Insulin again implicated in breast cancer

We have, for a long time, been wary that certain dietary habits are linked to and perhaps predispose people to cancer. The usual whipping boy here is ‘red meat’ – which is often said to be a potential trigger factor in, say, colon cancer. This belief will tend to add the comfort and security some people will get from eschewing red meat and other ‘fatty foods’ in favour of a diet rich in carbohydrate, including ‘complex carbohydrates’ like bread, potatoes, rice, pasta and breakfast cereals.

However, in recent years there has been some talk about the potential role supposedly healthy starch carbs have in cancer. These foods, particularly when eaten in quantity, can lead to high and sustained levels of glucose in the bloodstream, which in turn can lead to surges in the secretion of the hormone insulin. Insulin lowers blood sugar (which is good) by facilitating its transfer out of the bloodstream into the body’s cells. But it does other thing too, including stimulate the proliferation of cells, which enhances the risk of uncontrolled, rogue cell division that is the basis for cancer.

Previous research, has linked the consumption of the most blood sugar disruptive carbohydrates (high glycaemic index carbohydrates) with an increased risk of breast cancer.

Also, other worked has found that women suffering from ‘metabolic syndrome’ are at heightened risk of breast cancer after the menopause [1]. The potential relevance of this is that one of the common features of metabolic syndrome is ‘insulin resistance’ – a state where the body does not respond normally to insulin, which itself is thought to be the result of chronically elevated levels of insulin.

The same group of researchers responsible for the work on breast cancer and metabolic syndrome has recently published a study which has focused in on the potential link between insulin resistance and post-menopausal breast cancer risk [2]. What they found was that insulin resistance was more common in women with breast cancer than in those without (as expected).

Insulin resistance was assessed in these women using a standard test known as ‘HOMA-IR’ (homeostatic model assessment – insulin resistance) which calculates insulin resistance based on fasting levels of both glucose and insulin. One of the interesting things about this study is that it found that in the majority of women with insulin resistance, blood sugar levels were normal. Essentially, what this means is that the evidence for insulin resistance came from elevated levels of insulin (in the absence of elevated levels of blood glucose).

This does not mean, however, that the blood sugar levels in these women are truly normal. There are people, for example, who have normal fasting levels of glucose who find their blood sugar levels can rise very high when they consume carbohydrate in even quite-limited amounts.

The authors of the study suggest that assessment for insulin resistance might prove a useful tool in assessing breast cancer risk. In the meantime, women wishing to reduce their risk of metabolic syndrome and insulin resistance may do well to be wary about the blood sugar- and insulin-disruptive effects of starchy foods which some would have us believe are healthy and essential. Essential they are not, and increasing evidence shows them not to be particularly healthy, either.


1. Capasso I, et al. Metabolic syndrome affects breast cancer risk in postmenopausal women: National Cancer Institute of Naples experience. Cancer Biology & Therapy 2010;10(12):1240 DOI:10.4161/cbt.10.12.13473

2. Capasso I, et al. Homeostasis model assessment to detect insulin resistance and identify patients at high risk of breast cancer development: national cancer institute of Naples experience. Journal of Experimental & Clinical Cancer Research 2013;32(1):14 DOI:10.1186/1756-9966-32-14

6 Responses to Insulin again implicated in breast cancer

  1. Madeleine Morrow 5 April 2013 at 9:31 pm #

    Which starchy foods should women think about reducing? All carbs or only the high glycaemic index ones?

  2. Chris 7 April 2013 at 8:54 am #

    It is impractical to eliminate all sources of carbohydrate from the diet, albeit that carbohydrates can be reasoned to be the least essential of the three groups of macro-nutrients.

    Carbs are polysaccharides (molecules fabricated from multiple elements of glucose) that range from digestible to indigestible. If they are digested they are broken down to single elements of glucose. Ones that are readily digested register high on the glyceamic index. Fibre is /are indigestible polysaccharides whose presence in the gut and food types can raise the digestive load, slow digestion, and reduce the glycaemic effect.

    The risks here would appear to associate with the magnitude of glycaemic effects (spiking glucose by eating ‘fast’ carbs) and their habitual frequency.

    ‘Safe’, or ‘safer’, carbs are polysaccharides that arise in nature in association with other polysaccharides that resist digestion (‘fibre’, and with the emphasis upon soluble fibre).

    ‘Cooking’ is effectively a pre-digestive process that reduces the digestive load. Hence we may deduce a diet involving mostly raw green leaves would pass nutrients across the digestive divide in a way (slowly and steadily) that is more in keeping with need and would greatly reduce the risks. But it would also greatly diminish the time available for more enterprising activities above simply eating.

    A good halfway house would be to exclude the refined and high GI ‘white’ carbs like sugar, bread, and pasta. But you/we still need energy from somewhere.

    Fats can safely make up the deficit, and so long as we don’t over-consume polyunsaturated fats we should not be replacing one risk with another. Likewise it is probably better to become habituated to less sugar than it is to substitute sugar with sweeteners like aspartame. Refined, ‘white’ fats, spreads, and cooking oils, ones high in polyunsaturated fats, are as risky as refined ‘white’ carbs.

    Hoping that helps, Madeliene.

  3. Alexandra 12 April 2013 at 12:37 pm #

    Women can go a long way toward reducing their carbs/insulin simply be going back to old style breakfasts like bacon and eggs or (my favorite) eggs and Kerry Gold butter… skip the cereals and oats that are supposedly healthy because they are “complex carbs” This term, along with the term “whole grain” implies some sort of magical goodness that is really not deserved, it is ALL sugar. A higher fat breakfast with a nice dose of protein will eliminate the need for any mid morning snack..often another carb-fest.. later, have a good portion of meat or fish and some veggies and fat for lunch and you will be satiated until dinner. Cook and assemble meals from real foods that don’t come in packaging with long ingredient lists… you have time for this, make preparing and eating real foods a doesn’t take that much time every week and you will feel great.

  4. Ann 22 June 2013 at 8:05 am #

    I wonder if there is any connection here? I read with interest the connection with insulin and breast cancer. I had breast cancer 13 years ago, and I was a great carb fan. 13 years on I am eating less carbohydrate, my weight is down…. But I have developed a skin condition called Granuloma annulare. It can be linked to diabetes in a small number of cases. Has anyone any experience of this condition? Meanwhile I think I will reduce my carbs even more.

  5. MaryB 24 July 2013 at 4:32 pm #

    “It is impractical to eliminate all sources of carbohydrate from the diet, albeit that carbohydrates can be reasoned to be the least essential of the three groups of macro-nutrients.”

    Carbs are totally non essential and it is far from impractical to eliminate them. I keep my carbs under 20g a day as I am severely insulin resistant. I have upped my fat intake instead. This keeps me running with plenty of energy all day long. Any carbs I get are in the form of vegetables and non starchy vegetables at that.

    Since going low carb over 4 years ago, I’ve lost 60 pounds and kept it off. I have never felt better. It can be done. Ketosis is a good thing.


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