Resistant starch: the missing ingredient? Part 1

Just when you think you have everything in your diet dialed in, something new comes along and upsets your carefully constructed nutrition knowledge applecart. This particular compound has been getting nutritionists a little giddy with excitement for a while, and now it is receiving more and more media exposure causing everyday folk scratch their heads at the new wonder boy. It’s hard not to get swept away in general enthusiasm when our popular morning TV show touts Resistant Starch (RS) as a “sneaky fat fighter”.

Remember when things were simple and we were told to just eat more fibre? Well, that is so 1990s. CSIRO in Australia note that while Aussies eat more fibre than many other Western countries we still have the highest incidence of bowel cancer in the world. They call it ‘the Australian paradox’ (what number paradox is it now? I lose track). So looks like adding more fibre in form of All-Bran and bran muffins into our diet has done bugger all to keep those pesky intestinal cells from going bananas and turning into some evil little suckers. All hail resistant starch.

However, as most of you know, I am naturally a fairly skeptical person when it comes to dietary ‘miracles’, especially when the recommendations to increase RS in our diet from the above mentioned morning program look like this:

  • Eat more canned or soaked legumes such as kidney beans, chickpeas and butter beans.
  • Include more intact wholegrains, seeds and cereals, in your diet e.g. oats, barley corn and linseeds.
  • Eat fruit such as bananas before it’s ripe.
  • Eat salads that have been cooked and cooled, such as potato salad, rice salad and pasta salad.
  • Look for breads and cereals with added resistant starch

So what the hell is it? And are you missing out on this miracle food substance?

The official website named Resistantstarch.comAn Information Portal for Health Professionals (don’t you wish that broccoli had an official website?), gives us this definition:

”Resistant starch is the sum of starch and products of starch digestion not absorbed in the small intestine of healthy individuals”

It is also classified as the third type of fibre (together with soluble and insoluble) by several health agencies, including Food Standards Australia and New Zealand, and its MO is to bypass the normal absorption process in the small intestine straight to the colon where it is fermented by colonic bacteria (which also makes it a “prebiotic”).

There are plenty of resistant polysaccharides (starches) that you won’t find in your average shopping trolley and this is reflected in 4 types of RS. Here is a handy table from one of the published reviews (1) on RS (click for better resolution):

Source: Nugent 2005

Source: Nugent 2005

Kind of makes you wonder whether you should start munching on raw potatoes in spite of what Momma always told you and inflict your bean-eating habits on your nearest and dearest for the sake of digestive health. Or should you just trust the clever scientists who conveniently altered the chemical structure of polysaccharides via esterification in order to escape your digestive enzymes? Why are we doing this again?

Oh yes, the claims. I will be relying on the enthusiastic RS article (2) by an Australian dietician Robert Landon written for the official Resistant Starch website to provide the claims to benefits. My facetious comments will follow for your reading pleasure.

Satiety, metabolic health and obesity

I’ll start with this one because clearly this is the stuff that makes big headlines.

“Recent breakthrough research has linked the fermentation of resistant starch with increased levels of gut hormones (PYY and GLP-1) that play a role in satiety and potentially, long-term energy balance.”

“We believe the fermentation of resistant starch may be an effective, natural approach to the treatment of obesity.” says Dr Keenan, the study author.

You can read the study in question here (3) and decide for yourself if feeding 30 rats a carefully engineered concoction of corn oil, methylcellulose or high-amylose corn starch is applicable to human metabolism or behaviour around food. And more importantly, does the release of those “satiety” hormones correspond with actual satiety? Sadly, the previously mentioned (1) 2005 British Nutrition Foundation review by Nugent (peer-reviewed) mentions that the studies which looked at satiety as the end point appeared “to show a weak or no association between RS and satiety over the course of several hours or an entire day.”

Incidentally, I know of a way to increase GLP-1 and PYY levels in humans in a real world which does correspond with satiety: feed them a high protein diet.

This excerpt from the 2013 review on RS (4) made me laugh:

“The physiological effects of resistant starch make it extremely difficult to assess its impact on weight. Resistant starch increases stool bulk, luminal thickness, and bacterial numbers in the colon. These factors add to overall body weight, perhaps masking any differences that do exist due to resistant starch ingestion”

You know you need a new weight loss strategy if your current progress is easily masked by the weight of your poo. Just sayin’.

And I love it when researchers get excited about postprandial glucose and insulin levels. Sounds like this stuff is pretty important, eh?

“… a number of human studies have demonstrated the capacity for Hi-maize® resistant starch to elicit a positive impact on both postprandial glucose levels as well as insulin response.
Most recently, a human trial with maize-based resistant starch incorporated into test beverages showed effective reductions in the relative glycaemic response without any change in palatability”.

Again,  the review by Nugent is a little more cautious:

“There is a lack of consensus regarding the precise effects of RS on insulin and glucose responses: 15 studies have reported an improvement in these measures following the consumption of a RS-rich test-meal, while 10 have showed no, or a physiologically irrelevant effect. It is noteworthy that, to date, there are no reports of RS worsening insulin and glucose responses.”

Phew, it’s nice to know that at least this stuff doesn’t make our blood sugar go through the roof!

Several more recent studies looked at insulin sensitivity in men and women with slightly better results which were obtained by very high intakes of RS: up to 40-50g a day. A paper of note is by K.Maki et al published in the Journal of Nutrition in 2012 (5). The study subjects this time were human overweight and obese men and women broken into 3 groups: control group who received a digestible starch meal and 2 intervention groups, one with 15g of RS a day and the other with 30g of RS. They had to add the products to their usual daily meals for 4 weeks, followed by a 3 week wash out period and then a swap. They underwent a glucose tolerance test at the end of the study.

Insulin sensitivity between 3 groups. Source: Maki et al, 2012

Insulin sensitivity between 3 groups. Source: Maki et al, 2012

The reason why this study caused a bit more of a stir is because it showed better insulin sensitivity in men with a more achievable dose of RS: 15g/day than in men who consumed starches (do you see a little problem here?). Interestingly, there was no effect in women and there was no effect with higher doses. The big problem of this and other similar studies in my opinion is that their control (the column in black) was digestible starch. So in fact,  any difference in insulin sensitivity was relative to the equivalent in starch consumption in people who already have poor glucose tolerance judging by their abdominal girth.

But seriously, can we come up with a plausible explanation why RS starch may improve markers of glucose metabolism? Sure! It reduces the amount of absorbed glucose. This wasn’t too hard, was it? It’s a bit like comparing nicotine levels in full strength vs half strength cigarette smokers. If you smoke low nicotine cigarettes your nicotine levels will be lower. Hooray! We found a measurable improvement! Ahem, you could just stop smoking, of course.

[To all my sweet potato-loving friends, I am not suggesting that you stop eating carbohydrates. Just pointing out that if the only goal is to reduce glycaemic response one might decide to reduce dietary glycaemic input. Or add more protein. Or fat. And by the way, I consume large amounts of this orangy goodness on a daily basis.]

If you demolish your timber dining chair to shreds and sprinkle it onto your Coco-pops, it will also reduce your postprandial glucose levels. Don’t try this at home, kids.

And since we are trying to keep your family physician happy, how about that pesky cholesterol? While early animal studies were quite promising with significant reductions in triglycerides and total cholesterol, these were not replicated in human subjects. 13 human studies showed that RS had no effect on lipid metabolism (1). Sometimes we need a reminder that we are not rats in cages fed laboratory produced chow. Hang on…

So all in all, I wouldn’t be hanging your hat on RS as a shortcut to winning the obesity battle on a global or individual scale as yet. In my next post I will address the evidence behind RS effect on digestive health and, specifically, colorectal cancer. In the meantime, don’t go crazy with that potato starch.


1. Nugent, A. P. (2005), Health properties of resistant starch. Nutrition Bulletin, 30: 27–54. doi: 10.1111/j.1467-3010.2005.00481.x

2. Landon S, Resistant Starch Review published for

3. Keenan et al (2006), Effects of resistant starch, a non-digestible fermentable fiber, on reduction in body fat. Obesity, 14(9): 1523-34

4. Higgins J, Brown I (2013), Resistant starch: a promising dietary agent for the prevention/treatment of inflammatory bowel disease and bowel cancer. Current Opinion in Gastroenterology, 29(2):190-194

5. Maki et al (2012), Resistant starch from high-amylose maize increases insulin sensitivity in overweight and obese men. The Journal of Nutrition, 142(4):717-723

P.S. I will keep the comment section closed at this stage as I will probably address some of the questions and comments in my next post.



The definition of insanity…

It is now exactly 3 days until I start working. To say that I am nervous would be an understatement of the century. For now, I’ve been pushing any hospital-related thoughts to the deepest corner of my mind (from whence they tend to re-emerge just as I’m falling asleep causing me to break into cold sweat). My plans for my last few days of freedom and frivolity are to soak up as much sunshine as possible, ride my bike, watch really bad action movies from the last century (Lethal Weapon, yes, really) and overall do as little as possible.

In between all these exciting activities I also read the draft of the new Australian Dietary Guidelines, as a special type of punishment for my laziness. 288 pages of government-speak is no joke. I find myself re-reading the same paragraph 3-4 times and its meaning still devilishly eludes me. I don’t want my readers to suffer the same fate so I will be feeding you those pearls of wisdom one post at a time. Just a few statements and observations for you today.

“Diet is arguably the single most important behavioural risk factor that can be improved to have a significant impact of health”

I was very impressed with this profound statement in the Introduction. I am sure many of you feel like doing a little fist pump in the air: finally, the role of diet is getting recognised and appreciated not just as something that might make one fat and obese. But also as an important health determinant. Good stuff.

However, seeing diet as a “behavioural” problem has never sat well with me. We fall into that thinking all too easily. Ever glanced over an obese woman eating an ice-cream and did a little “tsk, tsk, tsk” to yourself? But overweight has not always been seen as primarily a  character flaw. One of Leo Tolstoy’s best characters, Pierre Bezukhov, (for those of you who braved “War and Peace”) is described as a big stout man. And no, it is not a reflection of his lack of willpower. And yes, he gets the girl in the end.

Venus and the Lute Player, Titian c.1560. Source Wikimedia Commons

Interestingly, because the media and government health agencies are so preoccupied with being PC, they use different tactics to accuse overweight and unhealthy people of being disgusting slobs without actually calling them “disgusting slobs”.

Here is one used in the Introduction to the Guidelines in the chapter dedicated to adherence.

“Adherence to dietary guidelines in Australia is poor”.

=disgusting slobs continue ignoring our well-meaning advice and insist on becoming a chronic disease burden while laughing into their French fries.

It is such a sad sentence I think they need an emoticon 😦

A couple of paragraphs later:

“There have been changes in the intakes of macro-nutrients over the past 3 decades, generally in the direction encouraged by previous dietary guidelines” (my bold italics)

Say what? The compliance is SO POOR that people change their intakes in accordance with your guidelines? (I wrote a post about one of the multi-million dollar lifestyle modification campaigns in Oz and the subsequent “non-adherence”.)

It all becomes clear when we see this statement in a table form.

Call me an optimist but looks like both men and women REDUCED their fat intake, INCREASED their fibre intake and INCREASED their carbohydrate intake.

Kiddies INCREASED their dietary fibre (somebody is actually eating their bran muffins!), INCREASED protein and INCREASED carbohydrate.

It also looks like reduction in fat didn’t result in reduction in total calories consumed. Bugger me! I thought fat being more calorie dense and all…

Does anybody need a reminder on how the obesity and overweight rates in Australia went while we were busy modifying our intakes “in the direction encouraged by previous dietary guidelines”?

“I don’t know why the sacrifice didn’t work.

The science was so solid.”

King Julien XIII, Madagascar 2

Have you been naughty? Government is here to help

I tell my daughter that Mum knows best. She is still at the age when she still believes me. But being a new age sensible parent, I do not shove my ideas down her throat while autocratically shouting “Coz I said so!”.

Say I need her to stop eating junk food. First I calmly tell her that sure, those donuts are scrumptious, but eating them can make her overweight and unhealthy. To impress on her the addictive nature of junk food, I bring her attention to smokers: they like smoking too, but it will invariably kill them. I point out the junk food ads on TV and tell her that Ronald McDonald might look like a fun guy but he uses his juggling skills for the power of evil by luring kids with candy and then sharing their money with mean cash-hungry executives. When we are out, I flicker my eyes towards an obese person calmly eating their totally-unhealthy-in-my-opinion lunch and mouth to her: “You see? This can happen to you too!” To support my position by referring to the third-party authority, I tell her of the latest scientific study. But because she is only little and needs my help understanding the scientific mumbo-jumbo, I interpret it for her in a simple way, skewing the results in my favour (it’s for her own good). I repeat the above ad nauseum, enlist the help of others, never losing an opportunity to either lecture openly or drop an insidious hint. And finally, I offer her a healthy alternative, a plate of Brussels sprouts. I sing praises to its fresh taste, point out a slim woman eating them at a restaurant, arrange it attractively on the plate and tell her that all scientists know that Brussels sprouts prevent nasty cancer in your gut.

Too much? Fair? At what point did you stop nodding your head and started to feel slightly nauseated? Maybe never, because after all, as parents, we have good intentions and we do know best. Where do you draw the line?

You might be surprised to know that these tactics are used on a daily basis on you. Stereotyping (“fat people are lazy slobs gorging on junk food”), junk science splattered all over the news (“saturated fat clogs your arteries”), thought-terminating clichés (“ensure a balanced diet”) and other classical propaganda techniques, which would make any Soviet apparatchik proud, are used with relish by the media and government agencies. We, as consumers, obediently play the game and accept them as inevitable evil.

Let’s look at the famous MeasureUp campaign, Phase I of the Australian Better Health Initiative, which burst into our lives in October 2008. The campaign was allocated $500 million from 2006-2010. It’s massive success (more on that later) saw the federal government shell out an additional $872.1 million until 2014. Its main objectives were to build “awareness of the link between chronic disease and lifestyle risk factors” and “generate appreciation of the significant benefits of achieving (those) changes”. Noble goals. Here is a video if you need a reminder.

A research study evaluating the campaign’s outcomes was conducted by the Department of Health and Ageing. Let’s see where all this money went. The charts below are from 2 of the evaluation reports which can be found here (scroll down to PDFs). Wave 1 indicates the beginning of the campaign (dec 2008), Waves 2,3,4 represent the later stages.

One of the premises of this campaign (and others like it) is that people are ignorant about nutrition. Some fresh-faced social sciences graduate decided that we clearly need MORE information on what is and isn’t good for us. Have a look at how this theory holds up.

Ahem, looks to me like more than 80% of audience recalls being lectured about health and chronic disease. In this country I can’t enjoy a gossip mag without being told that something on my dinner plate is going to kill me.

The next figure makes it clear that most of us are aware of how much exercise we are expected to do, what our waistlines are supposed to be like and how many cups of greens will keep our well-wishers happy.


So far so good.

The big message of the campaign concentrated on waist circumference. Measuring tapes featured prominently in all advertisements, healthy cut-offs for men and women were discussed (and acknowledged by consumers). So what are the outcomes?
Hmmm. Funny but it looks to me like only around 15% of respondents actually measured their waist. In fact, over 40% of people did nothing at all.

I guess, some people are so lazy, we don’t have a chance in hell to change them, right?

According to their own data, over 60% of Australians get sufficient levels of exercise. What is deemed as sufficient? 30 minutes of activity daily. My 2 x 20 minute crossfit workouts, 2 yoga/pilates sessions and 1 HIIT bike ride a week put me in an “insufficient” category.

And finally 72% of respondents eat 1 serving or less of fast food a day.

Did you notice the progress of the campaign from Wave 1 to Wave 4? Any improvement in physical activity? Or reduction in fast food consumption? Or maybe more vegetables? Scroll up and have a look. Let me know if you find anything that is worth over $1 billion dollars in Government funding. The evaluation report notes: “There has been a slight decline in the effectiveness of some aspects of Measure Up’s message communication”. That’s doublespeak for “In spite of being bombarded by our ads on TV, radio, magazines, internet, bus stops and shopping trolleys for two years, consumers seem to have tuned out”.

The campaign was deemed so successful that Phase II was rolled out earlier this year. “Swap It Don’t Stop It” is sure to pick up where its predecessor left off.

“The definition of insanity is doing the same thing over and over and expecting a different result” Albert Einstein (attrib.)