What Kind of Fiber is Best?

If you’re constipated, hungry all the time, or weight loss resistant, fiber can support you. 

There is more than one type of fiber however. 

So this comprehensive post is in answer to all the questions Flipping50 students and community ask about fiber!


Looking for ways to add fiber easily? Hop down to recipes below for combinations that are both high fiber, high protein, and (mostly) low carbohydrate. As you’ll read here, that can be a challenging combination (high fiber, low carb).

What is Fiber?

It is a type of carbohydrate that you can’t digest.

What Kind of Fiber is Best?

Spoiler alert: you want a variety of fiber types in your diet every day. So, no one type is best. Different types have different roles. Read on to identify types of fiber and examples of them  so you can see where your diet may be falling short or imbalanced with fiber types.

Different Types of Fiber:

Soluble fiber attracts and dissolves in water then turns to gel during digestion. This slows digestion. That means potentially that meals will keep you full longer. It helps lower glucose levels, blood pressure and cholesterol. Nuts and beans, peas, and some vegetables contain soluble fiber. This helps trap toxins and excess estrogen and eliminate it in waste. Without soluble fiber, these toxins can be reabsorbed by the body.

  • Oatmeal
  • Chia seeds
  • Nuts
  • Beans
  • Lentils
  • Apples
  • Blueberries
  • Brussels Sprouts

Insoluble doesn’t dissolve in water. This fiber helps food pass more quicky through the stomach and intestines. It helps prevent constipation. Fruits, vegetables and grains contain insoluble fiber.

  • Quinoa
  • Brown rice
  • Leafy greens
  • Almonds, walnuts, sunflower seeds

Some foods are a mix of both types of fiber, for instance:

  • Flax 2/3 insoluble 1/3 soluble
  • Sweet potatoes – a mixture of insoluble and soluble

Other terms you'll see

Resistant Fibers – soluble fermentable – Acts as a prebiotic. Promotes healthy colons and make stools easier to pass. Delay blood sugar rise after meals because they slow digestion. Found in cooked and cooled and potatoes, unripe bananas, and legumes. Minimal laxative effect and stabilizes blood sugar and cholesterol levels.

Viscous – with a gel-like quality

Fermentable – acts like food for gut bacteria that break down and ferment it

Lignins – insoluble fiber in flaxseeds, nuts, unripe bananas that has a laxative effect.

Guar gum – soluble fermentable fiber from seeds that is often added to foods as a thickener. May help stabilize blood sugar and cholesterol levels.

Inulin – soluble fermentable fibers in onion, asparagus, artichokes. Has a laxative effect, stabilizes blood sugar levels, and improves cholesterol levels

Pectins – soluble highly fermentable fiber found in apples, berries and other fruit. Minimal laxative effect. Slows digestion and stabilizes blood sugar and cholesterol.

Manufactured Fibers:

Psyllium – soluble viscous nonfermentable fiber. A laxative effect (and for that reason is an ingredient in Over the Counter laxatives and high-fiber cereals. May support blood sugar or cholesterol levels.

Polydextrose and polyols – soluble fiber made of glucose and sorbitol. Has a mild laxative effect. Added to improve texture or as a sweetener, minimal positive effect on health, and not tolerated well by some.

Inulin – derived from plant sources and modified to be added to foods or fiber supplements. (You’ll see this ingredient in protein bars).

How Does Fiber Reduce Constipation?

Fiber can help with constipation. However, too much fiber too fast can result in constipation. Go gradually and increase your water intake at the same time. These fiber types support regularity.

Soluble – binds to water to soften and bulk stool

Insoluble – mildly irritate the intestinal lining to secret water and mucus to encourage movement of stool

Prebiotic fibers – increase water in intestines

Increase fiber coming from a wide variety of sources for best results. Flipping 50’s Fiber Boost is made of multiple food sources, for instance, compared to psyllium, a single source.

For many midlife women, going low carb, or Keto, often causes constipation. Substituting zucchini noodles for your pasta may be a good trade to reduce gluten foods or carbs, but you also give up 11 g of fiber per cup.

Substituting cauliflower “oatmeal” or porridge for oatmeal reduces carbs too. That means you give up a few grams of soluble fiber and swap it for fewer grams of insoluble.

Review your diet to be sure you have a good variety of fiber sources if you’re following a low carb or Keto diet may help if you have issues with regularity.

How Much Fiber Do I Need?

Dietary fiber is an essential nutrient that we often forget to incorporate into our daily diet. Average intake for Americans is below 15gm/day. That is existentially lower than our ancestors. A Paleolithic-period man ate an average of 130gm of fiber daily! Wow! The current USDA recommended intake is 25mg daily for women. 

The recommendation for women over 50 is 21 grams. But, wait for it: average intake at best is 16 grams a day. It’s also recommended at 14 grams fiber per 1000 calories. Say you’re eating about 2000 kcals a day, then 28 is your minimum. Literally, these slightly varied guidelines both come from USDA.gov. Confusing right?

Finally in more recent research we see that nutrition is not complete without the addition of sufficient fiber to meet gut and colon nutritional needs. Diets containing more than 50 g of fiber per day are associated with low colon cancer risk. Current dietary fiber requirements are based on cardiovascular health ignoring needs for colon health. Add to that the benefits of fiber for weight loss support, and you have a persuasive argument for fiber.

How Does Fiber Support Weight Loss?

For midlife women there are two ways. First, toxins we consume (from foods or drinks, we breath in, or absorb through our skin) get stored in fat by your body. It’s self-preservation by getting the toxin out of circulation. It does make the body reluctant to release fat, however. Hence, reducing exposure to toxins is a good idea!

Second, and specific to women in midlife, is supporting elimination of excess estrogen. Eliminating regularly supports the elimination of both toxins and excess hormones you don’t want. A condition called Estrogen Dominance is caused either by poorly metabolizing estrogens, or high stress which blocks progesterone making estrogen high relative to it, is improved by increasing the amount of fiber consumed.

Fiber also helps keep you full. This satiety factor is a big asset. In fact combining protein (something you want to be sure you have enough of anyway) and fiber at meals is a craving killer.

What Foods Are High in Fiber?

It’s not what you think.

A portion of fiber in a hefty salad made with Romaine (higher than spinach or iceberg) adds a whopping 2 grams of fiber to you day. That’s the highest comparing different reports on salad greens. Some sources say spinach, has .7 grams fiber per 2 cups.

Focus instead on the nuts, seeds, avocado slices that you top your salad with. Add apple chunks or berries to increase fiber. Add beans or chunks of sweet potato and that’s when you begin making real progress with fiber. If you tolerate whole grain croutons you’ll get more fiber there than in your greens, but less than in beans. That said, it is insoluble fiber so it may help you move things along, but it’s not going to make much dent in a goal of 30-50 grams of fiber a day.

Note: Reading articles or charts about foods high in fiber can be very misleading. Foods are often listed by amounts that you’d never eat in one sitting, making them appear overly high fiber. That includes avocado and prunes. You’re not going to consume a whole avocado at one sitting (though it’s tempting if it’s sitting on a nacho, right?) nor would a full cup of prunes at once be a good idea. (Dried fruit is high in sugar for one, and two if they did have a laxative effect on you, watch out!)

Sometimes though, this type of fiber will constipate. Especially if your diet overall isn’t very high in a mixture of fiber types and foods. Diversity is good. If you’re one of those women guilty of eating the same thing every day and week to week, your gut health is probably suffering.

If you skip the water necessary for “high fiber” to do its job, that doesn’t help matters either.

Our need for higher fiber diets comes from an abundance of highly processed foods over the past decades. Part of the answer by some researchers is the manufacturing of high fiber foods. The irony is not lost. But all is not negative when it comes to processed items. We’re going to use them in some capacity. We need to find the best way to manufacture sustainably. Flipping 50 Fiber Boost is one example, (as are our Flipping 50 protein powders – I said I’d never offer, yet because the poor options on the shelves left no choice, I changed my tune after 30 years).

Surprisingly Low Fiber Foods

Think those salads are fiber-rich? Two cups of spinach contains just 1.4 g fiber. You’ve got a way to go baby.

One cup of cauliflower is only 3g fiber. That contributes to a daily fiber intake but if you’re replacing brown rice or black bean pasta with your cauliflower you’re taking a significant drop in fiber.

Zucchini noodles have just .5 g fiber for each cup. So, again if you’re replacing carb foods with low or no carb foods, you want to be careful and conscious.

Cooked broccoli (and most cooked vegetables have fewer grams of fiber than raw).

A wonderful food for other reasons, 1 cup cooked cabbage has just 1.8g fiber

Sources also vary greatly in their data on fiber in foods. One source stated 5 grams fiber per cup raw broccoli, another said 2.4 g fiber per cup. So, it is a wild west. Consider your priorities, your health habits (digestive state and regularity) along with weight loss goals when you’re considering foods. Ultimately, you can’t lose weight creating an unhealthy environment, so pay attention to how you feel while losing and your results will have much more staying power.

This doesn’t make these foods low in nutrients! It does suggest a need to take in the whole picture based on your goals and the feedback your body is giving you. Constipation, gas, or bloating, aren’t normal.

Will Fiber Make Me Bloated?

It shouldn’t! If you already have an imbalance in your gut microbiome (fancy word for good: bad gut bacteria), adding more fiber or too much too soon could cause bloating. In that case, you’ll want to learn more about your gut to be sure you’re absorbing all the nutrients you consume. You also want to look at your diet over a lifetime. Not that it’s healthy but if you’ve had a low fiber diet, your body will need time to adjust if you’ve had a low fiber history.

What does a low fiber diet look like? It could be a higher number of processed foods: white bread and rice instead of wheat, brown, or wild. It might be more meat and few starchy vegetables. A diet low in beans, legumes, berries, nuts, and seeds. Not having any one of those wouldn’t indicate a low fiber diet but if there’s a pattern in your diet of infrequently consuming all or many of those, then you’ve likely had a low fiber diet.

What if you are regularly bloated and no change in diet or addition of pre or probiotic foods or supplements has helped? It may be time to consult a functional doctor. A stool test could help determine what is happening with your gut. A food sensitivity test could help you determine what foods you don’t realize are causing issues. Share all the details with them. What you have accepted as “normal for you” may actually be depleting you of nutrients long term. Short term? You could feel so much better.

7 Signs You’re Eating Too Little Fiber

  • Your stools are like pebbles. Or, as one of my friends refers to them, rabbits.
  • You don’t “go” for days and think that’s normal.
  • You have significant belly fat. [Visceral belly fat, in this case]
  • You’re insulin resistant. [You may not know it yet, but if you’re depositing belly fat, and can’t lose weight, even looking at carbs causes weight gain, chances are as a midlife woman you are insulin resistant]
  • You’ve increased your protein without an adjustment in your fiber. [By default many women who increase protein and cut out fibrous foods which can cause insulin spikes. The key to keeping insulin levels low is avoiding sweets along with consuming more fiber.]
  • Your CRP numbers reveal chronic inflammation
  • High LDL

How Do I Eat Enough Fiber Without Having Too Many Carbs?

In calorie-restricted diets the most successful predictor of reduction in body weight was dietary fiber. Carb sensitivity, or insulin resistance, is a concern for midlife women. So, options for increasing fiber morning to night are included in the High Fiber Meals That Are High in Protein included below.

What Are Some Examples of High Fiber Meals?

See the recipes I link to below the references for a suite of ideas to take you from morning to evening. You probably have already learned some foods in your diet are working! These will give you some easy boosts! 


That Are High in Protein, and Not too High in Carb

(more coming soon: check back!) 

Pear, Avocado, Kale Smoothie

Better Than Oatmeal Cauliflower Porridge

Quinoa Breakfast Bowl

Brussel Sprouts Salad

White and Black Bean Turkey Chili

Salad Lovers: High Fiber Salad Additions:

  • ½ cup Artichoke hearts 4.8 g fiber (I also throw these on pizza!)
  • 1 cup Hearts of Palm 3.5 fiber
  • ¼ cup Pumpkin seeds 6 g fiber (you’re not going to use that many- but also great on smoothies)

Smoothie Lovers: Higher Fiber Smoothie Additions:

  • 1 medium Pear 6g fiber
  • 1 medium Apple 4g fiber
  • 1/3 cup Avocado 4g fiber
  • 2 T Chia seeds 6g fiber
  • 1 cup frozen spinach 3g fiber

Sweet Tooth Dessert-Lovers:

  • 1 cup raspberries 8 g fiber
  • Chia Seed Pudding (up to 11 g fiber)

Soup Lovers: High Fiber Soup:

  • ½ cup cooked Lentils 8 g fiber
  • 1 cup most beans 8g fiber

This is by no means an exclusive list. Hopefully what it does is makes it easy to see you CAN easily bump your food-based fiber intake. If you struggle some days, you can choose “adds” like Fiber Boost to support you! Pair protein and fiber for a high satiety craving killer.

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