Here's our recently-formalized disclosure:
Examine.com is an unbiased nutrition and supplement resource. We are not influenced by commercial interests, product manufacturers, or any other organization, and we will not advertise products or brands. Examine.com does not accept donations, third-party funding, or sponsorship of any kind. One hundred percent of our revenue is generated through our three products: the Examine.com Research Digest, Supplement-Goals Reference, and the Supplement Stack Guides.
We've been approached by a variety of corporations and other organizations during the last four years, who ask if they can help fund us, provide us with products, and a variety of other requests. Every single time, we say no.
They aren't evil by any stretch of the imagination. If you feel like you have a product or cause that can help human health, why not advocate for it?
But judging products or taking a stance simply isn't what we do.
Instead, we provide as much information as possible, summarizing otherwise complex findings. We don't judge particular branded products, and the data on our site changes as the research changes.
There are plenty of experts on the web, and a thousand times as many so-called experts. Our goal is to provide you with verifiable knowledge, to help you develop your own expertise.
If you look up the term "antioxidant" on pubmed, you get around 423,000 papers. And that number will continue to climb each week.
So let's say you just want to know whether to take antioxidants or not. What does the most recent research say, and how does it apply to you? Here are a couple options:
If you have a few dozen hours free and some background in biochem, physiology, and epidemiology, as well as full-text access to medical journals, then you may be able to get some insight.
But academic writing is not so fun to read. To put it mildly. Forget melatonin, try reading one whole issue of a journal from front to back.
Or you could just subscribe to the Examine.com Research Digest.
Our second monthly issue just came out, and it covers some of the most important trials from the past few weeks. The trials explore the impact of antioxidants on muscle, the latest on the microbiome, and a variety of other highly applicable topics.
We have around a dozen researchers and physicians check the reviews, and try our hardest to give an objective perspective. Hundreds upon hundreds of hours go into each issue.
Reading ERD will put you several steps ahead of most anyone interested in nutrition and supplementation. Not even nutrition researchers (and certainly not physicians) have the time to find the most important trials each month, read the full text, and get the perspective of a variety of experts on each one.
And knowledge is power -- not just for your own health, but for your friends and family.
We genuinely enjoy what we do. And we aim to make accessible what was formerly locked in ivory towers in dry, inacessible language. Try out an issue and see if it piques your curiosity.
Today, Examine.com presents a page on L-alanyl-L-glutamine, a dipeptide molecule similar to alanine and glutamine, also known by its brand name, Sustamine.
Dipeptides are made up of two amino acids. They are sometimes referred to as nature’s prodrug. A prodrug is a compound that becomes active when it is metabolized by the body. In a way, L-alanyl-L-glutamine is a prodrug for glutamine.
Glutamine is an amino acid that plays a critical role in muscle function and development. However, it’s not a very useful supplement. After supplementation, glutamine ends up predominantly in the intestines and liver, which provide the body with glutamine on an as-needed basis. This prevents glutamine from having any performance-enhancing or muscle-building effects. It may, however, be a useful supplement for intestinal health and muscular endurance.
L-Alanyl-L-Glutamine is claimed to allow glutamine to get past the liver and intestines, since its dipeptide structure is thought to act like a prodrug. Unfortunately, current evidence is not promising, suggesting that supplementing L-alanyl-L-glutamine does not provide more benefits than glutamine itself.
L-Alanyl-L-Glutamine is very water-soluble, which means it may play a promising role in IV nutrition. Plus, it’s way easier to dissolve in a drink, so it may be gentler on the digestive system, which is important for endurance athletes.
L-Alanyl-L-Glutamine is a more water-soluble glutamine. If you’re thinking of supplementing glutamine for intestinal health or endurance exercise, L-alanyl-L-glutamine may be a better option, since the increased water solubility poses a lower risk for intestinal distress.
The Examine.com editors have finished the page on bioactive compounds in chocolate. Collectively, these molecules are called Cocoa Extract.
Most of the interest in cocoa extract is due to its high (-)-epicatechin content. Low doses of (-)-epicatechin are associated with benefits related to blood flow, due to improved nitric oxide (NO) synthesis.
Unlike most pre-workout supplements, which provide L-Arginine in an effort to unreliably increase nitric oxide, (-)-epicatechin works at the rate-limiting step of NO production by stimulating the enzyme that produces it. This results in improved blood flow to the brain and reduced blood pressure. This effect may be able to reduce the rate of cognitive decline in older adults. One study even found healthy people supplementing (-)-epicatechin experienced a protective effect in the kidneys due to improved oxygenation.
Improving nitric oxide synthesis also improves insulin signaling. This is why low doses of (-)-epicatechin improve insulin sensitivity, particularly in muscle tissue. Evidence from animal studies suggests this may improve physical performance and facilitate effective energy use in muscles.
Eating dark chocolate (50 – 85% cocoa), baker’s chocolate, and semisweet chocolate provides a low dose of (-)-epicatechin and results in the same effects as cocoa extract supplementation. About 25-40 grams of chocolate is equivalent to the standard (-)-epicatechin dose. This is about 200 calories of chocolate. The more cocoa chocolate contains, by weight, the less is needed to achieve the same (-)-epicatechin dose. White and milk chocolate do not contain enough catechins to provide the health benefits associated with dark chocolate.
We're going to keep this short and sweet.
Over 1250 people have already bought the Examine.com Research Digest, and they are absolutely loving all they’ve learned in just the first issue. Just search on twitter and see the overwhelmingly positive response.
With that said - the price goes up 20% once the clock hits midnight PST.
If you’re a professional, this saves you time and money, and it keeps you on top of the latest research.
Get it now: Examine.com Research Digest
Still not convinced? We're so confident that ERD will bring massive value to your knowledge and career that we have a no questions asked 30 day money back guarantee.
Want a quick sneak peek? Click here see our sample review - "Umami appetizers backed by science".
Remember - the sale ends tonight. Get the Examine.com Research Digest.
In recent years we’ve seen some terrible headlines:
There's a giant problem out there in health and fitness right now - the immense gap between the research and the practitioner.
At the same time, people are busier than ever, and keeping abreast of the latest scientific research is extremely difficult.
What is ERD exactly? It's a monthly digest which helps you easily digest new and relevant research.
Each month ERD scours over 8 recent nutrition and supplement studies, breaks them down and delivers them to you in an easy to follow format
This is immensely valuable because rather than wasting your time and focusing the minutiae, we take a step back, look at the big picture, and tell you what’s important.
You could say "It's the smartest way to stay on top of the latest nutrition research."
Best of all, ERD has an all-star panel who cover the 8 studies each month. With 15 active contributors to ERD, we cover the research from all angles. When you read our analysis, you'll know you're getting the full picture.
For the next few days, membership to ERD will be available at a special 20% off introductory sale. By subscribing to ERD you get:
Finally, you also get access to a member’s only private forum where you can discuss our reviews and analysis.
Put it all together, and the Examine.com Research Digest is the perfect tool for professional development while being a massive time saver.
We’ve been analyzing scientific research in supplementation and nutrition for over 3.5 years now. We’ve had over a dozen people with varied backgrounds from pharmD to PhD to double PHDs/MDs who have researched, submitted, and reviewed our work.
And you know what we’ve found?
No one man or woman can do it alone.
You need a team. You need a review process. You need a panel of experts.
And that’s what makes ERD (Examine.com Research Digest) so powerful. And why it’s a must have for anyone who takes their nutrition seriously.
Every month, we will tackle 6-8 recent nutrition/supplement studies. We will analyze them. We will look at their study design. What the results were. What questions were answered, and what new questions arise. And most importantly: how all this research applies in the big picture (you know - making it applicable).
We're bridging the gap between the practitioner and the research.
But when you read it, you’ll be reading something that over a dozen people will have looked over.
First you’ll have our primary researchers. These are people who have experience conducting research. They’ll go in, look at the study, and break it down. They’ll bring about all the salient points - everything you need to know.
Next you’ll have the editors. These are people who’ve been part of peer-review (which is basically what we’ve built!) They’ll pore over every citation, every single claim. They’ll make sure the analysis stands up to the most intense scrutiny.
And finally, we’ll have our reviewers. These are leaders who have decades of experience to draw from, both theoretical and practical. They’ll look over the reviews to make sure it all make sense.
Five researchers. Four editors. Six reviewers. 15 people coming together to make sense of nutrition research.
Best of all - there’s no single field of study that everyone comes from. RDs, PhDs, pharmDs, MDs - you’ll know that each review has gone through review and revision from a wide breadth of people.
You’ll know that what you’re reading is the result of a council of brilliant minds, all coming together to make sure you’re kept abreast with the latest research.
If you're interested, you need to get on the ERD Earlybird Waitlist.
You’ll get access to ERD 24 hours before we open it up to our 50,000+ Examine.com Insiders, to our 30,000+ Facebook Fans, and to our 25,000+ visitors/day to Examine.com.
The first 350 people to buy ERD will get it at an exclusive price that won’t be made available ever again.
ERD is going to be a game changer.
The truth doesn’t sell well. Throw in a 24-hour news cycle, difficult-to-understand studies, and media companies scramble for the latest viral hit, and it’s no surprise that misinformation spreads like wildfire.
There are some myths that pop up in the media again and again. We’ve investigated the ten biggest myths spread by the media.
Carbohydrates have gotten a bad rap in the media. Critics have been especially tough on bread, since it also contains gluten. In contrast to the reports claiming that any amount of gluten is universally dangerous, the evidence is more nuanced. Small amounts are more likely to produce symptoms in those with intestinal disorders, but in others the dose-response relationship for effects isn't well studied.
The relationship between carbohydrates and insulin is a breeding ground for nutrition myths. Insulin was one of the very first hormones to be discovered, and it was also the first hormone to be investigated in the context of sensitivity. Early evidence led people to believe that an increased carbohydrate intake causes insulin insensitivity. This is moreso true for diabetic and insulin resistant people (usually obese individuals) overeating carbohydrates, but the myth persists even for lesser intakes.
While gluten gets all the attention, other compounds may be as or more important for people without celiac disease who suspect that they have gluten sensitivity. For example, some of the same researchers who discovered that gluten intolerance exists in people who don’t have celiac disease did a much more thorough follow-up study, and concluded that gluten was not necessarily to blame in those with irritable bowel syndrome. They suggested that compounds falling under the category of FODMAPs (which are present in a variety of plant foods) may be a greater issue.
The Truth: Carbohydrates have been vilified long enough. As long as you don’t overindulge and exclude other food groups, starches are not inherently harmful. While some are sensitive to wheat, the gluten isn't necessarily to blame, and other foods may also be implicated.
If there’s one thing the media is good at, it’s scaring you away from perfectly innocent foods.
Eggs have been demonized because their yolks, which are chock full of nutrients, also contain high levels of cholesterol. Though that sounds scary, eating food high in cholesterol doesn’t translate to increased cholesterol in your blood.
The actual research shows that unless you have a pre-existing condition, eggs are a fantastic source of protein, fats, and nutrients. Their association with cardiovascular disease is a myth.
The Truth: Eggs are a great source of protein, fats, and other nutrients. Their association with cardiovascular disease and high cholesterol is severely overblown.
More: Are eggs healthy?
Absolute statements like this one are the nutrition myth’s best friend. Cancer is particularly difficult to discuss in absolutes. After all, almost everything we eat has the potential to cause cancer.
For example, antioxidants could both promote and hinder cancer growth, but the effect is usually too small to notice.
Some compounds, like polyaromatic hydrocarbons (PAHs), found in smoked meats, have been found to damage the genome, which is the first step to potential cancer. Current evidence suggests that red meat can pose a cancer risk for people with poor diets and lifestyle choices. If you don’t smoke, have a consistent exercise schedule, and eat your vegetables, red meat’s effect on cancer is nothing to worry about.
The Truth: The fears about red meat and cancer are exaggerated. Eliminating other risks of cancer, like smoking, and practicing healthy lifestyle choices will render the risks of red meat negligible.
The traditional way to lose fat for a long time was a low-fat diet. But just like eating cholesterol doesn’t directly increase your cholesterol levels, eating fat doesn’t make you fat.
The myth that saturated fat causes cardiovascular disease is not true. Food quality is what matters - there’s a big difference between eating a grass-fed steak and a fast food hamburger.
The Truth: Saturated fat itself will not lead to heart disease or cardiovascular disease. In fact, low fat diets shunning saturated fat are likely detrimental for testosterone production.
Most myths are rooted in a grain of truth. It’s true that people with salt-sensitive hypertension (SSH) should avoid salt because it raises their blood pressure.
A recent study however, suggests there is no association between salt consumption and hypertension, a condition characterized by abnormally high blood pressure.
Instead, evidence suggests high body weight, as measured by BMI, is associated with elevated blood pressure.
The Truth: Salt intake isn’t associated with high blood pressure, except for people with SSH. Still, the average North American consumes double the recommended intake of sodium. Excessive sodium may not raise blood pressure, but it is associated with other health issues.
Whole grain bread is claimed to be better than white bread because of its high fiber and micronutrient content. Plus, it has a lower glycemic index as well as insulin index, which means it results in lower insulin release after a meal.
All of this is true, but the media frequently fails to mention that the actual differences between white and whole wheat bread are relatively small. Whole wheat bread’s ‘high’ fiber content is not so high compared to fruits and vegetables. Even though many micronutrients are removed during the processing of white bread, many loaves are later fortified with additional nutrients.
One actual difference between wheat and white bread is the phytic acid content in wheat. Phytic acid binds to dietary mineral like iron and zinc, which can slightly reduce their absorption in the body. More importantly, phytic acid also has a protective and anti-inflammatory effect on the colon. So there’s a little bit of bad, and a little bit of good. Wheat and white bread still provide a similar number of calories, and both contain gluten and related proteins.
The Truth: White and whole wheat bread are not that different. Though whole wheat bread is claimed to be healthier, neither contains a high level of micronutrients.
The human body’s preferred energy source is glucose (a sugar). Fructose, another sugar, can also be used for energy until the liver is full of glycogen. Once fructose can no longer be used for energy, it is converted into fatty acids.
Early evidence led to the belief that fructose could cause fatty liver disease, as well as insulin resistance and obesity. By extension, high fructose corn syrup (HFCS) is frequently said to be unhealthy, since it is high in fructose.
Liquid HFCS has a fructose content of 42-55%, with some variation due to production methods. Sucrose, also known as table sugar, is 50% fructose. Unless you are consuming over 100 grams of sugar a day, the different of -8% to +5% will make no difference.
The Truth: HFCS and table sugar are very similar from a health perspective. Though HFCS may sometimes contain more fructose, the difference is negligible.
Carbohydrates and fats are often blamed for various health issues. The third macronutrient receives its share of attention in the news, too. Protein has been blamed for bone and kidney damage.
Let’s tackle these claims one at a time. An early study on protein detected that protein consumption was linked to increased urinary calcium, which was thought to lead to reduced bone mass over time. Later studies determined that urinary calcium was a poor measure for bone mass, and that protein actually had a protective effect or no effect on bone. Better research debunked the earlier research.
Another early study determined that high protein diets increased glomerular filtration rate (GFR), a marker for waste filtration in the kidneys. Some lept to the conclusion that increased GFR was a sign that increased protein put too much stress on the kidneys. Later research however, has shown that kidney damage does not occur as a result of a diet high in protein.
The Truth: Protein, even in large amounts, isn’t harmful to your bones or your kidneys.
How often do you hear the claim that whole foods are better than supplements? It’s been repeated so often that the word ‘natural’ has a positive connotation, and ‘synthetic’ or ‘chemical’ has a negative one.
As is often the case with absolutes, it’s not so simple. For example, supplemental vitamin K has much better bioavailability than its plant-based equivalent, due to the plant's vitamin K being tightly bound to membranes. Useful non-vitamins can also be more effective in supplemental form. One example is turmeric, which is often coupled with black pepper extract when supplemented. Otherwise, turmeric's bioavailability is quite low when consumed in food form.
Many supplements have a natural and synthetic form. This allows them to be accessible to many people. For example, if vitamin B12 could not be synthesized, it would be very expensive and an unsuitable supplementation option for many vegans, who need a consistent source of vitamin B12 due to their diet.
The Truth: Vitamins from food are not necessarily better than vitamins from supplements. This is a very broad statement, proven incorrect by the many examples of supplements fulfilling a vital health role that natural sources could not.
It’s easy to trace this myth back to its origin. Digesting a meal does raise your metabolism by a little bit, but the only way to sustain this elevated rate is to eat more food.
In fact, some studies suggest having smaller meals more often makes it harder to feel full, potentially leading to increased food intake.
The Truth: Though digestion increases the metabolic rate, this effect is negligible when compared against the actual caloric content of the food consumed.
You’ve likely heard all 10 of these myths repeated at one time or another somewhere in the media. Identifying misinformation can be difficult because it’s very pervasive.
And really, this is just the tip of the iceberg. You can just look at the way the media handles the latest studies - just look at the recent low-carb vs low-fat study. It requires a team of experts to really look into the evidence and figure out what can be applied.
Want to know more about which supplements work and which are a waste of time? Enter your email to join our free 5-day course on supplementation.
It’s based on what our expert researchers have found over years of research. Evidence-based, no bull.
The Examine.com editors have finished a page on Polygala tenuifolia, or as it’s known in traditional Chinese medicine, Yuan Zhi. Polygala tenuifolia is one of the 50 fundamental herbs in traditional Chinese medicine, and it’s often included in decoctions intended to improve cognitive health and well-being.
Unfortunately, only one human study has been conducted on Polygala tenuifolia. Researchers observed that healthy people supplementing Polygala tenuifolia experienced benefits to spatial organization, making it easier to organize and order diagrams and pictures. Memory retention and formation was not affected.
Animal research, however, suggests Polygala tenuifolia may have a restorative effect on cognition. Studies investigating animal models of cognitive decline and aging found that Polygala tenuifolia has a powerful effect when given to aging rodents. Healthy rodents, however, experienced no major benefits to cognition.
The aging rodents may have experienced cognitive benefits because Polygala tenuifolia supplementation increases brain growth factors, like brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF). It also has an antioxidant effect in the brain. Much more research is needed to investigate these mechanisms and how they may apply to supplementation.
Polygala tenuifolia may also have an antidepressant effect similar to ketamine, a rarely-prescribed antidepressant, since it has hallucinogenic and habit forming properties. After oral supplementation, both Polygala tenuifolia and ketamine cause a fast-acting and potent antidepressant effect. These compounds have a similar effect because both interact with the N-methyl-D-aspartate (NMDA) receptor.
Polygala tenuifolia is a promising brain enhancing herb, but much more research is needed before it can be recommended as a supplement. Preliminary evidence suggests it provides the most benefit when supplemented by people suffering from cognitive decline, while healthy people experience little to no benefit.
If you're a savvy nutrition enthusiast, you probably know that a variety of diets can improve health and lead to weight loss. But in the media, low-carb and low-fat diets have waged an epic battle over the past few decades. The latest comes from a year-long study of obese patients, which claims to shed new light on the topic.
Does this study tell us anything helpful, or does it just confirm what we already know? Headlines in the past 24 hours have largely touted the study as eye-opening, even tying it into the newly low-carb (and much thinner) Lebron James.
While most journalists are chasing the sensationalist story: “low carb proven to be superior,” few actually delved into the study to see what researchers found. When you read the full study, key nuggets jump out that most people have missed. Let's dive right in and break down the details. If you're short on time, read the blue boxes now and then come back and read the details later.
We'll analyze this paper using the PICO method, which researchers often use to frame randomized trials. It stands for:
[P]opulation - The study focused on obese people in Louisiana. Unlike most previous trials, this one included a sizable non-white population. Black people made up a little over half of the group.
[I]ntervention - Participants were split into two groups: the low carb group were told to eat less than 40 grams of carbs per day while the low fat group was to take in less than 30% of their calories from fat. The low fat group also aimed to keep saturated fat under 7% and carbs around 55%, which is in line with the current U.S. dietary guidelines.
[C]omparator - This just refers to the control group. The researchers wanted to know the effects of a low-carb diet (the intervention) and compared it against a low-fat diet (the comparator). The comparator is often the current standard of care. In this case, the low-fat diet was very close to what physicians typically prescribe for people at risk for heart disease.
[O]utcome - The outcomes researchers were most interested in were weight loss and cardiovascular risk factors like LDL, HDL, and waist circumference. They also measured a few other factors, like markers for diabetes.
This study was a bit different than previous low-carb trials. None of the participants had diabetes, heart disease, or kidney disease. Having healthier participants means that the researchers could apply the results to a broader group, not just people who were already sick. One thing that wasn't emphasized in the paper or media: almost 90% of the participants were female! If you're using this study to guide dietary recommendations for obese males, just note that only 9 out of 75 people in the low-carb group were men.
It should be noted that calories were not directly controlled. The participants reported an average intake of 2,000 calories per day before either diet - this seems implausible and emphasizes how inaccurate self-reporting can be.
Furthermore, The low-carb group started at a lower daily caloric intake than the low-fat group. By the end, both were eating slightly more and at roughly the same amount of calories.
Study participants were mostly obese women who didn't have diabetes or heart disease. The low carb group was told to eat less than 40 grams of carbs per day while the low fat group was to take in less than 30% of their calories from fat.
There was more to the intervention and comparator than just "low-carb" and "low-fat." Each group actually had two co-interventions along with their recommended macronutrient targets: Meal replacement: Participant were given a meal replacement bar or shake every day. These meal replacements were either low-carb or low-fat, as was appropriate based on their prescribed diet.
Counseling: The participants met up in small group counseling sessions, along with a dietician, in order to learn about dietary guidelines and receive support.
Both of these co-interventions likely impacted the real-world applicability of the study. If we assume that the best diet is one that a person can stick to, the addition of counseling and meal replacement (to ease the transition) greatly helped to prevent dropout. The completion rate was about 80%, which is very high for a diet study.
Both groups got a daily meal replacement shake or bar, and both groups also had regular dietary counseling. This likely increased compliance but might reduce applicability, especially if sticking to the diet is the hardest part.
Regardless of what the researchers intended, the study ended up comparing a diet that was just barely low-carb (with added protein) and a diet that could barely be classified as low-fat.
The low-carb group, while instructed to consume under 40 grams of carbs, did not manage that low of a number. The lowest average carb intake for the group as a whole was 93 grams per day at six months in, and the highest was 127 grams at 12 months in (down from 242 grams a day). Even the low-fat group ended up decreasing their carb intake considerably, but much less than the low-carb group.
That being said, the similarity of the low-fat diet to the macros of the standard American diet might have played a small role in the study results. The intervention group was prescribed a diet that many of the participants were not familiar with. Shiny new diets often provide benefits just because they are new. On the other hand, the low fat group underwent less drastic dietary changes. Unfortunately it's tough to design the perfect control group, and the perfect control group might even control for too many variables and be too difficult to follow, making the trial results difficult to apply.
As an example, let's say an astute researcher realizes that "low-carb" and "low-fat" are not indeed monolithic diets, and that two fat sources can have drastically different effects (e.g. fish oil versus hydrogenated soybean oil), as can two carb sources (e.g. fruit and a twix bar). If this researcher decides to test low-carb against low-fat but control for food quality and carb/fat sources, the trial could get very messy. Recommending an entirely new diet is hard enough, but getting extremely specific with food recommendations could lead to half the sample dropping out. Point being: everyone's a critic when it comes to analyzing studies, but designing a realistic trial is not that easy.
The low-fat group wasn’t that different in fat content from the standard American diet. The low-carb group was barely low-carb and also ate more protein.
Why did the low-carb group miss their carb targets so badly, not even getting close to 40 grams a day? Well, they are human. Some got close to 40 grams, some probably had life get in the way or just found out they really can't handle low-carb diets. Despite not reaching the target, the group did cut their carb intake by about 50% by the end of the trial, compared to baseline levels.
The low-fat group had a much easier change to make. Their baseline fat intake was around 35%, so to target 30% or less was not a very drastic change. Indeed, they ended up hitting 30% fat almost right on the nose after 12 months. Interestingly, at three months in, 25% of the low-fat group reported headaches, compared to only 8% of the low-carb group. Headache rates were much closer at later time points, and other adverse events were fairly similar between groups.
The low-carb group didn’t get close to the target of 40 grams of carbs - they were roughly 300% higher (127 grams on average). Changing your diet is difficult.
Note that the study did not report much on what exactly the participants ate. But we can surmise that the participants didn't end up eating diets much more rich in whole foods than they did before. Both groups ate around 17-18 grams of fiber at the beginning of the study. The new diets caused the groups to eat less fiber. Although eating less in general can lower fiber intake, the two groups likely did not adhere very strongly to the dietary guidelines encouraged by their counseling sessions, since women were recommended 22-28 grams of fiber a day.
It's also interesting that the low-carb group had a similar fiber intake as the low-fat group, so the argument that avoiding carb-rich grains is detrimental due to lower fiber intake doesn't hold true here.
The study didn’t report on the specifics of what foods were eaten, and neither group likely had large increases in fruit and vegetable intake. Both ate an almost equivalent amounts of fibre.
The most publicized result from this trial was weight loss - that the low-carb group had greater weight loss than the low-fat group. Both groups ate about the same number of calories (low-carb clocking in a bit lower). Both groups also ate more calories as the trial went on, with both experiencing an initial drop of about 500 kcal when their diets were given. Although non-significant, the low-fat group ate around 100 calories more at 12 months than at 3 months and the low-carb group ate around 200 calories more.
When looking at the maintainability of diet, both groups had similar caloric intake at 12 months.
Low-carb eaters also experienced a significant increase in lean mass as well, whereas the low-fat group actually lost a bit of lean mass.
Unfortunately fat mass was measured by bioelectrical impedance, not DEXA or a comparably accurate method. If you own one of those bodyfat-measurement bathroom scales, you know that their large measurement variances makes it hard to draw conclusions. Bioelectrical impedance relies heavily on total body water to calculate fat mass, and low carb diets are known to reduce water weight fairly rapidly which could potentially explain some of the rapid weight loss observed.
Since body fat and lean mass were measured through bioelectrical impedance, one can safely ignore any claims about exact fat loss and muscle gained.
Don’t make the mistake of attributing the group results to individuals. For example, weight loss in the low-carb group varied considerably, with some participants losing around 3 kg and some losing over 12 kg. The trial results don’t mean that you should expect to lose some specific number of kilograms on a low-carb diet. In addition, the first three months is when the weight loss happened in both groups. After that, each group experienced a slight uptick in weight, on average. This is another finding that is sometimes skimmed over by media reports.
Weight loss varied quite a bit between individuals within groups, and mostly happened within the first 3 months of the 12 month study.
A better gauge of fat loss would be the waist circumference. At 3 and 6 months in, the low carb group had a greater reduction in waist circumference. By 12 months in, the low fat group had caught up, and the decrease was the same in both groups.
Waist circumference decreased most rapidly in the low carb group, but was roughly the same between the groups at 12 months in.
Although the paper doesn't get into mechanisms much, we can guess why the low-carb group did better with weight loss and lean mass gain. Protein intake ended up being significantly higher in the low-carb group, which bodes well for weight loss and muscle preservation. The participants were instructed to not change their activity levels, although this was not really measured in the study. Thus, any potential effects of the diets on physical activity were nipped in the bud.
Fat loss in the low-carb group could have been partially due to a higher protein intake, which has been shown to have a positive effect on fat loss.
Considering the similarity in waist circumference reduction and both groups eating similar amounts of calories by the end, coupled with the increase in protein by the low carb group and water weight lost when reducing carbohydrates, it would be disingenuous to state that “low carb is superior to low fat for long term weight loss”.
The low-carb group had a higher HDL to total cholesterol ratio than the low-fat group, which is a strong predictor of heart disease. They also had lower triglycerides, in addition to a lower calculated heart disease risk score. Plus, their LDL dropped a bit more than in the low-fat group. To top it off, the low-carbers had a greater decrease in C-reactive protein, a measure of inflammation in the body.
Despite these improved markers, we can't be quite sure what caused them. Although the low-carb group increased their percentage of saturated fat out of total daily calories, they ended up eating about the same total grams of saturated fat compared to baseline, due to taking in fewer calories per day. The low-fat group on the other hand drastically cut down their daily grams of saturated fat. How much of the improvement in heart disease predictors was due to macronutrient changes rather than weight loss isn't known.
Also, the trial is not really conclusive on the subject of heart health since it didn't measure actual heart disease events nor did it look at LDL particle count and density, which are important predictors of disease. The researchers also measured blood pressure and some indicators of diabetes, but the groups didn't differ much on those parameters.
Many predictors of heart disease were improved by the low-carb diet, but the study was not designed to isolate the specific dietary cause of the improvement.
There were several important questions that the trial didn't answer. For example, was the weight loss and cholesterol improvement due to the low carb level or some other factor? It's possible that the low-carb group ate less simply because there were fewer options for them to eat, since many packaged foods sold at grocery stores are high in carbs.
Would the same result happen if you restricted, let's say, all packaged foods instead of carb-rich foods? Or taken to a ludicrous extreme, what if you limited foods that started with vowels? All of these reduce your food options, which is one way through which low-carb diets could lead to weight loss. Some of the weight loss could also be the result of a bit less glycogen (stored carbohydrate) in the liver and muscles. Glycogen can weigh a couple pounds or more due to its high water content, but less of it is stored in the body during a low-carb diet.
The researchers touted the trial's wider applicability compared to previous trials, since the study included more black people than previous studies. But the trial also happened to include zero Asian people and very few Hispanic people. Not to mention very few males! Combined with the fact that all of the participants were obese but with no history of heart disease or diabetes, this may limit the applicability of the trial.
The study didn’t answer the question of what it is about the low-carb diet that encourages weight loss, as it isn’t necessarily due to carb levels.
This trial is a mixed bag. It included a relatively large number of participants and ensured a high completion rate with counseling sessions and meal replacements. And since there was no calorie goal set, the trial could test just how a low-carb diet affected food intake in obese people.
But rather than proving that a low-carb diet leads to weight loss, the study shows that directing people to consume less carbohydrates might increase dietary protein intake. Was it the increased protein? Was it just fewer carbs (remember, this was not truly low carb)? Was the lower carbs/higher protein/higher fat diet simply more filling? And how does that apply to non-obese individuals? These are four very important questions that come out of this study.
Decreasing carbs and increasing protein leads to superior weight loss. The question is: what caused it, the decrease in carbs or the increase in protein?
At 12 months in, both groups were at roughly the same calories and had lost roughly the same amount on their waist circumference.
The claims of muscle gains and superior fat loss should be ignored as they were measured using bioelectrical impedance, which is essentially useless.
How does this trial inform public policy? Well, the U.S. dietary guidelines have long warned against saturated fat and encouraged carbohydrate intake. Unfortunately weight loss is often oversimplified to carb and fat intake, even though protein could have a big impact. When forming public policy on weight loss, a focus on quality foods rather than micromanaging macronutrients would be a step in the right direction. Factors like sleep and stress might have a bigger impact on weight than any one nutritional factor.
Directing people to consume less than 40g of carbs is not feasible policy. Carb intake may go down, but will likely remain over 100 grams/day.
A low-carb diet improved cardiovascular disease predictors, but the study was not designed to isolate whether the cause was weight loss or macronutrient intake.Perhaps the biggest takeaway is that media headlines are not always informative, and it takes a thorough reading of the study and some methodological knowledge (much of the nitty gritty, which wasn't mentioned here) to understand what the paper really says.
A more accurate headline would have been: “If you are obese, decreasing carbs and upping protein may lead to greater weight loss, but sticking to any diet that has you eat less will lead to weight loss.”
Examine.com will soon start publishing a digest that analyses the latest nutritional studies and their context in the bigger picture. Be sure to sign up as an Examine.com Insider below to be notified when we publish our next analysis.