Groundnut oil is simply another name for peanut oil, which contains a high percentage of monounsaturated fat, but more saturated fat than canola oil and more polyunsaturated fat than olive oil.
All polyunsaturated fats help lower total cholesterol and LDL ("bad") cholesterol, but generally have no effect on HDL. A study from India published in 2006 in the Yale Journal of Biology and Medicine did show that feeding diabetic rats groundnut oil lowered the animals' total cholesterol, LDL, triglycerides and also raised HDL ("good") cholesterol, but that's the only study I've found showing that peanut oil increases HDL. Most of the studies that have looked at the effect of peanuts and peanut oil on human heart health have shown that the oil and peanuts help lower total cholesterol and LDL but do not increase HDL.
HDL is called "good" cholesterol because in this form cholesterol travels away from the arteries and back to the liver for eventual elimination from the body. The higher your HDL, the lower your risk of heart disease. Studies on cholesterol and heart disease have suggested that each increase of 4 milligrams per deciliter of blood (mg/dl) in HDL results in a 10 percent decrease in the risk of adverse coronary events. In contrast, LDL ("bad") cholesterol can combine with other substances and build up in the walls of arteries to form "plaque." Over time, this plaque damages arterial walls, causing them to narrow and harden. Also, the rough surface of plaque can provide a site for blood to clot, sometimes completely blocking an artery, or forming an embolus that can travel elsewhere in the body and cause a stroke.
If you're looking for ways to increase your HDL, try the following lifestyle approaches:
- Emphasize low-glycemic-load carbohydrates in your diet.
- Lose weight if you're too heavy.
- Get regular aerobic exercise. (I recommend starting any new exercise program slowly and aiming for 30-45 minutes daily.)
- Moderate alcohol intake can raise HDL - emphasis on "moderate."
Pharmaceutical companies are scrambling to find drugs that raise HDL as effectively as statins lower LDL but so far have not come up with any that are safe and effective.
As far as cooking oil is concerned, I recommend relying on extra virgin olive oil. For a neutral-tasting oil, I prefer organic, expeller-pressed canola oil. If you do use peanut oil, be sure to use organic, expeller-pressed products.
Andrew Weil, M.D.