The more masticating the better when it comes to aiding digestion and eating less.
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Question: Recently you mentioned that eating whole grains and seeds was good for one. It’s noticeable, however, that a large proportion of such grains and seeds just “pass right through”. Given that, what if any nutritional value or benefits do these foods have?
Answer: While not a topic for polite company, a quick look before you flush could save your life; blood in bowel motions, for instance, can be a sign of bowel cancer and should be checked promptly by a doctor. Keeping an eye on proceedings can help with detection of other digestive issues, too. Undigested food fragments in bowel motions normally aren’t a problem, unless accompanied by changes in bowel habits, or weight loss, in which case a doctor’s visit is advised.
High-fibre plant-derived foods, such as whole grains and seeds, are typically the source of such undigested fragments. In fact, dietary fibre is actually defined as the fractions of the edible parts of plants that are resistant to digestion and absorption in the small intestine. But although these fibrous fragments aren’t digested in the small intestine, they’re still useful for our health. Dietary fibre absorbs water and adds bulk to bowel motions, helping to reduce transit time and dilute harmful body waste compounds. This all makes for better bowel health.
Scientists originally thought dietary fibre provided no energy. But we now know certain fibres are fermented in the large intestine by gut bacteria. The bacteria produce short-chain fatty acids and gases; these fatty acids are absorbed into our body, providing a small amount of energy.
Having said all that, it’s important to recognise that our mouths play an important role in digesting fibrous food. For starters, our teeth are designed to cut, tear and pulverise solid food into smaller particles that are mixed with saliva into a soft mass ready for swallowing. We produce 1-1.5 litres of saliva a day, of which 99.5% is water. The rest is made up of minerals and other compounds such as digestive enzymes. The water in saliva allows food molecules to dissolve so that we can taste them and, importantly, allows digestive reactions to occur. Watching a lump of pasta slowly dissolve in a beaker of saliva remains one of the more memorable laboratory demonstrations I witnessed at university. It demonstrated the important point that saliva contains digestive enzymes. In fact, saliva contains two types.
Salivary amylase breaks down starches into smaller fragments. It works in the mouth and for up to an hour in the stomach before the stomach’s acidic environment inactivates it. The second enzyme, lingual lipase, is activated by the acidic environment of the stomach and therein breaks down dietary fats.
In the Victorian era, American Horace Fletcher, known as “the great masticator”, advocated chewing food 50-100 times. Fletcher seems to have had a good point, and one that’s particularly relevant in this era of obesity and hurried meals. A 2011 study in the journal Appetite reported that chewing food 35 times per mouthful, rather than 10 times, reduced food intake among study participants.
Furthermore, obese men were observed to chew their food less than lean men, in a 2011 study in the American Journal of Clinical Nutrition. Subsequent tests found increasing chewing per bite from 15 to 40 resulted in both lean and obese men consuming about 12% less energy from their meal, at the same lowering their levels of the hormone ghrelin. Ghrelin is thought to stimulate appetite.
More chewing obviously means meals take longer, which isn’t a bad thing. A 2011 New Zealand study, published in the Journal of the American Dietetic Association, found women who rated themselves as slower eaters had lower body mass indexes than women who ate quickly. So enjoy chewing your way slowly through those grains and seeds – whether you fully digest them or not, you’re winning.
Email: nutrition@listener.co.nz, or write to “Nutrition”, c/o Listener, PO Box 90783, Victoria St West, Auckland 1142.