Health effects of carbs: Where do we stand?

Should we eat carbs?
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Story highlights

  • In the 1990s, bread became bad, but we're getting a more balanced perspective now
  • To lose weight, we have to cut calories, and that can happen by cutting carbs or fat

(CNN)Bread glorious bread! It was once considered a status symbol, and has been a nutritious dietary staple for all classes for millennia.

But starting in the second half of the 1990s, bread became bad. So did the whole menu of starchy carbohydrates, such as pasta and potatoes, as well as sugary carbs including milk and cookies. Cue the Atkins Diet, and even "good for you carbs" such as fruits were off the table.
    The argument of Dr. Robert Atkins, Dr. Arthur Agatston (of the South Beach Diet) and many others was that, because low-carb diets reduce insulin in the body, they reduce fat accumulation and eventually lead to fat burning. The way they saw it, drastically slashing carbs, and consequently consuming more protein and fat, was the only way to lose weight.
    In the last decade, the medical view of carbs is becoming more balanced. To lose weight, we have to cut calories, and that can happen by cutting carbs or fat (or both), according to the recent report by the Dietary Guidelines Advisory Committee, which will inform the new U.S. Dietary Guidelines for Americans due out later this year. The report did not make specific recommendations to lower carbohydrates, although some criticize that omission.
    The important thing is to pick a diet you can stick to. Atkins might be easiest for some; experts have suggested the high-protein and high-fat diet helps us feel full longer. For others, a more balanced strategy, such as Weight Watchers, may be the way to go.
    Another nuance about carbs that has come out in recent years is that not all carbs are created equal. At least half the bread, pasta, rice and other grains we eat should be whole grains, such as whole-wheat and brown rice, instead of refined (think white bread, white bread), according to the U.S. Department of Agriculture My Plate recommendations.
    "I think Americans are slowly getting the message that ... breads and grains are fine as long as they are whole grains so we get fiber and nutrients," said Joan Salge Blake, clinical associate professor of programs in nutrition at Boston University.
    Blake attributes USDA's My Plate visual dietary guides with helping Americans understand that carbs are OK, especially if they are whole grains and "from Mother Nature," such as fruits and vegetables, and low-fat dairy, and balanced with protein and good fats.
    Through the ages, however, exceptions have come to bear. Let's take a look at the timeline.
    2 million B.C. headline: Man cannot live on meat alone
    The Paleo diet may be misunderstood: It might not have consisted of only meat, nuts, fruits and vegetables. Recent research suggests that starchy foods, especially potatoes, were also an important component of their diet. Meats alone might not have been enough to fuel early man's growing brain, and eating a healthy portion of carbohydrates might have been critical for our evolution into a highly intelligent species. Experts argue that, although recent Paleo-inspired diets heavy on meat and nuts might help us lose weight, they are probably not healthy overall.
    3,000 B.C. headline: Thank the gods for bread
    Two foods many of us consider carb-loading indulgences today — bread and beer — were staple foods in ancient Egypt and Greece. If there was anybody concerned about the health hazards of carbohydrates thousands of years ago, they could rest assured that many of the grains they ate, such as faro (now considered a healthy ancient grain), were high in fiber and minerals.
    800 B.C. headline: The upper crust should not eat crusty bread
    Our ancestors were pretty limited in their bread recipes when they started baking 30,000 years ago. They had to grind bread grains with rocks, which made a coarse whole grain loaf. But around 800 B.C., the Mesopotamians developed a method to grind grains into fine flour using flat, circular stones. This refined bread was hailed as a status symbol, but today it is seen as a less healthy form of bread.
    1864 headline: New kind of diet bans carbs
    In Victorian London, William Banting, a morbidly obese undertaker, embarked on a new kind of diet. Banting saw a surgeon, named William Harvey, who told him to cut out bread, potatoes, beer, sugar and milk. Harvey was inspired by a conference he had attended on diet and diabetes to create what is effectively a predecessor to the Atkins Diet. Banting dropped about 40 of his 200 pounds in a year and was so happy that he circulated his dietary advice in a free booklet called "Letter of Corpulence."
    1917 headline: Sliced bread is the best thing since -- ever
    Until the early 1900s, people had to slice their own bread. Cookbooks told them how to do it: Make thin slices with no crust for women and children, men could eat thick slices with crust. All that changed in 1917 when Otto Rohwedder, an American inventor, developed the first mechanical bread slicer. By the end of the next decade, 90% of store-bought bread came sliced.
    1920s headline: Low-carb diet calms seizures
    A ketogenic diet, (based on eating low enough level of carbohydrates to force the body to burn fat), was developed in the early 1920s for people with epilepsy. The amount of carbohydrates the diet prescribed puts the Atkins Diet to shame: only 2% of daily calories from carbs, 8% from protein and 90% from fats, compared with a breakdown of 4%, 32% and 64% in the Atkins Diet.
    Although the ketogenic diet fell out of fashion when antiepileptic drugs became available, it made a comeback in the 1990s, and today is recommended by the Epilepsy Foundation for children with hard-to-treat epilepsy. A 2008 study found the ketogenic diet was associated with a 75% decrease in seizures among children ages 2 to 16.
    1972 headline: Atkins says we have been dieting all wrong
    Dr. Robert Atkins turned the low-calorie, low-fat diets on their head when he published his book, Dr. Atkins' Diet Revolution. The diet advocates eating only 20 to 40 grams of carbohydrates a day, much less than the 200 to 300 recommended by the American Heart Association, and all the meat, cheese and fat you want. The principle is that, if you deprive your body of carbs, it will start burning fat for energy.
    Although doctors criticized the diet — and Atkins initially resisted the idea of studying the diet scientifically — research over the years has supported that it causes rapid weight loss and (or possibly because) it increases satiety. Following the diet for a year leads to about as much weight loss as Weight Watchers, although more people quit the Atkins Diet (48%) than Weight Watchers (35%), which combines healthy eating and moral support.
    1980s headline: Minimizing carbs could help manage cancer
    Studies started coming out in the 1980s that very-low-carb ketogenic diets could reduce the size of tumors in lab mice with a range of cancers, including prostate and brain. Since then, patient case reports have suggested that the diet, along with cancer therapy and vitamin supplementation, could possibly help keep malignant brain tumors from spreading and make breast cancer less aggressive, while possibly improving mood and sleep. The idea is that low levels of blood sugar as a result of a low-carb diet could starve cancer cells, which need more glucose than healthy cells.
    1991 headline: Carb-oholics!
    Carbohydrates are not just bad for your waistline — they can be habit-forming too, according to Drs. Rachael and Richard Heller. In their book, "The Carbohydrate Addict's Diet," the husband-and-wife team argues that our bodies make too much insulin after we eat high-carb foods, which in turn makes us crave more carbs. Over time, we can develop insulin resistance, which increases the risk of developing diabetes. To break free from this vicious cycle, they recommend having carbs for only one meal of the day and taking dietary supplements to control insulin levels.
    2002 headline: Cut carbs to help your heart
    Although the Atkins Diet made doctors worry the unbridled consumption of fats would boost heart disease, a 2002 study provided some of the first evidence to the contrary. The study, which was funded by the Atkins Foundation, found that healthy men who ate a very-low-carb diet for several weeks did not have higher levels of LDL (bad) cholesterol, and actually had lower levels of triglycerides (fat in the blood) and increases in HDL (good) cholesterol.
    More recent research suggests the message should be updated to say that low-carb diets can be heart-healthy if they are rich in plant-based fats, but not animal fats, which has been termed the "Eco-Atkins" diet.
    2004 headline: Dear masses, low-carb not exactly same as low-calorie
    The low-carb craze has hit a fever pitch. A survey finds that 22% of Americans want to cut carbs. Inspiration to do so is everywhere. The South Beach Diet came out in 2003 to offer a more realistic and possibly healthier way than the Atkins Diet to reduce carbs. (It is more open to consumption of "good" carbs such as fruit than Atkins and limits consumption of saturated fats.) It attracted high-profile followers, such as Bill Clinton.
    All the interest in slashing carbs spawns big business, too. Many chain restaurants, such as Ruby Tuesday and T.G.I. Fridays, add low-carb choices to their menu and grocery stores stock up on low-carb pastas, cereals, ice cream, etc. However, experts worry that many of these options are just as high in calories as their full-carb counterparts, and will not really help consumers lose weight.
    2012 headline: Grains hurt the brain, increase risk of Alzheimer's
    Some foods and diets have long been making headlines because of their potential role in brain health. Fruits, vegetables, Mediterranean diets and diets low in calories have all been linked to better cognitive function in older people. But sugary foods and carbohydrates have been suspected to harm brain health, and a 2012 study gave more credence to this possible effect.
    Among a group of Minnesota residents 70 to 89 years old, those who consumed the highest level of carbohydrates were 89% more likely to develop mild cognitive impairment or dementia over nearly four years, whereas those with diets high in protein and fat were 21% and 44% less likely, respectively. High-carb diets could impair cognition because they increase sugar levels in the brain and cause oxidative stress, the authors of the study suggested.
    2015 headline: For weight loss, cutting fat may be better after all
    A new study carries out the most stringent comparison of low-carb and low-fat diets. The verdict: People lose more weight on low-fat diets. In a small group of obese people, those who cut fat in their diet (by 85%) lost about 1.2 pounds in a week, whereas those who cut carbs (by 60%) lost about 0.7 pounds. Both diets had the same number of calories.
    The researchers point out that they came to the "opposite conclusion" as other studies, possibly because they held the participants in a lab for two weeks where they did not have access to any other food. Previous studies have mostly asked participants to follow a diet on their own, and hoped they didn't cheat and consume extra fat or carbs.
    Although the study may confuse or upset low-carb diet proponents, the lead author stated that, "(i)t doesn't take down the concept of a low carb diet: they make you less hungry and feel more full, people may stick to them better. ... This research is only taking down one proposal, which is that the only way you can lose body fat is by reducing carbs."
    2015 headline: Carbs as bad as cigarettes for lung cancer?
    Carb lovers among us could be at higher risk of developing lung cancer, even if they have never smoked, according to a new study.
    But it's not just any carbs. Those with a high glycemic index -- meaning they raise your blood sugar the most -- are the ones associated with increased lung cancer risk. Think white bread, white rice and Russet potatoes. In contrast, foods such as pasta, oatmeal and sweet potatoes have a low glycemic index.
    The researchers found that people who said their diets contained the most high glycemic index foods were 49% more likely to have been diagnosed with lung cancer compared with the people whose consumption of these foods was in the bottom 20th percentile.