Study: Meat Increases Risk For Colon Cancer; Starch Decreases Risk

HamburgerI’ve written about the link between meat and colon cancer; I’ve addressed epidemiological studies and mechanisms. Here’s a recent post: Evidence That Meat Increases Risk For Colon Cancer Is “Convincing”. This is what the British Journal of Cancer said in 2011:

The associations between consumption of red and processed meat with an increased risk of colorectal cancer were considered to be ‘convincing’.

There are no dietary guidelines concerning recommended levels of consumption of red and processed meat; as for alcohol, it is assumed that ‘less is better’ and that there is no threshold below which consumption presents no risk. In this section, we assume that the optimum (or target) is zero consumption.

They said any consumption of red or processed meat increases the risk for colon cancer. I thought those were strong words coming from a respected, mainstream, professional medical journal. It pretty much disembowels the phrase “in moderation.”

Here’s a new clinical trial out of Australia, a country whose people love their meat:

Dietary Manipulation Of Oncogenic MicroRNA Expression In Human Rectal Mucosa: A Randomized Trial, Cancer Prevention Research, August 2014

These findings support increased resistant starch consumption as a means of reducing risk associated with a [high red meat] diet.

Editorial: Resistant Starch May Reduce Colon Cancer Risk From Red Meat, Journal of the National Cancer Institute, October 2014

There’s so much evidence that eating meat contributes to colon cancer that both of these papers start off with a statement of presumed fact: “A diet high in red meat increases risk of colon cancer.” They fed their subjects meat anyway, for just 4 weeks:

Their study involved 23 healthy volunteers, aged 50–75 years. Participants were randomly assigned to either a high-red-meat diet (300g raw per day of lean beef or lamb) or that same diet plus a resistant-starch supplement called StarPlus (40g per day of butyrylated high-amylose maize starch). After 4 weeks on one diet, participants switched to the other for another 4 weeks.

They ate about two-thirds of a pound of meat each day. It was a crossover design, so participants acted as their own controls. They found:

A high-red-meat diet statistically significantly increased cell proliferation in the mucosa. Adding resistant starch to the meat diet reversed [some of this increase].

How can eating starch reduce cancer risk? The mechanism, as I’ve written about before, involves short-chain fatty acids (SCFAs) produced by bacteria in the colon as they consume starch left over from our digestion.

Unlike most carbohydrates, resistant starch passes undigested to the colon. There, gut microbes ferment it, yielding short-chain fatty acids, such as butyrate, which promote colon health. Those short-chain fatty acids, the study suggests, also reduce expression of microRNAs that are associated with severe colon cancer and that increase cell proliferation.

Heme iron and heterocyclic amines from red meat cooked at high temperature alter gene expression and increase proliferation. Butyrate from microbes decreases proliferation.

Resistant starch is not fiber in the way many people think of fiber:

This paper shows it’s not the bulk fiber – like bran muffins or Metamucil – that’s important for reducing cancer risk, [it’s] types of fiber, like resistant starch, that are metabolized by colonic bacteria.

Resistant starch is in green bananas; peas, beans, lentils, and other legumes; root vegetables (including potatoes that have been cooked and cooled, as in potato salad); whole grains (especially oats); and virtually all other plant foods consumed at room temperature or below. Even pasta made from processed wheat flour contains resistant starch, as long as it is cooked al dente and served cold or at room temperature.

RotiniCooling the starch after heating it rearranges the granules into a shape and structure that make it difficult for our digestive enzymes to access. We don’t derive as many calories from resistant starch as the Nutrition Facts label suggests because it passes unabsorbed into the colon. So, a bowl of hot pasta has more calories than a bowl of cold pasta, and the cold pasta (or potatoes, etc.) protects our colon to boot!

19 thoughts on “Study: Meat Increases Risk For Colon Cancer; Starch Decreases Risk

  1. David D

    Having never heard about “resistant starches” and the fact that I prefer my pasta/potatoes hot, I did a quick search. I am not sure how scientific this study is, but it states that reheating our cooled pasta/potatoes may be even better than just letting them get cold. You can view the write up here:

    Also, it seems that the calorie difference is minimal (we shouldn’t think we can eat everything we want too), but the colon benefits are significant. Do you agree?

    1. Bix Post author

      In this post I wrote back in 2008:

      based on this paper from 2006:

      I described the various types of resistant starches, or at least what was known then, and said, “repeated heating and cooling cycles will further increase the RS content.”

      So, they didn’t make a “brand new discovery.” If this was known for at least 8 years, why didn’t they know?

      There are several types of resistant starch (RS). Each has its own character. Sometimes it’s in the food even before it’s cooked and cooled (like a green banana, or a raw potato). Sometimes boiling lessens its resistant starch, sometimes it has no effect. Other variables that affect the amount of RS in a food include whether oil or spices are present as the food is cooled (they lessen RS), how the food was held prior to cooking (did it germinate? less RS), how long and at what temp the food was cooked, and of course, the condition of a person’s digestive enzymes. Young healthy people digest differently than older less healthy people. (I noted the people in this experiment were, apparently, of the former type.)

      Since there are so many variables, it’s difficult to put a number on how many fewer calories a food potentially supplies (this is true even when you are not considering RS, e.g. fat malabsorption). The resistant starch itself provides about 50% fewer calories, and up to 70% fewer in some studies. That’s not minimal … But foods are not made of pure RS! It’s a real moving target. Also, we do absorb bits of glucose and fat that our colonic bacteria excreted after eating the RS, and we derive calories from them. We consume another organism’s waste matter.

      Maybe I’ll repost this. I appreciate your comments because it gets me to reread these papers and I always learn something. More often than not, I see where I was wrong.

      1. K.

        ‘So, they didn’t make a “brand new discovery.” If this was known for at least 8 years, why didn’t they know?’

        But don’t the “repeated heating and cooling cycles” assume ending with cooling, i.e. an equal number of heatings and coolings. The disadvantage of that is that people don’t generally like such foods cold (though one make some sort of salad). The surprising, allegedly new, discovery would be the increase in RS of a hot state compared with the immediately preceding cold state, i.e a half-cycle after a whole number of cycles.

        1. Bix Post author

          The original 2006 paper did not say that you had to end a cycle with cooling. In fact, it said: “RS3 is measured chemically as the fraction, which resists both dispersion by boiling and enzyme digestion. It can only be dispersed with KOH or dimethyl sulphoxide. RS3 is entirely resistant to digestion by pancreatic amylases.”

          So, boiling RS3, they said, would not free it for digestion. After the RS3 was formed, it wouldn’t matter whether you ate it hot or cold, it would still be there. However, if you reheated and recooled it again, a second full cycle if you will, you could retrograde even more starch.

          I was curious about that so I conducted a few of my own experiments over the years. I tried reheating baked potatoes and rice and I could not get them to return to the state they were in before they cooled the first time, that is, before the RS3 was formed.

        2. K.

          I see. But the “new” BBC discovery is that the re-warmed food seemingly has _more_ RS than the cooled one, not just the same amount.

        3. Bix Post author

          The paper says that “RS increases on storage, especially low-temperature storage.” So, by the 3rd day, even before they reheated it, it would have had more RS than the day they ate it cold.

          You and David really do bring up a good point, about reheating. I agree with both of you when you say a hot meal is sometimes better than a cold meal. It’s good to know that you can eat it hot without losing the RS benefits.

  2. Bix Post author

    I want to say something about hunger, about this statement in that BBC article:

    “A rapid rise in blood glucose, followed by a rapid fall, can often make you feel hungry again quite soon after a meal.”

    That’s true. But they go on to say that eating pasta or potatoes can cause this. That’s not true, rather, it’s not accurate.

    There is often some degree of insulin resistance present in a person which is causing the blood glucose to rise in the first place, causing the overproduction of insulin to overcome it. So, it’s not the fault of the carbohydrate (pasta, potatoes) alone. And what contributes to insulin resistance? Dietary fat.

  3. anrosh

    Will making fresh pasta help ?

    And about potatoes – does storing the potatoes for a long time reduce how an actual potato should behave. ( does it store more starch – i really am ignorant ) Should we be worried about irradiation ?–seasonings-exposed-to-half-a-billion-chest-xrays-worth-of-radiation.aspx . Is that the reason of the epidemic caused by the starches and scientific studies should be looking at “ROOTS ” when analyzing ? Just asking .

    Mc Donalds have their own “breed of potatoes ” – so that they grow long enough to make french fries .

    I am still learning all this !
    Th you

  4. anrosh

    And so may be it is HOW THE POTATO is grown , makes potato the bad boy . And not after the potatoes is grown ?

    The natural question is – WHY is there an increase in diabetes and cancer, and autoimmune disorders? – And when did it start to happen ?

    1) AFer the prolific growth of compromising the environment of how crops are grown ?
    2) The continued processing of the food
    3) Compromising of genotypes

    4) After all technology and so called “knowledge ” is increasing – shouldn’t we solve more problems, when we are actually causing new ones and labeling them as “EMERGING” and finding a solution for them.

    Lies, Damned Lies and More with the scientific studies ? Does Aspiration truly kill us ?

    Just putting it out there . Th You

  5. anrosh

    Industry are asking colleges to do studies for them.

    the potato industry study will give funding to a university prof and the studies will reveal – how potatoe is good.
    And the meat industry and the corn industry and so on and so forth.

    each food is good in its own way , when it is eaten ” originally ” how it should be “correctly eaten “- unadulterated meat, non- iradiated potatoes , seasonal food , eating before sunset – we just over look how these variables are in our studies and come up with variables that are workable ?? should we be taking these studies with a pinch of salt. Having written all this the conundrum is – what is my solution ? Can I give any ? The workable is : can we live with it and truly execute it . Then industrial agriculture is not the answer.

    1. Bix Post author

      I used to trust University studies. Then I read how involved businesses are in these studies, even surreptitiously. I mean, Universities need money, and this is a great source. Then they show the product good. Why bite the hand that feeds you?

      1. anrosh

        because it feeds poison ? when academic minds aids the society in believing something which is not what should not be , society falls.

        Again , when peer reviewed journals , stands in “great standing” , and such studies are quoted left right and when such studies are documented there , isnt it hazardous .

        I will send you a link on your email, where a medical doctor talks about “medical studies”

        1. anrosh

          Again, if we eat poison we die.
          And if eat the food we die of “slow soft poison” –

          But there is a solution – for those who have yards , they can grow their own. Anyway the yards lay waste – growing grass, watering the grass and mowing and the cycle continues – without being put to good use. I have seen local counties make rules that things cannot be grown in a yard, you know the story.
          There is a work around too – cultivate the plants and share the fresh produce with the neighbors. Problem solved

          It is doable. people in switzerland are doing it by renting land.

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