Low carb. High carb. Good carb. Bad carb. It sounds like the beginning of something by Dr. Seuss. If only dietary carbohydrates were as simple as a children’s book! The reality? “Carb” is one of those nutrition buzzwords that leads to a lot of confusion.
Understanding the role of carbohydrates can help you eat a healthy diet and maintain a healthy weight — both important ways to reduce your risk of heart disease and stroke. Here’s what you need to know.
- Heart-Healthy Diet Headlines: Should You Cut Carbs?
- Are Certain Carbohydrates Unhealthy?
- Are Low-Carb Diets Best to Lose Weight?
- What about Carbohydrates & Heart Disease Prevention?
- A Reasonable Strategy for a Heart-Healthy Diet & Weight
- Heart risk from low-carb diets
- Where did the story come from?
- What kind of scientific study was this?
- What were the results of the study?
- What interpretations did the researchers draw from these results?
- What does the NHS Knowledge Service make of this study?
- Links to the headlines
- Links to the science
- Low-carb diets might not be the healthiest for a long life — 2 big new studies suggest they’re linked to a higher risk of death
- Healthy carbs like whole grains and beans aren’t bad for you
- That said, there are a few good reasons to go low-carb
There are only three nutrients that contribute calories to the diet: fat, protein and carbohydrates. Yup, that’s it. Just three. Most foods contain a mix of these nutrients — for example, yogurt contains carbs, protein and fat.
Carbs are the body’s main source of energy; carbs from food turn into fuel for the body. Some nutrition textbooks divide carbs into “simple” (sugars) and “complex” (starches and fibres). Simple carbs, like jam and honey, are broken down quickly by the body, causing a faster rise in blood sugar levels. Complex carbs, such as oatmeal, have more fibre, so are digested more slowly and don’t raise blood sugar levels as much. This keeps you full for longer and keeps blood sugar more stable.
Carbs are found in:
- beans and lentils
- milk and yogurt
- grains – bread, pasta, rice, quinoa, oats
- sugary foods: candy, ice cream, pastries
- snack foods: chips, pretzels, crackers
- sweet beverages: soda, juice
- sweeteners: jam, honey, syrups.
Many of the foods on this list are super healthy. So it’s a mistake to disparage a whole nutrient group just because some foods that contain carbs (like candy) are not nutritious. Take note: carbs themselves are not the enemy!
Good vs. bad carbs
Though dietitians are moving away from classifying foods as good or bad, these terms are widely used on diet-related websites, so we should define them. Your “good carbs” are generally the ones found in whole, unprocessed foods, which provide nutritional value from vitamins, minerals, fibre and antioxidants. So, vegetables, fruit, beans, lentils and whole grains contain “good carbs.” Include these in your diet.
The so-called “bad-carbs” are those in foods high in sugar, salt and/or fat. Examples are cookies, pretzels and soda. These foods are treats and should be limited.
What about white bread and pasta? They fall somewhere between good and bad carbs. They are not as nutritious as vegetables and whole grains, but not as nutrient-poor as cookies or candy. They contain some important nutrients, such as fibre, iron and folate.
Are low carb diets OK?
It is perfectly healthy to follow a low-carb diet, as long as it includes a variety of nutritious, whole, unprocessed foods. Low-carb diets can be good for heart health, since they may increase good cholesterol levels, and decrease blood pressure and triglyceride levels.
Studies show that some people successfully lose weight on a low carb diet, just as they can on a lower fat or Mediterranean-style diet. There’s no one right diet that will work for everyone. Ultimately, the best diet is one you can stick to in the long term. So if you love bread but hate meat, the low-carb diet may not be the right fit for you.
And remember, low-carb does not mean no carb! A low carb diet still provides at least 20% of the day’s calories from carbohydrates. Well-planned low-carb diets do include vegetables, fruit, beans and even small portions of whole grains, such as oats and quinoa.
So if your friend says “I don’t eat carbs” or “I’m following a low-carb diet,” it usually means they’ve cut back on sugar and bread. Hopefully it doesn’t mean they have stopped eating nourishing foods like vegetables, fruit and beans. If they have, you’re now equipped to educate them as to why that’s not a nutritious idea.
- Reduce your risk with more healthy eating advice.
- Try our dietitian-approved recipes.
Heart-Healthy Diet Headlines: Should You Cut Carbs?
Questions about carbohydrates – total amounts and particular food choices — seemed to be top-of-mind for many people when I was speaking about a heart-healthy diet at recent conferences.
Studies suggesting new approaches to weight management and heart disease prevention are making headlines. And patients are asking challenging questions to health professionals who care for them. Unfortunately, sometimes these headlines distract attention away from eating choices that research continues to identify as health-protective.
I’ve most recently been talking about nutrition in the headlines to several multi-disciplinary audiences of health professionals. Focused on heart health, they were eager for help putting headlines in context of overall research.
When speaking to professionals from cardiac rehab programs at the American Association of Cardiovascular and Pulmonary Rehabilitation (AAVPR) annual meeting, my topic was, “Nutrition News in Review: Clearing Through Headline Hype to Focus on Key Messages for Healthy Eating Strategies”. Shortly thereafter, I was back on the podium in Nashville speaking at the National Lipid Association (NLA) Fall Clinical Lipid Update addressing, “Talking to Your Patients about Trending Diets”.
In both presentations, I emphasized the need to support nutrition choices that are grounded in good science, while addressing people’s questions and concerns about headlines they see.
Are Certain Carbohydrates Unhealthy?
Some books and blogs have garnered attention with claims that it’s best to avoid broad categories of foods, such as gluten-containing foods, wheat in particular, or pulses (dried beans, peas and lentils). The rationale for such diets generally involves claims that these foods can promote inflammation or insulin resistance, or that they contain anti-nutrients that decrease our ability to absorb some nutrients.
I previously addressed concerns about compounds called phytates and lectins for readers of the American Institute for Cancer Research blog. The big picture of overall research does not show harm from phytates when wheat is included as part of healthful eating habits. If anything, they may benefit antioxidant and anti-inflammatory defenses. Although compounds called lectins are high in uncooked grains and dried beans, proper cooking makes content negligible.
Rather than being pro-inflammatory, long-term population studies link whole grains with lower risk of heart disease. Studies show protection with three modest servings daily, and it grows even stronger with more substantial amounts.
Dried beans, peas and lentils offer potential for a variety of health benefits. They seem to provide prebiotic support for a health-promoting gut microbiota and help reduce LDL cholesterol. And their combination of protein and fiber may promote satiety, thus helping weight management.
Carb Choices that Make Sense
Some people do have intolerance to certain grains or pulses, but a blanket assumption that gluten, grains or beans is at fault can lead you to omit foods that could be supporting health.
For the average U.S. adult to meet amounts of dietary fiber recommended for lower cancer risk, for example, means boosting fiber by 13 grams a day. Here, I discussed how that’s achievable, with one or two fiber-containing foods like vegetables, whole grains and beans swapped for less healthy foods at each meal. For more on why a variety of foods with fiber is the best strategy, check my AICR post. (For health professionals, I covered fiber in the diet in more depth here for Today’s Dietitian.)
Chronic low-grade inflammation and insulin resistance are serious concerns for heart health and overall health, too. For most people, eating habits associated with lower levels of inflammatory markers include a variety of relatively unprocessed plant foods. That’s vegetables, fruits, whole grains, pulses and nuts.
Unhealthy weight gain is tied to inflammation and insulin resistance. If you, like many adults, have pounds creeping up, look for realistic changes that can bring a modest weight loss. Take the focus off the search for a particular food as the sole problem or solution.
Are Low-Carb Diets Best to Lose Weight?
This was a hot topic at both of the cardiovascular conferences where I was presenting early this fall.
In carefully controlled research trials, low-carbohydrate diets average one or two pounds greater weight loss than low-fat diets at 3 to 6 months, but no difference at 12 months. Weight loss is generally more strongly related to how closely someone sticks to a diet than to whether the diet reduces calories by restricting carbohydrate or fat.
This highlights the need to identify changes that are most realistic for each individual.
In the DIETFITS trial published earlier this year, subjects were assigned to interventions targeting amounts of either carbohydrate or fat as low as each individual considered sustainable long-term. After one year, both groups had cut about 500 calories a day, with no difference in average weight loss. The only differences were that LDL (“bad”) cholesterol levels dropped in the low-fat group, whereas they increased slightly in the low-carbohydrate group. (That’s not really a surprise, since the group cutting carbs increased the saturated fat they were eating.) And blood triglycerides (another heart disease concern) dropped in both groups. This is as expected, since levels tend to decrease with weight loss. But the drop was substantially more in the low-carbohydrate group.
“All or nothing” rules may seem like they’d be easier to follow, yet this tends to be short-lived. In controlled trials, individuals vary, and average weight loss at 1 year on low-carb diets is no different than on low-fat diets.
What about Carbohydrates & Heart Disease Prevention?
An international study called the PURE study has made headlines linking high-carbohydrate diets with increased mortality rates. But the study draws heavily on poor and middle income countries in Asia. In many of these populations, a high-carbohydrate diet is often based primarily on white rice, with poor nutrient intake, poverty, and limited access to medical care. No surprise that carbohydrate is linked with poor health outcomes in that setting.
Conclusions are quite different when viewed in context of the ARIC study, which is based in the U.S. In this study, diets very low and very high in carbohydrate are both linked with greater heart disease deaths. Much more than a simplified answer about “carbs”, this study showed again what has been seen in past studies: health effects depend on food choices that make up our eating habits.
- Low-carbohydrate diets are linked with worse health outcomes when less carbohydrate means more animal sources of protein and fat.
- High-carbohydrate diets are linked with worse health outcomes when carbohydrate comes mainly from refined carbohydrate (like sweets, refined grains and sugar-sweetened drinks), without much fat or protein from plant sources (such as pulses, whole grains, nuts and healthful oils).
When we talk about health and changes in carbohydrate, fat or protein, it’s vital that we talk about the food choices that achieve those changes.
What about ketogenic diets?
One analysis pulled together 13 studies comparing diets low enough in carbohydrate to be ketogenic versus low-fat diets. After a year or more, ketogenic diets resulted in 2 pounds greater weight loss. That was “statistically significant”, but is a two-pound difference clinically significant for effects on health? Regardless of the effects on weight, ketogenic diets overall resulted in a greater decrease in blood triglycerides, but an increase in LDL (“bad”) cholesterol compared to low-fat diets.
This increase in LDL cholesterol with a low-carbohydrate, high-fat diet has also been reported in a study published since these presentations that involved only normal weight, young adults. LDL response varied widely, suggesting that if someone wants to try a low-carbohydrate approach to eating, it’s important to monitor effects on blood lipids like LDL. If ketogenic diets are reduced in calories to promote weight loss, or saturated fat is low (less than 8% of calories), they might not necessarily raise LDL levels.
A 2-year trial in people with type 2 diabetes used diets that reduced calories and also kept saturated fat low (no more than 10% of calories). One group of subjects did this with a ketogenic version of the diet, another with a version higher in carbohydrate but low in glycemic index (meaning the carbohydrates weren’t coming from sweets and refined grains). At one year and at two years, both diets achieved similar decreases in weight, blood pressure, A1C (a marker of blood sugar control in these people with diabetes), and LDL cholesterol. The ketogenic diet, however, achieved this with fewer diabetes medications and less glycemic variability throughout the day (which researchers suggest may lead to better long-term outcomes).
It’s great that more than one style of eating pattern may bring health benefits. But don’t underestimate the challenges to people who don’t have a research team supporting them as they try to implement an eating pattern like the one in this study. The more limits put on food choices, the harder it is to continue long-term in a realistically enjoyable lifestyle.
Cutting carbs for heart disease prevention? It’s not that simple. Research shows food choices matter for both fat and carbohydrates in a heart-healthy diet.
What Makes a Heart-Healthy Food Choice?
Interest in potential benefits of low-carbohydrate diets has stemmed from headlines suggesting that reducing saturated fat may not protect against heart disease as claimed. Putting those headlines in perspective, however, we can see that when studies compared all people with higher and lower amounts of saturated fat in their diets without considering their food choices, that’s when no benefit was seen for limiting saturated fat. Conclusion: swapping ice cream and fatty meat for fat-free cookies, sugar-laden soft drinks, and giant refined grain bagels doesn’t help.
Choices research most clearly supports:
- Low in saturated fat if… Studies that consider the healthfulness of what people eat when they reduce saturated fat show that people are less likely to develop heart disease when they replace foods high in saturated fat with more whole grains and unsaturated fats (from nuts, avocadoes, fish and healthful oils, for example).
- Plant-focused if… A plant-based diet is often recommended as a heart-healthy eating pattern that also helps lower cancer risk and promotes overall health. But when plant food choices emphasize sweets and refined grains, risk of heart disease increases. In contrast, when a plant-focused diet emphasized vegetables, fruits, whole grains, dried beans, nuts and healthful oils, heart disease risk was reduced by 25% compared to people who ate lowest amounts of these foods.
- Calories supporting a healthy weight… In a study of adults with risk factors for heart disease, decreases in blood cholesterol, a marker of inflammation (CRP), and insulin levels at 12 months were unrelated to whether the diet focused on cutting carbohydrate, fat or calories. Changes in these risk factors were significantly related to weight loss. So for someone whose excess body fat is putting them at health risk, the question of what can help reach and maintain a weight that is healthy for him or her is worth individualized consideration.
- Supportive of long-term health… Studies showing that an eating pattern benefits weight at one year or two years are not able to address effects on long-term health. Evidence consistently shows health-protective effects of dietary fiber, nutrients and natural plant compounds in whole grains, vegetables, fruits, pulses (such as beans and lentils), and nuts. In that context, be cautious about assuming that benefits of cutting carbohydrate in short-term studies will necessarily translate to long-term health.
A Reasonable Strategy for a Heart-Healthy Diet & Weight
Instead of jumping to cut all carbohydrates, start with cutting down on carbohydrate-rich foods that do not provide health-protective compounds.
- Sweets and sugar-sweetened drinks account for a large part of the carbohydrate in the average American’s diet. How low can you cut these choices without feeling so deprived that you are at risk for binges? Truly occasional use will not be a barrier to a healthy weight or heart health.
- Look at your portions of refined grains: white bread, rolls, crackers, and rice. What about refined grain cereals and bars? According to the Dietary Guidelines for Americans, many people exceed recommended amounts. If you’ve been among those going overboard, swap a few for whole grains, and cut portions of others.
- Make non-starchy vegetables the biggest portion on your plate. In addition to whole grains, include modest portions of other nutrient-rich foods with carbohydrates, such as starchy vegetables, fruits and pulses. And choose protein sources that have healthful fat, such as nuts, fish and poultry (and I don’t mean deep-fried chicken wings). Explore meatless possibilities, too.
After living with those steps for a while, if someone strongly prefers a trial with a very low-carbohydrate diet, it’s best to work with a registered dietitian nutritionist (RDN) for help including health-protective foods. Anyone with diabetes needs to coordinate a plan with their healthcare provider for monitoring safety and adjusting medications if needed. For people who are not simply cutting back on excess unhealthful carbohydrates, but targeting very low levels, based on potential that’s been seen for unhealthy changes in risk factors for heart disease, it makes sense to follow the latest American Diabetes Association standards of care and see their healthcare provider after three or four months (if not sooner) to evaluate results and create a plan for next steps.
Bottom Line on Carbohydrates in a Heart-Healthy Diet:
Headlines may make low-carbohydrate diets seem more successful for weight loss. Controlled studies show them to be one option, not necessarily a better option. Eating habits full of low-nutrient carbohydrate-rich foods are associated with heart disease and provide excess calories that can lead to an unhealthy weight. But that doesn’t justify jumping to minimize all carbohydrates. The association of high-fiber, nutrient-rich choices with heart health and overall health makes another approach a smart starting point. Target an eating pattern that includes moderate portions along with healthful sources of protein and fat. If that doesn’t bring the desired results, meeting with a registered dietitian nutritionist can address whether what’s needed is a new approach, or simply more help making this targeted pattern a realistic and enjoyable way to eat.
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Dansinger ML, Gleason JA, Griffith JL, et al. Comparison of the Atkins, Ornish, Weight Watchers, and Zone Diets for Weight Loss and Heart Disease Risk ReductionA Randomized Trial. JAMA. 2005; 293(1):43–53.
Gardner CD, Trepanowski JF, Del Gobbo LC, et al. Effect of Low-Fat vs Low-Carbohydrate Diet on 12-Month Weight Loss in Overweight Adults and the Association With Genotype Pattern or Insulin Secretion: The DIETFITS Randomized Clinical Trial. JAMA. 2018; 319(7):667–679.
Johnston BC, Kanters S, Bandayrel K, et al. Comparison of Weight Loss Among Named Diet Programs in Overweight and Obese Adults: A Meta-analysis. JAMA. 2014;312(9):923–933.
Li Y, Hruby A, Bernstein AM, et al. Saturated Fats Compared With Unsaturated Fats and Sources of Carbohydrates in Relation to Risk of Coronary Heart Disease. J Am Coll Cardiol. 2015; 66(14):1538-1548.
Micha R, Shulkin ML, Peñalvo JL, et al. Etiologic effects and optimal intakes of foods and nutrients for risk of cardiovascular diseases and diabetes: Systematic reviews and meta-analyses from the Nutrition and Chronic Diseases Expert Group (NutriCoDE). PLoS ONE 2017; 12(4): e0175149.
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TUESDAY, Aug. 28, 2018 (HealthDay News) — People who slash carbohydrates from their diets may shorten their lifespan, a new study suggests.
Using data on nearly 25,000 Americans, researchers found that the one-quarter who ate the fewest carbs each day also had a higher risk of dying over the next six years. Specifically, they had higher death rates from heart disease, stroke and cancer.
The research was presented Tuesday at the European Society of Cardiology’s annual meeting, in Munich, Germany.
While the study couldn’t prove cause-and-effect, experts said the findings spotlight the potential impact of such diets — or any “extreme” way of eating — on long-term health.
Low-carb diets typically involve eating a lot of protein, mostly meat and dairy products, and consuming less vegetables, fruit and grains. The Atkins and Keto diets are two examples of this kind of eating regimen.
In fact, a study published earlier this month linked both high-carb and low-carb diets to an earlier death, said Connie Diekman, a registered dietitian who was not involved in the new research.
In that study, researchers found that Americans who typically ate a moderate amount of carbs — 50 to 55 percent of their daily calories — lived the longest, on average.
None of those studies prove that the carb content of people’s diets was the key factor in longevity, Diekman stressed.
But she said it all suggests, once again, that moderation is the wisest course.
“If you want to protect your health — and work to help prevent disease — the best advice is to avoid extreme eating patterns, and focus on a good balance of plant and animal food sources,” said Diekman, who directs university nutrition at Washington University in St. Louis.
The study’s lead researcher cautioned on low-carb diets, specifically. “Low-carbohydrate diets might be useful in the short term to lose weight, lower blood pressure and improve blood control,” Dr. Maciej Banach, of the Medical University of Lodz, in Poland, said in a statement.
“But,” he added, “our study suggests that in the long term they are linked with an increased risk of death from any cause, and deaths due to cardiovascular disease, cerebrovascular disease and cancer.”
Nov. 19, 2002 (Chicago) — Fire up the barbee! Researchers from Duke University say that six months on the high-fat, low-carbohydrate Atkins Diet adds up to more weight loss and better cholesterol than a low-fat, high-carbohydrate diet.
And if that isn’t surprising consider this: Those researchers delivered the burger-friendly news at the American Heart Association’s Scientific Sessions 2002.
Eric Westman, MD, Duke University obesity researcher, says he decided to study the Atkins Diet after treating several patients who were “losing significant weight using the Atkins diet.” But Westman says he didn’t expect the high-fat regimen to do better than “the standard low-fat, high-carbohydrate diet that we use at the Duke Diet Center.” The study was funded by the Robert Atkins Foundation.
Westman assigned 120 obese volunteers — 75% of them women — to either the Atkins diet or to a low-fat diet that restricts fat to less than 30% of total calories. The participants following the Atkins diet got less than 10% of calories from carbohydrates, while 60% came from fat. The Atkins diet also includes the use of fish oil, borage oil, and flaxseed oil supplements.
After six months the Atkins diet group lost about 14% of their starting weight or an average of 30 pounds, which was considerably better than the 20-pound or 9% loss for the low-fat dieters.
Moreover, the Atkins group posted an impressive 11% increase in HDL “good” cholesterol compared to just a 1% improvement for people on the low-fat diet. At the same time triglycerides — another blood fat and suspected risk factor for heart disease — decreased a whopping 49% on the Atkins diet.
Neither diet had any significant effect on LDL “bad” cholesterol.
Westman tells WebMD that he thinks the Atkins diet “works” because people stay on it and lose more weight. Weight, he says, appears to be the real key to reducing heart disease risk factors. But he says that he still doesn’t recommend the Atkins diet. “We really need a large, well designed study,” he says. The National Institutes of Health is expected to start such a study early next year.
Heart risk from low-carb diets
New research suggests that “low-carbohydrate Atkins-style diets could increase risk of heart disease and stroke”, reported the Daily Mail . Research in animals has found that “‘low-carb’, high-protein diets can lead to a ‘significant’ build-up in plaque in arteries” and “make it harder for the body to form new blood vessels”, the Daily Mail ‘s article on low-carb diets said. It also said one of the researchers has warned that the effects do not show up in the usual tests.
This study looked at the effects of the low-carbohydrate high-protein diet in mice and found it to be associated with greater build-up of fatty deposits in blood vessels than a diet that had more carbohydrate and less protein, but similar amounts of fat.
As this research is in mice, it is unclear to what extent these findings apply to humans. It will no doubt prompt more research into this diet and into identifying an easy way to measure the effects it might have on the blood vessels. People trying to lose weight should try to do so by exercising and eating a healthy balanced diet that can be sustained long term.
Where did the story come from?
The research was carried out by Dr Foo and colleagues from Harvard Medical School and other research centres in the US. The study was funded by the Leducq Foundation Network of Research Excellence, the American Heart Association, the National Institutes of Health, Judith and David Ganz and the Maxwell Hurston Charitable Foundation. It was published in the peer-reviewed scientific journal Proceedings of the National Academy of Sciences of the USA .
What kind of scientific study was this?
This animal study looked at the effects of a low-carbohydrate high-protein diet on the cardiovascular systems of mice. Low-carbohydrate diets, such as the traditional Atkins diet, are used by many as a way of losing weight, but some of these diets are high in protein and fat.
These researchers were particularly interested in the effects of the low-carbohydrate and high-protein aspects of the diet, and so used test diets that had similar amounts of fat. The long-term effects of low-carbohydrate high-protein diets on the cardiovascular system are unknown.
The researchers used male mice that were genetically engineered to develop atherosclerosis when they were given a diet designed to mimic a typical Western diet (43% carbohydrate, 42% fat, 15% protein and 0.15% cholesterol).
Atherosclerosis is the thickening of the walls of the arteries due to the accumulation of fatty substances such as cholesterol. It can lead to heart attacks.
The mice were put on one of three diets one week after weaning. These were:
The Western diet and LCHP diet had similar amounts of calories, fat and cholesterol.
The mice were weighed after 12 weeks on the diet, and their aortas (the main artery leading out of the heart) examined for signs of atherosclerosis after six and 12 weeks. Other signs of heart disease risk were also measured, including levels of cholesterol and other kinds of fats in the blood, levels of insulin and glucose, and levels of chemicals that indicate inflammation (which is involved in the formation of the fatty build-ups in the arteries).
The researchers assessed whether the diets affected cells called endothelial progenitor cells (EPCs). These move into areas where blood vessels are susceptible to atherosclerosis, and may help to repair the blood vessels. A reduction in EPCs indicates greater risk of cardiovascular problems.
The researchers also looked at the effects of the diets on the mice’s ability to form new blood vessels when blood supply (and therefore oxygen) was cut off from the tissues (ischaemia). To investigate this, normal laboratory mice were fed the Western-style or LCHP diet for four weeks. After this period the researchers surgically cut off blood flow to one of the mice’s back legs and looked at how long it took for blood flow to re-establish itself, which indicates how well new blood vessels are being formed.
What were the results of the study?
The genetically engineered mice on the LCHP diet gained less weight over 12 weeks than those on the Western-style diet or standard food. Mice that were fed the LCHP diet had significantly greater fatty deposits in their aortas after six and 12 weeks than mice that were the Western-style diet or standard food. Mice fed on the Western-style diet had larger fatty deposits in their aortas than mice on standard food.
The mice on the LCHP diet did not show differences in the levels of cholesterol or chemicals relating to inflammation in their blood compared to those on the Western-style diet. However, they did show a reduction in the number of EPCs compared to mice that were fed on the Western or standard diets. This suggests that the mice would have limited ability to repair damaged blood vessels.
The researchers also found that mice fed on the LCHP diet showed less ability to regrow new blood vessels in response to a loss of blood supply to their back legs than mice fed on a Western diet.
What interpretations did the researchers draw from these results?
The researchers conclude that in an animal model of atherosclerosis, low-carbohydrate high-protein diets have adverse effects on blood-vessel health, and that typical markers of cardiovascular risk, including cholesterol levels and signs of inflammation, do not show this. They are not sure whether it is the low-carbohydrate or high-protein content that has these effects. They say that caution is needed if these findings are to be extended to humans, but raise their concerns that typical blood markers may not reflect the effects of the low-carbohydrate high-protein diet on cardiovascular risk.
What does the NHS Knowledge Service make of this study?
This study looked at the effects of a low-carbohydrate high-protein diet in mice, and found that it was associated with a greater build-up of fatty deposits than a diet that had more carbohydrate and less protein, but similar amounts of fat. As this research is in mice, it is unclear to what extent these findings apply to humans.
It is important to note that both the LCHP diet and the Western-style diet had a similar fat and cholesterol content. This means that some aspect of protein or carbohydrate metabolism contributed to the increased build-up of the cholesterol-rich fatty deposits in the mice on the LCHP diet. This is clearly a complex effect that will need further evaluation and the finding will prompt more research into how this diet has its effect.
The message for humans remains unchanged: people aiming to lose weight should try to do so by eating a healthy balanced diet that can be sustained in the long term and ensuring that they are physically active.
Analysis by Bazian
Edited by NHS Website
Links to the headlines
Low-carbohydrate Atkins-style diets could increase risk of heart disease and stroke.
Daily Mail, 25 August 2009
Low-carb diets ‘damage arteries’.
BBC News, 25 August 2009
Links to the science
Foo SY, Heller ER, Wykrzykowska J et al.
Vascular effects of a low-carbohydrate high-protein diet.
PNAS 2009, Published online before print August 24
There is some evidence that a low-carbohydrate diet may help people lose weight more quickly than a low-fat diet (31,32)—and may help them maintain that weight loss.
- For example, POUNDS LOST (Preventing Overweight Using Novel Dietary Strategies), a two-year head-to-head trial comparing different weight loss strategies, found that healthy diets that varied in the proportions of different macronutrients (carbohydrates, protein and fats) worked equally well in the long run, and that there was no speed advantage for one diet over another. (33)
- The DIRECT study compared low-carb, low-fat, and Mediterranean-style diets and found that after 2 years, weight loss and maintenance were better for low-carb and Mediterranean-style diets as compared to low-fat diets.
- The diets also had different effects on heart disease risk factors.
The low-carb diet was most beneficial for lowering triglycerides, the main fat-carrying particle in the bloodstream, and also delivered the biggest boost in protective HDL cholesterol.
If interested in trying a lower-carbohydrate diet, try to include some fruits, vegetables, and whole grains for essential vitamins, minerals, and phytonutrients. (1) Learn more about healthy diets for weight loss.
Low carbohydrate diets and heart disease
Research shows that a moderately low-carbohydrate diet can help the heart, as long as protein and fat selections come from healthy sources.
- A 20-year prospective study of 82,802 women looked at the relationship between lower carbohydrate diets and heart disease; a subsequent study looked at lower carbohydrate diets and risk of diabetes. Women who ate low-carbohydrate diets that were high in vegetable sources of fat or protein had a 30 percent lower risk of heart disease (4) and about a 20 percent lower risk of type 2 diabetes, (34) compared to women who ate high-carbohydrate, low-fat diets. But women who ate low-carbohydrate diets that were high in animal fats or proteins did not see any such benefits. (4,34)
- More evidence of the heart benefits from a lower-carbohydrate approach comes from a randomized trial known as the Optimal Macronutrient Intake Trial for Heart Health (OmniHeart). (35) A healthy diet that replaced some carbohydrate with protein or fat did a better job of lowering blood pressure and “bad” LDL cholesterol than a healthy, higher-carbohydrate diet.
- Similarly, the small “EcoAtkins” weight loss trial compared a low-fat, high-carbohydrate vegetarian diet to a low-carbohydrate vegan diet that was high in vegetable protein and fat. While weight loss was similar on the two diets, study subjects who followed the low-carbohydrate “EcoAtkins” diet saw improvements in blood lipids and blood pressure. (36)
31. Foster GD, Wyatt HR, Hill JO, et al. A randomized trial of a low-carbohydrate diet for obesity. N Engl J Med. 2003;348:2082-90.
35. Appel LJ, Sacks FM, Carey VJ, et al. Effects of protein, monounsaturated fat, and carbohydrate intake on blood pressure and serum lipids: results of the OmniHeart randomized trial. JAMA. 2005;294:2455-64.
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If you’re looking for a heart-healthy weight-loss diet to try, it appears that low-carbohydrate might be more effective than low-fat.
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A recent study found that a low-carb diet is better for losing weight and reducing cardiovascular disease risk than a low-fat one.
Researchers at Tulane University randomly assigned 148 men and women to follow either a low-carbohydrate diet or a low-fat diet. None of the participants had heart disease or diabetes when the study began.
Participants assigned to the low-carbohydrate diet were told to maintain an intake of digestible carbohydrate – meaning total carbohydrate minus total fiber – of less than 40 grams daily. Those assigned to the low-fat diet were told to maintain less than 30 percent of their daily energy intake from fat, with less than 7 percent coming from saturated fat and 55 percent from carbohydrates. Neither diet included a specific calorie or energy goal. And the participants in each group were asked to avoid changing their physical activity levels during the study.
After a year, people on the low-carb diet had greater decreases in weight, fat mass and other cardiovascular disease risk factors, such as cholesterol levels, than those on the low-fat diet.
Those in the low-carb group lost an average of almost 8 pounds more than those in the low-fat group and blood levels of certain fats that are predictors of risk for heart disease, also decreased more in the low-carb group.
The researchers say that the underlying mechanisms that may account for the differences in weight loss by diet are not fully known. But another recent study indicates that low-carbohydrate diets may have a more favorable effect than low-fat diets on how your body burns calories.
The researchers say that low-carb diets have been a popular strategy for weight loss, but their cardiovascular effects have been unknown until now.
“A low-carb diet is effective way to lose weight and improve cardiovascular risk factors. However, the diet is difficult to maintain long-term,” says registered dietitian Kate Patton, MEd, RD, CSSD, LD. Ms. Patton, a registered dietitian in Cleveland Clinic’s Preventive Cardiology & Rehabilitation Section, did not take part in the study.
“Once you transition off a low-carb diet, follow a Mediterranean diet for a heart-healthy approach to reducing cardiovascular risk factors,” Ms. Patton says.
Complete findings for the study, “Effects of Low-Carbohydrate and Low-Fat Diets: A Randomized Trial,” appear in the journal Annals of Internal Medicine.
- Low-carb diets are a popular way to lose weight, but a growing body of research suggests they may also lead to premature death when followed for long periods.
- A new study of more than 24,800 adults in the US found that those who limited their carb intake had a 32% higher risk of death from any cause than people who ate high-carb diets.
- That finding aligns with other new data of more than 447,500 people around the globe.
- Limiting carbs might be a good strategy for weight loss, but experts say it’s not a great plan to follow in the long term.
Low-carb diets have many iterations, each with a devoted following. Atkins dieters eat lots of meat and eggs before slowly and carefully reintroducing carbs, while the ketogenic diet urges people to severely cut carbs and focus on upping their fat intake from foods like butter, cheese, and avocados.
But increasingly, scientists are discovering that going low-carb may not do you any favors in the long run.
A study presented Tuesday at the European Society of Cardiology Congress 2018 looked at the self-reported eating patterns of 24,825 people in the US over more than a decade.
The researchers separated participants into four quartiles, from lowest- to highest-carb diets. They found that Americans in the bottom 25% of the pack, who ate barely any carbs, had a 32% higher risk of death from any cause than those who had the highest carb intakes.
They also found that low-carb dieters had a 51% increased risk of dying from coronary heart disease and a 35% increased risk of dying from cancer relative to people in the top 25% of carb eaters.
The researchers compared those results with data on the diets of 447,506 people around the world and found that overall, low-carb dieters had a 15% increased risk of death.
The researchers think this may be because replacing healthy, fiber-rich carbs — like whole grains and certain vegetables — with more meat can lead to danger.
“Our study suggests that in the long-term they are linked with an increased risk of death from any cause, and deaths due to cardiovascular disease, cerebrovascular disease, and cancer,” Maciej Banach, a professor at the Medical University of Lodz in Poland who helped write the study, said in a release.
Healthy carbs like whole grains and beans aren’t bad for you
This new study comes on the heels of another worldwide investigation into death data published in the Lancet earlier this month. It found that people who ate a moderate amount of carbs and focus on whole, healthful foods like veggies, legumes, and nuts tended to live longer than people who limited their carbohydrate intake.
It’s more evidence that the best long-term diet strategy is a regimen rich in vegetables, filling whole grains, and healthy fats from naturally oily sources like olives and avocados.
“Try to make choices that fill your plate with plants,” Sara Seidelmann, a cardiologist and nutrition researcher at Brigham and Women’s Hospital in Boston who led the Lancet study, previously told Business Insider.
She said it’s not clear whether a plant-based diet that is also low-carb might be a healthy long-term strategy because no one really eats that way.
“It’s not a natural eating pattern,” she said.
Instead, when people dump carbs, they often reach for more animal proteins and fats.
Eating more butter and meat can increase your blood pressure, and the World Health Organization says that processed meats like hot dogs, ham, bacon, and sausage can cause cancer. It’s possible that any kind of red meat, processed or not, could be linked to an increased risk of colorectal cancer. And some fish carry high levels of nitrates, which can cause cancer in animals.
What’s more, low-carb dieters who trade grains and fresh produce for more meat and fish may unwittingly acidify their urine, putting them at risk for developing kidney stones.
That said, there are a few good reasons to go low-carb
Still, low-carb diets offer real benefits for certain people.
The ketogenic diet — keto for short — was originally developed to help curb epileptic seizures in children. Cutting sugar and eating more fat has been found to help control seizures when drugs can’t and to stop them completely in some cases.
Going keto can also help control blood glucose levels in adults with Type 2 diabetes. That’s also why it can be an effective short-term weight-loss treatment.
“Low-carbohydrate diets might be useful in the short term to lose weight, lower blood pressure, and improve blood glucose control,” Banach said in the release. His study suggests that the link between early death and low-carb diets is stronger for people who aren’t obese, lending credence to the idea that it might be all right to cut carbs if you need to lose a lot of weight.
Cancer doctors also think that keto diets may play a role in making certain types of treatment more effective, and they’ve studied how cutting sugar from mice’s diets helps one class of cancer drugs more effectively kill tumors. Human trials of this drug-diet combo are set for this fall.
But for most people, restricting carbs is done by ramping up their intake of meat and other proteins and forgoing high-fiber, carb-heavy foods like beans, carrots, and legumes that help keep you satisfied until your next meal.
That said, cutting back on carbs does help dieters eat healthier in one important way: It reduces their sugar intake.
Sugar is essentially all carbs, and research has clearly shown that eating sugar can lead to all kinds of health problems — like weight gain, heart disease, high blood pressure, and diabetes — if left unchecked.
“If we’re talking about a Mountain Dew from 7-Eleven, I would agree that carbohydrate in that context is bad,” Edward Weiss, an exercise scientist, recently told Business Insider. But he said that processed carbs like white bread and sugary snacks that lack fiber and vitamins shouldn’t be equated with healthy carbs like whole vegetables and whole grains.
“These are the healthiest foods we know of,” he said. “To avoid them is, I think, really taking a chance and doing self-experimentation with something that might have long-term negative effects.”