White bread or whole-wheat? It may depend on your gut

By Lisa Drayer, CNN

Updated 0747 GMT (1547 HKT) June 16, 2017

Chat with us in Facebook Messenger. Find out what's happening in the world as it unfolds.

It's thumbs up today, but the news on carbs has not always been positive. Take a look at the arguments for and against carbohydrates through the centuries:

Photos: Carbohydrates' health history

Carbohydrates' health history: Where do we stand now? – It's thumbs up today, but the news on carbs has not always been positive. Take a look at the arguments for and against carbohydrates through the centuries:

Hide Caption

1 of 8

Eating a healthy portion of carbohydrates might have been critical for our evolution into a highly intelligent species.

Photos: Carbohydrates' health history

2 million B.C.: Man cannot live on meat alone – Eating a healthy portion of carbohydrates might have been critical for our evolution into a highly intelligent species.

Hide Caption

2 of 8

Bread and beer were staple foods in ancient Egypt and Greece. Pictured is a limestone statuette of an Egyptian servant pressing out the fermented barley-bread from which beer was brewed.

Photos: Carbohydrates' health history

3,000 B.C.: Thank the gods for bread – Bread and beer were staple foods in ancient Egypt and Greece. Pictured is a limestone statuette of an Egyptian servant pressing out the fermented barley-bread from which beer was brewed.

Hide Caption

3 of 8

American inventor Otto Rohwedder developed the first mechanic bread slicer. By the end of the 1920s, 90% of store-bought bread came sliced.

Photos: Carbohydrates' health history

Early 20th century: Sliced bread is the best thing since ... ever – American inventor Otto Rohwedder developed the first mechanic bread slicer. By the end of the 1920s, 90% of store-bought bread came sliced.

Hide Caption

4 of 8

The principle of Dr. Robert Atkins' diet is that, if you deprive your body of carbs, it will start burning fat for energy.

Photos: Carbohydrates' health history

1972: Atkins says we have been dieting all wrong – The principle of Dr. Robert Atkins' diet is that, if you deprive your body of carbs, it will start burning fat for energy.

Hide Caption

5 of 8

Studies started coming out in the 1980s that low-carb ketogenic diets could reduce the size of tumors in lab mice with a range of cancers, including prostate and brain.

Photos: Carbohydrates' health history

1980s: Minimizing carbs could help manage cancer – Studies started coming out in the 1980s that low-carb ketogenic diets could reduce the size of tumors in lab mice with a range of cancers, including prostate and brain.

Hide Caption

6 of 8

Carbohydrates are not just bad for your waistline, they can be habit-forming, too, according to "The Carbohydrate Addict's Diet" by Drs. Rachael and Richard Heller.

Photos: Carbohydrates' health history

1991: Carb-oholics! – Carbohydrates are not just bad for your waistline, they can be habit-forming, too, according to "The Carbohydrate Addict's Diet" by Drs. Rachael and Richard Heller.

Hide Caption

7 of 8

A 2012 study gave credence to the theory that sugary foods and carbohydrates harm brain health.

Photos: Carbohydrates' health history

2012: Grains may hurt the brain – A 2012 study gave credence t