Blood lipids include triglycerides and cholesterol, and if either level is too high, it is called "hyperlipidemia". Some people are born with high blood lipids, but more people have them because they are eating the wrong kind of oil.
Modern people consider lard to be "saturated fat," which can cause high blood lipids and heart disease, making it a health hazard. Therefore, they all eat vegetable oil. This is because everyone has heard that vegetable oil is "unsaturated fat" and can lower cholesterol, making it better for the body. In fact, vegetable oil is very prone to oxidation. Therefore, it only lowers cholesterol when it is cold-pressed, fresh, and natural—in other words, when the active properties of the unsaturated fat are still present. Such vegetable oil is indeed healthier than lard. However, most vegetable oils on the market are extracted using chemical solvents, with a shelf life of 2 to 3 years. By the time they leave the factory, they are no longer in their natural state. If used for frying, the high temperatures will produce oxidized fats. When consumed, these can easily clog blood vessels. These rancid and oxidized fats are dozens of times more harmful than lard. Lard, on the other hand, is highly stable, not easily spoiled or oxidized, and is therefore much safer.
Additionally, many people are accustomed to storing vegetable oil near the stove. The long-term exposure to high temperatures can cause the oil to go bad. Consuming improperly stored oil is a major hidden health risk. This is also one of the reasons why, over the past few decades since vegetable oil replaced lard for cooking, cardiovascular diseases have not decreased but have instead increased.