Every time I enter the supermarket, I see shelves overflowing with all sorts of oils: peanut oil, corn oil, soybean oil, rapeseed oil, blended oil, salad oil, olive oil, and so on—it's dazzling and overwhelming. Sometimes I just end up buying a random bottle. So, do you buy your oil randomly too? What's so good about olive oil, and why is it so expensive? Which oils are suitable for cold dishes, and which for hot dishes? What kind of oil is best for frying? We've invited nutritionist Gu Zhongyi to answer your questions about choosing and using oils healthily.

　　Netizen: Which is healthier and better: peanut oil, soybean oil, rapeseed oil, corn oil, or sunflower seed oil?

　　Gu Zhongyi: Among these, low-erucic acid rapeseed oil is not bad. Corn oil and sunflower oil have unique flavors. Similar to soybean oil, they have too high a proportion of n-6 polyunsaturated fatty acids, while according to the general dietary structure of Chinese people, the proportion of n-3 polyunsaturated fatty acids should be increased.

　　Netizens: What's so good about olive oil? Why is it so expensive? Is it really as good as the advertisements say? Can babies eat it?

　　Gu Zhongyi: Olive oil is rich in monounsaturated fatty acids. Because it plays an important role in the traditional Mediterranean diet, which has been proven by many studies to be very healthy, olive oil is recommended by many people. There is relatively more evidence of olive oil's health benefits than other oils. However, even abroad, there are many fake olive oils. Low-erucic acid rapeseed oil has a composition very similar to olive oil, and genetically modified rapeseed oil is much cheaper and offers better value. As for the advertisement you mentioned, I haven't seen it. Actually, most cooking oils are suitable for infants, but it's completely unnecessary. Exclusive breastfeeding is recommended for the first 6 months, followed by complementary foods as needed.

　　Netizen: Is sesame oil from northern China any good? Is hot-pressed sesame oil any better?

　　Gu Zhongyi: First, you need to determine what sesame oil is. In some places, cold-pressed sesame oil is called flaxseed oil, while hot-pressed sesame oil is called sesame oil. Some raw materials may also contain some rapeseed. In some places, sesame oil is actually black sesame oil, which is often used as a standard ingredient in postpartum meals... In fact, none of them are particularly magical. Hot-pressed sesame oil is definitely not recommended because it increases the oxidation reaction. During the Spring Festival of 2016, the State Food and Drug Administration also reported sesame oil with excessive peroxide value.

　　Netizen: What kind of cooking oil does Teacher Gu use at home?

　　Gu Zhongyi: I usually check what I can buy with my meal card at the hospital convenience store... The last time I bought oil online, I bought genetically modified soybean oil, mainly because it's convenient to buy in small packages. I usually cook mainly steamed dishes, so I use very little oil.

　　Netizens ask: Which oils are suitable for cold dishes, and which are suitable for hot dishes? What kind of oil is suitable for frying?

　　Gu Zhongyi: Soybean oil, flaxseed oil, wheat germ oil, and extra virgin olive oil are more suitable for making cold dishes. Regular rapeseed oil and peanut oil can be used for stir-frying. Palm oil, coconut oil, and medium- and long-chain fatty acid cooking oils are more suitable for frying.

　　Netizen: When cooking, is it better to mix several types of oil together, or to use different oils for different dishes? How should I choose?

　　Gu Zhongyi: Of course, it's better to use them separately according to temperature than to mix them. I personally don't recommend using blended oils, even though they might be more cost-effective, because the ingredient ratios aren't clear enough. Actually, refined olive oil and tea oil have a wider range of uses and can handle most frying and stir-frying.

　　Netizen: I've seen my roommate fry chicken wings with olive oil. Is that a reliable method?

　　Gu Zhongyi: Many people think of olive oil as something very precious and only suitable for cold dishes. Extra virgin olive oil, due to its higher content of antioxidants and flavor compounds, is indeed only recommended for cold dishes or general cooking. However, refined olive oil can be used at higher cooking temperatures. Specifically, using extra virgin olive oil to pan-fry chicken wings is definitely not recommended. However, considering the high amount of subcutaneous fat in chicken wings, most households only need to brush them with a small amount of oil when pan-frying and won't heat them for a long time, so occasional use in this way is not a big problem.

　　Netizen: How much n-3 series oil should I consume daily, and how do I choose the right one?

　　Gu Zhongyi: I don't quite understand what you mean by n3 series oil? As for common cooking oils, flaxseed oil has an n3 series polyunsaturated fatty acid content of over 50%, which is good for cold dishes, but not suitable for heated cooking.

　　Netizen: How should I use the almond oil and perilla seed oil provided by my company? Can I use them directly for cooking?

　　Gu Zhongyi: Almond oil has a relatively high content of monounsaturated fatty acids, similar to olive oil. It's fine for simple stir-frying unless cooking at very high temperatures. Perilla seed oil is somewhat similar to flaxseed oil, with a high content of linolenic acid. It's not suitable for high-temperature cooking; it's better suited for simple cold dishes or stews.

　　Netizen: My husband is overweight, and I haven't been able to lose weight since giving birth. What kind of oil should I eat that won't cause more fat accumulation and make me gain weight?

　　Gu Zhongyi: Soy sauce.