How Does Cooking Affect the Nutrient in Foods?
- Nutrition
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One of the best ways to improve our health is by eating foods that are rich in nutrients. Doing so can improve your energy levels and your health.
But then, your cooking method has a major effect on the number of nutrients in your food.
In this article, we will examine the effect that various cooking methods have on the nutrients in foods.
Cooking often alters the nutrient content of foods
When food is cooked before eating, digestion of that food is improved and absorption of nutrients is enhanced (1, 2).
For instance, the protein contained in cooked eggs is far more digestible than that of raw eggs (3).
But then, some cooking methods drastically reduces the nutrient content of certain foods.
The nutrients listed below are often affected when food is cooked. Cooking reduces the amount of the following nutrients:
- Water-soluble vitamins: The B vitamins – thiamine, riboflavin, niacin, pantothenic acid, pyridoxine, folic acid, and cobalamin; vitamin C.
- Lipid-soluble vitamins: Vitamins A, D, E & K.
- Minerals such as potassium, calcium, sodium, and magnesium.
Boiling, poaching & simmering
Boiling, poaching, and simmering are all similar cooking methods. They are water-based forms of cooking.
What differentiates these cooking methods is the temperature of the water in which they are cooked.
- Boiling: 100°C or 212°F
- Poaching: 82°C or 180°F
- Simmering: 85 – 93°C or 185 – 200°F
Vegetables are generally rich in vitamin C, but most of them is lost when they are cooked in water.
It is worth noting that boiling foods causes a drastic reduction in their vitamin C content compared to any other cooking method. Spinach, broccoli, and lettuce may lose at least 50% of their vitamin C content when boiled (4, 5).
Because of the water-soluble nature of vitamin C and its extreme sensitivity to heat, it can easily be destroyed or leech out of veggies when immersed in hot water.
B vitamins have a very high sensitivity to heat. At least 60% of niacin, thiamin, and other vitamins of the B family may be lost when you simmer your meat.
But then, when you consume the liquid containing the juices of the meat, you retain 100% of the minerals and at least 70% of the vitamins (6).
Conversely, boiling fish preserves its omega-3 fatty acid content compared to microwaving or frying (7).
Broiling and grilling
Broiling and grilling are similar methods of cooking. Cooking with these methods is done with dry heat.
When you grill food, the heat source is placed below the food. On the other hand, when broiling, the heat comes from above.
Grilling is a well-known and widely-used method of cooking due to the unique flavor it gives food.
But then, you should know that at least 40% of the minerals and B vitamins may be lost when you broil or grill your food (6).
There are concerns about the carcinogenic effects of polycyclic aromatic hydrocarbons (PAHs). PAHs are formed when fat drips onto a hot surface while grilling meat.
Research shows that it is possible to reduce the amount of PAH by 41-89%. This happens when smoke is minimized and the drippings are taken off (8).
Microwaving
Microwaving is a safe, convenient, and easy cooking technique.
The nutrients in food are best preserved when food is cooked for a short time, while exposure to heat is drastically reduced (9, 10).
Research has shown that microwaving retains the antioxidant activity of mushrooms and garlic (11, 12).
However, between 20 – 30% of vitamin C in vegetables is lost when you microwave it, which is quite insignificant when compared to other cooking methods (5).
Baking & roasting
Baking and roasting refer to cooking with dry heat in an oven.
Many chefs use “baking” and “roasting” interchangeably. However, baking is mostly used for flour-based foods such as muffins, bread, cakes, etc. while roasting is used for meat.
Nutrient losses are minimal with baking and roasting.
But then, because of the prolonged exposure to high temperature, the B vitamins in meat may reduce by as much as 40% (6).
Stir-frying & sautéing
Stir-frying or sautéing means cooking food in a small amount of oil or butter medium in a saucepan over medium-high heat.
Both stir-frying and sautéing share similar techniques. The difference is that stir-frying involves a lot of stirring, a higher temperature, and a shorter cooking time.
Generally, it’s a healthy way to prepare food.
Cooking without water, and for a shorter time prevents the loss of B vitamins, and adding fats improves the absorption of antioxidants and plant compounds (6, 13, 14).
A particular study found that more beta-carotene was absorbed from stir-fried carrots compared to raw ones (15).
In a second study, there was an 80% increase in lycopene levels when people ate tomatoes sautéed in olive oil rather than without it (16).
Conversely, stir-frying causes a significant reduction in the vitamin C content of red cabbage and broccoli (5, 17).
Frying
By frying food, it means that you are cooking the food in a large amount of fat (mostly oil) at a very high temperature. The fried food is usually coated with bread crumbs and batter.
Frying is quite popular because it causes a coating or seal to form over the food, which ensures that the inside retains its moisture and is cooked evenly.
Frying also makes food taste better.
But then, it is important to note that not all foods should be fried.
Fatty fish are excellent sources of omega-3 fatty acids, which have numerous health benefits. Unfortunately, omega-3 fatty acids are quite delicate and at risk of damage when exposed to high temperatures.
For instance, studies have shown that frying tuna causes a massive (70-85%) degradation of its omega-3 content, compared to baking (18, 19).
On the other hand, when you fry food, you preserve its B and C vitamins. Frying potatoes increases its fiber content by converting its starch into resistant starch (20).
Prolong heating of oil causes the formation of aldehydes. Aldehydes are toxic, carcinogenic, and increases the risk of many diseases other than cancer (21).
The number of aldehydes formed depends on certain factors such as the type of oil used, the duration of cooking, and the temperature. When you reheat oil, you also increase the formation of aldehydes.
If you intend to fry your food, try not to overcook it, and use healthy oils when frying.
Steaming
Steaming is a great method of cooking. It preserves nutrients, such as water-soluble vitamins, which have a high sensitivity to water and heat (4, 5, 6, 17).
Studies have shown that steaming spinach, broccoli, and lettuce causes just a 9-15% reduction in their vitamin C content (5).
But there’s a slight disadvantage to steaming. Steamed food tastes bland. But you can remedy this by adding some butter and oil or seasoning after cooking.
How can I maximize nutrient retention during cooking?
The following tips can help you minimize nutrient loss while cooking:
- Use very little water when boiling or poaching.
- The liquid that remains in the pan after cooking veggies is nutrient-rich. Consume it.
- Do not discard the meat juices that drip into the pan.
- Never peel vegetables until you are done cooking them. Or, you may refrain from peeling to maximize their nutrient and fiber density.
- Cook your vegetables in small amounts of water to minimize loss of B vitamins and vitamin C.
- Cooked vegetables should be consumed within a day or two. Exposing the food to air causes a continuous decline in its nutrient content.
- Cook your food whole when possible. By doing so, less of it is exposed to water and heat.
- Vegetables should be cooked for just a few minutes when possible.
- Poultry, meat, and fish should be cooked using the shortest cooking time required for safe consumption.
- Never use baking soda when you’re cooking vegetables. Baking soda produces an alkaline environment which causes loss of vitamin C.
Tonika Bruce, MSN, RN, MBA. is an accomplished nurse leader, published author, and personal development expert passionate about advancing healthcare management and quality patient outcomes.
She taps into the years of experience in healthcare management to produce credible and easy-to-understand health and leadership content. Her exceptional work has been featured in reputable publications, including Forbes, Recruiter, Inc, and the Color of Wellness magazine.
