Why does food lose its nourishment

Cooking: the standard procedure as a nutrient killer?

Experts define cooking as "cooking in liquid at a temperature of around 100 degrees Celsius". Pasta, rice or certain vegetables are placed in bubbly boiling water and cooked over medium heat until they are firm to the bite.

Which nutrients are lost in cooking?
Cooking in plenty of liquid causes high losses of the water-soluble vitamins B1, B2, B6 and C. If the cooking water is not then part of the dish - as is the case with soup, for example - conventional cooking reduces the specified vitamins in the dish by up to 60 Percent. This also applies to vegetables that are cooked in their shell, such as jacket potatoes.

Cooking changes the nutrient content positively and negatively
A Chinese study examined the effect of different preparation and cooking methods on the nutritional content of rice. As a result, conventional cooking caused

  • a loss of B vitamins and bioactive phytic acid
  • a loss of zinc and manganese
  • better availability of iron, magnesium and calcium.

The harmful effects on vitamins and phytochemicals became more pronounced the higher the cooking temperature.

Are there any health risks involved in cooking?
Those who habitually cook their food in plenty of water should at least occasionally eat meals with increased vitamin C and vitamin B content through grain products and raw vegetables in order to compensate for a possible deficiency.

Overall, however, conventional cooking offers the advantage of largely killing potential microorganisms. Some foods are also more digestible when cooked: the toxic phasin in legumes is broken down when heated and the carotenoids from carrots, pumpkin and sweet potatoes are better available to the organism when cooked than raw.

Steaming: slow cooking for the health bonus?

Steaming describes cooking in a little water or in steam at around 100 degrees Celsius. Fish, meat or vegetables are put into a saucepan with just enough liquid to cover the bottom. Alternatively, the food is placed in a sieve insert through which the steam from the liquid boiling underneath flows.

What about nutrient retention when steaming?
Since steamed foods come into contact with significantly less liquid, water-soluble ingredients such as vitamins B and C are not washed out as much. The loss of vitamins for the eater is also minimized if the liquid is used to prepare the dish at the end of cooking - for example, as a sauce. Housekeeping experts expect a loss of ten to 25 percent for the water-soluble minerals and vitamins when steaming.

Are there any health risks?
Steaming is per se a particularly nutrient-friendly and digestible cooking method. People who want to lose weight prefer to use them, since most of the fat can be dispensed with when steaming. However, too little fat in the meal inhibits the absorption of certain vitamins such as A, D, E and K. Even steamed dishes should therefore be refined with a little cold-pressed vegetable oil.

Baking - How Many Vitamins Fizzle out in the Oven?

When baking in the oven, the food cooks in dry heat at around 120 to 250 degrees Celsius. The method is suitable for bread, cakes and pizza, as well as for certain types of vegetables such as potatoes, sweet potatoes and pumpkin. If, on the other hand, a roast is prepared in a covered pot in the oven, it is called braising.

How much is the nutrient loss when baking?
The advantage here is that the food does not come into contact with water. Baked potatoes in the oven are one of the gentlest cooking methods for starchy tuber. However, as some ingredients are sensitive to heat, baked goods lose around ten to twelve percent of their vitamins B and C content.
If you value a low-calorie diet, you can take a few simple steps to ensure this when baking.

Are there any health risks?
When preparing foods rich in carbohydrates in the oven, the by-product acrylamide is formed at high temperatures. It forms when sugars such as fructose and glucose, the amino acid asparagine and a low water content in food come together with heat above 120 degrees. From 180 degrees, some baked goods even show a sharp increase in their acrylamide content.

According to research by the European Food Safety Authority (EFSA), the intake of acrylamide increases the potential cancer risk for consumers of all ages. Its metabolite, glycidamide, is the most likely cause of tumor growth and gene mutations in animal experiments. In order to reduce the acrylamide intake - especially in children who quickly consume a relatively large amount of it based on their weight - the following rules must be observed when baking:

  • Baked rolls and toast should be baked golden yellow instead of brown in the oven. The lighter the crust of the baked goods, the less acrylamide they contain.
  • Ovens with top and bottom heat should be heated to a maximum of 200 degrees Celsius for dough and potato products; Ovens with circulating air to a maximum of 180 degrees.
  • For french fries, cutting larger and thicker potato sticks and using baking paper will help lower the acrylamide levels. After half the cooking time, ideally turn the fries once on the other side.
  • Egg yolks and baking powder in biscuits reduce the acrylamide levels, deer horn salt as a leavening agent and roasted almonds and nuts increase them.

Grilling - does a lot of smoke cause major risks?

Grilling is the generic term for various cooking methods that have one thing in common: The cooking process uses radiant heat from charcoal or a gas flame and contact heat with the grillage. But within this framework there are different grill methods:

  1. Direct grilling: Here the food lies directly above the heat source and is briefly exposed to very high temperatures of around 230 to 290 degrees. Hobby and professional grillers like to use this method to sear steaks and chops.
  2. Indirect grilling: Inside a closed grill, the ingredients are not located directly above the heat source, so that the heat generated causes them to cook evenly throughout the interior of the grill. Temperatures of 160 to 200 degrees are common, but reduced cooking temperatures are also possible if the time is extended accordingly.
  3. Smoking in the smoker: The smoker is particularly widespread in the USA, where meat was given the characteristic smoke aroma in this way as early as the 19th century. Due to the special design of the device, the cooking space and fireplace are separate so that the ingredients are prepared using indirect heat. Thanks to the closed cooking space, the smoker is also suitable for cooking at low temperatures (70 to 90 degrees). Wood chips or pieces that burn up inside the connected fire box provide the smoke that pulls through the cooking space and gives the meat a typical smoky aroma.
How many vitamins are lost when grilling?
Like the oven, every grill also works with dry heat - the loss of water-soluble vitamins and minerals is therefore relatively low at ten to twelve percent.
Are there any health risks?
When grilling, there is a risk of carcinogenic substances forming - such as the so-called polycyclic aromatic hydrogens (PAH) or heterocyclic aromatic amines (HAA). Consuming large amounts of these substances is considered to be risky with regard to adenomas, which in turn are the precursors to colon cancer. The formation of HAA cannot be completely avoided when grilling, because it always forms when protein-containing foods are heated. However, the content increases significantly if the products are grilled too hot or for too long.
What should barbecue fans pay particular attention to?
The PAH content of grilled food is particularly high when it comes into direct contact with smoke gases. This happens primarily when the fat and marinade from the meat drips into the embers, burns there and then comes into contact with the food as smoke. Deglazing the grilled food with beer improves the aroma, but also generates smoke and thus higher PAH values ​​in the food.

Which types of meat are not suitable for grilling?
Caution is advised when pickling meat is heated on the grill at high temperatures. Cured food contains nitrite curing salt, which can be converted into nitrosamines when exposed to high heat. These substances are considered to be a risk factor for esophageal and stomach cancer.

Roasting - A Greasy Pleasure?

Frying in the pan is undoubtedly one of the most popular cooking methods in this country when it comes to steak and schnitzel. Hot oil cooks meat and fish at around 140 to 190 degrees Celsius and gives them an appetizing crust through the so-called Maillard reaction. In this process, sugar and proteins in the food are converted into dark and aromatic colors, the so-called melanoidins, in a multi-stage process.

Does frying damage the nutritional content?
Since the food in the frying pan is exposed to heat for a relatively short time and there is no water involved, the loss of vitamins is also relatively low at seven to ten percent. When it comes to the health value of fried foods, many people believe that the well-cooked proteins in fried meat are easier to use. A bloody steak would therefore be more difficult to digest than a piece of meat that has been cooked through or "well done".

A French study in 2017 revealed that this difference is of little consequence for young consumers. Meat eaters from the age of 70 can metabolize well-cooked meat much more efficiently and gain a higher content of the amino acid leucine than from cooked meat.

Are there any health risks?
When frying, the slightly lower temperatures potentially produce less acrylamide than in the oven. However, due to the high fat absorption of the respective foods, especially breaded meat and fish pieces, the cooking method is only suitable for a daily healthy diet to a limited extent.

The type of frying fat is also decisive for the health value of the food. A distinction is made between fats with a high smoke point, which contain predominantly saturated fatty acids, and fats with a low smoke point, which are rich in unsaturated fatty acids. Although the latter are preferable in salads, they run the risk of burning when frying and releasing carcinogenic substances.

Fats and their smoke point

  • High smoke point fats (over 200 degrees): palm fat, peanut oil, clarified butter, refined sesame oil, refined grapeseed oil, refined olive oil, refined rapeseed oil
  • Medium smoke point fats (160 to 190 degrees): butter, virgin olive oil, roasted sesame oil, argan oil, walnut oil, virgin rapeseed oil
  • Low smoke point fats (below 160 degrees): safflower oil, hemp oil, linseed oil

Sous-vide - haute cuisine with health benefits?

In the sous vide process, food is cooked in a vacuum bag inside a water bath. The temperatures are in the range between 50 and 90 degrees. Because the heat is moderate and there is no contact with water, particularly aromatic and juicy dishes are successful. Meat and fish that are cooked in a vacuum are then fried for about 30 seconds on each side so that the Maillard reaction creates additional roasting aromas.

How gently does Sous-Vide affect the nutritional content?
During sous vide cooking, the water-soluble vitamins B and C do not come into contact with liquid, so that losses are minimal. Some minerals and trace elements are even found in higher proportions in vacuum-cooked foods. A study in which beans, peas, lentils and pearl barley were prepared using the Sous-Vide method found significantly higher levels of iron, potassium, zinc and copper. The food here provided up to 800mg more per serving than conventionally cooked dishes.

Does sous vide cooking pose any health risks?
If food is prepared for a very long time (over four hours) at comparatively low temperatures of 50 to 60 degrees, the risk of food germs multiplying during this time increases. Vacuum-cooked food is not sterile after preparation, like meals cooked at the boiling point, and should therefore be consumed immediately or frozen immediately.
It also depends on the suitable materials: Sous-vide bags must be tested by the manufacturer for limit values ​​for harmful substances in order to guarantee that no components of the plastic migrate into the food during the water bath.

Does sous vide cooking pose any health risks?
If food is prepared for a very long time (over four hours) at comparatively low temperatures of 50 to 60 degrees, the risk of food germs multiplying during this time increases. Vacuum-cooked food is not sterile after preparation, like meals cooked at the boiling point, and should therefore be consumed immediately or frozen immediately.

It also depends on the suitable materials: Sous-vide bags must be tested by the manufacturer for limit values ​​for harmful substances in order to guarantee that no components of the plastic migrate into the food during the water bath.

Frying - Better Than Its Reputation?

When deep-frying, food is cooked floating in hot fat, whereby the temperature of 160 to 170 degrees is quite a bit lower than in the frying pan and in the oven. The Maillard reaction gives meat a tasty crust, while breadcrumbs and pastry casings are baked until golden brown in the fat.

How many nutrients are lost in the deep fryer?
As far as the nutrient loss of water-soluble minerals and vitamins is concerned, the deep fryer produces dishes that are better than their unhealthy reputation: only seven to ten percent of the nutrients mentioned are lost here.

What are the health risks?
There is a risk of acrylamide formation in the deep fryer, but it is somewhat lower than in the oven. If you deep-fry French fries below 175 degrees and limit the time to 3.5 minutes, the creation of harmful substances is significantly reduced. In addition, the choice of fat is decisive for the potential health impact of deep-frying - after all, the eater ingests relatively large amounts of it through breading and pastry casings.

Which fat is suitable for deep-frying?
Even if it is generally said that cold-pressed vegetable oils are more beneficial to health than refined ones, this does not necessarily apply to the deep fryer. When native vegetable oils are heated to a high temperature, trans fatty acids can form here, which in turn are considered a risk factor for arteriosclerosis and heart attacks.

Refined oils or vegetable fats such as coconut or palm fat, which mainly consist of saturated fatty acids, are better. If the deep-frying fat is filtered after the first run, it can definitely be used one or two more times. For good results at low temperatures, cut meat and vegetables into relatively flat pieces so that when the shell turns golden brown, their insides are cooked through.

Microwaves - vitamin-friendly radiation sources

Here, the water molecules are made to rotate within the food with the help of electromagnetic waves and the food in question is heated up in a very short time. This method is suitable for both defrosting and reheating as well as cooking food.

How many vitamins are lost in the microwave?
Since the microwave works with relatively short cooking times and little liquid is required, the water-soluble vitamins in particular are largely preserved. Depending on the length of the cooking time, you have to assume a loss of between five and 25 percent.

Do the rays damage health?
In fact, human tissue, especially the eyes, can be damaged by exposure to microwaves. As a rule, however, the common microwave oven models shield this radiation from the outside to almost 100 percent. If the door of the microwave no longer closes properly or if it is cracked, the appliance should no longer be used. Against all concerns, the electromagnetic waves in the food do not form any carcinogenic residues. Another advantage of the microwave: Since there is little browning, most foods do not produce any acrylamide.

Conclusion: It always depends on the individual case

With water, with oil, with hot air - the world of cooking methods is diverse and is constantly getting new dimensions through innovative kitchen helpers. It is not possible to make general judgments about the health suitability or unsuitability of a method.
The fact is: when cooking gently with little liquid, most of the nutrients are retained. But all other cooking methods - if you follow certain rules - are definitely justified in a varied diet.