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Eating nutritious foods can improve your health and energy levels.
Surprisingly, the way you cook your food has a major effect on the amount of nutrients it contains.
This article explores how various cooking methods affect the nutrient content of foods.
Almost all foods consumed need some form of cooking and processing for making it fit for consumption. The nutrients we receive from the meals depend largely on the extent of cooking practices used. Some of the nutrients are lost during cooking. Cooking also has its benefits like:
- It increases palatability
- It makes food easily digestible
- Pathogenic micro-organisms are destroyed, thus safe.
- The appearance of food improves
Food prepared in large quantities in institutional kitchens or food processing plants is more prone to loss of nutrients if adequate care is not taken to preserve its nutrients. In the initial stages of cooking the soaking of food in water leads to leaching of vitamins and minerals. These losses can be minimized by washing the uncut fruits and vegetables and not soaking them in water.
Nutrient content is often altered during cooking
Cooking food improves digestion and increases the absorption of many nutrients .
For example, the protein in cooked eggs is 180% more digestible than that of raw eggs .
However, some cooking methods reduce several key nutrients.
The following nutrients are often reduced during cooking:
- water-soluble vitamins: vitamin C and the B vitamins — thiamine (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), pyridoxine (B6), folic acid (B9), and cobalamin (B12)
- fat-soluble vitamins: vitamins A, D, E, and K
- minerals: primarily potassium, magnesium, sodium, and calcium
Summary
Although cooking improves digestion and the absorption of many nutrients, it may reduce levels of some vitamins and minerals.
Boiling, simmering, and poaching
Boiling, simmering, and poaching are similar methods of water-based cooking.
These techniques differ by water temperature:
- poaching: less than 180°F (82°C)
- simmering: 185–200°F (85–93°C)
- boiling: 212°F (100°C)
Vegetables are generally a great source of vitamin C, but a large amount of it is lost when they’re cooked in water.
In fact, boiling reduces vitamin C content more than any other cooking method. Broccoli, spinach, and lettuce may lose up to 50% or more of their vitamin C when boiled.
Because vitamin C is water-soluble and sensitive to heat, it can leach out of vegetables when they’re immersed in hot water.
B vitamins are similarly heat sensitive. Up to 60% of thiamine, niacin, and other B vitamins may be lost when meat is simmered and its juices run off.
However, when the liquid containing these juices is consumed, 100% of the minerals and 70–90% of B vitamins are retained
On the other hand, boiling fish was shown to preserve omega-3 fatty acid content significantly more than frying or microwaving
Summary
While water-based cooking methods cause the greatest losses of water-soluble vitamins, they have very little effect on omega-3 fats.
Grilling and broiling
Grilling and broiling are similar methods of cooking with dry heat.
When grilling, the heat source comes from below, but when broiling, it comes from above.
Grilling is one of the most popular cooking methods because of the great flavor it gives food.
However, up to 40% of B vitamins and minerals may be lost during grilling or broiling when the nutrient-rich juice drips from the meat .
There are also concerns about polycyclic aromatic hydrocarbons (PAHs), which are potentially cancer-causing substances that form when meat is grilled and fat drips onto a hot surface.
However, researchers have found that PAHs can be decreased by 41–89% if drippings are removed and smoke is minimized
Summary
Grilling and broiling provide great flavor but also reduce levels of B vitamins. Also, grilling generates potentially cancer-causing substances.
Microwaving
Microwaving is an easy, convenient, and safe method of cooking.
Short cooking times and reduced exposure to heat preserve the nutrients in microwaved food
In fact, studies have found that microwaving is the best method for retaining the antioxidant activity of garlic and mushrooms
Meanwhile, about 20–30% of the vitamin C in green vegetables is lost during microwaving, which is less than most cooking methods
Summary
Microwaving is a safe cooking method that preserves most nutrients due to short cooking times.
Roasting and baking
Roasting and baking refer to cooking food in an oven with dry heat.
Although these terms are somewhat interchangeable, roasting is typically used for meat while baking is used for bread, muffins, cake, and similar foods.
Most vitamin losses are minimal with this cooking method, including vitamin C.
However, due to long cooking times at high temperatures, the B vitamins in roasted meat may decline by as much as 40% .
Summary
Roasting or baking does not have a significant effect on most vitamins and minerals, except for B vitamins.
Sautéing and stir-frying
With sautéing and stir-frying, food is cooked in a saucepan over medium to high heat in a small amount of oil or butter.
These techniques are very similar, but with stir-frying, the food is stirred often, the temperature is higher, and the cooking time is shorter.
In general, this is a healthy way to prepare food.
Cooking for a short time without water prevents the loss of B vitamins, and the addition of fat improves the absorption of plant compounds and antioxidants.
One study found that the absorption of beta carotene was 6.5 times greater in stir-fried carrots than in raw ones .
In another study, blood lycopene levels increased 80% more when people consumed tomatoes sautéed in olive oil rather than without it .
On the other hand, stir-frying has been shown to significantly reduce the amount of vitamin C in broccoli and red cabbage .
Summary
Sautéing and stir-frying improve the absorption of fat-soluble vitamins and some plant compounds, but they decrease the amount of vitamin C in vegetables.
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Frying
Frying involves cooking food in a large amount of fat — usually oil — at a high temperature. The food is often coated with batter or bread crumbs.
It’s a popular way of preparing food because the skin or coating maintains a seal, which ensures that the inside remains moist and cooks evenly.
The fat used for frying also makes the food taste very good.
However, not all foods are appropriate for frying.
Fatty fish are the best sources of omega-3 fatty acids, which have many health benefits. However, these fats are very delicate and prone to damage at high temperatures.
For example, frying tuna has been shown to degrade its omega-3 content by up to 70–85%, while baking causes only minimal losses
In contrast, frying preserves vitamin C and B vitamins, and it may also increase the amount of fiber in potatoes by converting their starch into resistant starch.
When oil is heated to a high temperature for a long period of time, toxic substances called aldehydes are formed. Aldehydes have been linked to an increased risk of cancer and other diseases .
The type of oil, temperature, and length of cooking time affect the amount of aldehydes produced. Reheating oil also increases aldehyde formation.
If you’re going to fry food, don’t overcook it, and use one of the healthiest oils for frying.
Summary
Frying makes food taste delicious, and it can provide some benefits when healthy oils are used. It’s best to avoid frying fatty fish and minimize the frying time of other foods.
Steaming
Steaming is one of the best cooking methods for preserving nutrients, including water-soluble vitamins, which are sensitive to heat and water
Researchers have found that steaming broccoli, spinach, and lettuce reduces their vitamin C content by only 9–15%
The downside is that steamed vegetables may taste bland. However, this is easy to remedy by adding some seasoning and oil or butter after cooking.
Summary
Steaming is one of the best cooking methods for preserving nutrients, including water-soluble vitamins.
Tips to maximize nutrient retention during cooking
Here are 10 tips to reduce nutrient loss while cooking:
- Use as little water as possible when poaching or boiling.
- Consume the liquid left in the pan after cooking vegetables.
- Add back juices from meat that drip into the pan.
- Don’t peel vegetables until after cooking them. Better yet, don’t peel at all to maximize their fiber and nutrient density.
- Cook vegetables in smaller amounts of water to reduce the loss of vitamin C and B vitamins.
- Try to eat any cooked vegetables within a day or two, as their vitamin C content may continue to decline when the cooked food is exposed to air.
- Cut food after — rather than before — cooking, if possible. When food is cooked whole, less of it is exposed to heat and water.
- Cook vegetables for only a few minutes whenever possible.
- When cooking meat, poultry, and fish, use the shortest cooking time needed for safe consumption.
- Don’t use baking soda when cooking vegetables. Although it helps maintain color, vitamin C will be lost in the alkaline environment produced by baking soda.
Summary
There are many ways to preserve the nutrient content of foods without sacrificing taste or other qualities.
The bottom line
It’s important to select the right cooking method to maximize the nutritional quality of your meal.
However, there is no perfect cooking method that retains all nutrients.
In general, cooking for shorter periods at lower temperatures with minimal water will produce the best results.
Don’t let the nutrients in your food go down the drain.
Various effects seen on the nutrients are primarily because of the HEAT, ALKALI, and ACID.
Effect Of Heat On The Nutrients
- In carbohydrates, cooking has a beneficial effect as it leads to gelatinization of starch and caramelization of sugar which gives color and flavor to food.
- Proteins get denatured thus access to enzymes and digestibility increases.
- Moist heating of pulses improves protein quality.
- Chemical reactions take place when oil is continuously heated. Reactions like hydrolysis, oxidation, and polymerization of the oil. Oil becomes dark and foamy, such an oil should not be used for consumption
- Blanching inactivates certain enzymes that lead to undesirable browning.
- Heat labile vitamins are lost.
- Fat-soluble vitamins are lost during fat frying if a product is not coated properly.
Effect Of Alkali On Nutrients
- Alkali is used during cooking and processing to soften vegetables. Pinch of sodium bicarbonate added to green vegetables helps in brightening the green color.
- B complex vitamins and Vit.C are destroyed in an alkaline medium.
- Excessive cooking in the alkaline medium not only destroys vitamins but makes the texture mushy and gives a soapy taste to the product.
Effect Of Acid On Nutrients
- An acidic medium while cooking helps to preserve water-soluble vitamins and retards enzymatic browning of certain fruits and vegetables.
- Vegetables and pulses take a longer time to cook in an acidic medium as acids precipitate pectin and harden vegetables.
- Vegetables lose their color, so to overcome this allow the volatile acids to escape first, hence greens should be cooked without lid for the first few minutes.
Guidelines For Preserving Nutrients
- Wash vegetables, fruits and rice in just a sufficient amount of water. It is advisable either to cook in a minimum amount of water or to use the cooking water in soups and gravies.
- Cutting vegetables to small pieces and exposing them to air before cooking leads to loss of vitamins particularly vitamin C. Thus it is advisable to cut large pieces and cook for a shorter period.
- The 3 R’s of cooking to conserve nutrients are:
- Reduce the amount of water
- Reduce the length of the cooking period
- Reduce the amount of surface area exposed
- Oil heated repeatedly should not be consumed as repeated heating during frying leads to the production of toxic substances due to pre-oxidation and rancidity.
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