2 April 2006

Food for Thought

Potato Lovers Look Back to a Healthy Future
There’s a ‘modest positive association between the consumption of potatoes and the risk of type 2 diabetes in women’ write the authors in a prospective study reported in the February 2006 issue of the American Journal of Clinical Nutrition. ‘This association was more pronounced when potatoes were substituted for whole grains.’ The Harvard investigators conducted a prospective study of 84,555 women, aged 34 to 59 years with no history of chronic disease, who were enrolled in the Nurses' Health Study. The women completed a validated food frequency questionnaire and they were followed up for 20 years with repeated dietary assessments. During the study, 4,496 participants were diagnosed as having type 2 diabetes. After adjustment for age and dietary and non-dietary factors the researchers found that those with the highest potato intake (around one serving a day) had a modestly elevated risk of developing type 2 diabetes (about 20% higher). The link was strongest among obese women, who are already at increased risk of the disease, suggesting that heavy potato consumption may pose a particular problem for them, the researchers point out. ‘These data support a potential benefit from limiting the consumption of these foods in reducing the risk of type 2 diabetes,’ conclude the authors. ‘Substitution of these sources of carbohydrate with lower glycemic, high-fibre forms of carbohydrates such as whole grains should be encouraged.’


Cutting back on potatoes is something many people on a low GI diet find hard to do. So what’s the answer?
First of all, there’s no need to say ‘no’ to potatoes altogether just because they may have a high GI. They are fat free (when you don’t fry them), nutrient rich and filling. Not every food you eat has to have a low GI. So enjoy them but in moderation.

Secondly, look for the lower GI varieties of potato or serve them in a way that reduces the glycemic response. University of Toronto researchers found that the GI of potatoes ranged from 56 to 89 depending on variety and cooking method (Journal of the American Dietetic Association). Precooking and reheating potatoes or consuming cold cooked potatoes (such as potato salad) reduced the glycemic response. The highest GI values were found in potatoes that were freshly cooked and in instant mashed potatoes. Margareta Leeman and her colleagues at the University of Lund in Sweden found that preparing potatoes the day before and serving them cold as potato salad with a vinegary vinaigrette dressing can lower the GI (European Journal of Clinical Nutrition). In Low GI Eating Made Easy, dietitian Kaye Foster-Powell suggests steaming small new potatoes (with their skin for added nutrients), or bake a jacket potato and add a tasty topping based on low GI beans, chickpeas or corn kernels.

Third, remember that potatoes are a relative newcomer to the Western dinner plate. Athough the Spanish brought them back to Europe from South America in the mid-sixteenth century, people tended to regard them with suspicion and fit only for animals. They didn’t become a regular part of the European diet until the late eighteenth century. And it wasn’t until the nineteenth century that we really developed a taste for them replacing traditional wholegrain staples such as wheat, barley, rye and oats, which have much lower GI. So look back to a healthy future and add variety to your meals by enjoying wholegrains, legumes, pasta, noodles, basmati rice on a regular basis and potatoes occasionally. You’ll reduce the overall GI and GL of your diet and your risk of chronic disease.


JohnD said...

Why didn't you suggest replacing normal potatos with Sweet potato (Ipomoea batatas) which have a GI of 44 and are just as delicious as potatoes and so easy to prepare (just microwave them in a covered container).

Anonymous said...

How is cold cooked potato lower in GI than normal potato?

gi group said...

Like potatoes, sweet potatoes are a relative newcomer to the Western dinner plate. It also seems as time goes by and more testing is done, that we have both high and low varieties of sweet potatoes just as we do of potatoes (check out the GI database).
We know it's not easy for the consumer to identify which is which in the supermarket, so the take home message is essentially:
Reduce potato intake;
Replace them sometimes with sweet potatoes, irrespective of their GI, because they are good for you;
Eat more whole cereal grains such as barley, buckwheat, bulgur, oats, quinoa, lower GI rice varieties, rye, spelt and wheat (and foods made from them like noodles and pasta) because they also provide fibre and protein and are an important source of many vitamins and minerals;
And eat more legumes which are also a major source of protein, vitamin B, iron and zinc.

gi group said...

Cooking potatoes and letting them go cold increases the resistant starch and this is what slows digestion and lowers the glycemic impact. We have published a number of research reports on this in GI News. Use the Google SEARCH feature to check them out.

beruang said...

what makes sweet potato lower in GI? is it because high fructose content? thanks

ginny said...

I have been recently diagnosed with Type 2 Diabetes. Everything I read says to switch dressings to Vinegret type dressings. The smell of vinegar alone is repulsive to me. Are there other choices out there without adding vinegar.

hermin said...

oh - but i thought i heard Prof Jennie Brand-Miller mentioning that GI only takes into account AVAILABLE carbohydrates? on the other hand, resistant starch is not completely digested, so it's not 100% available, is it? please correct me if i've got it wrong. thanks.

gi group said...

Try making a vinaigrette dressing with olive oil and freshly squeezed lemon juice. There are many traditional recipes. Some add a little garlic or mustard. It's over to you.

gi group said...

Resistant starch is not part of the available carbohydrate but it's often inadvertently included because methods of analysis are sub-optimal. In either case (included or excluded) it makes little or no difference to the GI. At most it represents 10% of the total starch present. Cooled potatoes have a lot of RS but they are still a high GI food.