Flax Alters Gut Bacteria, Reduces Insulin Resistance

flax change gut bacteria and reduce insulin sensitivity

Flax changes gut bacteria. Photo by Alisha Vargas

Yes, most of us know by now that flax is healthy. Mostly we think of how flax (Linum usitatissimum L.) provides good fiber.

And yes, flax does provide some good fiber – at a significant 30 percent dietary fiber – but flax goes far deeper than just fiber.

How deep, you ask?

Flax changes gut bacteria

Research from the Novo Nordisk Foundation Center for Basic Metabolic Research at Denmark’s University of Copenhagen found some stunning results after a test using 58 women.

The women were post-menopausal, which means they past the age of menopause. This was qualified as one year after their last menstruation. The age of the women ranged from 40 to 70 years old. The women also had a body mass index of between 30 and 45 kilograms per meter squared. Yes, they were clinically obese. Outside of this, none of the women had any chronic disease, including diabetes type-1 or type-2. Also, none of the women were taking probiotic supplements prior to the study.

For six weeks, the women were given one of three treatment plans:

• A probiotic supplement with Lactobacillus paracasei (9 billion CFUs per day)
• 10 grams of ground flaxseed fiber (mucilage)
• Placebo – blinded

The ground flaxseeds were given in breakfast buns while the placebo group also ate breakfast buns. The probiotics were given in sachets and placebo sachets were given to the other groups.

Gut bacteria also tested

Prior to the study, the women were tested for gut bacteria. They were also given a test for insulin resistance – a test called HOMA-IR – along with blood testing that measured a number of markers.

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After the six weeks, the flaxseed group showed a significant increase of probiotic bacteria in their guts. They found the flax increased populations of 33 genetically different probiotic species. Species that increased in abundance included Bilophila wadsworthia, Parabacteroides merdae and Parabacteroides johnsonii

In addition, the flaxseed group guts showed a reduction of eight species of bacteria – which included Eubacterium, Ruminococcus and Faecalibacterium species. Faecalibacterium species such as F. prausnitzii species. The flaxseed group also had significant decreases of Ruminococcus lactaris species and others.

In contrast, the probiotic supplement group did not show significant changes in their gut bacteria. Outside of a small increase in that specific strain, there was little difference between the gut bacteria in the probiotic group versus the placebo group:

“This study showed a very limited effect of L. paracasei F19 on the gut microbiota and metabolic markers, which were non-significant compared with the placebo group.”

There is the possibility that this significant lack of effect among the probiotic group was due to a lack of prebiotics among the group. We’ll discuss this below.

Flax significantly reduces insulin resistance

The researchers found that only the flax group showed a significant reduction in insulin resistance. This is the same as an increase in insulin sensitivity.

The flax group also had a significant reduction in serum C-peptide along with reduced insulin levels. In persons without diabetes this is a good sign, showing increased glucose sensitivity among the cells. Increased glucose sensitivity means that more glucose is getting into the cells where it belongs – instead of roaming around the bloodstream where it can cause problems with the blood vessels.

As insulin resistance is common among those who are overweight, these are significant findings. Other research has shown that increases in insulin sensitivity often accompanies an easier ability to reduce weight – especially when healthy foods are included in the diet.

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Not the first insulin study on flax

This is not the first time flax has shown up on the insulin sensitivity radar. Several studies – mostly animal studies – have illustrated that flax decreases insulin resistance. Also, human research has shown that flax can help reduce weight.

A 2015 study from the school of medicine at the University of Saskatchewan determined in their research that flax and the lignans within flax improve glycemic control. They also found that the secoisolariciresinol diglucoside (SDG) within flaxseed reduces blood levels of glucose by as much as 75 percent.

Why didn’t L. paracasei reduce insulin resistance?

Curiously, the probiotic supplemented group in the Danish study did not show a significant changes in insulin sensitivity. This is curious because other studies involving L. paracasei have shown a significant effect upon insulin sensitivity and weight loss. The whole reason the researchers used L. paracasei is because of this background of research showing L. paracasei reducing insulin resistance.

Other research has also shown that supplementation with L. paracasei increases other probiotic bacteria in the gut. This also wasn’t shown in this Danish study.

For example, a 2011 study from Estonia’s University of Tartu found that colonization with L. paracasei was associated with lower blood glucose levels. And a 2001 study from Sweden’s Huddinge University found that supplementation with L. paracasei along with a prebiotic led to increases in many species of probiotic bacteria.

The conclusion the Danish researchers came up with was that the L. paracasei did not colonize well in the subjects, possibly because there was a lack of prebiotics in their diets.

Three important take-home lessons

The Danish study on flax and L. paracasei illustrated three important ‘take home’ lessons:

• Flaxseeds provide an important source of prebiotic fiber and this has the effect of feeding and reorganizing populations of bacteria in our gut. The precise nature of this reorganization still requires research.
• Flaxseeds significantly decrease insulin resistance – shown by reduced blood glucose, decreased insulin and serum C-peptide.
• Supplementation of probiotics will have little effect unless they are combined with the intake of prebiotics. Certainly, flax is a prebiotic, but there are many others.

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The bottom line is that our probiotic bacteria must be well taken care of. Yes, supplementing probiotics is good, but we must also feed them.

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Brahe LK, Le Chatelier E, Prifti E, Pons N, Kennedy S, Blædel T, Håkansson J, Dalsgaard TK, Hansen T, Pedersen O, Astrup A, Ehrlich SD, Larsen LH. Dietary modulation of the gut microbiota–a randomised controlled trial in obese postmenopausal women. Br J Nutr. 2015 Aug 14;114(3):406-17. doi: 10.1017/S0007114515001786.

Prasad K, Dhar A. Flaxseed and Diabetes. Curr Pharm Des. 2015 Nov 12.

Štšepetova J, Sepp E, Kolk H, Lõivukene K, Songisepp E, Mikelsaar M. Diversity and metabolic impact of intestinal Lactobacillus species in healthy adults and the elderly. Br J Nutr. 2011 Apr;105(8):1235-44. doi: 10.1017/S0007114510004770.

Sanders ME, Marco ML. Food formats for effective delivery of probiotics. Annu Rev Food Sci Technol. 2010;1:65-85. doi: 10.1146/annurev.food.080708.100743.

Sullivan A, Palmgren AC, Nord CE. Effect of Lactobacillus paracasei on Intestinal Colonisation of Lactobacilli, Bifidobacteria and Clostridium difficile in Elderly Persons. Ecol – Environ Microb. 2002 Mar doi:10.1006/anae.2001.0377


  • Case Adams, PhD

    Ph.D. in Natural Health Sciences, Doctorate in Integrative Health Sciences, Board Certified Alternative Medicine Practitioner, California Naturopath. Diplomas in Blood Chemistry, Clinical Nutritional Counseling, Homeopathy, Aromatherapy, Colon Hydrotherapy, certificates in Pain Management and Case Management/Contact Tracing. Has authored more than 30 books and hundreds of periodical articles on natural medicine. Recreational activities include surfing, sailing, running, biking, swimming, SUPing, hiking. Contact: case(at)caseadams(dot)com.

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