, McDonald's used beef tallow as one of the fats in their frying oils. It gave them a beef flavor. When saturated fats were frowned on they were replaced with vegetable oils, but the beef taste went with the tallow. So they came up with a "natural flavor" made with hydrolyzed proteins of wheat and milk meaning that for celiac people, these fries are not an option as they contain wheat, and vegans won't like the milk.

Hydrolyzed Proteins, MSG and Sodium

When proteins like gluten, found in wheat or casein found in milk are treated with hydrochloric acid and heated, they undergo a process known as hydrolisis, and break down into their building blocks, aminoacids. Modern techniques also hydrolyze proteins using heat, acids and bases to regulate the pH, and enzymes to breakdown the protein. Salt is usually a residue in acid-treated protein, while enzyme hydrolyzed protein receives added salt to preserve it.

During hydrolisis, proteins will also release an aminoacid called glutamic acid, which will combine with salt to form monosodium glutamate or MSG, a flavor enhancer. However MSG won't appear on the ingredient list as it wasn't added, it is a byproduct of hydrolyzing protein. Scopp (1991) reports that "the presence of MSG in food may be difficult to detect since the terms "natural flavor," "flavoring," or "hydrolyzed vegetable protein (HVP)," all may appear on food labels to refer to MSG, according to current FDA food labeling codes. HVP typically contains 10-30% MSG". (4).

The United States Department of Agriculture (USDA)(2013) (5) also states that "the presence of MSG does not need to be disclosed on labeling. Labeling is required when MSG is added as a direct ingredient."

MSG is therefore one of the sources of sodium in French fries, the other two are the added salt and the Sodium Acid Pyrophosphate that is added to the potato coating to prevent it from browning during the deep frying process.

The Frying Oils

Frying at home is done using one single vegetable oil. But fast food restaurants blend different types of oils to obtain a mixture that won't decompose and form taste-altering compounds at the high frying temperatures used in mass-produced frying. This is called the smoke point. For this reason McDonalds uses "canola Oil, Corn Oil, Soybean Oil, Hydrogenated Soybean Oil," blending them to obtain a high smoke point temperature.

When cooking oils and fats are used, they are heated to temperatures that range between 315 and 375°F (157-190°C); the repeated use of the same oil at high temperatures produces free fatty acids (FFA) that accumulate in the oil and lower its smoke point, provoking smoke at cooking temperatures. The FFAs oxidize as heat plus the oxygen in the air combine with them to produce oxidized fatty acids or OFAs, these degrade into substances that cause unpleasant flavors or odors that alter the fried foods.

Additionally, frying products that contain carbohydrates (breaded food and potato fries) makes the sugars in the carbs and the protein turn brown, a process known as caramelization. This darkens the oil and stains the fried food.

Depending on the cooking load, cooking oils and fats have a shelf life of 2-10 days in the frying vats, and must be discarded or treated to remove FFAs, OFAs and browning agents.

Browning during cooking and frying produces a compound acrylamide, linked to cancer.

To avoid disposing of the oil, it is processed by patented filtering method, using a man-made amorphous magnesium silicate (6), that "removes soluble contaminants, thereby slowing the degradation of the oil and fat. In addition to removing food particles, the magnesium silicate decolorizes and deodorizes leaving clearer, cleaner and fresher oils and ⁄ or fats."

So unlike home frying, where you discard the old cooking oil when you notice it has lost its original properties, oils in restaurants' deep fryers are processed by cycling them through a bed of powdered artificial mineral and filter paper (as shown in this video) adding yet another step of "processing" to an ultra-processed food.

Oil Quality Matters

Oil olive is best for frying

However, there are other factors to consider apart from the smoke point. For instance the oil's oxidative stability is critical too. Stability depends on the antioxidants in the oil and the type of fats found in the oil (saturated, mono or polyunsaturated), and the degree of refining it has undergone.

Fast food restaurants blend different oils to obtain a mix that will have a higher smoke point, and is cheap. But there is an option that has only one ingredient, and is far healthier than refined chemically extracted oils: olive oil.

bottle with olive oils and some fresh olives
Olive oil, a natural healthy ingredient. Source

Advantages of frying with olive oil

Extra Virgin olive oil is an unrefined plant oil extracted by cold pressing that is low in polyunsaturated fats (7).
By the way, the smoke point of olive oil is comparable, and in some cases higher than, other refined oils such as soybean, sunflower, peanut, canola, and corn oils yet olive oil has many advantages when it comes to frying:

  • It can be reused and reheated safely: Refined olive, corn, soybean, and sunflower oils were used as cooking oils for deep-frying at two different temperatures, 160 and 190 °C, and for pan-frying of potatoes at 180 °C for 10 successive sessions under the usual domestic practice. Several chemical parameters were assayed during frying operations to evaluate the status of the frying oils. Refined olive oil, as frying oil, was found to be more stable than the refined seed oils. In fact, this oil has proven the greatest resistance to oxidative deterioration, and its trans-fatty acid contents and percentages of total polar compounds were found to be lower at 160 °C during deep-frying. Finally, chemometric analysis has demonstrated that the lowest deterioration of the quality of all refined oils occurred in the refined olive oil during deep-frying at 160 °C and the highest deterioration occurred in the refined sunflower oil during pan-frying at 180 °C. (9)
  • It can be heated to high temperatures for long periods of time. A study compared extra virgin olive oil to sunflower oil; they were heated to 374°F for 40 hours in an industrial fryer. The study found that extra virgin olive oil performed better than sunflower oil (10). It also performed better when overheated, producing fewer volatile aldehydes than canola oil at 464°F (11).
  • Being low in polyunsaturated fats (PUFAs) and high in monounsaturated fats, it produces less toxic aldehydes during frying; experiments that fried potatoes in reused oils showed that these toxic compounds are absorbed by the food and ingested: "the use of PUFA-rich sunflower oil gave rise to significant reuse-dependent levels of each class of these aldehydes in [the potatoes] whereas only negligible amounts were found in these when MUFA-rich extra virgin olive [was] employed as frying media" (12).

The International Olive Council (IOC), the authority on olive oil, recommends a lower temperature for frying in olive oil than the one used in fast food restaurants; for high water content vegetables and for potatoes the heat should be Medium (266-293°F or 130-145°C).

Bioactive compounds in Olive Oil enhance your fried food

Unlike refined chemically-extracted grain oils, extra virgin olive oil has many bioactive phytochemicals (plant chemicals) that are good for your health. These are absorbed by the fried food:

Frying with ... olive oil, may improve the overall quality of the fried food. Frying in olive oil may lead to the incorporation of bioactive compounds from the oil in the food and to decreased levels of oxidation products, positively affecting the fried food's nutritional properties del Pilar et al., (2015) (8)

Potatoes are good for you

Despite the health risks caused by eating French fries, potatoes are a nutrient-rich food. The United States Department of Agriculture (USDA) includes potatoes as a "starchy vegetable" in its national food guide and recommends that adults eat 4 to 6 cups (4.5 oz or 125 g) per week of starchy vegetables. In the UK, on the other hand, it isn't included as a vegetable or fruit in the "5-A-Day" veggies plus fruits guideline (13)


Potatoes add magnesium, potssium, vitamin C, folate, Vitamin B6, and fiber to the diet.

But skip the French fries

British adults eat on average 1⁄3 lb per portion (149 g) of "fried chips" (French fries) and eat roughly one-quarter of their potato intake fried: 140 g of fries per week (5 oz.) (13)

In the US, potatoes are the most eaten vegetable with 49.2 lb (22.3 kg) per person per year in 2017. Of these 25 lb (11.3 kg) are either fried or frozen and used for frying (14).

Most of the potatoes sold in the US in 2023 are processed, either frozen for fries, fried, canned or dehydrated and half of them are sold frozen to make French fries (15).

Remember that a small size helping of McDonald's french fries weighs on average 2.6 oz or 75 g, and it contains 230 calories (11.5% of the Daily Value for an adult based on a 2,000 calorie diet), 11 g of total fat (14% Daily Value), 31 g of total carbs (11% Daily Value) and 190 mg of sodium (8% Daily Value). You can do without this. Your health and body will appreciate it.

References and Further Reading

(1) Veronese N, et al. (2017). Fried potato consumption is associated with elevated mortality: an 8-y longitudinal cohort study. Am J Clin Nutr. 2017 Jul;106(1):162-167. doi: 10.3945/ajcn.117.154872. Epub 2017 Jun 7. PMID: 28592612

(2) McDonald's. Ingredients List French Fries. Accessed Dec. 1, 2023.

(3) A. F (2013) The Effects of Hydrogenation on Soybean Oil. Soybean - Bio-Active Compounds. InTech. Available at:

(4) Scopp AL. (1991). MSG and hydrolyzed vegetable protein induced headache: review and case studies. Headache. 1991 Feb;31(2):107-10. doi: 10.1111/j.1526-4610.1991.hed3102107.x.

(5) United States Department of Agriculture (USDA). Natural Flavors on Meat and Poultry Labels. Are MSG and hydrolyzed protein related? . Last Updated: Aug 09, 2013.

(6) U.S. Patents. (1985). Patent US4681768A.

(7) The North American Olive Oil Association. Why olive oil is the best oil for frying. Accessed Dec. 1, 2023

(8) Jessica del Pilar Ramirez-Anaya et al., (2015). Phenols and the antioxidant capacity of Mediterranean vegetables prepared with extra virgin olive oil using different domestic cooking techniques. Food Chemistry, Vol 188, 2015, p 430-438,ISSN 0308-8146,

(9) Akram Zribi et al., (2014). Monitoring of Quality and Stability Characteristics and Fatty Acid Compositions of Refined Olive and Seed Oils during Repeated Pan- and Deep-Frying Using GC, FT-NIRS, and Chemometrics. Journal of Agricultural and Food Chemistry 2014 62 (42), 10357-10367 doi:10.1021/jf503146f

(10) M.D. Guillen, P.S. Uriarte, (2012). Study by 1H NMR spectroscopy of the evolution of extra virgin olive oil composition submitted to frying temperature in an industrial fryer for a prolonged period of time. Food Chemistry, Vol 134:1, 2012, p 162-172, ISSN 0308-8146,

(11) Fullana A, Carbonell-Barrachina AA, Sidhu S. (2004). Comparison of volatile aldehydes present in the cooking fumes of extra virgin olive, olive, and canola oils. J Agric Food Chem. 2004 Aug 11;52(16):5207-14. doi: 10.1021/jf035241f. PMID: 15291498

(12) Moumtaz S, Percival BC, Parmar D, Grootveld KL, Jansson P, Grootveld M. (2019). Toxic aldehyde generation in and food uptake from culinary oils during frying practices: peroxidative resistance of a monounsaturate-rich algae oil. Sci Rep. 2019 Mar 11;9(1):4125. doi: 10.1038/s41598-019-39767-1. PMID: 30858398

(13) Gibson, S. and Kurilich, A.C. (2013). Potatoes in the UK dietNutrition Bulletin, 38: 389-399.

(14) United States Department of Agriculture (USDA), Fries on the rise: Nearly half of potatoes now go into frozen products. Last updated: Tuesday, August 29, 2023. Accessed Dec. 1, 2023

(15) United States Department of Agriculture (USDA), Potatoes and tomatoes are America’s top vegetable choices. Last updated: Tuesday, November 26, 2019. Accessed Dec. 1, 2023

About this Article

French Fries are unhealthy, A. Whittall

©2023, 06 Dec. 2023. Update scheduled for 06 Dec. 2026.

Tags: diet, food, health risks, olive oil, French fries, ultra-processed foods, processed foods.

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