Not All Fats Created Equal

Polyunsaturated fats may be better for the heart than saturated fats

/ Author:  / Reviewed by: Joseph V. Madia, MD Beth Bolt, RPh

(RxWiki News) Fats are a necessary part of the diet. But choosing the wrong type of fat may be the difference between a harmless snack and an unhealthy choice for the heart.

A recent study showed that, while people gained the same amount of weight from eating extra muffins daily, those whose muffins were made with polyunsaturated oils like vegetable oil had better cholesterol levels than people who ate muffins made with saturated fat like butter.

The group that consumed polyunsaturated fats also had better cardiovascular health than those in the saturated fat group, the study authors found.

This study was done by Ulf Risérus, MMed, PhD, of Uppsala Science Park in Sweden, and colleagues.

The researchers studied 39 adults who were around 27 years old. For seven weeks, the adults ate their normal diet and exercised as they usually did. But they ate extra muffins each day to gain about 3 percent of their total body weight. The muffins were all made in the same lab with the same ingredients — except for the fat used.

The participants ate about four extra muffins each day — although they ate only three if they gained weight too quickly.

Nineteen subjects ate muffins with polyunsaturated fat, and 20 ate muffins with saturated fat. None of the participants knew which type of fat was in the muffins they ate.

Saturated fats, such as butter, stay solid at room temperature. Unsaturated fats, like olive oil, are liquid at room temperature. Saturated fats increase LDL (low-density lipoprotein) cholesterol, which is often referred to as "bad" cholesterol. LDL cholesterol collects on the walls of blood vessels. This can make it hard for blood to travel to and from the heart. Saturated fat can also cause lower ratios of total cholesterol to HDL (high-density lipoprotein) — or "good" cholesterol, which helps excrete fats from the body.

At the end of seven weeks, the participants had gained about 2.2 percent of their total weight, but those who ate muffins made with polyunsaturated fats had better cholesterol levels than people whose muffins were made with saturated fat.

Those who ate muffins made with saturated fat had about 9 percent more "bad" cholesterol than people who ate muffins with polyunsaturated fat. The polyunsaturated fat group also had about 18 percent lower total-to-"good" cholesterol levels.

"Even in early adulthood, it is important to avoid high-calorie foods and weight gain, but also it is important to consume sufficient amounts of polyunsaturated fats from ... vegetable oils," Dr. Risérus said in a press release.

Both groups had signs of being insulin-resistant. Insulin is a hormone that helps absorb sugar to be used for energy. People who are insulin-resistant have insulin that is not completely absorbing the sugar in their cells. Insulin resistance is a sign of prediabetes.

Dr. Risérus said he believed the ill effects from eating saturated fats can be easily reversed once the person stops eating them.

Deborah Gordon, MD, a nutrition expert and operator of an integrative medical practice in Ashland, Oregon, took issue with the chains of fats used in this study.

"The saturated fat chosen (palm oil) was a long chain saturated fat," Dr. Gordon said. "The shorter chain saturated fats found in animal fats or the monounsaturated fats (avocado, olive, nuts) were not included in this trial, and thus the finding of palm oil's effects can't be generalized to other fats."

Dr. Gordon said that the omission of certain types of fat is relevant, as it may eventually be determined that different types of saturated or unsaturated fats, with different chain lengths, probably work differently in the body.

The study authors recommended that people replace the saturated fat they eat with unsaturated fats like avocados, olive oil, nuts and canola oil.

This study was published Oct. 15 in the Journal of the American Heart Association.

The Swedish Research Council funded the study. The authors disclosed no conflicts of interest.

Review Date: 
October 15, 2014
Last Updated:
October 20, 2014