Nutrient Losses During Cooking

Why we cook

Beyond the variety of flavors and textures that healthy recipes and the culinary arts give us, cooking helps make our food safe, increases some nutrient absorption, and breaks down components that would otherwise make the raw versions inedible. 

Food safety

It's estimated that one in ten people become ill after eating contaminated food each year (1). Cooking helps preserve food and kill harmful bacteria, viruses, or parasites. This is especially important for perishable, high-protein foods such as meat, poultry, fish, and eggs. 

Check out Foodsafety.gov for minimum cooking temperatures. 

Nutrient absorption 

Cooking helps release some nutrients and makes them more available for absorption because it is difficult for our bodies to break down dietary fiber. Instead, our gut bacteria do. 

Cooking helps break down some of the fiber. For example, lycopene is an antioxidant that gets released when cooked. This has been thought to be responsible for reducing the risk of some cancers and heart disease (2). Cooking protein foods, such as eggs, can also significantly increase protein absorption when compared to its raw version (3). 

Destroys anti-nutrients 

Anti-nutrients are compounds typically found in plants that can interfere with nutrient absorption (4). Some can even be harmful. Potatoes contain solanine which can cause diarrhea, stomach upset, and vomiting, but cooking helps destroy it, so they’re not harmful to eat. High heat cooking and soaking can also degrade some antinutrients (5).  

Nutrient losses during cooking: what the science says

The United States Department of Agriculture (USDA) created a list of the vitamin and mineral losses that occur using different cooking methods. This was conducted on 290 foods. The primary nutrients impacted were vitamin C, B vitamins: folate, and thiamin (6). Other research showed that vitamin K and minerals are also decreased during some cooking methods. 

Vitamin C

In one study which evaluated the effect of different cooking methods on the vitamin content of vegetables, higher retention of vitamin C was found after microwaving; the lowest retention was found after boiling (7). In another study, they found that the vitamin C content of broccoli, spinach, and lettuce may decrease by up to 50% when cooking (8). Steaming vegetables such as broccoli can best help preserve these nutrients as well as antioxidants (9). 

B vitamins

Since B vitamins are water-soluble, they are easily lost during cooking methods, such as boiling, which includes a lot of water. In one study, only 40% of folate (vitamin B9) was retained, while thiamin (vitamin B1) can have a loss of 20-80% during cooking. Niacin (B3), biotin (B1), and pantothenic acid (B5) tend to be more stable (10). Potatoes are best cooked at a low temperature for a longer amount of time. This helps retain the folate. It's best to keep the skin on during cooking as well. 

Fat-soluble vitamins 

In terms of fat-soluble vitamins (A, D, E, K), cooking some vegetables actually created a higher content of vitamin E and A. Vitamin K loss varied. In one study, microwaving caused the greatest loss of vitamin K in crown daisy and mallow vegetables while it caused the most negligible loss in spinach and chard (7). Fat-soluble vitamins such as vitamin A, D, E, and K may get leached into fats, such as when cooking with oil.

Minerals

When minerals including sodium, potassium, calcium, magnesium, iron, zinc, copper, manganese were tested with different cooking methods, cooking losses were particularly high in minerals of vegetables. The most minerals were lost during squeezing after boiling and soaking in water after being thinly sliced. Followed by parching, frying, and stewing (11). 

Prevent nutrient losses during cooking   

• Water-soluble vitamins and minerals: get leached into water when cooked, so it’s best to limit the amount of water and not overcook (12). 
• Fat-soluble vitamins (A, D, E, K): some vitamins get released into oil, so it can be helpful to microwave them or cook them in little oil. 
• Eat boiled food with the soup or water used for cooking.
• Add a small amount of salt during boiling. 
• Avoid too much boiling. 

For more details on cooking methods, check this out: How Should You Prepare Your Vegetables And Legumes For The Most Nutrient Content?

In summary, the key is to cook but not overcook your foods. Make sure to get a balanced diet that includes a variety of nutritious foods. This will help replace any nutrients that may have been lost during your cooking process. 

Not sure if you’re cooking food for the right amount of time? No problem! We’ve got plenty of recipes to help teach you the optimal cook time. Check out Lifesum today. 

All of the content and media on Lifesum is created and published for information purposes only. It is not intended to be used as a substitute for medical advice or treatment. Users should always consult with a doctor or other health care professional for medical advice.