A History of Science-Based Tips

Over the last many years, the Nutrition Diva podcast has discussed the effect of cholesterol on overall health many times. Today, we bring you some of the most impactful, data-based and diva-delivered information on the subject. We’ll touch on foods like coconut oil, oats, and eggs before wrapping things up with a lesson on how to raise your good cholesterol.

We kick things off with the Nutrition Diva discussing the impact – if any – that coconut oil has on cholesterol. 

How does coconut oil affect cholesterol? 

I have a good listener question for you this week.

Catherine writes:

I’ve lowered my saturated fat intake in an effort to reduce my cholesterol. Over the past several months, I’ve managed to bring it down about 40 points by reducing my red meat consumption.

I’ve also started to look for substitutes for full-fat dairy products like ice cream. Some of these, such as coconut milk based frozen desserts, have quite a bit of saturated fat. Is there a difference in the saturated fat of these two products in terms of how they affect my health?

As Catherine has discovered, reducing your saturated fat intake from food can be an effective way to reduce your blood cholesterol levels. Far more effective, in fact, than reducing your intake of dietary cholesterol. But saturated fats are a whole family of different fatty acids.

Here’s a quick review for those of you who might need a refresher on your fatty acid chemistry:

All fatty acids are “hydrocarbons,” meaning that they are built from carbon and hydrogen atoms. The carbon atoms form a sort of backbone, to which hydrogen atoms attach in various configurations.

When each of the carbons in the chain is linked to two hydrogen atoms, we say that it is fully hydrogenated, or saturated. (If some of the carbons have only one hydrogen partner, it’s an unsaturated fatty acid.) 

Saturated fats come in a variety of lengths, though. Butyric acid is a stumpy little thing, only 4 carbons long. Butyric acid is found in butter. (Butyric/butter sound similar, which makes that easy to remember.) Stearic acid, on the other hand, is a rangy 18 carbons long. Meat is relatively rich in stearic acid. (You can remember this because stearic sounds like “steer.”) Lauric acid, found in coconut oil, is in the middle, with 12 carbons. (I’m afraid I don’t have a handy mnemonic device for that one.)

So the question is whether all saturated fats tend to increase blood cholesterol or only some of them. And, by extension, is butter better or worse for your cholesterol than beef or coconut oil? Or, as Catherine is wondering, would a frozen dessert high in coconut oil be better or worse than full-fat ice cream?

You would think that this question would have been settled by now. But there’s not as much research as you might expect—and the results are a bit mixed. The effects of different fatty acids on cholesterol levels vary, depending on the total amount of fat and saturated fat in your diet, as well as whether or not you have other risk factors for cardiovascular disease.

All the different types of saturated fats (including those in coconut oil) tend to increase total cholesterol levels, but there are some significant differences in their effects on HDL (the “good” cholesterol) and LDL (the “bad” kind).

So, here’s my best advice, based on the research I reviewed. If cholesterol is a concern, you are probably wise to limit your saturated fat intake (from all sources) to no more than 10% of calories. (For the typical adult, that’s about 20 to 25 grams per day.) Monounsaturated fats, such as those in olive oil and avocado, are really your best bet. (And here’s a fun fact: Most cuts of beef contain roughly equal amounts of monounsaturated and saturated fat.)

That’s not true of butter, which is mostly saturated. I really like the taste of butter, so I blend up a stick of butter with an equal amount of olive oil to make a “better butter” that is about half and half monounsaturated and saturated fat. As another plus, it’s spreadable straight out of the fridge, so it won’t tear up your toast.

But, back to Catherine’s original question: in terms of the effects on cardiovascular risk, a coconut-based frozen dessert would appear to be a better choice than full-fat ice cream. Both might have comparable amounts of saturated fat, but the saturated fatty acids in coconut oil are less likely to drive up LDL (“bad”) cholesterol.

However, if you’re trying to reduce your total cholesterol levels, you’d probably want to save the full-fat frozen desserts for special occasions—and in that case, I think you can afford to have whichever one tastes better to you.

Eggs and Oat Bran: The Cholesterol-Fiber Paradox

If cholesterol from food doesn’t affect blood cholesterol levels, why does eating soluble fiber reduce cholesterol? Nutrition Diva explains this apparent paradox. 

A listener named Dan asked:

We’re told that eating foods like oatmeal, which contains soluble fiber, can help lower cholesterol. My understanding is that this works because the fiber binds to the cholesterol in your food, preventing its absorption.

But we’re also told that the amount of cholesterol in your food doesn’t make much difference because, if you get more in your diet, your body just produces less.

If the soluble fiber is reducing absorption of dietary cholesterol, but dietary cholesterol doesn’t matter, then why would that reduce your serum cholesterol?

This is a great question but one that requires a bit of a deep dive to answer. But if this is not the place for deep dives into nutrition nerd-dom, I don’t know where is!

How dietary cholesterol affects blood cholesterol

About 80% of the cholesterol that’s circulating through your body right now was manufactured in your body, not extracted from your food. Most of that de novo cholesterol production happens in the liver, but small amounts are also manufactured in the small intestine.

And Dan’s absolutely right: The liver will ramp its production of cholesterol up or down in response to your dietary intake. Take in more cholesterol through food and the liver will make less, and vice versa. (Cholesterol production in the small intestine is not affected by that feedback loop, however.)

To some extent, the amount of cholesterol that you absorb from food is genetically determined. Some people are “hyper-absorbers” and for them, the amount of cholesterol in their food may have a bigger impact on their blood cholesterol levels.

But for most people, dietary cholesterol intake doesn’t have a significant impact on total blood (serum) cholesterol levels. More to the point, cholesterol intake does not appear to impact the risk of heart disease. This is why we are no longer advised to limit our consumption of dietary cholesterol (unless, of course, you’re one of those hyper absorbers).

If you’re looking for a dietary culprit for high blood cholesterol levels, look to saturated fat and refined carbohydrates, not cholesterol. Eggs and shrimp, which are both high in cholesterol, are virtually carb-free and relatively low in saturated fat.

How soluble fiber affects blood cholesterol

According to the National Lipid Association:

“Soluble fiber can bind cholesterol in the intestine and remove it from the body. Eating 5 to 10 grams of soluble fiber a day can help lower total and LDL-cholesterol by 5 to 11 points, and sometimes more.”

You might imagine that when you eat eggs and oatmeal for breakfast, the soluble fiber in the oatmeal attaches to the cholesterol in the eggs and escorts it out of your body. And because you didn’t absorb the cholesterol from the eggs, the liver will compensate by making more, and the two effects will cancel each other out.

But the cholesterol that the fiber is binding to and removing from your body is not necessarily from foods that you eat. And this may explain the apparent paradox.

A lot of the cholesterol that your liver makes is used in the production of bile acid, which is released into the small intestine to help your body digest and absorb fat. In fact, your body converts about 500 mg of cholesterol a day to produce bile acids. That’s almost twice as much as most people take in through food, which is why the liver has the ability to produce more.

Most of the bile acids that are secreted into the small intestine get reabsorbed into the bloodstream as they pass through the ileum, which is the last stretch of small intestine that food goes through before entering the large intestine. At that point, the only things that get absorbed back into the body are water and electrolytes. Everything else gets eliminated as waste.

But soluble fiber binds to bile. So instead of those bile acids being reabsorbed and recycled, they are eliminated. That means the liver has to produce more bile to replace what is lost. Your liver then pulls more cholesterol out of your blood in order to make more bile acids—and that’s the primary mechanism by which soluble fiber reduces blood cholesterol levels. 

Adding soluble fiber to your diet will have a bigger impact on your blood cholesterol than reducing the amount of cholesterol in your food. Studies show that this is true both for people with and without high cholesterol.

It’s also true for people who are also taking statin drugs because statins reduce cholesterol through a completely different mechanism. Cholesterol is produced via a long chain of biochemical reactions known as the mevalonate pathway. Statins block the very first reaction in this pathway, which effectively shuts down the rest of the pathway. This decreases the amount of cholesterol that the liver can produce, thereby lowering blood cholesterol levels.

The link between high cholesterol and heart disease

But does lowering blood cholesterol really reduce the risk of heart disease? Some research suggests that the link between high cholesterol and heart disease is not nearly as straightforward as we have been led to believe. Although high levels of cholesterol (especially LDL cholesterol) are associated with an increased risk of heart attack, the majority of heart attack victims have normal cholesterol. And while the use of statin drugs does appear to reduce mortality, there may be other factors at work. In addition to reducing cholesterol levels, for example, statins also reduce inflammation—which is another risk factor for heart disease.

The decision to prescribe a statin drug should ideally be based on more than just one’s LDL cholesterol levels.  The amount, type, and ratios of other blood fats, age, sex, personal and familial health history and other risk factors should all be taken into consideration.

But whether or not your doctor feels that a cholesterol-lowering medication is right for you, eating soluble fiber offers a variety of benefits. In addition to lowering your cholesterol, they can also help modulate appetite and help with weight management, as well as promote the growth of beneficial bacteria in your gut.  You can get soluble fiber in oatmeal and oat bran as well as apples, pears, plums, barley, chicory root, Jerusalem artichokes, mushrooms and garlic. Fiber supplements made from psyllium husk (Metamucil) or wheat dextrin (Benefiber) are also good sources.

How to Raise Your HDL

Having more HDL or “good” cholesterol in your blood reduces your risk of heart disease. Here are three ways to increase your good cholesterol level.

When people pay attention to their cholesterol levels, they’re usually focused on trying to