What do psyllium and flaxseed do for your blood sugar?

Taking psyllium just before a meal slows the absorption of sugars because it forms a thick gel in the intestine. That gel formation is precisely what makes the difference: fibres that do not form a gel do not produce this effect. The result is a lower blood sugar peak: in people with type 2 diabetes, the rise after breakfast was 14% smaller and after dinner even 20% smaller compared with people who received a placebo. Particularly notable is the so-called 'second-meal effect': at lunch, without any additional psyllium being taken, the blood sugar peak was still 31% lower than in the placebo group.

It is not only about peaks after eating. With 5 grams of psyllium three times a day for six weeks, fasting blood sugar also fell, meaning the value measured in the morning before breakfast. After eight weeks of use at two times 5 grams per day, the long-term indicator of blood sugar regulation also declined (the value that reflects how high blood sugar has been on average over the preceding two to three months). Psyllium also reduced the amount of insulin the body had to produce after a meal, by around 12% after breakfast. Fewer insulin peaks is beneficial in the long term for the body's sensitivity to that hormone.

Psyllium was well tolerated in all available studies, with no serious side effects. People who used metformin appeared to experience fewer gastrointestinal complaints from that medication when also taking psyllium. Psyllium is a highly water-absorbing fibre: always drink plenty of water with it, otherwise you increase the risk of constipation. If you have diabetes and use medication, discuss with your doctor whether and how you wish to add psyllium, because it actively lowers blood sugar on top of your existing treatment.

The available studies have nothing to say about flaxseed. No study is included that has tested the effect of flaxseed on blood sugar, so a comparison with psyllium cannot be made on the basis of these sources.