Can You Get Enough Fiber on a Low Carb Diet?

Christy writes:

“I need your expertise! I am overweight and suffer from polycystic ovarian syndrome (PCOS). For that, I’m told to follow a low-carb diet. But I also have mildly elevated cholesterol and a familial tendency toward fatty liver disease. For that, I’m told to eat lots of fiber and whole grains, which are loaded with carbs. So what should I do?”

Maybe you’ve found yourself in a dilemma similar to Christy's, where dietary recommendations for one health concern directly conflict with dietary advice for another. For example, I remember getting an email a few years back from a woman who had both IBS and diverticulosis and was wondering about her doctor’s advice to eat a high-fiber diet. While that can certainly help with diverticulosis, it can make IBS worse!

See also: Should I Eat a High Fiber or Low Fiber Diet for Diverticulitis?

In some cases, your best bet may be to work with a nutrition professional, who can not only help you sort through and reconcile conflicting recommendations but can also help you translate them into practical solutions such as meal plans and shopping lists.

That was definitely the case for the woman with IBS and diverticulosis and it might also be a good idea for Christy. In the meantime, however, I think I can help resolve Christy’s dilemma—because the recommendations to increase fiber and decrease carbohydrates are not as contradictory as you might think.

Why Is Low Carb Better for PCOS?

Let’s start by taking a closer look at the idea that people with PCOS need a low carb diet. As I talked about in a previous episode on PCOS, people with this condition are likely to have some degree of insulin resistance, meaning that they have trouble managing their blood sugar. Going on a strict low carbohydrate diet is one way to deal with insulin resistance but it’s not the only way.

I prefer a less drastic approach, where we focus on reducing the carbs that are doing the most damage (and contributing the least nutrition) but avoid throwing the baby out with the bathwater.

First, you’d want to eliminate sweetened beverages, fruit juice, candies, pastries, desserts and other things made with sugar and white flour. These are high glycemic carbohydrates, meaning that they are quickly digested and absorbed into the bloodstream. Eating a lot of high glycemic carbs when you have insulin resistance or blood sugar issues is like pouring gasoline on a fire.

See also: What is High Glucose?

Other, more nutritious sources of carbohydrates, such as whole fruit, dairy products, legumes, and whole grains aren’t high glycemic foods--but they’re not low glycemic either.  They can certainly be included in your diet. The trick is to consume them in moderation. So, for example, while whole grains are a better choice than refined grains, you still might limit your consumption of whole grain foods to just a couple of servings per day. 

Non-starchy vegetables are almost 100% carbohydrate—but these are very low glycemic carbs (not to mention nutritional superstars) No need to limit them.

Just to review: You’re going to largely eliminate high glycemic carbohydrates like sweetened beverages, desserts, white bread and other things made with white flour. You’re going to moderate your intake of moderate glycemic carbohydrates like whole fruit, dairy, legumes, and whole grain foods. And you’re going to load up on low glycemic carbohydrates.like non-starchy vegetables. So far, so good.

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How to Get Enough Fiber on a Low Carb Diet

Now let’s take a look at the dietary recommendations for high cholesterol and/or fatty liver disease. Both of these conditions benefit from a diet that is higher in fiber. A good goal is 25 to 30 grams of fiber per day.

Soluble fiber, in particular, reduces the amount of fat and cholesterol that is absorbed from foods and processed by the liver. Sure enough, eating foods that are high in soluble fiber, such as oats and legumes, can help lower your LDL cholesterol levels--but this may not all be due to the fiber!

These foods also happen to contain phytosterols, which I just talked about in a recent podcast on corn oil. As you may recall, phytosterols are plant compounds that work to block absorption of cholesterol from foods by occupying the cellular parking spots where cholesterol would normally park.  This article on phytosterols includes a chart that lists the phytosterol content of many foods.

The good news is that you can get all the fiber you need without overloading on carbs. A bowl of high fiber cereal for breakfast, a cup of black bean soup for lunch, some fresh fruits and vegetables along the way, and you’re there. Although whole grain breads have more fiber than their white flour counterparts, they have a somewhat undeserved reputation for being high in fiber. Other foods, such as legumes, bran, avocados, artichokes, broccoli, and berries are even better sources of fiber (and lower in carbs).

Weight Loss Also Helps

Finally, it’s worth pointing out that all of these conditions (PCOS, fatty liver, and high cholesterol) generally improve when you lose weight.  Any diet that helps you shed excess pounds should help, even if it’s not particularly low in carbohydrates or high in fiber. As it happens however, the low-glycemic, moderate-carb diet we’ve just outlined is also great for weight loss, because low- to-moderate glycemic  foods help quell your appetite.

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