Guest blog by Vicky Ware
Fibre for Health
Fibre is a really important component of a healthy diet, yet the amount we’re eating has decreased. Our ancestors didn’t have much choice but to eat lots of fibre – almost everything that was easy for them to get hold of (I include ‘plant’ in that category when compared to ‘angry bison’ !) contained it. They may have eaten up to 30 times more fibre than modern humans 1. Now though, we’re perfected refining foods down to the bare ‘essentials’. We have access to calorie dense foods that are low in bulk, meaning we can eat lots of them – there simply wasn’t access to the number of calories in a fizzy sugar containing drink in the past without also eating a lot of fibre. So, what’s all the fuss about fibre anyway? Let’s take a look.
Types and Sources of Fibre
Scientists still haven’t come up with one clear definition for what fibre is 2. This is because there are lots of types of fibre, just as there are different types of fat. When thinking about what to eat, it’s useful to think of two types of fibre, soluble and insoluble. Although a lot of fibre-containing foods have both types, they tend to contain more of one than the other.
Soluble fibre dissolves in water and is found in:
- golden linseeds 3
Soluble fibre passes through the small intestine undigested, because humans don’t have the enzymes needed to break it down. Once in the colon the fibre is fermented by the bacteria found there, who do have the required enzymes.
Products of the bacterial fermentation can sometimes be absorbed directly into the blood stream – short chain fatty acids are an example of this. These are thought to be really important for gut health and can actually be used by the cells lining your intestine, for energy 4;5;2.
Soluble fibre can alter hormone levels in your body and be turned into vitamins once digested by the bacteria in your gut 6;7.
Psyllium husks are a great source of soluble fibre. These can be added to foods you eat to increase you soluble fibre intake 8. Cocoa is another great, and delicious, way to up your soluble fibre intake 9.
Insoluble fibre is found in:
- brown rice
- wheat bran
- seeds 3
It ‘bulks out’ the food we eat and slows the rate at which our bodies absorb nutrients 10.
Carbohydrate is absorbed more slowly when it is eaten as part of a high fibre meal. This slower absorption means less of a spike in blood sugar when you eat carbohydrate, which may explain why people who have high fibre diets are less likely to develop diabetes 11.
Insoluble fibre also speeds the passage of food through the intestines, by providing solid mass against which the muscular contractions of the intestines can push to move food through the bowels. Less time in the gut allows less time for your body to digest meaning fewer calories taken from the food you eat 10. This might be why people eating high-fibre diets are less likely to be overweight 12.
What is Fibre Good For?
Studies have shown that people who have a higher intake of dietary fibre have a lower risk of death – from all causes 13. That’s not to say that eating fibre is going to stop you from getting run over by a bus but it does mean that there seems to be a strong link between eating enough fibre and being healthy. This link might be because of the fibre itself or it might be that people who eat more fibre make other health conscious decisions like eating fruit and vegetables 14. However, there is evidence that fibre itself directly benefits our health.
Dietary fibre has been shown to reduce chances of:
- heart disease 15
- high cholesterol 16
- high blood pressure 17
- metabolic syndrome 17
- obesity 17
- type II diabetes 18
- being overweight 19
- inflammatory bowel disease, and 20;8
- stroke 21.
A high fibre diet has been shown to reduce the levels of inflammatory markers found in the body, suggesting that fibre is anti-inflammatory. Lots of diseases ranging from cardiovascular disease to cancer have a basis in inflammation so this could be one of the reasons fibre seems to be so good for health 15.
Eating 14 grams of fibre for every 1000 calories consumed is considered protective against cardiovascular disease 22.
It’s not just in the gut where fibre has its anti-inflammatory effect. Increasing the amount of fibre you eat can reduce allergic airway responses in the lung 23.
Dietary fibre has been shown to make people feel fuller for longer, meaning they eat less food 24. In fact, fibre might help people who are obese lose weight 12. This may be because eating fibre decreases the amount of energy your body can take from the food you eat, takes longer to chew and makes you feel physically fuller just because it takes up more space in your stomach 10;25.
How Much Should We Eat?
The Recommended Daily Allowance (RDA) for fibre is between 18-30 grams – although it’s thought the average person eats less than this 2. However, some experts think then RDA should be a lot higher, as our ancestors are likely to have eaten much more than we do. Archaeological evidence found a group of prehistoric people ate up to 135 grams of a specific fibre per day – not including other fibres in their diet 12;26.
Although there is an RDA for fibre, scientists and regulators are not really sure how much we should be eating 6. One of the problems is the lack of a clear definition of what ‘fibre’ is, as we discussed above. There isn’t yet an RDA for each type of fibre, although, as we’ve seen, they play different roles in health 6.
If you’re anything like the average Western human, you’re probably not eating enough fibre. Eating more is likely to make you feel better in the short and long term, especially as fibre containing foods tend to be nutrient dense so you’ll up your daily intake of other essential vitamins and minerals, too. Foods such as meat and dairy products contain no fibre but they’re not high on other health giving nutrients either, so it’s a win-win on the foods containing fibre front.
It’s not difficult to up your fibre intake. A high fibre meal will be largely plant based. Incorporating more fruits and vegetables into your diet and swapping refined grains such as white bread, pasta or rice for whole grain versions will take you a long way towards your daily fibre intake. I find you can, also, sneakily add lentils to meals such as stews to increase the fibre content.
If you want to up the intake even further, adding supplements to your food such as psyllium husks for soluble fibre and wheat bran for insoluble fibre will ensure you’re getting your daily requirement. I find porridge is the easiest place to add these.
Vicky has a degree in Biological Sciences with a focus on biochemistry and immunology and is currently studying for a MSc in Drug Discovery and Protein Biotechnology. She is also an endurance athlete.
- Pappas, 2012. Ancient Poop Gives Clues to Modern Diabetes Epidemic.
- Slavin, 2013. Fiber and Prebiotics: Mechanisms and Health Benefits.
- WHF, 2015. Fibre.
- Cook, 1998. Review article: short chain fatty acids in health and disease.
- Wong, 2006. Colonic health: fermentation and short chain fatty acids.
- Kuo, 2013. The interplay between fiber and the intestinal microbiome in the inflammatory response.
- Lewis, 1997. Lower serum oestrogen concentrations associated with faster intestinal transit.
- Bijkerk, 2009. Soluble or insoluble fibre in irritable bowel syndrome in primary care? Randomised placebo controlled trail.
- Sarria, 2012. Hypotensive, hypoglycaemic and antioxidant effects of consuming a cocoa product in moderately hypercholesterolemic humans.
- Baer, 1997. Dietary fiber decreases the metabolizable energy content and nutrient digestibility of mixed diets fed to humans.
- Bourdon, 1999. Postprandial lipid, glucose, insulin, and cholecystokinin responses in men fed barley pasta enriched with beta-glucan.
- Howarth, 2001. Dietary fiber and weight regulation.
- Yang, 2014. Association between dietary fiber and lower risk of all-cause mortality: a meta-analysis of cohort studies.
- Jones, 2010. Is it the fibre or the co-passengers?
- Sarria, 2015. Effects of bioactive constituents in functional cocoa products on cardiovascular health in humans.
- Gunness, 2010. Mechanisms underlying the cholesterol-lowering properties of soluble dietary fibre polysaccharides.
- Moreno Franco, 2014. Soluble and insoluble dietary fibre intake and risk factors for metabolic syndrome and cardiovascular disease in middle-aged adults: the AWHS cohort.
- McKeown, 2002. Whole-grain intake is favourably associated with metabolic risk factors for type 2 diabetes and cardiovascular disease in the Framingham Offspring Study.
- Thomas, 2013. The short-chain fatty acid acetate reduces appetite via a central homeostatic mechanism.
- Hou, 2011. Dietary intake and risk of developing inflammatory bowel disease: a systematic review of the literature.
- Threapleton, 2014. Dietary fibre intake and risk of ischaemic and haemorrhagic stroke in the UK Women’s Cohort Study.
- Slavin, 2008. Position of the American Dietetic Association: Health Implications of Dietary Fiber.
- Huffnagle, 2014. Increase in dietary fiber dampens allergic responses in the lung.
- Burton-Freeman, 2000. Dietary Fiber and Energy Regulation.
- Slavin, 2007. Dietary fibre and satiety.
- Leach, 2010. High dietary intake of prebiotic inulin-type fructans in the prehistoric Chihauhuan desert.
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