Wondering what fits into a keto diet — and what doesn’t? “It’s so important to know what foods you’ll be eating before you start, and how to incorporate more fats into your diet,” says Kristen Mancinelli, RD, author of The Ketogenic Diet: A Scientifically Proven Approach to Fast, Healthy Weight Loss, who is based in New York City. We asked her for some guidelines.
Just made these, without a silpat (I used parchment) and with a wonky cookie sheet (I desperately need a new one, and will have one before I make these again) but they were great! I really wanted chicken noodle soup, as I woke up this morning with a sore throat.. These are awesome!! Very little taste, not eggy at all, and my chicken soup really hit the spot! Thanks!
It was worth the try since so many of the recipes on this site are wonderful — but I’ll make a little real pasta for an occasional cheat day, or I’ll just add lots of sauteed mushrooms to the bolognese sauce and just have a bowl of sauce. If I try this again I’ll shape the dough into small gnocchi and serve with a butter- or cream-based sauce. That might work because I won’t be thinking “pasta.”
I have great respect for Harvard Medical School. I notice that they support their readers posting comments and I am most appreciative of the article and all the many thoughtful comments by the readers. The readers seem to have the most expertise here and I hope that the doctor who wrote the article will think long and hard about the comments by readers. After 35 years of clinical practice in mental health, I notice that all issues of emotion involve medical issues, nutrition, and the gut bacteria. I would say that these issues and all of the executive brain functions seem to improve with ketogenic principles. For those that apply it in a flexible and smart manner, it appears to improve every area of their lives. I strongly encourage the author of the article to take one class via The Institute for Functional Medicine. If he is open to more learning he can take more classes and get certified. I’m sure a fine doctor, he will be an even better doctor and personally healthier, if he gets more training. Are we all open to new learning(especially us healthcare providers)?
I’d heard recommendations of using only egg whites with psyllium, but whole eggs are more convenient. Besides, egg yolks are a natural leavener, so including them, makes the bread rise better in combination with the baking powder. Fortunately, whole eggs worked! It turns out that my friend, Lisa from Low Carb Yum, used whole eggs in her coconut flour psyllium husk bread, too.
A: The most common ways to track your carbs is through MyFitnessPal and their mobile app. You cannot track net carbs on the app, although you can track your total carb intake and your total fiber intake. To get your net carbs, just subtract your total fiber intake from your total carb intake. I have written an article on How to Track Carbs on MyFitnessPal.

Louise holds a Bachelors and Masters in Natural Sciences from Cambridge University (UK). She attended Columbia University for her JD and practiced law at Debevoise & Plimpton before co-founding Louise's Foods, Paleo Living Magazine, Nourishing Brands, & CoBionic. Louise has considerable research experience but enjoys creating products and articles that help move people just a little bit closer toward a healthy life they love. You can find her on Facebook or LinkedIn.


Nutritional ketosis has been proposed as a mechanism through which hunger may be suppressed. A recent meta-analysis investigated the impact of diet on appetite and shed some light on this possible phenomenon (11). The meta-analysis included 12 studies which investigated the effect of either a very low energy diet (VLED: defined as <800 calories per day) or ketogenic low-carbohydrate diet (KLCD: defined as CHO consumption of <10% of energy or <50 g/day, but ad libitum consumption of total energy, protein and fat). Interventions ranged from 4 – 12 weeks and weight loss was from 5.0 to 12.5 kg. In all studies nutritional ketosis was confirmed in VLED and KLCD via circulating levels of β-hydroxybutyrate. Interestingly, both groups reported decreases in appetite. The results of this meta-analysis are noteworthy in two regards. The VLED groups were clearly and significantly hypocaloric, suggesting a state in which hunger should be increased, not decreased. Similarly, the KLCD groups experienced simultaneous reductions in weight and appetite, while eating an ad libitum diet. The results of this meta-analysis provide support for the theory that nutritional ketosis may exert an appetite suppressing effect.


Maintaining a state of ketosis is as simple as following the same dietary parameters that got the body into that state in the first place. If you limit carbohydrates and sugars in your diet, your body will opt to burn the healthy fats you consume for energy. However, when cutting carbs from your diet it is very important to focus on limiting net carbs, which is simply the number of grams of total carbohydrates in a portion of food minus the grams of fiber. Constipation is a very common issue for new adherents to the ketogenic diet, and it is caused by foregoing fiber in an attempt to limit total carbohydrates. So to prevent constipation from derailing your ketogenic diet, simply make sure you consume adequate levels of fiber!
The American Heart Association recommends eating six to eight servings of grains every day, which is a lot of carbohydrates. But whole grains also contain a lot of fiber, which is the basis for the recommendation. Fiber is bulky and slow to digest, so you feel full longer after a high-fiber meal. Fiber also aids in healthy elimination, which can keep you feeling – and looking – less bloated and sluggish. People who eat a high-fiber diet are at a lower risk for heart disease, strokes and certain types of cancers because fiber helps you avoid the insulin spikes that occur when you eat starchy carbs. Fiber also helps control your cholesterol levels.
Since going low-carb a few years ago, I simply let go of breakfast cereals as they were always a slippery slope for me. No big deal, I found other lovely foods to enjoy. With that said, I kept seeing this recipe in my line of (scrolling) vision and I thought, okay .. time to partake as the reviews were too good to ignore. So I went about my merry way and followed everything exactly and then realized when I already had the mixture patted into a pan, I forgot the sweetener LOL. Screw it, baked it anyway and topped with the sweetener/cinnamon mixture (I used xylitol) and honestly, this was perfect. If I had used the sweetener in the mixture, it may have been too sweet for me. At the same time, I am reading the comments about the importance of the proper sweetener IN the mixture but I despise Swerve (too heavy cooling reaction for me) and wouldn’t have used it anyway but I found a roundabout fix that did work for me. About 1/2 and 1/2 chunky texture to crumbs but those crumbs can be sprinkled on yoghurt or even as pie crust, as suggested above. I’ll definitely put this in the ‘keeper’ folder (along with the Zucchini Tart that is simply divine!). Thanks, Carolyn!!
I actually went on a ketogenic diet last year to see if it would help my migraines. I have a history of chronic migraines which would usually last 3 days, sometimes longer. Triptans help a lot but I don’t like having to take them. I stayed in ketosis for about 8 months and experienced a significant reduction in migraines, from feeling some type of headache (mild o r severe) almost everyday to 1 or 2x per month while in ketosis. Although I’m very healthy otherwise, I do think my migraines may have something to do with blood sugar fluctuations (despite previously eating a whole foods diet and no refined carbs), and keto totally stabilized this. I eventually came off of Keto because I’m not really a meat lover. When I came off, but remained low carb, my migraines stayed under control for the most part. When I increase carbs, they do return.
The KD stands in stark contrast to current macronutrient recommendations for both health promotion, as well as enhancement of athletic performance (7,21). The KD is characterized by a macronutrient distribution ratio consisting of approximately 70 – 80% fat, 10 – 20% protein and <5% carbohydrate (CHO), with daily CHO intake limited to ≤50 grams. Two of the most prominent and vocal researchers of the KD, Jeff Volek, PhD and Stephen Phinney, MD, PhD, in their book The Art and Science of Low Carbohydrate Performance, recommend protein consumption of 0.6 – 1.0 grams per lb of lean body mass, a figure which almost perfectly matches the commonly recommended protein intake for athletes (i.e., 1.2 – 2.0 g/kg bodyweight) (21,26). With CHO intake radically restricted and protein within the commonly recommended range, fat becomes the primary macronutrient target for manipulation.

While everyone needs to eat carbohydrates, some people need more carbs than others. People who are very active need to eat more carbs than people who are sedentary. Those with diabetes also usually need to limit the amount of carbohydrates they consume during each meal to help keep their blood sugar levels in check. Finally, people on low-carb diets such as the Atkins or South Beach diets may limit their carbohydrate intakes in an attempt to boost weight loss.
Creaming the butter properly with the sweeter is paramount here to build a nice structure for the cookies (think rise and crunch!). And creaming with sweetener, in case you haven’t done it before, takes a bit longer to incorporate than with good-old sugar. But don’t give up, and keep going until you’ve got the sweetener well incorporated into soft and fluffy butter.
Also, I wanted to let you know what a fabulous addition your recipes were to our Christmas. I made the orange spritz cookies which were well received by those with diabetes, my gluten free friends, and everyone! I made them Christmas Eve. Christmas morning, I made your apple coffee cake and it was fab along with eggs, sausage and fruit. Thank you so much!

Providing additional support Paoli et al. (17) examined the effect of a modified KD diet (~55% fat, 41% protein, and 4.5% CHO) on performance and body composition in gymnasts. In a crossover design, researchers compared independent 30-day dietary regimens consisting of “normal diet” (WD; 46.8% CHO, 38.5% fat, and 14.7% protein) and modified KD in nine elite male gymnasts. There were no significant changes from pre to post during either dietary intervention for measures of physical performance, indicating the absence of significant dietary CHO did not negatively impact physical ability. The post-KD measurements, however, saw a significant decrease in fat mass (pre: 5.3; post:


Low carb egg pasta is typically tasteless, with a similar consistency to regular flour. You will love it for its macro content, combining the protein from eggs with the fat from the cream cheese. Eggs are one of the most affordable, nutrient dense foods you can buy, with zero carbs, 7 grams of fat and 6 grams of protein[*]. Cream cheese is a keto-friendly dairy product, as long as you buy from a high quality source.
Hi Pete, We used American cheese because that’s what is on a Big Mac and we were making Big Mac Bites. Also, it’s a misconception that American cheese is not real cheese, it all depends on what you buy. The individually wrapped cheese sliced labeled “cheese product” aren’t real cheese but you can purchase American cheese from the deli counter which is real cheese. If you want to double-check just ask to see the label before purchasing. Boar’s Head makes a great REAL American cheese.
Hi Kathy, I would persevere with coconut flour. Many people say it doesn’t work like regular flour, and while that may be true, I have learned to work with it. I ensure I use enough eggs, enough sweetener and flavours or enough salt and spices to overpower the subtle coconut flour taste. I have a whole new category in my recipe finder just for coconut flour recipes. Wy not give may flourless berry sponge a try to begin with, I love it and my kids make it all the time, even as cupcakes too.
Sharon M. Nickols-Richardson, PhD, RD, , Mary Dean Coleman, PhD, RD, Joanne J. Volpe, Kathy W. Hosig, PhD, MPH, RD, “Perceived Hunger Is Lower and Weight Loss Is Greater in Overweight Premenopausal Women Consuming a Low-Carbohydrate/High-Protein vs High-Carbohydrate/Low-Fat Diet,” The Journal of Pediatrics: Vol 105, Issue 9: 1433–1437; September 2005. http://www.sciencedirect.com/science/article/pii/S000282230501151X.
Most people are used to how white flour works, but when they try to bake or cook with low-carb flour, they most likely will notice some differences. Depending on the source of the flour — and how many carbs, fat and protein calories it has — the flour may well react differently. For example, flour with high protein may clump easier; the flour also may brown or burn quicker than regular flour. This means cooks and bakers may have to experiment with the flour to learn how it works.

Here are a few of the most common side effects that I come across when people first start keto. Frequently the issues relate to dehydration or lack of micronutrients (vitamins) in the body. Make sure that you’re drinking enough water (close to a gallon a day) and eating foods with good sources of micronutrients. To read more on micronutrients, click here >
In 1921, Rollin Turner Woodyatt reviewed the research on diet and diabetes. He reported that three water-soluble compounds, β-hydroxybutyrate, acetoacetate, and acetone (known collectively as ketone bodies), were produced by the liver in otherwise healthy people when they were starved or if they consumed a very low-carbohydrate, high-fat diet.[10] Dr. Russell Morse Wilder, at the Mayo Clinic, built on this research and coined the term "ketogenic diet" to describe a diet that produced a high level of ketone bodies in the blood (ketonemia) through an excess of fat and lack of carbohydrate. Wilder hoped to obtain the benefits of fasting in a dietary therapy that could be maintained indefinitely. His trial on a few epilepsy patients in 1921 was the first use of the ketogenic diet as a treatment for epilepsy.[10]
Well, I am going to give this another try. I have great difficulty in eating greens , or drinking them, also I am not fond of fats, years and years of low fat diets have totally screwed my metabolism,and taste buds. I will read this page every day to keep my mind focused. Start tomorrow when I get up …… I work nights which can cause me problems as well. When I tried this diet before, I got terrible cramp, now I realise I wasn’t drinking enough water. Anyway.here goes.
Drink lots of water. This is especially crucial on a low carb or keto diet. Why? When you eat carbohydrates, your body stores the extra as glycogen in the liver, where they are bound to water molecules. Eating low carb depletes this glycogen, which allows you to burn fat – but it also means you are storing less water, making it easier to get dehydrated. Instead of the traditional recommendation of 8 cups of water per day, aim for 16 cups when following a low carb lifestyle.
I had to make a few changes though. First, what makes a donut taste like a donut is nutmeg. I added a few gratings and cut the cinnamon down to about half. Second, I live in South Korea and almond milk almost always contains sugar and is very expensive. I used heavy cream and then added a splash of water when the batter was very thick. Third, I don’t have erythritol, but I do have a stevia and erythritol blend so I used that.
Ketogenic cereals can be a bit of a challenge, so why not try out this blueberry one! It is crunchy and delicious and has all the slow release energy you will need to get through the morning. This makes a great after-school snack for kids and helps them get away from sugary snacks. If you like this one you could experiment with other flavors – for example, try cherry extract instead of blueberry!
Baking with coconut flour is a little tricky since it absorbs a lot of water. For every 1 cup of coconut flour, you'll need to add 1 cup of water and six eggs. Substitute 1/4 to 1/3 cups of coconut flour for every 1 cup of all-purpose flour. Another option is a blend of 3 parts almond flour to 1 part coconut flour. Coconut flour is a little higher-carb than nut or seed flours with 16 grams of carbohydrates per 1/4 cup.
I was worried. I read my ingredients and follow the instructions to the letter. I made the little bow ties. I put them in the freezer for 15 minutes and I fried them in garlic and olive oil. They were so good. I think they would definitely stand up to any sauce that you added to them (after they were fried) I can’t wait to try them as fried ravioli. I’m also going to stuff a few with ricotta and sauerkraut, fry them, dress them with sour cream, and call them a pierogi.
.. it can be heavy on red meat and other fatty, processed, and salty foods that are notoriously unhealthy. What is unhealthy about red meat. We should know that acrilamides, pyrroles in burnt meat (and veges) from BBQ and over-heated cooking inflames the colon. According to Clark H R, PhD ND an inflamed part allows easy entry for the cancer nucleus and cancer complex, to start and fuel a malignancy at that location.
Over the long-term the KD poses possible risks as well, although the evidence remains unclear on this topic. Consumption of a high fat diet, particularly saturated fat, is associated with increased cardiovascular risk (23) and consumption of saturated fat has been shown to acutely induce insulin resistance and raise blood triglyceride levels (12). Nevertheless, many KD studies have documented improvements in markers of cardiovascular risk, including improvements in vascular function (24) reduction in inflammatory markers (10), and other markers of cardiovascular health (13,20). Methodological issues, such as clear definitions of dietary interventions, may play a significant role in obscuring the underlying principles, however, it is clear that more targeted research is warranted.

Use fat as a lever.  We’ve been taught to fear fat, but don’t! Both keto and low carb are high fat diets. Fat is our source of energy as well as satiety. The key to understand, though, is that fat is a lever on a low carb or keto diet. Carbs and protein stay constant, and fat is the one you increase or decrease (push the lever up or down) to gain or lose weight, respectively. So if your goal is weight loss, eat enough fat to be satisfied, but there’s no need to “get your fats in” once you’re satisfied.
Organic Soy Flour. Soy flour is derived from ground soybeans. It is somewhat similar to coconut flour in that it is quite dry and easily absorbs ingredients. It also has more protein than the keto flours we mentioned above and is an excellent source of dietary fiber. By buying organic soy flour, you can avoid GMO soybeans and the pesticides that are commonly used on them.
The following measurements were made every other week: anthropometric and vital sign measurements; urine testing for ketones; and assessment for hypoglycemic episodes and other symptomatic side effects. Weight was measured on a standardized digital scale while the participant was wearing light clothes and shoes were removed. Skinfold thickness was measured at 4 sites – the average of 2 measurements at each site was entered into an equation to calculate percent body fat [12]. Waist circumference was measured at the midpoint between the inferior rib and the iliac crest using an inelastic tape; 2 measurements were averaged in the analysis. Blood pressure and heart rate were measured after the participant had been seated quietly without talking for 3 minutes. Certified laboratory technicians assessed urine ketones from a fresh specimen using the following semi-quantitative scale: none, trace (up to 0.9 mmol/L [5 mg/dL]), small (0.9–6.9 mmol/L [5–40 mg/dL]), moderate (6.9–13.8 mmol/L [40–80 mg/dL]), large80 (13.8–27.5 mmol/L [80–160 mg/dL]), large160 (>27.5 mmol/L [160 mg/dL]). Hypoglycemic episodes and symptomatic side effects were assessed by direct questioning of the participant and by self-administered questionnaires.

Place sheet pan in a preheated oven at 475°F and lower heat to 350°F. Bake for 5 to 8 minutes. Watch closely as you need to avoid overcooking. If small bubbles start to appear, lower heat to 300°F and continue baking for 2 to 3 minutes until all sides and center are done. (You can test for doneness just like testing a cake with a toothpick, if you wish).
Hi Kathy, Almond flour doesn’t rise very much, but if they didn’t at all, it might be that you need newer baking powder. Falling apart is also likely due to the baking time I had in the original recipe, and I’ve updated it for a better result. Check the post for new tips! Cookies sound like an interesting idea, too, though I think the batter might be too liquid to form them.
Congratulations on this recipe! It’s fantastic. I’ve tried a number of low carb bread recipes, not many of which I’ve bothered to make a second time. Made this one today and it came out beautifully, with a nice texture akin to that of wheat bread. The loaf isn’t very tall but it works and I will make it regularly. Grilled cheese sandwich, here I come!
Almond flour recipes typically require more eggs and more leavening agent to help them rise properly. I also like to add a little dry protein, like whey protein powder, as I find this can help [with rising?].  Almond flour recipes may also contain less oil and liquid as well, to account for the high fat content of the nuts. In my experience, low carb, gluten-free batters are thicker than their conventional counterparts. Resist the urge to thin them out, as you may end up with a soggy mess.
One downside to a ketogenic diet for weight loss is the difficulty maintaining it. “Studies show that weight loss results from being on a low-carb diet for more than 12 months tend to be the same as being on a normal, healthy diet,” says Mattinson. While you may be eating more satiating fats (like peanut butter, regular butter, or avocado), you’re also way more limited in what’s allowed on the diet, which can make everyday situations, like eating dinner with family or going out with friends, far more difficult. Because people often find it tough to sustain, it’s easy to rely on it as a short-term diet rather than a long-term lifestyle.

I made this bread several times now using ground flaxseed in place of the psyllium powder and it came out perfect every time. I decided to try it as a sweet bread and added 1/2 cup raisins, 1 Tbsp. cinnamon, 1/4 cup erythritol and 2 Tbsp. Splenda. After it was done I iced it with 1/2 cup powdered sugar mixed with enough milk (about 1 Tbsp. to keep it thick but a little runny. Now I have a healthy, delicious, loaf of cinnamon raisin bread. Thanks for the great recipe!
Shirataki noodles are available in many shapes -- spaghetti, fettucini, macaroni -- and can be purchased plain. Products like Miracle Noodle and NoOodle Noodles sell this type, which tends to be extra-slippery, nutritionally void (they are mostly made up of water) and close to calorie-free. Other brands, like House Foods and Nasoya's Pasta Zero blend the yam flour with tofu or chickpeas, which adds just a few calories and grams of carbohydrates and fiber.

Hwu believes risks of cardiovascular disease and diabetes — which are both associated with high blood pressure, glucose and cholesterol — may be reduced by following the ketogenic diet, based on research. A recent study from Johns Hopkins found a ketogenic diet was not only safe, but effective for adults who had certain severe forms of epilepsy, supporting previous research.

50 NET carbs is quite high because you are probably eating more like 70-100 total carbs. If you can cut down to 30 NET carbs you may see results. You really need to make sure you’ve upped your fat so you won’t be hungry. After writing this post I’m now actually counting TOTAL carbs instead of NET and sticking to just 30 total carbs a day which is what has helped the scale move. Also be sure to get other measurements for yourself besides the scale. You could be losing inches and fat like I did for the 6 week pics.
Some people on a keto or low carb diet choose to count total carbs instead of net carbs. This makes it more difficult to fit in more leafy greens and low carb vegetables (which are filled with fiber), so you should only try that if you don’t get results with a net carb method. And, start with reducing sugar alcohols and low carb treats before deciding to do a “total carbs” method.
BEST ANSWER: Yes, at Bob’s Red Mill, we have made a commitment to purchase only non-GMO grains. All of our products are made from ingredients that were grown from identity-preserved, non-GMO seed. You can read our Sourced Non-GMO Pledge here: http://www.bobsredmill.com/non-gmo For more information about our GMO policy, please call our customer service team: 1-800-349-2173.
Once I tried it, though, it quickly became a favorite throughout my childhood. But instead of breakfast, one of my favorite parts of the day was sitting down with a bowl of cereal in the afternoon – be it with my latest art project, in front of the TV, or even a homework assignment. I had the house to myself, and that “me time” between school and evening activities was this introvert’s bliss.
I really appreciate this article. I have done low Carb for the most part for over 15 years and was able to keep my weight down. Now that I have gone through menopause is just keeps getting harder. I try doing keto but tend to fall off the wagon a lot and go back to low Carb or Weight Watchers. Simple ideas would be great. I think some keto bloggers make it seem that you have to create difficult recipes. Thanks for all you do.
Measuring blood ketones is the most reliable method. There is a home blood test you can use, but the strips can be very expensive. An alternative is to measure ketones in the urine with a dipstick test, which is much more accessible and inexpensive. However, this method is much less reliable and as time goes on and the body adapts to ketosis, it becomes even less reliable.

I have been on a low carb keto diet for more than a year. As T2DM my A1C dropped from 9% to 5.4% & I discontinued meds. All my lipids improved even with ample healthy saturated fat. More than a year now so I wonder why this would be a short term improvement when its obvious that I will not go back to a high A1C and taking 3 diabetes medications including sulphonylureas. It is clear from this article that you lack the necessary experience that would be gained from wholeheartedly trying the diet or monitoring patients doing it properly like me. I would be probably be facing my first amputation if I believed the negativity in your article. So for people with diabetes who may be dissuaded by your article. Ignore it and take back your health by restricting carbs (<25 g a day) or as low as you reasonably can below 130g while being satisfied that you are getting adequate nutrition.


Hi Louise, I haven’t tried that product so can’t say for sure if it’s a good choice, but it sounds like it is if the recipe worked for you – which is great! Feel free to add herbs, spices, or garlic powder if you want some flavor to the bread. I kept it plain to be used for many different applications. The number of slices will depend on how thick you cut them and the size of your pan. 

The most common and relatively minor short-term side effects of ketogenic diet include a collection of symptoms like nausea, vomiting, headache, fatigue, dizziness, insomnia, difficulty in exercise tolerance, and constipation, sometimes referred to as keto flu. These symptoms resolve in a few days to few weeks. Ensuring adequate fluid and electrolyte intake can help counter some of these symptoms. Long-term adverse effects include hepatic steatosis, hypoproteinemia, kidney stones, and vitamin and mineral deficiencies.
Almond flour and almond meal are not the same thing. Almond meal is ground up almonds (with the skins) whereas almond flour is finely ground blanched almonds without the skins. Both work but the almond flour will give you better results (the almond meal tends to be a little dense and oily). Almond flour can be purchased online and almond meal can be found at health food stores.

Hi James, One of the best things about a low carb or keto diet is you probably won’t be hungry. It’s a very satiating lifestyle. As for calories, they still matter, but whether you need to count or not varies from person to person. Some people succeed by just eating low carb or keto foods, others need to be more strict and count. If you want to find out the right amounts for you, check the macro calculator.
Made in mini muffin pans, will have to oil them better next time so they come out easier. Taste great, although sadly more like a muffin than donut (the shape doesn’t help, lol). I may try to thicken it up to deep fry next time. Was out of cinnamon so I used pumpkin spice. Not so strict on low-carb and wanted the kiddos to like them, so offered cinnamon/sugar, powdered sugar, and toasted coconut for coating. I recommend the coconut! Browned in a dry skillet makes it nice and crunchy… just how to make it stick was the only drawback.

Purnell JQ, Hokanson JE, Marcovina SM, Steffes MW, Cleary PA, Brunzell JD. Effect of excessive weight gain with intensive therapy of type 1 diabetes on lipid levels and blood pressure: results from the DCCT. Diabetes Control and Complications Trial. JAMA. 1998;280:140–146. doi: 10.1001/jama.280.2.140. [PMC free article] [PubMed] [CrossRef] [Google Scholar] 
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