Nutrition

Our appetite-control hormones are affected by chewing, according to some studies.

A number of studies show a clear link between increased chewing and reduced food intake.

Question:

I’m puzzled by the wholegrain-is-better-than-crushedgrain debate ( Nutrition, December 2). Whatever grain I eat gets a good crushing from my teeth. Is the mixing in of saliva during the crushing the factor?

Answer:

When we change the form in which food is eaten, this may affect some of the body’s unseen subsystems. For starters, when food is ground up before consumption, we’re effectively removing the chewing action from our digestive process. But does that matter? Chewing provides motor feedback to the brain on the necessary mechanical effort required, which gives the brain insight into the food’s texture. Chewing also exposes food particles to oral sensory receptors to help us detect and experience the flavour. These things contribute to our eating and digestive experience.

It also seems to affect appetite-control hormones. For example, one study found that chewing food 40 times instead of 15 times was associated with lower blood levels of ghrelin (which stimulates appetite) and higher levels of cholecystokinin

(CCK, believed to reduce appetite).

Research into the subject has been variable, though. Some studies have found that extra chewing had little or no effect on hormone levels, whereas others found chewing affected ghrelin and CCK concentrations, as well as the amounts of insulin and blood triglyceride. So, when a puréed soup was eaten, rather than a chunky soup, insulin and triglyceride levels were higher.

Interestingly, the Swedish study highlighted in the December 2 Nutrition column (“Crushing it”) found the physical texture of a diet also affected insulin and triglyceride levels. That is, a diet of pulverised food (ground-up lentils and wholemeal bread rather than wholegrain bread, for example) led to higher glucose and insulin responses and higher LDL cholesterol levels – all undesirable for our health. Was this partly the result of the reduced chewing?

Hormone levels aside, a number of studies show a clear link between increased chewing and reduced food intake. In other words, the more we chew our food, the less we eat. So, eating a diet laden with food that requires little or no chewing, thanks to food processing, could measurably increase the energy intake.

And yes, although our teeth do a great job of crushing our food, they’re not as uniformly effective as an industrial mill at reducing wholegrains to a fine flour.

Still, we don’t know what effect, if any, processed grains versus whole grains have on our health. We can only speculate based on the findings of the Swedish study (which was a more extreme version, given all the foods in their diet were ground up) and other studies that suggest chewing may influence the body’s hormone levels.

If you love wholemeal bread, stick with it. Healthy eating is about being

flexible and finding a style that fits your preferences.

Question:

Nuts and seeds, such as linseeds, almonds, sunflower seeds and coconut, are commonly ground up for ease of spreading on fruit or to use in smoothies. Are nuts and seeds more nutritious when eaten whole?

Answer:

Never mind superfoods, nutrition professionals have an old saying that “the best vegetable is the vegetable you eat”. And the same is quite possibly true for nuts and seeds.

We don’t fully understand the health effects of eating ground-up nuts and seeds rather than those in a whole state. However, a review by the Heart Foundation concluded that nut butters (such as peanut butter) were good for protecting against cardiovascular disease, coronary heart disease, myocardial infarction and sudden death. Given that nut butters are

made with ground-up nuts, it seems likely that the pulverised versions are still nutritious, and certainly their healthy fats make them a great addition to a smoothie.

So, enjoy them in whatever form you like.