How Does Fiber Help Lower Blood Sugar?

Dr Jedha, Host

Hello wonderful people, Dr Jedha here and thanks for joining me for episode 73. When you’ve been out surfing the wild west web, without a doubt you’ve heard fiber mentioned in relation to pre or T2Diabetes. 

When it comes to managing blood sugar and overall health, fiber is often highlighted as a key nutrient—but what makes it so special? If you’ve ever wondered whether fiber lives up to the hype, today’s episode is for you. We’ll unpack exactly how fiber works, its specific benefits for pred and T2diabetes, and how you can make the most of it in your daily life. By the end of this episode, you’ll have a clear understanding of why fiber is such a valuable tool in managing blood sugar naturally.

02:09

Let’s start by defining what fiber is. 

When we talk about fiber, technically speaking we are referring to a type of carbohydrate—but it’s not the kind that impacts your blood sugar. Fiber is unique because your body doesn’t digest or absorb it like other carbs, so it doesn’t raise your blood sugar levels. Instead, it can play a role in supporting your overall health.

Now, there are many different types of fiber, but the two main types we’re most familiar with are soluble and insoluble fiber. Each has different benefits, and both are important.

Soluble fiber dissolves in water, forming a gel-like substance in your digestive tract. Think of foods like chia seeds, flaxseeds, avocados, and vegetables such as zucchini or asparagus. This gel slows down digestion and helps reduce the absorption of sugar  and carbohydrates into your bloodstream. 

On the other hand, insoluble fiber doesn’t dissolve in water. Instead, it forms a lattice-work structure in our gut and moves along the digestive tract, adding weight and bulk to waste material and assisting with digestion. Insoluble fiber is good for maintaining regularity and supporting gut health. Foods like nuts, seeds and vegetables are excellent sources of insoluble fiber.

Fiber is not classified as an essential nutrient. The body can function without dietary fiber because it does not digest or absorb fiber as a source of energy or nutrients. Unlike essential nutrients, fiber doesn’t have a biochemical role critical for survival. Similarly, fiber deficiency doesn’t lead to a specific deficiency disease. That doesn’t mean fiber isn’t helpful. While it’s not essential, fiber is considered beneficial as it can play a role in promoting overall health and preventing disease.

04:20

Let’s take a closer look at those benefits now. 

In terms of prediabetes and T2Diabetes, it’s the soluble fiber that is of particular interest and benefit to you. Some researchers suggest that adding soluble fiber can account for an average 35% variance in your peak glucose levels, which means it may help lower blood sugar levels by quite a lot!

To examine this more closely, I looked at meta-analyses of randomized controlled trials—these are the highest form of evidence as they bring all the data from clinical trials together to determine effects of certain things, in this case fiber. 

In one review, all but one clinical trial indicated a reduction in A1c levels from increasing dietary fiber intake, with an average A1c reduction of 0.66%. That was the average when considering both types of fiber, but if we look at soluble fiber alone, the average A1c decrease was 0.86%. Another recent review found that intake of soluble fiber decreased A1c by an average 0.47%, while another found an average, and another found a 0.63% A1c reduction. So overall, fiber, particularly soluble fiber can help decrease A1c levels by 0.47% to 0.86%, so what this indicates to us is that the addition of soluble fiber to your eating plan can certainly help with better long-term blood sugar control.

In terms of fasting blood sugar levels, one review found increasing fiber by an average of 10g/day for 8 weeks leads to reduction of 15.5 mg/dL or 0.80 mmol/L. Another found this reduction to be slightly higher at 16.7 mg/dL or 0.93 mmol/L. Both soluble and insoluble fibers contribute to lowering fasting blood sugar levels. But again, soluble fiber wins out here, showing more pronounced effects. 

In terms of postprandial blood sugar levels, that’s your levels when testing 2-hours after meals. In one interesting study, people were given soluble fiber at breakfast, whether from food sources or supplements. The results suggested an 18% difference in postprandial glucose when breakfasts were rich in fiber. The higher fiber intake was around 9 grams, ensuring around 5.4g came from soluble fiber, compared to the usual fiber intake of 2.4g for breakfast and just 0.8g of soluble fiber. 

07:44

From the reviews, we also see insulin resistance decreasing and insulin sensitivity improving, which is very important. We see these results in lower levels of fasting insulin and lower HOMA-IR scores, which is a test frequently used in studies to assess people’s level of insulin resistance. Enhanced insulin sensitivity allows cells to utilize glucose more effectively, reducing blood sugar levels.

There are additional benefits of soluble fiber, these include improving cholesterol levels, including total cholesterol and LDL cholesterol. Soluble fiber helps lower LDL cholesterol by binding to bile acids in the digestive tract, causing them to be excreted rather than recycled, effectively reducing LDL levels. Additionally, soluble fiber slows the absorption of dietary cholesterol, further supporting improved cholesterol profiles.

Dietary fiber serves as a prebiotic, nourishing beneficial gut bacteria. Fermentation of fiber by these bacteria produces short-chain fatty acids (SCFAs), which have been shown to improve insulin sensitivity and modulate inflammation—both critical factors in blood sugar regulation. Soluble fibers also promote the growth of beneficial gut bacteria, which helps reduce inflammation, the type of inflammation that tends to target our cells and contribute to ill health, systemic inflammation.

Even in well-controlled studies where the food intake has been identical apart from the fiber intake, we see that the increased daily fiber intake improves blood sugar control, decreases hyperinsulinemia (which is unnecessary high insulin levels), and lowers cholesterol levels. 

09:56

Another important thing is we do observe that people who have higher fiber intake have a 20-30% reduced risk of developing type 2 diabetes. 

A few other benefits of fiber is that high-fiber foods tend to be more filling so they help us feel fuller longer, rounding out our appetite. Fiber can help improve our metabolism, since fiber makes us chew and we need to chew to stimulate enzymes and acids needed for proper digestion. 

All of these things are positive outcomes for your health. 

11:11

Now you know about all the potential benefits of fiber intake, you may be wondering, how much fiber to aim for each day. 

Well, when it comes to fiber, the daily recommendation is 25 to 38 grams of fiber per day for adults. But here’s the thing, research shows us that most people only consume about half of that—often just 15 grams a day, sometimes less. One of the primary reasons for this is that most modern packaged foods are made with refined ingredients that are stripped of fiber. The fact that our intake of ultra-processed foods has increased, means our intake of healthy whole foods has decreased, and alongside that our fiber intake. Increasing your fiber intake to meet these recommendations — 25 to 38 grams of fiber per day — can make a huge difference in managing blood sugar, improving insulin resistance, improving gut health, cholesterol, inflammation and many other factors, as we discussed earlier. 

Reviews indicate you need to increase your fiber intake for a minimum of 6 weeks to see any changes in A1c and overall you need to have an increased intake higher than 8.3g day extra than what you’re consuming now. But, as we just mentioned, aiming for an overall daily intake of 25-30 grams is ideal. 

12:40

And what about where to get that fiber from? We’ll get to that in a moment but first I want to address one of the biggest misconceptions about fiber. When people think about fiber, they often think of wheat bread, whole-grain breads, brown rice, oats, and other grain products. In fact, if you go surf the wild west web, you’ll come across all sorts of articles pronouncing the benefits of fiber in whole grains for people with pre and T2Diabetes. Well, truth be told this type of info is rubbish. 

While it’s true that foods like bread, oats, rice and wholegrains do contain fiber, these foods are not recommended because they are very high carbohydrate foods, you want to minimize these in your eating plan. Even the American Diabetes Association (ADA) acknowledged in their 2017 Standards of Medical Care report, that “whole grain consumption was not associated with improvements in glycemic control in type 2 diabetes” – or in other words, eating whole grains doesn’t help you manage blood sugar and A1c levels! There has been no evidence to suggest otherwise, that wholegrains actually help with prediabetes and type 2 diabetes treatment. And as we spoke about all the way back in episode 2, treatment of a health condition is vastly different from prevention of a health condition. You go searching out there on the wild west web. You read information online that you think is meant to be for type 2 diabetes treatment, but what you don’t know is that whoever has written that information doesn’t know how to research properly and they are just sharing blanket statements that refer to diabetes prevention. Lots of information out there on the wild west web is based on evidence for diabetes prevention, not diabetes treatment. It’s not the same. So when it comes to the topic of fiber, you’re going to see a lot of rubbish. 

Yes, fiber can help but the misconception is that you don’t need to eat grain-based foods to get adequate amounts of fiber.

Let me give you some examples:

• 1 cup brown rice = 3.5 g fiber
• Half an avocado = 6.7 g fiber
• 1/4 cup oats = 2 g fiber
• 1 tablespoon chia seeds = 4 g fiber

Both the avocado and chia seeds provide a rich source of beneficial soluble fiber, and much more fiber than brown rice or oats and without the carbohydrate load. 

Soluble fiber can be found in artichoke, asparagus, winter squash, Brussels sprouts, broccoli, onion, garlic, leeks, carrots, beans, legumes, blueberries, seeds and nuts.

Just focus on eating lots of fresh foods, lots of fresh vegetables, nuts and seeds and small amounts of beans and legumes.

Essentially if you do that, you will get ample fiber from eating non starchy vegetables, nuts, seeds and other whole foods but you won’t get all those high carbs that can send your blood sugar soaring!

You can also go and listen to episode 6 on what to eat to treat diabetes, as this covers different foods in more detail. 

Another misconception I want to address is the fiber in processed foods. Fiber is often added to processed foods like cereals, snack bars, and baked goods to improve their nutritional profile. However, the source and type of fiber in these foods can vary greatly. Many processed foods use isolated fibers like inulin, resistant dextrin, or cellulose, which may not offer the same broad health benefits as fiber naturally found in whole foods. While added fiber can contribute to your overall intake and may improve digestive health or glycemic response, it’s important to consider the overall nutrient composition of the food. It’s easy for people to think, okay this food has lots of fiber so it’s a good food, but if it has a long list of other ingredients and is highly processed, it doesn’t matter how much fiber it has, a junk food is a junk food. While adding fiber can make a food more blood sugar-friendly, it’s not a free pass to consume lots of processed foods. Focusing on naturally fiber-rich whole foods remains the best strategy for managing blood sugar.

18:22

So we’ve talked about the benefits of fiber, how much to have per day and what types of foods to focus on to increase your fiber. What about increasing fiber through supplements. 

The good news is, soluble fiber from foods is important, and supplementing with soluble fiber can add similar benefits to those outlined in the reviews we discussed earlier, A1c reductions, decreases in fasting blood sugar and fasting insulin levels and improvements in postprandial, after meal blood sugar levels. 

There are various different fiber supplements that can have benefits, for example Glucomannan, Psyllium Husk, Acacia Fiber, Inulin and others. Today I will focus on psyllium husk, and we will leave more info about this on our website in the shownotes and for members, inside the members library. 

So psyllium husks are derived from a shrub called Plantago ovata. Psyllium husks are a soluble fiber, the type that is highly beneficial to you. Like other soluble fibers, psyllium produces that mucous gel-like substance in your intestine, and this slows the absorption of glucose and carbohydrate into your bloodstream. But psyllium is like a concentrated form of soluble fiber and this can have very powerful effects for improving blood sugar levels. 

Studies have shown that after 8 weeks of supplementing with psyllium, fasting blood sugar reduces by an average of 43 to 52.6 mg/dl (2.4 to 2.9 mmol/l), by anyone’s measure that’s a substantial reduction. In terms of A1c reductions, studies have shown decreases of 0.6 up to 1.6% from 8 weeks of supplementation. Studies indicate blood sugar levels are improved throughout the day and postprandial blood sugar is aroun 11-20% lower in those supplementing with this beneficial fiber. Studies have also shown it can assist with weight loss, and of course, it helps reduces LDL cholesterol and total cholesterol, enhances insulin sensitivity and it is one of the most useful supplements to promote healthy digestion and relieve constipation, so overall psyllium husks are a powerful natural dietary supplement that can aid in blood sugar control, cholesterol management, and digestive health. 

If getting enough fiber through your eating plan is a struggle or you want to up the fiber for it’s known benefits, then adding psyllium husk as a supplement can be beneficial. 

According to research, a safe and effective dose is approximately 5 g, up to 3 times per day. To supplement it directly, mix psyllium husks with at least 8-ounce (250ml) of water and take 20-30 minutes before meals, morning and night if taking twice a day. After taking it, make sure you wash it down with some additional water. Again, if you’re interested to learn more about psyllium, the best supplements and more info about dosages and timing, head to our website for the show notes of episode 73, and for members, find many resources inside the members library, including this info on psyllium, fiber-rich food charts, a fiber guide and more. 

So, to wrap up, fiber is an incredible ally in your health journey. Whether you’re increasing your intake through non-starchy vegetables, nuts, seeds, or adding a supplement like psyllium husk, the benefits for blood sugar control, cholesterol management, insulin sensitivity, inflammation and other things are clear—fiber has nothing but positives to add to your eating plan, and adding more fiber to your daily routine may be one of the easiest places to start, or one of the easiest ways to power up your results.

Remember, you can find additional notes and resources alongside episode 73 on our website, or for members, inside the members library. 

Thanks for tuning in to join me today. Until next time, take care. 

Dr Jedha, over and out.