Foundational Health Series
Why Fiber Matters
Read on kevferrell.com
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Reboot - Health & Longevity
Supplement Spotlight: Fiber
Back in 2007, when I was still competitively bodybuilding, I hired a coach for the first and only time to help with contest preparation. I had finally accepted that doing everything myself left room for blind spots and unnecessary last-minute changes.
One recommendation has stayed with me for almost 20 years: take psyllium husk every day, and keep taking it for the rest of my life.
I haven’t been perfect about that. But for most of the years since, and certainly in more recent years, it has been part of my daily routine.
That’s why dietary fiber is the next instalment in my Foundational Health Series, following creatine and omega-3.
These issues are practical reference guides to the benefits, risks, sources and everyday use of things I consider foundational to health. This one covers fiber from food as well as supplements.
I am not a doctor. This is what I have learned, what I do, and how I think about the evidence.
Why Fiber Matters
Fiber is easy to overlook when we are paying attention to the macros - protein, carbohydrates, fats - and overall caloric intake. Its reputation as something you take to stay regular also understates what it can do.
Different fibers can also help lower LDL cholesterol, moderate the rise in blood sugar after meals, supply fuel for the gut microbiome. Higher dietary fiber intake is also associated with lower colorectal cancer risk.
Those benefits are desirable, even when the individual effects are modest. They also depend on the type of fiber, the amount consumed and the person taking it.
My view is straightforward: The benefits of fiber are broad and evidence-backed. Most people don’t consume enough from their diet, myself included. The risk of getting too much is not harmful (although it might cause some temporary discomfort). So supplementing makes sense to me for almost everyone.
What Is Dietary Fiber?
Dietary fiber includes carbohydrates that our digestive enzymes cannot fully break down in the small intestine. They reach the large intestine, where some are fermented by microbes and others help retain water or add bulk.
The different types of fiber include:
- Soluble: which dissolves in water.
- Insoluble: which does not.
- Viscous: forms a thick gel, which helps explain their effects on cholesterol and digestion. Psyllium and oat beta-glucan do this.
- Fermentable: gut microbes use it as fuel. Fibers such as inulin and resistant starch provide material for microbial fermentation.
These categories overlap. A soluble fiber does not automatically form a gel, and a gel-forming fiber is not necessarily highly fermentable. Psyllium forms a gel but is relatively resistant to fermentation. Whole foods usually provide a mixture.
Evidence-Based Benefits
1. Digestive Health
Different types of fiber help support digestive health in different ways. Insoluble fibers, found in foods such as whole grains and vegetables, add bulk to help waste move through the digestive tract. Certain soluble fibers, like psyllium, hold water and form a gel, helping soften waste and making it easier to pass.
Eating a variety of fiber-rich foods gives you a mix of these benefits. Vegetables, fruit, legumes, whole grains, nuts and seeds all contribute. Getting enough fluid also helps fiber do its job.
The response is individual. Increasing fiber too quickly can cause discomfort. Whether you’re adding food sources or a supplement, build up gradually and adjust based on how you feel. More is not automatically better.
2. Cholesterol and Cardiovascular Health
Viscous fibers can trap some bile acids in the gut so they are excreted rather than recycled. The liver then uses cholesterol to replace them, helping lower circulating LDL cholesterol.
A review of 28 randomised trials, involving 1,924 participants, found that psyllium at a median dose of about 10 grams daily lowered LDL by an average of 0.33 mmol/L, or roughly 13 mg/dL.
That is a meaningful reduction.
While fiber is a consistent and reliable tool for lowering LDL, if cholesterol reduction is your goal, monitoring regular bloodwork tells you more than how you feel. Fiber can play a supportive role, but may not be enough on its own.
3. Blood Sugar Control
Gel-forming fibers slow the movement and absorption of nutrients, which can reduce the size of the blood sugar rise after a meal. Taking a viscous fiber with or shortly before a meal is the way to achieve this effect.
The strongest improvements in longer-term glucose control tend to occur in people who already have impaired control. A meta-analysis of psyllium trials found the greatest benefit in people with type 2 diabetes, smaller effects in prediabetes, and no significant glucose lowering in people whose levels were already normal.
Fiber can support diabetes management, but changes should be coordinated with the clinician managing medication.
4. Satiety and Weight Management
Some fibers help meals feel more filling. This may make it easier to manage appetite and total food intake, although the weight loss seen in supplementation studies is generally modest and varies by fiber type.
It is useful support for eating habits. The total amount and composition of what you eat is still what’s most important.
5. Gut Health
Fermentable fibers feed the gut microbiome, which produces short-chain fatty acids, including butyrate. Butyrate supplies energy to cells lining the colon and participates in pathways involved in the gut barrier and immune regulation.
Getting a variety of plant foods helps here. Different fibers serve different functions, which is a good reason to keep food variety alongside supplementation.
6. Long Term Health and Cancer Risk Reduction
A major review published in The Lancet linked higher dietary fiber intake with lower rates of several chronic diseases and premature death, including lower colorectal cancer risk.
Much of that evidence comes from observational studies. People who eat more fiber also tend to eat differently and practise other healthy habits, so we can’t credit fiber alone. Nor can we assume a supplement reproduces every benefit of a diet rich in whole fibrous foods. But the association is strong.
Dietary Sources
Top dietary sources include beans, lentils, oats, barley, whole grains, berries, apples, pears, vegetables, nuts and seeds.
Whole foods bring vitamins, minerals and other plant compounds along with their fiber. They also provide a wider mix of fibers than a single supplement. So the goal is to get a variety.
If you limit carbohydrates, like I often do, pay particular attention to what remains in your diet. Berries, nuts, seeds, avocado and non-starchy vegetables all contribute. Eating fewer starches doesn’t automatically mean you’re not getting a variety of fiber.
What About Cooked and Cooled Starch?
I don't normally eat large amounts of potatoes, pasta or rice. When I do eat them, I often like them after they have been cooked, cooled and then reheated. You've probably heard about this.
Cooling cooked starch can cause some of it to recrystallize into resistant starch, which resists digestion in the small intestine and can be fermented in the colon. This resistant starch can remain after reheating, although the amount depends on the food and how it is prepared.
The cooked and cooled food still contains digestible carbohydrates and calories, so the portions still matter.
How Much Do You Need?
You should focus on total daily fiber intake, not targeting a certain amount of each type.
As an example, Health Canada's reference intakes give the following daily amounts for generally healthy adults:
This Lancet meta-analysis showed that consuming at least 25 grams of total fiber per day is associated with a reduction in disease risk and mortality, with evidence suggesting that higher intakes could provide additional benefits.
The total includes food and supplements. If you already get enough from a varied diet and tolerate it well, you may not need a supplement. However, I still think it’s prudent. If you are falling short, start by understanding the size of the gap.
Choosing a Supplement
Plain psyllium husk is the simplest and most reliable option. It’s my first choice. Its effects are well studied, and it keeps the ingredient list to one. You can find it in most health food sections or online.
Metamucil is a popular way to take psyllium. but I prefer plain psyllium husk. I want the fiber without additional flavourings, sweeteners or other ingredients I don’t need.
I do like Momentous Fiber+ (here is a discount link) that was created in collaboration with Arnold Schwarzenegger. It offers a mixture of fiber sources, combining psyllium husk, resistant potato starch and rice bran hull. A blend doesn’t automatically mean it’s better than plain psyllium for every goal. And it’s much more expensive. So I mostly stick to plain psyllium.
Whatever you choose, read the label for the type of fiber, the amount of dietary fiber per serving and the additional ingredients that you don’t want.
My Protocol
My favourite regular food sources include blueberries (daily in a smoothie), strawberries, raspberries, apples, bananas, green vegetables, raw nuts, avocado. I also eat oats and whole grain bread periodically, along with occasionally potatoes, rice or pasta, preferably cooked and cooled.
Because I don't eat all of these foods every day, and I limit my overall carbohydrate intake, I also supplement daily. My usual amount is around 5 to 10 grams of psyllium husk fiber, adjusted for what the rest of my intake looks like that day.
Plain psyllium agrees with me, and I feel better inside and out when it is part of my routine.
Starting Safely and Staying Consistent
Start with a small label-directed serving and build gradually over a few weeks. There is no benefit in forcing a large dose that leaves you uncomfortable.
- Use enough liquid. Mix psyllium with at least a full glass of water, about 250 ml. I often add mine to a protein shake. Drink promptly before it becomes too thick. Never swallow the powder dry.
- Check medication timing. Fiber can affect absorption of some drugs and other supplements. Make sure you research or ask a pharmacist how far to separate it from your medications.
- Pay attention to tolerance. Increase gradually, and reduce the amount if bloating develops. Persistent pain or other ongoing digestive symptoms deserve medical advice.
For everyday use, consistency and tolerability matter more than chasing the highest possible intake. Sometimes less is more.
Final Word
Almost 20 years after that conversation with my diet coach, psyllium still has a place in my daily routine.
The benefits are well supported, the routine is simple, and there are really no drawbacks. It works well for me. It's a practical option I recommend considering.
That’s what earns it a place in my Foundational Health Series.
Previous Foundational Health Series installments
Foundational Health Series: Creatine
Foundational Health Series: Omega-3
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Until next week,
Kevin
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