Healthy, nutritious food provides us with lasting energy (calories) to get through the day, nutrients for growth and development, and essential vitamins and minerals to maintain good health. Without it, the body cannot function at optimal capacity.
Primordial humans consumed raw food. Either they consumed animals that fell prey to hunting or food that grew naturally from the soil. The act of cooking is a fairly new method for food preparation especially when taking into account the duration of human history and it begs the question, “Does heat kill the nutrients in food?”
The answer is not simply a yes or no.
Exposing food to heat will definitely alter the nutrients and enzymes found in your food but the degree at which they are altered depends on what type of food is being cooked and the heating process involved.
When food isn’t cooked or heated, nutrients and enzymes are left intact, but exposing food to heat above 120° F or 49° C may kill enzymes.
Additionally, vitamins and minerals may also be denaturalized or destroyed during the heating process.
Obviously, we want our bodies to absorb as many nutrients from food as it can to receive the most benefit, but not all of us are accustomed to eating raw food. Luckily, it doesn’t have to be all or nothing. Cooking food also has its advantages such as reduction in “malignant microbes”, an increase in certain phytonutrients, and easier digestibility.
This article will review different heating and cooking methods and the effect they have on nutrients and enzymes of certain food.
Different Cooking Methods and Their Effects on Nutrients
Steaming is one of the best cooking methods for retaining nutrients. Even though the taste of food may come out more bland compared to other food preparation methods, the nutrient content remains higher. This includes water soluble vitamins.
A study done in 2013 found that steaming broccoli and spinach reduced vitamin C by only 11-14 %. (1)
Grilling is one of the most popular forms of cooking since it is touted as one of the ‘healthy’ options. Food seems to have more flavor through this method, and it helps take out some of the fat content, a useful tool when cooking with high fat cuts of meat. However, there are concerns about the carbons that result from grilling.
The polycyclic aromatic hydrocarbons (PAH) have been linked to cancer. This usually occurs from the smoke that is generated by any drippings onto hot coals. (2)
PAH are particularly evident when grilling meat. As meat is grilled and melting fat drips onto a hot surface, carcinogenic smoke rises. During grilling, a significant amount of B vitamins are lost as well as certain minerals in the food.
Microwaving is an easy and convenient way to heat and cook food. It is also one of the better methods for retaining nutrients due to short cooking times. Shorter cooking time results in reduced exposure to heat which helps food retain nutrients. (3)
With broccoli, spinach, and other green vegetables, 20-30% of vitamin C is lost through microwaving. The percentage lost is significantly less than with most cooking methods. (4)
Just be sure to use microwave-safe containers to ensure that you are not allowing toxins to seep into your food. Regular plastic for example, such as those used in sour cream or yogurt, are not meant to be used for heating and thus can warp or melt in the microwave. These can release chemicals into your food which can lead to a string of negative health effects.
Roasting does not have a significant impact on the loss of vitamins and minerals. However, when it comes to meat, due to the long cooking time at higher temperatures, B vitamins may decrease significantly. (5)
Roasting, like grilling, helps take out excess fat from meats. However, roasting also takes much longer than other cooking methods since it is more of a slow cooking method. So while it may be less carcinogenic than grilling, it is still not an ideal choice for preserving the nutrient content in your food.
5. Sautéing and Stir Frying
Sautéing and stir frying are two methods that are basically the same. Both improve the absorption of fat soluble vitamins and nutrients from plants, but they decrease the amount of vitamin C in certain food.
With both, food is heated in a pan over heat with a small amount of butter or oil. The only difference is that with stir frying, the food is stirred often, the cooking temperature is higher, and the heating time is shorter.
By cooking a short time without the use of water, B vitamins are retained. With the addition of fat (butter or oil), the absorption of the plant nutrients and antioxidants is improved. (6)
Beta-carotene was found to be 6.5 times higher in carrots when they were stir-fried as opposed to being eaten raw. (7) Tomatoes, when sautéed with olive oil, had an increase in lycopene of about 80%. (8) However, stir frying did show a decrease in vitamin C in red cabbage. (9)
Frying is one of the most popular cooking methods and can definitely improve the taste of food. Unfortunately, frying is also one of the worst methods when it comes to nutrient retention.
Heating this way involves large amounts of fat at a very high temperature and often times, food is drenched in a type of batter or in bread crumbs.
Some food, such as salmon and tuna, should not be fried at all. Rich in omega-3 fatty acids, these fatty fish are very delicate and the nutrients are easily destroyed at high temperatures. Frying fish such as tuna has been shown to denaturalize it’s omega-3 content by up to 85%. (10)
Additionally, when oil is heated to high temperatures over an extended period of time, poisonous substances called aldehydes form (11), not to mention the excess calories added due to the oil that is absorbed into the food during the cooking process.
Boiling is one of the easiest methods for heating food, but if you boil your vegetables or fruit, you are losing a lot of essential and key nutrients.
Vegetables and fruit contain many water-soluble vitamins. The longer vegetables or fruits are submerged in water, the more vitamins seep out. The loss of vitamins increases when you add heat to the process.
Many nutrients are heat sensitive and are easily destroyed when exposed to heat for a prolonged period of time. Vitamins and minerals such as potassium, sodium, calcium, magnesium phosphorous, iron, manganese and copper decrease significantly by about 65% when boiling. (12)
How to Preserve the Nutrient Content of Food
There are many ways to preserve the nutrient content in food. Here are some suggestions:
1. Eat food raw.
Not necessarily meat, but when it comes to fruits, vegetables, nuts, and seeds, eating what mother nature provided without altering its ecological balance is the most beneficial way to get live nutrients into your system. A raw diet has many health benefits if you can minimize cooking or heating.
2. Dehydrate your food.
Dehydrating or drying food only minimally affects its nutrient content. By drying your food yourself, you can produce a high-quality nutrient-dense meal. Also, it is easy to plump up again when cooking.
Dehydrating food is a great way to preserve your food without adding actual preservatives. Hunters use this method for preserving meats when traveling since they don’t have access to a freezer or canning equipment.
3. Microwave but keep the cooking times short.
Surprisingly, microwaving seems to be the lesser evil when it comes to cooking. Microwaving is better because of the short cooking time. You get results with minimal destruction of enzymes and nutrients.
4. When boiling or poaching, use as little water as possible.
Since nutrients leach out into the water, keep the water to use in soups, stews, broths, or other places you may need to cook with water. Find a way to consume the nutrient-rich liquid left after boiling.
5. Don’t peel the vegetables or fruit before cooking them.
When food is cooked whole, less of it is exposed to heat and if boiling, fewer nutrients will leach out.
Keeping the skin on may increase cooking time slightly, but it is well worth the preservation of nutrients.
6. Use the shortest cooking time manageable.
Less is more. When cooking with fruit or vegetables, heat for only a few minutes. With meat, poultry and fish, use the shortest cooking time deemed safe. Use a cooking thermometer to gauge the correct temperature of meats to ensure that you’re not cooking them for longer than necessary.
There is a lot of truth behind raw detox diets after all. The amount of nutrients lost during heating will vary depending on the food and the process used to cook the food, so it is important to select the right cooking process to maximize the nutritional content of the food. There is, however, no precise method of heating that will retain all the nutrients.
If it is safe, try consuming food in its raw, natural form as often as you can or cook them in a way that will reduce as much nutrient loss as possible.
Bottom-line: eating raw, cooking for shorter periods of time at lower temperatures, and using minimal water will produce the best results for retaining nutrients.
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