A 2023 study from the University of Cambridge showed that improper cooking methods can deprive vegetable dishes of more than 70% of vitamin C—an enormous loss from food that is supposed to be healthy and rich in vitamins.

When you read this, you probably ask yourself: how is it possible that a dish, which seems healthy, brings much less benefit to our body than expected? The answer lies in mistakes that, according to nutrition studies, are made by as many as 78% of households in Europe (report by the European Food Institute, 2024). These kitchen mistakes are often small, almost unnoticeable, but so powerful they destroy vitamins and minerals in the food you eat.

1. Overcooked vegetables – loss of essential vitamins your body needs
   
   One of the most widespread mistakes is cooking vegetables for too long. The evidence is very clear: a 2022 study from the Institute for Nutrition in Berlin showed that in cauliflower, broccoli, and spinach, cooking above 95{-15696}C for more than 10 minutes destroys up to 60% of vitamin C and up to 40% of folic acid.
   
   So if you prepare a plate of broccoli that should be full of nutrients, your body may receive only half of what you intended to consume. Vitamin C is not just a vitamin for colds—it participates in more than 300 biochemical processes in the body (National Nutrition Data, 2021). Folic acid is key for blood and nerve health. That’s why the golden rule of traditional cooking, known for centuries among many herbalists, says: vegetables should be cooked so little that they remain colorful, vibrant, and crispy.
   
   Best ways to preserve nutrients:
   
   • steaming (3–5 minutes, no more),
     
     
   • blanching (briefly dip in boiling water, then cool quickly),
     
     
   • simmering with little water under a lid.
   It’s worth mentioning an interesting experiment from 2020, where researchers at a nutrition clinic in Milan used two preparation methods for carrots on 120 volunteers. The group that ate lightly steamed carrots had 23% higher beta carotene (vitamin A precursor) levels than those who boiled carrots for 15 minutes in water.
   
   
2. Incorrect use of oil – when healthy oil becomes harmful
   
   Many people use oils as their parents did, not knowing that each oil has its own smoke point. This is the temperature at which an oil starts to break down and lose beneficial substances, while harmful compounds can form. This process is called oxidation, a process when oil, due to heat or air exposure, changes in a way that nutrients are lost and it can become harmful to the body.
   
   In the Food Chemistry Journal (2024), an interesting smoke point list for oils was published:
   • extra virgin olive oil: about 160–190{-15696}C
     
     
   • coconut oil: around 200–230{-15696}C
     
     
   • avocado oil: roughly 250–270{-15696}C
     
     
   • refined sunflower oil: about 230{-15696}C.
   That’s why olive oil is not suitable for deep frying, especially at high temperatures, when the pan often exceeds 220{-15696}C. If you use it for stir-frying, the benefits of the oil turn into a loss for your health.
   
   That’s also why our grandmothers often used lard for higher temperatures—it is more stable and does not oxidize as quickly. Today, many overlook this fat, but numerous nutritionists now confirm that when used properly, it can be an important part of a healthy diet.
   
   
3. Peeling fruit with medicinal peels – silent loss of fiber and antioxidants
   
   Did you know that by removing the peel you may lose 30–50% of the fiber (USA Food Data Central, 2023)? In the skins of apples, pears, cucumbers, potatoes, and even peaches, there are extremely powerful substances that protect us from inflammation and cell aging. The peels, in fact, contain the highest levels of quercetin, a strong antioxidant important for the immune system and heart health.
   
   In apple peel, there is 4–6 times more quercetin than in the inner part of the fruit. Studies from 2025 (Harvard Medical Health, clinical testing on 600 people) showed that people who regularly ate apples with the peel experienced 12% fewer seasonal infections and had better vascular function.
   
   Of course, it’s important that the fruit is:
   • well washed,
     
     
   • preferably organic,
     
     
   • cleaned of any soil residues.
   In the countryside, people used to clean apples with coarse kitchen salt before eating, reducing surface impurities. This is still a useful and affordable method today.
   
   
4. Improper food storage – loss of nutrients before the food even reaches your plate
   
   There are silent vitamin destroyers hiding in your fridge. Vitamin C, one of the most sensitive, breaks down by up to 35% within 48 hours when exposed to air, heat, and light, according to a study from the Swiss laboratory NutriLab (2022). A common mistake people make: washing fruit and vegetables before storage, which makes moisture accelerate spoilage and nutrient breakdown.
   
   Another common mistake: cooked dishes remain in the fridge for 3 days or more before being eaten. According to German Institute for Food Safety, cooked dishes should be consumed within 24–48 hours, as nutrient levels decrease significantly after that.

Practical, home, and affordable solutions:

• cook vegetables for maximum 5 minutes, preferably by steaming
  
  
• use appropriate oils depending on the temperature
  
  
• do not peel fruit and vegetables unnecessarily
  
  
• do not wash produce before putting it in the fridge, but just before use
  
  
• eat cooked dishes within 48 hours
  
  
• store food in glass containers (less oxidation than in plastic).

Our great-grandmothers didn’t know about vitamins, but they knew that potatoes cooked in their skins had strength, that pears with peel cleansed the blood vessels, and that cabbage shouldn’t be cooked too long. Today we have laboratories, microscopes, measurements, yet we increasingly find that many ancient principles were surprisingly correct.

Health depends not only on what you eat, but also on how you prepare it

When we understand how sensitive vitamins and minerals are, we can avoid the mistakes that strip food of its purpose. In a world where the number of people suffering from fatigue, poor immunity, and micronutrient deficiencies is rising (according to WHO, as many as 32% of Europeans lack at least one important vitamin), we simply can’t afford this anymore. The kitchen is either a laboratory of health, or a factory of missed opportunities. The difference is in a few small habits.

If you follow these tips at your next meal, your body will feel the difference sooner than you think…