What is inulin?

Inulin is a water-soluble dietary fibre present in about 15% of flowering plants. Most of us consume a few grams of it each day, with some of the inulin coming from plants and some from inulin added to food products (for example, the ingredient “chicory root fibre” is mostly inulin). 

Inulin belongs to a class of fiber known as “fructans” and comprises chains of fructosyl units, plus one glucose link to another unit (“moiety”) at the end. As a prebiotic, inulin promotes the growth of “healthy” gut bacteria, such as Bifidobacteria, after being fermented by microorganisms in the large intestine. In turn, inulin exerts an array of health benefits, from improving gut function to reducing bodyweight and inflammation.

Effects of inulin on lifespan and healthspan 

While some people have speculated that inulin might affect lifespan (according to the Interventions Testing Program, inulin doesn’t affect mouse lifespan), that’s not the reason we include inulin in Coastline. Instead, a key reason we include inulin is because it counters gut dysbiosis, and dysbiosis is one of the revised hallmarks of aging. It can be strange to think that you’re literally home to trillions of microorganisms (bacteria, yeasts, viruses) residing on you and in you. When your cells and your residents live in harmony, you each do each other many favours. For example, the microbes in your gut help you fend off pathogens, digest food, and even make vitamins for you, while the food you eat provides them the nutrients they need to flourish. Sometimes, however, you fall out with your residents — maybe you upset them when you bomb them with antibiotics or ply them with alcohol. Your usually amicable symbiosis breaks down, they start to work against you, and such dysbiosis seems to be not just a passenger but a driver of aging. Indeed, moving gut microbiota from old mice to young mice amplifies other hallmarks of aging, whereas transplanting the microbiota from a young mouse to an old one has anti-aging effects in the immune system and brain of the senior mouse.

There are various ways of positively affecting the composition of your microbiota, and some relatively simple changes can quite profoundly shift the dynamics of the gut microbiota. These include consuming prebiotics, non-digestible ingredients that your microorganisms metabolise, favourably changing the microbiota composition and resulting in benefits for the microorganisms’ host. Inulin is among the best, if not the best studied prebiotic, supporting the growth of “healthy” bacteria. These include Bifidobacteria, a genus that produces important metabolites that help counter inflammation. Short-chain fatty acids are among the beneficial metabolites made by the gut microbiota after inulin intake. The most abundant of these are acetate, butyrate, and propionate, and short-chain fatty acids serve numerous helpful roles. For example, they provide energy for the epithelial cells that line the gut, in turn bolstering the integrity of the gut lining and helping ensure that problematic substances don’t cross the gut’s barrier. 

A healthy gut microbiota helps you to manufacture many metabolites and micronutrients, and it can affect the gut in ways that improve the uptake of beneficial ingested nutrients too. For example, inulin has been found to increase the uptake of calcium, ultimately increasing bone mineral density. Last, perhaps the most widely discussed action of dietary fibre in the general population is its effects on bowel movements. By facilitating the growth of healthy gut microorganisms, inulin can soften stools and increase their frequency, making it helpful for many people who have constipation. 

The effects of inulin on hallmarks of aging other than dysbiosis have been less thoroughly researched. However, since the microbiota have pervasive effects on immune system regulation, inulin can reduce the chronic inflammation hallmark too, as shown by its ability to reduce C-reactive protein. Further, since inulin can slow the rate at which foods empty from the stomach, inulin might reduce the rate at which glucose appears in the blood. Theoretically, this should reduce the size of blood sugar spikes over time, making less glucose in the blood available to stick onto proteins (“glycation”) and thereby impair their functions, improving proteostasis, another hallmark. This idea is supported by research on people with poor blood sugar control, among whom inulin can improve blood sugar control and so reduce glycation of hemoglobin, a protein in red blood cells. This hasn’t always been found, but studies have documented either negligeable effects or small improvements in glycated hemoglobin (HbA1c) over time. 

Positive effects of inulin on human health

Gut health has impressively far-reaching consequences, and it’s now common for people to speak about various gut-organ axes, such the “gut-brain axis”. The core idea is that there’s a two-way relationship between what goes on in the gut and how the organ in question functions, and a growing mass of research shows that inulin intake affects a variety of health outcomes, even ones that superficially don’t seem strongly related to the digestive system. Let’s look at some examples of this. 

Inulin helps keep bodyweight in check

Before getting to inulin, it’s worth noting that most of us live in an obesogenic environment, and surplus fat mass in many ways contributes to accelerated aging, in a somewhat tissue-specific way. For example, excess bodyweight chronically loads your joints, so weight gain increases risk arthritis. Part of this might be due to chronic inflammation too. Too much bodyfat produces and releases various inflammatory chemicals, contributing to aging, even in remote tissues. Over time, excessive food intake leads to fat deposition in places where fat shouldn’t be (“ectopic” fat) too, wreaking cardiovascular and metabolic havoc. And the list goes on. At Coastline, we want to make products that help improve your body composition by building muscle and bone and keeping bodyweight and fat in check, which brings us to inulin. In addition to positive effects of inulin on the gut microbiota, immune function, and blood sugar control, inulin ingestion tends to slightly reduce bodyweight, perhaps in part by reducing ghrelin, a food intake-promoting hormone. 

Inulin is good for cardiovascular health

Inulin’s effects on bodyweight and inflammation alone would make it good for cardiovascular health, but inulin might favourably affect cardiovascular health in other ways too, for inulin consistently reduces LDL cholesterol and triglycerides, both of which are typically somewhat related to cardiovascular risk (the former is more so). The mechanisms by which inulin affects blood lipids aren’t completely clear, but they probably include reduced liver cell expression of genes involved in blood lipid synthesis, increased lipid breakdown, and increased excretion of bile salts and cholesterol in the feces. 

Inulin can boost cognitive function

The little research done so far has highlighted inulin’s promise in supporting both cognition and mood. Regarding cognition, a 12-week study of twins aged ≥ 60 focused on whether an inulin-type fructan product affected how people responded to resistance training. Everyone did the training and took a branched chain amino acid supplement. However, one group took an inulin prebiotic (3.375 mg inulin and 3.488 mg fructo-oligosaccharides), the other a maltodextrin placebo. Once again, the addition of inulin favourably affected the gut microbiota, and while there was no difference in changes in physical function between the inulin and placebo groups, the prebiotic improved cognition. 

Inulin might help lift mood

A 5-week study in relatively healthy adults with mild-to-moderate anxiety and depression symptoms split participants into 4 groups. One was a placebo (10 g per day maltodextrin), one consumed an inulin-type fructan (8 g per day oligofructose plus 2 g maltodextrin), one consumed the inulin-type fructan (8 g per day) plus 2 g per day 2'fucosyllactose (a trisaccharide present in breastmilk), and one consumed the 2 g per day 2'fucosyllactose plus 8 g of the maltodextrin placebo. Both the inulin-type fructan and the inulin-type fructan plus 2'fucosyllactose groups experienced prebiotic effects, as expected. The inulin-type fructan, the inulin-type fructan plus 2'fucosyllactose, and the 2'fucosyllactose groups all had improvements in measures of depression, anxiety, and a hormonal marker of stress named the cortisol awakening response, which is the spike in cortisol production that occurs around the end of the sleep period to ready your body for the day ahead. The inulin-type fructan and the inulin-type fructan plus 2'fucosyllactose groups had the most pronounced positive effects on mood, however. Based on these findings, inulin-type fructans can support brain health, particularly in older adults and in people who feel stressed, anxious, or down. 

Our use of inulin

Regarding dose, there is 4 g inulin in the morning step of Coastline. This is consistent with the individual doses of inulin used with meals in many studies of inulin. Note that while the daily dose of inulin-type fructans used in most studies is between 3 and 21 g, that’s because studies that use higher doses have participants take inulin several times a day, and many have people escalate their doses over time, working up to high amounts. 

Regarding timing, inulin is in the morning step of Coastline. This step is intended to be taken with the first meal of the day, and inulin is in it to help keep blood sugar and appetite responses to the meal in check. Notably, your blood sugar response to a meal influences your blood sugar responses to the next meal, a phenomenon dubbed the “second meal effect”. So, by curbing your blood sugar response to the first meal, inulin might help minimise blood sugar responses to later meals too. Magnesium is also in the morning step, and inulin-type fructans have been shown to increase magnesium uptake over time, in turn improving bone health. We always seek ingredient synergies in our products!

Regarding form, inulin chains range in length from 2 to 60 units. Short-chain inulins are slightly sweeter and more water soluble than their long-chain counterparts, which form microcrystals when added to water, giving a thicker, fat-like mouth feel. We use a relatively short-chain inulin in Coastline, for most of our customers consume Coastline cold and long-chain inulin products are not very soluble in cold water.

Inulin typical dietary intakes and safety

The majority of people don’t consume enough dietary fiber, and less than 10% of people in America consume the recommended 14 g fiber per 1000 Calories of food. Inulin is one of the major sources of fiber in most people’s diets though, and since inulin is present in so many plants, most of us consume several grams of it each day. Inulin intakes vary by country, and average daily consumption seems to vary between about 1 and 10 g per day, depending on location.

Inulin is perfectly safe. However, individual doses higher than about 5 g can produce digestive discomfort and flatulence (that’s the microbes fermenting the inulin), so we use a dose that tends to be easy to digest but that is also above the minimum dose been shown to be beneficial in clinical trials.