High starch diets associated with increased risk of type 2 diabetes

High starch diets associated with increased risk of type 2 diabetes
<http://www.drbriffa.com/2010/08/06/high-starch-diets-associated-with-increased-risk-of-type-2-diabetes/>

By Dr John Briffa
Posted on 6 August 2010

Last week one of my blogs
<http://www.drbriffa.com/2010/07/27/diabetes-costs-out-of-control-and-why-this-is-no-surprise-given-standard-dietary-advice-for-diabetics/>
focused on story regarding the spiralling costs of medication for
diabetes. I suggested that one reason for this is that many diabetics
are advised to eat a diet rich in starchy carbohydrate, yet these foods
generally are very disruptive to blood sugar levels. Yes, that's right –
diabetics who by definition tend to run high blood sugar levels are
often advised to eat plenty of foods that cause high blood sugar.

In that blog post I cited a study which showed that low carbohydrate
eating allowed more than 95 per cent of type 2 diabetics to reduce or
eliminate their medication. This, by the way, does mirror what I see in
practice. Low-carb eating is not a sure-fire way of controlling blood
sugar in every individual with diabetes, but one thing I know for sure
is that by an large this is a highly effective strategy (and for quite
obvious reasons too, I think).

Could low-carb eating have some value in the prevention of type 2
diabetes? In theory, yes. And here's why:

As distinct from type 1 diabetes (in which the pancreas produces little
or no insulin), many individuals with type 2 diabetes make lots of
insulin, it's just not doing its job properly. This situation is
described as 'insulin resistance', and the more insulin one secretes
over the course of one's life, the more likely one is to become insulin
resistant. Eating less blood sugar-disruptive carb could, therefore,
lead to generally lower levels of insulin and less risk of insulin
resistance.

Some type 2 diabetics are suffering from a degree of 'beta-cell
exhaustion'. It is the beta cells in the pancreas that make insulin. The
harder these cells are worked during our lifetime the more likely they
are to get exhausted. Now we have the potential of low levels of
insulin. The risk here is that some people can end up secreting low
levels of not-very-effective insulin.

Anyway, one doesn't need a PhD to realise that eating a lower carb diet
will generally lower insulin levels and make less demands on the
pancreas. In short, common sense dictates that a carb-controlled diet
should help prevent type 2 diabetes.

The best way to confirm or refute this concept would be to randomise
people to a high- or low-carb diet, follow them up over time
(preferably, several years) and see if the lower-carb dieters had lower
risk of type 2 diabetes compared to the higher-carb eaters. I can't find
such a study in the scientific literature, and have a hunch such a study
is unlikely ever to be done.

The next best thing is to look at populations (preferably large ones)
and see if, over time, there is any relationship between carbohydrate
intake and risk of type 2 diabetes. This is precisely what a group of
researchers from the Netherlands did recently, and their findings were
published on-line this week in the American Journal of Clinical Nutrition.

In this study, almost 38,000 adults were followed for an average of 10
years. The researchers looked at the relationship between not just carb
intake and type 2 diabetes, but also the tendency of those carbs to
disrupt blood sugar. Specifically, the researchers assessed the
relationship between the glycaemic index (GI) and glycaemic load (GL).
The glycaemic index is a measure of the speed an extent to which a
standard weight of food releases glucose into the bloodstream. The
glycaemic load takes into account the amount of carbohydrate eaten too,
and therefore generally gives a better indication of the overall amount
of blood sugar disruption that comes from food.

In some of their analyses the researchers took account of factors that
might affect diabetes risk including age, sex, levels of physical
activity and other dietary factors. In these analyses it was found that:

/Higher carbohydrate was associated with a 20 per cent increased risk of
type 2 diabetes/

/Higher dietary GI was associated with an 8 per cent increased risk of
type 2 diabetes/

/Higher dietary GL was associated with a 27 per cent increased risk of
type 2 diabetes/

/Higher sugar consumption was not associated with a statistically
significant increase in risk of type 2 diabetes/

/Higher starch consumption was, however, associated with a 23 per cent
increased risk of type 2 diabetes/

The authors also quote other studies that have attempted to discern
what, if any, dietary GI or GL has with diabetes risk. While not all
studies show a link, six /do/ (and therefore are consistent with the
findings of this latest study). So, by my calculations that's now seven
studies we have linking high GI and/or GL with enhanced diabetes risk.

Now, I know there will be some that claim that the evidence is
'inconclusive' here, but that's a matter of opinion. To my mind,
science, and of course common sense, support the idea that if we're keen
on doing what we can to protect ourselves from type 2 diabetes, we need
to be a bit careful with those carbs, and not swallow whole without
thinking the conventional advice that tells us we can safely and happily
have our fill of them.

*References: *

1. Sluijs I, et al. Carbohydrate quantity and quality and risk of type 2
diabetes in the European Prospective Investigation into Cancer and
Nutrition–Netherlands (EPIC-NL) study. Am J Clin Nutr 4 August 2010
[epub ahead of print]