Answer
The correct statement about trans-fatty acids is:
They are produced when polyunsaturated oils are hydrogenated.
Explanation
Let's break down each statement:
- They are synthesized by the body.
This statement is false. Trans-fatty acids are not synthesized by the human body. They are primarily produced industrially in a process called hydrogenation.
- Their amounts are never listed on food labels.
This statement is false. In many countries, including the United States, food manufacturers are required to list the amount of trans fats on nutrition labels.
- They are produced when polyunsaturated oils are hydrogenated.
This statement is true. Trans fats are created through an industrial process that adds hydrogen to liquid vegetable oils to make them more solid, known as hydrogenation.
- They do not contain double bonds.
This statement is false. Trans fats do contain double bonds, but unlike the cis configuration found in unsaturated fats, the hydrogen atoms in trans fats are on opposite sides of the double bond.
- They lower blood LDL cholesterol when consumed.
This statement is false. Trans fats increase levels of low-density lipoprotein (LDL), or "bad" cholesterol, and decrease levels of high-density lipoprotein (HDL), or "good" cholesterol, which can contribute to heart disease.
For more information on trans-fatty acids, you can refer to this link.
