High GI Carbs Give Rise To Fatty Livers

[Guest guest]

Jeff, there must be some validity to the glycemic index after all. As

you have said the TYPE of carb (natural, high fiber) is the key.

High GI Carbs Give Rise To Fatty Livers

24 Sep 2007

A new US study on mice suggests that a diet rich in carbohydrates with

a high glycemic index (GI) not only expands waistlines but may also

lead to fatty liver, a condition that results in liver failure and death.

The study is published in the September issue of the journal Obesity

and is the work of Dr Ludwig, director of the Optimal Weight for

Life program at Children's Hospital Boston, and colleagues.

Fatty liver is increasing in line with rising rates of obesity among

Americans. The researchers hope to confirm their findings in a newly

launched clinical trial with overweight children and to show that the

trend can be reversed through changes in diet.

Fatty liver is becoming especially common among children, said Ludwig.

Although many adult cases can be caused by alcoholism, that is not so

in children, where between 1 in 4 and 1 in 2 overweight American

children are thought to be affected by non-alcoholic fatty liver

disease (NAFLD).

That means millions of children are at elevated risk of getting full

blown liver disease in adulthood, said Ludwig, who called it a " silent

but dangerous epidemic " .

" Just as type 2 diabetes exploded into our consciousness in the 1990s,

so we think fatty liver will in the coming decade, " he added.

High GI foods include white bread, white rice, most processed grains

such as breakfast cereals, and concentrated sugar. They raise blood

sugar quickly because the starch is broken down into sugar quickly.

These are also called rapidly absorbed carbohydrates (RAC).

Ludwig said the French delicacy " pâté de foie gras " (literally " pâté

of fatty liver " ) was made by feeding ducks and geese on a diet rich in

high GI grains.

Low GI foods include most vegetables, fruits, beans and unprocessed

grains. The starch in them is digested slowly and therefore eating

them raises blood sugar slowly. This is also called slowly absorbed

carbohydrate (SAC).

Ludwig and colleagues carried out the study using two groups of

laboratory mice. One group of mice were fed a high GI diet based on a

type of cornstarch that is digested quickly, and the other a low GI

diet, based on a more slowly digested cornstarch.

Both groups of mice consumed the same total number of calories, fat,

protein and carbohydrate. The only difference was the GI value of the

carbohydrate.

Both groups of mice weighed the same after 6 months. But there was a

difference in fat deposits in the two groups.

The mice on the low GI diet had normal amounts of fat in their bodies,

they were " lean " , whereas the mice on the high GI diet had double the

amount of fat throughout their bodies, in their blood and in their livers.

Ludwig explained that sugar released from high GI food ramps up

insulin production, which tells the body to make and store fat. This

is a burden to the liver because the pancreas produces the insulin and

sends it straight to the liver, resulting in liver insulin levels way

above the rest of the body.

Fatty liver usually has no symptoms, but it raises the risk of liver

inflammation, which can lead to hepatitis, which is sometimes fatal.

A study on people living in Italy who ate high GI food showed they had

fattier livers, but the study wasn't tightly controlled, whereas this

study on mice shows that high GI carbohydrates can cause fatty liver

in animals, regardless of other diet and lifestyle factors.

" Our experiment creates a very strong argument that a high-glycemic

index diet causes, and a low-glycemic index diet prevents, fatty liver

in humans, " said Ludwig.

He and his team have just lauched a clinical trial involving

overweight children aged from 8 to 17 who will be randomized to either

a high GI or a low GI diet. They hope to show that a low GI diet can

reverse fatty liver in overweight children.

Ludwig explained that the current standard treatment for being

overweight involves putting children on low fat diets, but that

doesn't work for many children with fatty liver:

" We think it's a misconception that the fat you're eating goes into

the liver, " he said.

Ludwig has a theory that obesity, sedentary lifestyles and eating too

many refined carbohydrates are " synergistically " driving a fatty liver

epidemic in children.

The irony, said Ludwig, is that low fat diets only make things worse,

because they replace fat with sugar and starch (mostly high GI) that

increases fat deposits in the body.

" Two low fat Twinkies, billed as a health food, contain the same

amount of sugar as an oral glucose tolerance test, a test used to

determine how much sugar someone can digest, " said Ludwig.

" Hepatic Steatosis and Increased Adiposity in Mice Consuming Rapidly

vs. Slowly Absorbed Carbohydrate. "

Scribner, B., Pawlak, Dorota B., Ludwig, S.

Obesity 2007 15: 2190-2199.

ABSTRACT

Hepatic steatosis and increased adiposity in mice consuming rapidly

vs. slowly absorbed carbohydrate

B. Scribner, Dorate P. Pawlak, S. Ludwig

Objective

Non-alcoholic fatty liver disease (NAFLD) is fast becoming a major

public health concern, coincident with the increasing prevalence of

obesity. Although lifestyle greatly influences development of NAFLD,

the specific dietary causes remain largely unknown. The purpose of

this study was to determine whether a diet high in rapidly absorbed

carbohydrate (RAC) vs. slowly absorbed carbohydrate (SAC), controlled

for confounding dietary factors, causes NAFLD in mice with similar

body weight. An animal model was chosen because of logistical and

ethical challenges to conducting this study in humans.

Research methods and procedures

Male 129SvPas mice were fed diets high in either RAC (amylopectin;

high glycemic index) or SAC (amylase; low glycemic index) for 25

weeks. Diets were controlled for macronutrient and micronutrient

content, differing only in starch type. Body weight and composition

were measured throughout the study. Hepatic and plasma triacylglycerol

concentrations were quantified at the end of the study.

Results

Body weight was not significantly different between the two groups.

However, total body adiposity increased twice as much, in absolute

terms, in the mice fed RAC vs. SAC (12.2+/- 2.9% vs. 6.1 +/-4.2%

p<0.0001). Hepatic triacylglycerol content was two-fold greater in the

RAC group. (20.7 +/- 9.4 vs. 9.6 +/-4.9 mg/g, p=0.01). In addition,

plasma insulin and triacylglycerol concentrations were higher in the

RAC group.

Discussion

A diet high in RAC causes accumulation of fat in liver, adipose tissue

and blood in mice. Therefore, a low glycemic index diet may help

prevent or treat NAFLD in humans.