October 21, 2006
High Glycemic Index Diet Kidney Cancer Risk?

A retrospective study finds an association between higher glycemic index foods and kidney cancer.

Comparing the highest with the lowest quintile of intake, consumption of bread, pasta and rice, and milk and yogurt increased the risk of RCC by 94%, 29%, and 27%, respectively.

Conversely, intake of poultry, processed meat, and vegetable appeared to reduce the risk by 26%, 36%, and 35%, respectively.

Other foods such as fruits, red meats, cheese, potatoes, eggs, and fish had no effect.

The study collected information about past dietary habits - and studies of this sort suffer from faulty memories of interviewees.

The researchers included Francesca Bravi, MD, of the Istituto di Ricerche Farmacologiche "Mario Negri" in Milan.

Between 1992 and 2004, Bravi's team interviewed 767 patients with renal cell carcinoma at Italian hospitals. They also interviewed 1,534 patients without kidney cancer.

Patients completed surveys about their diets during the previous two years. The questions covered 78 foods and beverages.

A diet of high glycemic index foods might increase the risk of cancer by elevating insulin-like growth factor hormones such as IGF-1 and IGF-2.

"As for other common cancers, the increased risk of renal cell carcinoma for elevated cereals intake may be due to the high glycemic index of these foods, and their possible involvement in insulin-like growth factors," the investigators wrote.

In lower level species such as nematodes knocking out an equivalent IGF gene increases life expectancy.

I would expect an ideal diet to lower IGF hormones, lower LDL cholesterol, boost HDL cholesterol, lower triglycerides, lower inflammation markers such as C Reactive Protein (CRP), and lower markers for oxidative stress. So what would such an ideal diet look like?

If high glycemic index foods cause higher kidney cancer risk then I'm surprised that potatoes do not show up as boosting kidney cancer risk. But David Mendosa's very useful Glycemic Index (GI) and Glycemic Load (GL) chart shows some potatoes have fairly low glycemic indexes. Though note the considerable measured variation (56 to 111) just among Russet potatoes. Do fresher potatoes have higher GI? Does boiling versus baking cause a difference in GI?

Note on rice: The glycemic index of rice varies in predictable ways. The sticky rice found in Chinese restaurants has a GI over 100. But a high 28% amylose rice tests at GI 27 and Basmati rice at 67 to 60. Uncle Ben's rice appears to vary in GI by country (different varieties sold in different places?) and different type (e.g. slower and faster cooking types). If a brand name rice seller such as Uncle Ben's would market a low GI rice I'd buy it. As things stand I'm eating Basmati and Uncle Ben's rices.

Update: Uncle Ben's converted rice has low glycemic index and in 3 experiments done in the US and Canada ranges from 38 to 50. So that's probably the most readily available low glycemic index rice in the US and Canada.

Update II: I am also surprised that pasta consumption has a positive association with kidney cancer risk. The type of wheat used to make pasta has a much lower glycemic index than the type of wheat used to make bread. Most of the pastas have glycemic indexes below 50. But even lower glycemic index foods that are carbohydrate-based do break down in the intestines and feed into the bloodstream. So eat enough and you'll get a sugar surge.

Share |      Randall Parker, 2006 October 21 12:41 PM  Aging Diet Cancer Studies


Comments
Allan L said at October 23, 2006 6:20 AM:

Omitted from the discussion of glycemic index are cooking time and brown rice. I have had Type II diabetes long enough that I am developing a partiality for rice "crunchy-style," and potatoes al dente. And brown rice tastes great and is more nutritious than white.

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