Important Health Effects of Dietary Fiber

Dietary fiber consists of non-starch polysaccharides (NSP) and many other plant components such as resistant starch, resistant dextrins, inulin, lignin, chitins, pectins, beta-glucans, and oligosaccharides.

Video 1.  Is the Fiber Theory Wrong? (YouTube link)

Dietary fiber can contribute to your overall good health and longevity, and can have a positive impact on lowering risk of diseases related to Western diets, which include:^[1]

• Cancers^[25,26]
• Diabetes^[27]
• Tumor formation
• Disordered laxation
• Autoimmune diseases
• Coronary heart disease^[28]
• Inflammatory bowel disease
• Mineral related abnormalities

by feeding and promoting healthy gut bacteria.

In this article, we will cover the health effects of fiber from two prospectives:

• Traditional wisdom 
• Mostly from digestive system perspective
• Gut Microbiota 
• Mostly from immune system perspective

Traditional Wisdom

Proven benefits of dietary fiber include fewer colon polyps and thus less risk of colon cancer.  Dietary fiber is also thought to help prevent iron overload, which could promote inflammation in the colon that leads to mucosal damage, since fiber binds to iron and helps the metal pass out of the body through the digestive tract.^[5]

• Insoluble fiber
• Insoluble fiber you consume is passed through your gut undigested and sweeps out it like a broom
• Benefits
• It is an effective laxative to relieve your constipation or irregular stools
• Soluble fiber
• Soluble fiber attracts fluid in your gut, creating a slow-moving gel
• Benefits
• It slows digestion, which allows vitamins and minerals to absorb through intestinal walls
• For example, daily consumption of dietary fiber significantly increases calcium absorption and enhances bone mineralization during pubertal growth^[11]
• It can help lower plasma cholesterol levels and help to normalize blood glucose and insulin levels

Gut Microbiota

Intestinal epithelial barrier

The total surface area of the gastrointestinal system is approximately 300 to 400 sq. m.  However, only a single epithelial layer separates you from enormous amounts of antigens of both dietary and microbial origin.

Sitting on top of this cell lining is a layer of mucus that is also an important part of the intestinal epithelial barrier. This barrier's job is to regulate everything that passes between your intestine and the rest of your body.

Together with the immune cells located in your gut, which represents almost 70% of the entire immune system, the barrier helps control how your immune system reacts to anything foreign. When the barrier is weak or comprised, you have a condition called leaky gut syndrome which can potentially increase your risk of autoimmune diseases.

Short-chain fatty acids

Dietary fiber can be fermented into short chain fatty acids (SCFAs) in your guts. SCFAs have a number of health promoting effects:^[1,14]

• Lowering the pH of the colon
• Inhibiting growth of pathogenic organism
• Increasing mineral absorption
• Serving as a vital fuel source for the colonic epithelium and key regulators of immune homeostasis
• Which serves as the prototypical example of the symbiotic nature between the microbiome and the host in terms of diet and metabolism

Of the SCFAs, butyrate is considered to be the preferred fuel of cells of colon (i.e. colonocytes).  Without butyrates for energy, colon cells can undergo autophagy (self digestion) and die.^[18]

Video 2.  How The Gut Microbiota Affects Our Health with Dr. Erica & Dr. Justin Sonnenburg (YouTube link)

Beneficial gut bacteria
Most gut bacteria reside only in the colon (which has a volume of 0.4 liters). SCFAs are produced by these beneficial colonic bacteria (probiotics) that feed on, or ferment prebiotics, which are plant products that contain adequate amounts of dietary fiber. 
In the video above, Dr. Sonnenburg found that microbes in the guts of Americans make more enzymes that degrade mucins, compared with those in the Hadza who still lead a historic hunter-gatherer way of life in Tanzania. These enzymes allow bacteria to harvest carbohydrates from the mucosal lining of the gut, rather than from plant fiber.^[20]
In other words,

“If you’re not feeding your gut microbiome with dietary fiber,” Dr. Sonnenburg said, “your gut microbiome is literally feeding on you,” 

which may result in changes in microbiota localization and barrier disruption in the distal gut. Interactions between resident microbes and host leading to immune dysregulation may explain several diseases that share inflammation as a common basis. 
Besides serving as foods to colonic bacteria, scientists have also found that polyphenols bound to the fiber may have a significant physiological impact within the large intestine, affecting microflora development and intestinal antioxidant status by producing metabolites that can be absorbed through the mucosa.^[13]

Sources of Dietary Fiber 

In recent years, it become clear that in order to be truly healthy, you need a healthy gut. Dietary fiber is used as food for your beneficial bacteria, and a healthy microbiome is essential to optimizing your health. For example, they produce compounds that help regulate your immune function and even improve brain health.
Dietary fiber can be found from the following food sources:

• Insoluble fiber 
• Blackberry seeds, celery, dark-green leafy vegetables, green beans, skins of onions, and whole grains
• Soluble fiber
• Apples, barley, beans, berries, citrus fruits, cucumbers, oats, nuts, peas and psyllium.

Note that many whole foods contain both soluble and insoluble fiber.  Dr. Mercola recommend consuming a minimum of 35 grams of fiber and ideally > 50 grams from whole foods per day.^[12] Also, be warned that your gut may not be used to these amounts of fiber, you will want to gradually increase to those levels, as they can cause gas and bloating and even constipation until your microbiome readjusts.

References

1. V Kumar, A K Sinha, H P Makkar, G de Boeck, K Becker. Dietary roles of non-starch polysaccharides in human nutrition: a review. Crit Rev Food Sci Nutr. 2012;52(10):899-935
2. How The Gut Microbiota Affects Our Health with Dr. Erica & Dr. Justin Sonnenburg
3. Gut Bacteria Can Fluctuate With the Seasons
4. Paleopoo: What We Can Learn from Fossilized Feces
5. Why You Should Always Use Organic Red Onions
6. J. I. Wurzelmann et al., "Iron Intake and the Risk of Colorectal Cancer," Cancer Epidemiology, Biomarkers and Prevention, 5, no. 7 (July 1, 1996): 503-7.  PMID: 8827353.
7. Justin Sonnenburg on "The Good Gut"
8. Mucins in the mucosal barrier to infection
9. Scientists bust myth that our bodies have more bacteria than human cells
10. Dr Greger on dietary fibers
11. S A Abrams, I J Griffin, K M Hawthorne, L Liang, S K Gunn, G Darlington, K J Ellis. A combination of prebiotic short- and long-chain inulin-type fructans enhances calcium absorption and bone mineralization in young adolescents. Am J Clin Nutr. 2005 Aug;82(2):471-6.
12. Fat for Fuel (Dr. Mercola)
13. F Saura-Calixto. Concept and health-related properties of nonextractable polyphenols: the missing dietary polyphenols. J Agric Food Chem. 2012 Nov 14;60(45):11195-200.
14. J R Goldsmith, R B Sartor. The role of diet on intestinal microbiota metabolism: downstream impacts on host immune function and health, and therapeutic implications. J Gastroenterol. 2014 May;49(5):785-98.
15. The Good Gut: Taking Control of Your Weight, Your Mood, and Your Long-term Health
16. Justin Sonnenburg and Erica Sonnenburg Publications
17. Starving our microbial self: the deleterious consequences of a diet deficient in microbiota-accessible carbohydrates
18. Donohoe, Dallas R.; Garge, Nikhil; Zhang, Xinxin; Sun, Wei; O'Connell, Thomas M.; Bunger, Maureen K.; Bultman, Scott J. (2011). "The Microbiome and Butyrate Regulate Energy Metabolism and Autophagy in the Mammalian Colon". Cell Metabolism. 13 (5): 517–26. 
19. Lupton, Joanne R. (February 1, 2004). Microbial Degradation Products Influence Colon Cancer Risk: the Butyrate Controversy. vol. 134 no. 2: J. Nutr. pp. 479–482.
20. Sonnenburg JL, Xu J, Leip DD, Chen CH, Westover BP, Weatherford J, Buhler JD, Gordon JI. Glycan foraging in vivo by an intestine-adapted bacterial symbiont. Science. 2005;307:1955–1959.
21. ‘Ridiculously Healthy’ Elderly Have the Same Gut Microbiome as Healthy 30 Year-Olds
22. Gut microbes could help trigger multiple sclerosis
23. Constipation and Its Remedies (Travel and Health)
24. Which Food Fights Cancer Better? (Travel to Health)
25. Aune D, Chan DS, Lau R, et al. Dietary fibre, whole grains, and risk of  colorectal cancer; systematic review and dose-response meta-analysis of prospective studies.  BMJ. 2011;343:d6617.
26. Aune D, Chan DS, Greenwood DC, et al.  Dietary fiber and breast cancer risk: a systematic review and meta-analysis of prospective studies.  Ann Oncol. 2012;23(6):1394-402.
27. Yao B, Fang H, Xu W, et al.  Dietary fiber intake and risk of type 2 diabetes: a dose-response analysis of prospective studies, Eur J Epidemiol. 2014;29(2):79-88.
28. Threapleton DE, Greenwood DC, Evans CE, et al. Dietary fibre intake and risk of cardiovascular disease: systematic review and meta-analysis. BMJ. 2013;347:f6879.
29. The Effects of Nutritional Yeast for Cancer
• A clinical study demonstrated improved wound healing using oral beta-glucans 
• In Japan, there have been 22 randomized controlled studies on the use of beta-glucans as an adjunct cancer treatment. Researchers found that “yeast beta-glucan can enhance the effect of anticancer chemotherapy or radiation therapy and have a positive effect on the survival and quality of life of cancer patients.” 
30. Bouhnik Y et al. Effects of Bifidobacterium sp fermented milk ingested with or without inulin on colonic bifidobacteria and enzymatic activities in healthy humans. European Journal of Clinical Nutrition 1996 Apr; 50(4):269-73.
31. Gyawali R et al. The role of prebiotics in disease prevention and health promotion. Chapter 12 in Dietary Interventions in Gastrointestinal Diseases, 2019. Pages 151-67.
32. Mahboobi S et al. Effects of prebiotic and synbiotic supplementation on glycaemia and lipid profile in type 2 diabetes: A meta-analysis of randomized controlled trials. Advanced Pharmaceutical Bulletin 2018 Nov; 8(4):565-74.
33. Nowak A et al. Antigenotoxic activity of lactic acid bacteria, prebiotics, and products of their fermentation against selected mutagens. Regulatory Toxicology and Pharmacology 2015 Dec; 73(3):938-46.

"There is only time for loving" — Mark Twain

Lyrics

May each day in the week be a good day
May the Lord always watch over you
And may all of your hopes turn to wishes
And may all of your wishes come true

May each day in the month be a good day
May you make friends with each one you meet
And may all of your daydreams be mem'ries
And may all of your mem'ries be sweet

The weeks turn to months and the months into years
There'll be sadness and joy, there'll be laughter and tears
But one thing I pray to heaven above
May each of your days be a day full of love

May each day in the year be a good day
May each dawn find you happy and gay
And may all of your days be as lovely
As the one you shared with me today
May each day of your life be a good day
And good night.

Health Effects of Iron Overload and Benefits of Blood Donation

Iron overload—a buildup of extra iron—without treatment can permanently damage organs such as the liver, heart, and pancreas; endocrine glands; and joints.^[23] Excess Iron can also increase your risk of cancer, heart disease, and premature death.^[24]

In this article, we will cover the following topics:

• Negative health effects of iron overload
• Benefits of blood donation for most people
• Note that always consult a physician for ferritin testing, full iron panel, and any phlebotomy/donation plan. Self-managed aggressive reduction risks anemia.

Serum Ferritin Test

Ferritin is a protein that stores iron and acts as a buffer against iron deficiency and iron overload. It is found in most tissues as a cytosolic protein, but small amounts are secreted into the serum where it functions as an iron carrier. Therefore, plasma ferritin is a good indirect marker of the total amount of iron stored in your body. However, ferritin is also an acute-phase reactant, meaning levels can rise due to inflammation, infection, liver disease, or malignancy, even without true iron overload.

Premenopausal women generally have lower serum ferritin than men because of menstrual blood loss, with typical averages around 25–50 ng/mL. Men of the same age often show higher levels, roughly 100–150 ng/mL. Clinical guidelines usually flag possible iron overload when ferritin is consistently above 300 ng/mL in men or above 200 ng/mL in premenopausal (and postmenopausal) women, especially when transferrin saturation exceeds 45%. 

To confirm iron overload, always work with a physician (such as a hematologist or gastroenterologist) to obtain:

• A full iron panel (ferritin and transferrin saturation)
• HFE genetic testing when appropriate
• C282Y homozygosity—the main genetic risk for hereditary hemochromatosis—is most common in people of Northern European ancestry (about 1 in 200–500, and even higher in Ireland), while it is rare to extremely rare in Hispanics, African Americans, and Asians. Because penetrance is low, genetic testing is recommended only for those with elevated iron markers or a family history, rather than for routine population screening.
• Evaluation for secondary causes such as inflammation, alcohol use, or obesity-related conditions

Disclaimer: This information is for educational purposes only and is not a substitute for professional medical advice; always consult a qualified healthcare provider before making decisions about testing, blood donation, or iron management.

Potential Risks of Confirmed Excess Iron 

• Mitochondrial damage: Iron builds up in mitochondria, generating ROS and causing lipid, protein, and mtDNA damage.^[22]
• Obesity: Higher ferritin predicts future weight gain and obesity, even after adjusting for inflammation.^[16-18]
• Increased infection risk: Excess iron fuels bacterial, fungal, and protozoal growth, weakening the body’s “nutritional immunity.”^[19]
• Diabetes: Elevated ferritin is strongly linked to higher type 2 diabetes risk due to oxidative stress on beta cells.^[13-15]
• Cardiovascular disease: High heme‑iron intake and excess iron promote LDL oxidation and endothelial injury, raising stroke and heart‑disease risk.^[11,12,15]
• Neurodegenerative diseases: Iron accumulation contributes to Alzheimer’s, Parkinson’s, and related disorders by promoting toxic protein aggregation.^[8-10,27]
• Cancer: Ferritin is often elevated in cancers and correlates with worse outcomes, largely reflecting inflammation or tumor activity.^[4-7]
• Osteoporosis: Excess iron increases bone breakdown and oxidative stress, contributing to bone loss, especially in hemochromatosis.^[3]

These risks are best documented in cases of true iron overload rather than mild elevations. Most harm stems from oxidative stress, particularly through the Fenton reaction. The evidence is largely associative, and clear causation is not well established outside severe overload.

Video 1.  Australian man with 'golden arm' makes final blood donation at 81 (YouTube link)

Blood Donation

Your body has limited natural excretion of iron (~1–2 mg/day), so buildup can occur from genetics, repeated transfusions, or excessive intake. The most effective, safe, and low-cost method for confirmed overload in non-anemic patients is blood removal via regular blood donation (if eligible) or therapeutic phlebotomy (doctor-prescribed).  

Each standard unit (~450–500 mL whole blood) removes approximately 200–250 mg of iron. Ferritin typically drops ~30–50 ng/mL per unit, varying by individual.

Potential Additional Benefits of Blood Donation

• Longevity & ferritin: Lower iron stores may reduce oxidative stress, but there’s no solid proof that blood donation increases lifespan.
• Cancer risk: Donors often show lower cancer rates, possibly due to lower iron or the “healthy donor effect.” Evidence from randomized trials is limited.^[7]
• Cardiovascular health: Some older studies suggested fewer heart attacks and strokes in frequent donors, but newer research shows mixed or minimal effects.
• Insulin sensitivity: Lowering iron through donation may temporarily improve insulin sensitivity and slightly reduce diabetes risk in some studies.^[15]
• Other possible benefits: Small improvements in blood pressure, lipids, or oxidative stress have been reported. Donors also receive routine health screenings.

Note that these benefits are not guaranteed and mostly come from observational data. Frequent donation can cause iron deficiency, especially in premenopausal women, so medical guidance is essential.

This updated table is precautionary but avoids over-reduction, reflecting Mercola's balanced, evolved perspective. Always prioritize medical advice over general tables—excessive donation risks anemia.^[22,29]

References

1. China liver problems boost demand for US blood plasma
2. Four Unexpected Benefits of Donating Blood
3. L. Valenti et al., "Association between Iron Overload and Osteoporosis in Patients with Hereditary Hemochromatosis," Osteoporosis International, 20, no. 4 (April, 2009): 549-55.
4. A. A. Alkhateeb and J. R. Connor, "The Significance of Ferritin in Cancer: Anti-Oxidation, Inflammation and Tumorigenesis," Biochimica et Biophysica Acta, 1836, no. 2 (Dec 2013):245-54.
5. J. I. Wurzelmann et al., "Iron Intake and the Risk of Colorectal Cancer," Cancer Epidemiology, Biomarkers and Prevention, 5, no. 7 (July 1, 1996): 503-7. PMID: 8827353.
6. Y. Deugnier, "Iron and Liver Cancer," Alcohol, 30, no. 2 (2003): 145-50.
7. L. R. Zacharski et al., "Decreased Cancer Risk after Iron Reduction in Patients with Peripheral Arterial Disease: Results from a Randomized Trial," JNCI:Journal of National Cancer Institute, 100, no. 14 (2008): 996-1002.
8. M. A. Lovell et al., "Copper, Iron and Zinc in Alzheimer's Disease Senile Plaques," Journal of the Neurological Sciences, 158, no. 1 (June 11, 1998): 47-52.
9. K. Jellinger et al., "Brain Iron and Ferritin in Parkinson's and Alzheimer's diseases," Journal of Neural Transmission, 2 (1990): 327.
10. G. Bartzokis et al., "Brain Ferritin Iron as a Risk Factor for Age at Onset in Neurodegenerative Diseases," Annals of the New York Academy of Sciences, 1012, (2004): 224-36.
11. B, J, Van Lenten et al., "Lipid-Induced Changes in Intracellular Iron Homeostasis in Vitro and in Vivo," Journal of Clinical Investigation, 95, no. 5 (1995): 2104-10.
12. N. Stadler, R. A. Lindner, and M. J. Davies, "Direct Detection and Quantiication of Transition Metal Ions in Human Atheroslerotic Plaques: Evidence for the Presence of Elevated Levels of Iron and Coper," Arteriosclerosis, Thrombosis, and Vascular Biology, 24 (2004): 949-54.
13. J. M. Fernandez-Real et al., "Serum Ferritin as a Component of the Insulin Resistance Syndrome," Diabetes Care, 21, no. 1 (1998): 62-68.
14. J. Montonen et al., "Body Iron Stores and Risk of Type 2 Diabetes: Results from the European Prospective Investigation into Cancer and Nutrition (EPIC)-Potsdam Study," Diabetologia, 55, no. 10 (2012): 2613-21.
15. J. M. Fernandez-Real, A. Lopez-Bermejo, and W. Ricart, "Iron Stores, Blood Donation, and Insulin Sensitivity and Secretion," Clinical Chemistry, 51, no. 7 (June 2005): 1201-5.
16. D. J. Fleming et al., "Dietary Factors Associated with the Risk of High Iron Stores n the Elderly Framingham Heart Study Cohort," American Journal of Clinical Nutrition, 76, no. 6 (2002): 1375-84.
17. T. Iwasaki et al., "Serum Ferritin Is Associated with Visceral Fat Area and Subcutaneous Fat Area," Diabetes Care, 28, no. 10 (2005): 2486-91.
18. S. K. Park et al., "Association between Serum Ferritin Levels and the Incidence of Obesity in Korean Men: A Prospective Cohort Study," Endocrine Journal, 61, no. 3 (2014): 215-24.
19. G. Ortiz-Estrada et al., "Iron-Saturated Lactoferrin and Pathogenic Protozoa: Could This Protein Be and Iron Source for Their Parasitic Style of Life?" Future Microbioloty, 7, no. 1 (2012): 149-64.
20. L. Zacharski, "Ferrotoxic Disease: The Next Great Public Health Challenge," Clinical Chemistry, 60, no. 11 (November 2014): 1362-4.
21. P. Mangan, Dumping Iron: How to Ditch This Secret Killer and Reclaim Your Health, Phalanx Press, 2016, locations 308-12.
22. Fat for Fuel (Dr. Mercola)
23. What is hemochromatosis?
24. Dietary Iron Overload as a Risk Factor for HepatocellularCarcinoma in Black Africans
• Among 24 patients, the risk of developing HCC in the iron-loaded subjects was 10.6-fold relative to individuals with normal iron status.
25. Kaluza J, Wolk A, Larsson SC. Heme iron intake and risk of stroke: a prospective study of men. Stroke. 2013 Feb;44(2):334-9.
26. Use of Platelet-Rich Plasma (PRP) in Regenerative Therapies (Travel to Health)
27. Normal prion protein regulates iron metabolism
28. Influence of Iron on Bone Homeostasis
29. Diagnosis and Management of Hemochromatosis: 2011 Practice Guideline