Does the amount of cholesterol you eat affect the cholesterol levels in your blood?

DEAR DOCTOR K:

Does the amount of cholesterol you eat affect the cholesterol levels in your blood?

DEAR READER:

I’m glad you asked this question, because I think doctors and the news media have not made it clear.

For decades, doctors and food scientists have warned against the dangers of eating foods high in cholesterol. That seemed to make sense. First, high blood levels of so-called “bad” (LDL) cholesterol definitely are bad for your health. Second, it seems logical that the more cholesterol you take into your body when you eat, the higher the cholesterol in your blood.

But there’s growing agreement among nutrition scientists that cholesterol in food has little effect on cholesterol in the bloodstream. This topic was discussed last year by the scientific advisory panel for the not-yet-released 2015 Dietary Guidelines for Americans. A summary statement from their meeting stated that “Cholesterol is not considered a nutrient of concern for overconsumption.” Translation: You don’t need to worry about cholesterol in your food.

What has changed? The cholesterol in your body comes from two sources. Some comes from the cholesterol in your food, but most is made by your liver. If your liver is stimulated to make lots of cholesterol, levels rise in your blood.

What stimulates the liver to make cholesterol? Primarily, saturated and trans fats. Below, I’ve listed foods that are rich in saturated fats and foods rich in trans fats. Saturated fats are abundant in red meat, butter and full-fat dairy products. Trans fats are abundant in stick margarine, commercially baked goods and fried foods.

Now, I’m not saying you should never eat foods rich in saturated fats or trans fats — just that you should eat them infrequently.

And I’m not saying you should now eat as many eggs, shrimp and other cholesterol-rich foods as you would like. Eating a lot of cholesterol can raise your blood cholesterol. For example, we’ve talked previously in this column before about eggs. Current science finds that it’s OK to eat an egg a day, except for diabetics or people at high risk for heart disease. But eating a lot more eggs than that is not a good idea.

I worry every time I pass on the latest results of nutrition research. That’s because, as with any type of research, the more you study the more you learn. And sometimes what you learn modifies what you previously thought; that can’t be avoided. What you have every right to expect, from your doctor and from columns like this one, is the best current understanding. But sometimes that understanding will be amended by new discoveries.

So when you’re shopping and looking at the Nutrition Facts label on foods, don’t ignore the amount of cholesterol in the food: Eating a lot of cholesterol-rich foods on a regular basis still is a bad idea. But pay more attention to the listing of saturated fats and trans fats. They are what you should avoid.

Foods rich in saturated and trans fats

Type of fat Main sources State at room temperature Effect on cholesterol
Saturated fat Whole milk, butter, cheese, and ice cream; red meat; chocolate; coconuts, coconut milk, and coconut oil Solid Raises both LDL and HDL
Trans fat Most margarines; vegetable shortening; foods containing partially hydrogenated vegetable oil; deep-fried chips; many fast foods; most commercial baked goods Solid or semi-solid Raises LDL; lowers HDL
Adapted from Eat, Drink, and Be Healthy: The Harvard Medical School Guide to Healthy Eating, by Walter C. Willett, M.D., with P.J. Skerrett (Simon & Schuster, 2005).