Fibre Optics Part 5
Beta Glucans
Follow This One Simple Rule
I have spent many years writing about food, health, and sustainability. If my writing has an overarching theme, it is this - food is complicated, and anyone telling you otherwise is trying to sell you something.
Simple food rules are always misleading, and generally terrible ways to live your life. ‘Eat Clean’, ‘Eat Paleo’, ‘Cut Fat’, ‘Cut Carbs’, ‘Go Carnivore’, ‘Go Vegan’, ‘Cut UPFs’, ‘Go Organic’, ‘Eat Local’, ‘Take this supplement’, ‘Sign up to this expensive health tracking app’ are all touted by people without the slightest interest in creating a healthier or more sustainable food system. Simple rules sell books, diets, products, subscriptions, and TV Programmes, but they don’t improve how we eat. Their advocates prey on our very human desire for simple solutions, when the reality of healthy, sustainable eating is, unfortunately, a complex one.
In Part 4, I discussed how eating foods with more intact plant cells is probably better for us than eating the same foods with broken cellular structures, which perhaps provides a mechanism to explain why associations between food processing and health outcomes might be independent of nutritional composition. The way we currently measure things, whole chickpeas are the same nutritionally as chickpea flour, but as the whole chickpeas have more intact cells, they are likely to create a very different metabolic response. As there are ways of preserving whole cells in processing, this is a potential route to making healthier processed food products.
So, perhaps I should break the writing habit of a lifetime and recommend that we follow the relatively simple rule of eating foods with more intact cells. This might get me a feature in next month’s Daily Mail with some ‘whole cell’ recipes, a weekly meal plan and some judiciously lit before and after photos to show the transformative effects. I might do quite well out of selling this simple food rule, at least before Michael Mosely steals the idea and launches his own version.
The Gel’s the Thing
Some beta glucans forming a delicious gel.
I’ve always been an advocate of increasing fibre consumption and believe that eating lots of intact plant cells is a good thing to do. But the reason that I’m not going to be appearing in a national newspaper in my underpants anytime soon, is that I also understand that things are just not that simple. Whole cells are great, but they are not a panacea. Some of the stuff bound up inside cells is actually pretty useful and there are times when releasing it as soon as possible might actually be of benefit.
Of course, when we talk about health, it is important to consider that different groups of people have dramatically different needs. Although many of us would probably benefit from our nutrients being a bit more tightly locked up in cells and so harder to digest, many others need readily accessible calories and foods that are easy to consume. The sick and the elderly often struggle to take on enough calories and nutrients, and the last thing they need is to be told to eat some lentils and steamed kale.
But even if we only consider the large numbers of people who would perhaps benefit from consuming fewer calories and eating foods that create a lower glycaemic response, whole cells might not always be the way to go. There are many substances locked up in cells that can benefit us greatly if they are more accessible. Several of these are not well understood, but one key type are Beta-Glucans. And the more we learn about these substances, the more incredible they seem to be.
Beta-Glucans are largely found within the cell walls of grains such as oats or barley. They are formed from long chains of glucose molecules, linked with the same sort of bonds found in cellulose (see Part 1), although every 3 or 4 bonds in the chain there is a beta link, which sits at a slightly different angle. This irregularity means that the glucose chains do not form regular crystalline structures, and so unlike cellulose are partially soluble in water, forming strong gels. It is this solubility and gel forming capacity that help give beta-glucans their exalted status as a health promoting super-ingredient.
As we have mentioned before, the solubility of different fibre and their ability to form gels when studied in a laboratory provides little clue to how the same substance might perform in the human gut. But with beta-glucans, there does appear to be a close relationship, and their gel forming does seem key to how they benefit our health. Famously, beta glucans are known to lower blood cholesterol, but there is also a relationship with delayed gastric emptying (perhaps increasing satiety), delayed glycaemic response, reduction of amylase activity (known to slow down digestion of carbohydrates) a decrease in the permeability of the intestine (so leading to slower absorption of nutrients), and an increase in bile salt excretion. It is thought that beta-glucans bind bile salts, helping them move more easily through the intestine so that they are either excreted or fermented by our gut bacteria. When this happens, our body makes more bile salts to replace those lost, a process that uses up cholesterol, so lowering the levels in our blood. This process means that food products containing high levels of beta glucans can legally carry a heart health claim.
In short, to summarise why beta glucans have a positive impact on health, they appear to form gels in our gut that slow down and regulate the absorption of nutrients, leading to a host of benefits. Slowing down digestion is generally a good thing, reducing the speed glucose is released into the blood, and allowing more stuff to pass lower down into the gut, so reaching the microbiome. Simple. Perhaps beta glucans are a good example of what nutrition influencers like to call a ‘superfood’. And as it seems important that they start forming gels as soon as possible, a higher level of processing of beta glucan containing ingredients is likely to have a positive effect, as this means that they will be freed up to do their thing, preferably as soon as they hit the stomach. The all-important gels can only form when beta glucans are released from their cellular structures, so the earlier you can do that, the better. Maybe I should call the Daily Mail and recommend my all new ‘Highly Processed Beta Glucan Diet’.
It's Never That Easy
Nutrition science would be a lot easier if more people were transparent like this individual, who is pictured being attacked by some giant biochemistry.
Of course, it is not quite that simple. In truth, it is actually pretty hard to know exactly what is going on in the gut, because the processes down there are a bit of a black box, very hard to observe without interfering. Ethics committees tend to dislike researchers cutting people open to look at gels forming in their intestines. Cameras or other sensors are uncomfortable and likely to affect normal digestive function. There are animal models, especially pigs, that can give us a clue, and various versions of artificial guts, but there are still plenty of unknowns.
It is fairly well established that gel forming and viscosity are important, and a lot of this depends on the molecular weight of the beta glucans being consumed. When it comes to practical decisions about whether an on-pack health claim can be made however, this is not considered. The molecular weight of beta glucans can vary hugely, with some up to 1000 times bigger than others, and even though research has shown that higher molecular weight beta glucans are more effective in reducing glycaemic response, all are considered the same when calculating on pack health claims.
The molecular weight of beta glucans varies with origin (e.g. oat vs barley), growing conditions, storage and extraction. Processes such as freezing, baking, boiling and extrusion are all known to reduce molecular weight by breaking up long chains, so decreasing the likelihood that effective gels will form. This might lead us to think that preserving the molecular weight of beta glucans is key, which usually means reducing the level of processing (get the Daily Mail back on the phone, it’s time for the all-new ‘Angry Chef Unprocessed Beta Glucan Plan’). Again however, it is probably not that simple. Really high molecular weight beta glucans are not very soluble, meaning that they are unlikely to be able to form gels at all. This means that there is probably an optimum level of processing, freeing up beta glucans from cells, breaking up some of the really large chains, but keeping chains long enough to form the right sort of gels.
The worry is that we actually know very little about what that optimum level of processing is. Perhaps unsurprisingly, there are some published studies of beta-glucans that have failed to show any positive health effects, probably because of the impact of molecular weight on solubility and/or gel forming. It is not the amount of beta glucan you eat that determines how well it works, it is the amount that dissolves in the upper gut, and the strength of gel it forms there. And that depends on a lot of things, some of which we just don’t know. Unfortunately for me, the ‘slightly processed, but not too processed beta glucan diet that involves measuring molecular weights, looking at preserved cell structures under a microscope and accepting a lot of uncertainty’, is never going to get me a pull-out feature in a Sunday magazine.
It is possible to create gels in a test tube and measure how strong they are, but this is unlikely to tell us exactly what is going on in the gut, where there are enzymes, nutrients, microbes, digestive fluids, and all sorts of other stuff going on. To date, even though science currently has a Rover sending back pictures from the surface of Mars, the viscosity of a beta glucan gel in the human gut has never been directly measured.
Things are not simple, and anyone telling you otherwise is selling something. Perhaps we should more routinely measure the molecular weight of beta glucans before making health claims, but as we do not really know the ideal size, would there be much point? Maybe we should not make any specific health claims at all, just encourage people to eat a variety of plant foods with different processing levels. But that sort of vague, non-specific health advice rarely cuts through.
There are also lots of other substances that form gels in the human gut and may potentially have health benefits, but these are even less well studied than beta glucans, with even more uncertainty. In fact, in unguarded moments, researchers working in this area will tell you that the only reason that there is such a focus on beta glucans is that they are easily categorised, extracted and measured, perhaps making them slightly easier to research.
As someone working in the development of food products, I am often torn between wanting to make health claims, and not wanting to confuse or mislead. Some special new varieties of barley have very high levels of beta glucans, meaning that it is relatively easy to get a heart health claim at low levels of inclusion. But the actual health impact is likely to depend on several factors. Some processing is probably good, but high levels of processing might negate benefits. I constantly try to improve the healthfulness of the foods I develop, but I currently have no clear insight into what an ideal level of processing is. And cynically, as things stand this doesn’t really matter, as my ability to make a health claim is only dependent on how much I put in.
As ever, more research is needed. I still recommend eating lots of stuff with beta glucans in, like oats and barley. I’d also say that foods with whole plant cells are pretty good, and most importantly, can be delicious. But the relationship between food and health is always complex, and there are never easy answers. Which is why there is always money to be made pretending that there are.