Monday, May 21, 2012

Rice consumption and health

Carbohydrate-rich foods lead to the formation of blood sugars after digestion (e.g., glucose, fructose), which are then used by the liver to synthesize liver glycogen. Liver glycogen is essentially liver-stored sugar, which is in turn used to meet the glucose needs of the human brain – about 5 g/h for the average person.

(Source: Wikipedia)

When one thinks of the carbohydrate content of foods, there are two measures that often come to mind: the glycemic index and the glycemic load. Of these two, the first, the glycemic index, tends to get a lot more attention. Some would argue that the glycemic load is a lot more important, and that rice, as consumed in Asia, may provide a good illustration of that importance.

A 100-g portion of cooked rice will typically deliver 28 g of carbohydrates, with zero fiber, and 3 g of protein. By comparison, a 100-g portion of white Italian bread will contain 54 g of carbohydrates, with 4 g of fiber, and 10 g of protein – the latter in the form of gluten. A 100-g portion of baked white potato will have 21 g of carbohydrates, with 2 g of fiber, and 2 g of protein.

As you can see above, the amount of carbohydrate per gram in white rice is about half that of white bread. One of the reasons is that the water content in rice, as usually consumed, is comparable to that in fruits. Not surprisingly, rice’s glycemic load is 15 (medium), which is half the glycemic load of 30 (high) of white Italian bread. These refer to 100-g portions. The glycemic load of 100 g of baked white potato is 10 (low).

The glycemic load of a portion of food allows for the estimation of how much that portion of food raises a person's blood glucose level; with one unit of glycemic load being equivalent to the blood glucose effect of consumption of one gram of glucose.

Two common denominators between hunter-gatherer groups that consume a lot of carbohydrates and Asian populations that also consume a lot of carbohydrates are that: (a) their carbohydrate consumption apparently has no negative health effects; and (b) they consume carbohydrates from relatively low glycemic load sources.

The carbohydrate-rich foods consumed by hunter-gatherers are predominantly fruits and starchy tubers. For various Asian populations, it is predominantly white rice. As noted above, the water content of white rice, as usually consumed by Asian populations, is comparable to that of fruits. It also happens to be similar to that of cooked starchy tubers.

An analysis of the China Study II dataset, previously discussed here, suggests that widespread replacement of rice with wheat flour may have been a major source of problems in China during the 1980s and beyond ().

Even though rice is an industrialized seed-based food, the difference between its glycemic load and those of most industrialized carbohydrate-rich foods is large (). This applies to rice as usually consumed – as a vehicle for moisture or sauces that would otherwise remain on the plate. White rice combines this utilitarian purpose with a very low anti-nutrient content.

It is often said that white rice’s nutrient content is very low, but this problem can be easily overcome – a topic for the next post.

16 comments:

Tuck said...

"Two common denominators between hunter-gatherer groups that consume a lot of carbohydrates and Asian populations that also consume a lot of carbohydrates are that: (a) their carbohydrate consumption apparently has no negative health effects; and (b) they consume carbohydrates from relatively low glycemic load sources."

I think that (a) is a pretty big assumption. The Chinese seem to be having all the same health issues that we do, now that they're regularly getting enough to eat:

"China diabetics raise stakes for healthcare reform"

I'm inclined to agree with you, since I suspect that the real issue is what and/or linoleic-acid-rich seed oils, but I don't feel comfortable yet exonerating carbs.

Ned Kock said...

Hi Tuck. In the China Study post that I linked (link below as well), the effect may indeed be due to other factors (e.g., rice consumption being correlated with wealth).

http://bit.ly/aW4XNa

But the fact that the health effect of rice consumption is there even when we control for total calorie intake goes against the main premise of that Reuters article you provided (thanks!) on diabetes in China.

Omega 6 fats overload cannot be excluded as a possible major confounder, but I’d be tempted to exclude calorie intake per se as a factor based on the China Study analysis.

George Henderson said...

It seems to me that, of the many factors protecting hunter-gathers who eat carbs, including honey, the foremost is the "intermittent fasting" eating patterns.
After all, there is experimental evidence that time-restricted feeding has exactly that effect
http://www.cell.com/cell-metabolism/abstract/S1550-4131(12)00189-1
and see various papers on "intermittent fasting" in humans.

One people begin eating regularly, the protection is lost.

john said...

It's pretty well-established, with much evidence presented on this blog, that rice is okay but probably not optimal. I don't think it's necessary [though many do (but badly), usually in response to an anti-low carber crying out about the Chinese or Japanese] to try to rationalize the seemingly good health of some Asian populations under the assumption that a high carb diet per se implies poor health. But I think George is right in that intermittent fasting gives one a lot more flexibility.

ben said...

Do you think Black rice has the same properties?

(I've always thought it to be much healthier because of the antioxidants but maybe that's not a good enough to eat it!)

dearieme said...

You object to bread: would I be better eating my cheese on oatcakes?

Anonymous said...

The selection of data seems to be somewhat inviting misinterpretations?
A comparison of rather dry food and a hydrated one?
What about pasta (cooked) instead of white bread? Do you still see the same differences?
What is more "filling" 50g of bread (that will get hydrated in the mouth and stomach) or 100g of cooked rice?

Luc

Ned Kock said...

Hi George. While a big fan of IF myself, I don’t think the effects of IF are all that different from those of intermittent LC or low calorie intake. Of course we are talking about low-toxin load foods here; mostly natural foods. There are some differences for sure, but they are frequently exaggerated.

Ned Kock said...

You go from brown to white rice by removing layers. Those layers tend to have a few more nutrients, but also more of the toxins that usually characterized seeds – plants don’t “want” animals to consume their seeds, they “want” animals to consume their fruits so that seed dispersion is maximized. The seeds are the plants’ next generation. In this context, seed toxins are a product of evolution.

Ned Kock said...

Hi Luc. I definitely think that it is healthier to consume wheat-based products after they absorbed some moisture. However, the toxin load of highly refined wheat tends to still be significantly higher than that of highly refined rice (white rice). I am talking about things like wheat germ agglutinin. And we also have the issue of gluten sensitivity and intolerance, which over time (dozens of years) may lead to low-grade forms of celiac even among those who are not genetically predisposed to celiac disease.

George Henderson said...

Thanks Ned.
And perhaps the effects of non-IF (i.e. constant feeding) are not that different from those of high-carb or high-calorie?
Constant feeding and round-the-clock food access as a factor that magnifies the harmfulness of bad diets.
So that the difference between two people who eat the same diet with different results can be down to timing...

v/vmary said...

i lived in taiwan for 7 years and my husband grew up there during a time of transition from a mainly agricultural society to an industrial one.

when my husband was a child, lard was used for cooking. then the population transitioned to soy bean oil. breast feeding also became less common for the same reasons it became less common in the US.

when i first went to taiwan i was 23. i immediately lost a lot of weight without even trying just by eating the native food (lots of rice and stuff cooked with soybean oil). i didn't drink milk and i didn't eat wheat products or sweets. i didn't watch tv because i didn't understand it, and i walked at least 1 to 2 hours a day. i didn't snack.

the only time during this period that i started to gain a little weight was when i would have maybe one or two candy bars a day before my chinese class. just that little bit of candy got me a little pudgier.

when i came back to the US i started to eat the SAD immediately (but not candy everyday) , but did not put on significant weight until 6 months later.

we know middle aged taiwanese who are getting a belly even while eating a traditional taiwanese diet heavy on fish/seafood (although with soybean oil). the key factor there seems to be excess calories in relation to activity (office job).

john said...

Ned,

There are some studies that compare intermittent fasting with calorie restriction (one I can remember on BDNF), and it seems intermittent fasting may be superior.

Ned Kock said...

Hi John. Of course that depends on how we define “superior”, and also how the effects are distributed in a population of individuals.

An approach may lead to health markers that appear to be better in the short term, but things end up not being necessarily better in the long term.

In the end, most people are interested in enhanced quality of life and longevity. The latter usually takes large longitudinal studies to ascertain. And we are still left with a lot of individual variation, which calls for careful individual assessment and customization.

As for QoL, IF seems to work very well for some, but also appears to be a major source of stress for others. As a source of sustained stress, IF may induce insulin resistance, in which case alternative approaches may work better – for example, eating little but more often may lead to better results. (Not that often – e.g., 3 times a day, as opposed to once or twice.)

I personally enjoy occasionally going 20+ hours without eating anything with calories in it, but not all the time. When I am busy with multiple FtF meetings, or distracted by work, IF’ing makes me feel good and is liberating.

Trying to force IF does not seem to work very well for me. My body tells me when to do it.

Ned Kock said...

I should say, my body and my schedule tell me when to do IF.

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