For years, you probably have been told that wheat bread is far better for you than its white counterpart, but a small, new study suggests that maxim may not hold true for everyone. 
 
 Researchers looked at how quickly blood sugar levels rose after eating (a process called the glycemic response) either white bread or sourdough-leavened wheat bread. The researchers found that the response seemed to vary by person, and that some people didn't have a bad glycemic response to white bread. 
 
 "Our study suggests that, in terms of glycemic responses, different people respond differently to even the same meal," explained study author Eran Segal, from the Weitzman Institute of Science in Rehovot, Israel. 
 
 "In the context of white bread, this means that some people respond badly to white bread and should probably avoid it, while others have a healthy response to it, given what we measured," Segal said. 
 
 "In a broader sense, what this means is that the 'one-size-fits-all' diets that are given to the population as a whole, without personalization, are probably not optimal for everyone," added study co-author Dr. Eran Elinav, who's also from the Weitzman Institute. 
 
 The researchers theorized that differences in the gut microbiome (the natural bacteria living in a person's intestine) may explain why people respond differently to different breads. The researchers added that they were able to predict what a person's glycemic response would be to a particular bread based on the makeup of their microbiome. 
 
 Both Segal and Elinav did report they are paid consultants for a company that offers personalized dietary advice based on an individual's gut microbiome. 
 
 At least one nutritionist wasn't convinced that people should give up on whole grains. 
 
 "This small, short-term study does not offer a free pass to eating tons of highly processed white bread," said Samantha Heller, a senior clinical nutritionist from New York University Langone Medical Center. 
 
 "Epidemiological research has shown that people who eat more whole grains, such as whole grain breads, crackers, cereals, brown rice and quinoa, have a reduced risk of type 2 diabetes, heart disease, inflammation, obesity and certain cancers," Heller noted. 
 
 In addition, she said, whole grains have a balance of vitamins, minerals and other nutrients that white bread doesn't. Plus, Heller said, fiber is the "preferred meal for gut microbiota." 
 
 The study included 20 people from Israel. They were between 27 and 66 years old. Eleven were female, the researchers said. 
 
 Each volunteer spent a week eating white bread and a separate week eating artisanal sourdough-leavened whole wheat bread. 
 
 They ate bread first thing in the morning. Half the time, they were allowed butter on their bread. They couldn't eat anything else beginning the night before, and then for two hours after eating the bread. They also weren't allowed to exercise for two hours after eating, because all of these things can alter the glycemic response. 
 
 Across the groups, the researchers found a similar response to the breads when averaged together. There were no significant overall differences based solely on the bread and glycemic response. The researchers also said there didn't seem to be a difference in the gut microbiota based on which bread was eaten. 
 
 "Our study challenges the common belief that types of food that are considered healthy are indeed healthy. We know that people are different in their genetic makeup and lifestyle, and here we show that people have rather stable and person-specific microbiomes," said Avraham Levy, one of the study's researchers. He's also from the Weitzman Institute. 
 
 "These differences between people affect how they respond to even the same meals, which means that foods which are considered healthy may not be as healthy for everyone, and vice versa," Levy said. 
 
 The scientists noted that more research needs to be done. Funding for the study came from the Israeli Ministry of Science, Technology and Space, as well as from private foundations and donors. 
 
 In the meantime, a number of groups recommend eating whole grain foods instead of processed white foods. These groups include the U.S. federal government, the American Heart Association, the American Cancer Society, the American Diabetes Association and the Academy of Nutrition and Dietetics. 
 
 The study was published June 6 in the journal Cell Metabolism. 

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 Is white bread better for you than brown sourdough?​ It depends on your gut 
 
 What’s the background? 
 
 Bread makes up about 10% of the daily calories consumed by adults. Now a study by researchers at the Weizmann Institute of Science in Israel has delved into whether fresh wholegrain sourdough is better for you than industrially produced white bread containing refined wheat flour as well as preservatives and emulsifiers. 
 
 The team were looking at the impact of eating the different types of bread on bacteria and other gut flora (collectively known as the “microbiome”) and various clinical measures, such as levels of cholesterol, blood sugar and minerals. 
 
 What did the study involve? 
 
 Twenty participants had their gut microbiomes analysed and blood tests taken before they were randomly assigned to one of two regimes. One group of 10 were given specially prepared wholegrain sourdough for a week, while the other group were asked to eat industrially produced white bread. After a two-week break, the groups switched their bread type. During the study, the participants increased their consumption of bread, so that on average it accounted for 22% of their daily calorie intake. Participants did not eat wheat from any other source. 
 
 I love sliced white bread. It’s the best thing since … er, sliced white bread Read more 
 
 Let me guess, sourdough was better for you? 
 
 In a word, no. “The really shocking result was that on everything that we looked at, we didn’t find any difference between the effects of the two breads,” said Eran Segal, a co-author of the research. In addition, the participants’ gut microbiomes appeared unchanged by munching on different types of bread. 
 
 So it doesn’t matter which bread I eat? 
 
 Not quite. When the team looked closer at the results, they found that there were considerable differences between participants’ responses to the different breads – meaning that when the results were pooled together, on average no differences were seen. “We found that half of the people had a higher blood glucose response to white bread, the other half had a higher blood glucose response to the sourdough bread,” said Segal. The team were also able to predict, based on the makeup of the participants’ microbiomes, to which bread they would have the stronger response. “White bread might not be bad for you. In fact, for some people it might be better than sourdough bread. In other words it is really personal,” said Segal. 
 
 Are there any drawbacks to the study? 
 
 While all 20 participants ate both types of bread, it is still a small number of individuals and each type of bread was only eaten for a week – it might be that longer is needed to see differences. “Also [the study] doesn’t clearly describe the rest of the diet ... what other vegetables and things people might be eating, which might have an effect,” said Duane Mellor, a dietitian and spokesperson for the British Dietetic Association, who added that different types of sourdough, and ways of making the bread, could lead to different results. 
 
 Is your gut making you sick? Read more 
 
 That said, when the researchers looked at the impact of the increased bread consumption, regardless of type, they saw noticeable changes over a host of measures, from the levels of “bad” cholesterol to levels of various enzymes. “Adding a significant amount of bread to your diet basically even for one week is already going to impact your blood parameters,” said Segal. However, it might have been that participants changed other areas of their diet while taking part in the study, and there was no control group of individuals who did not change their bread consumption. 
 
 What’s the upshot of this? 
 
 Primarily, the study highlights that individuals can differ considerably in their response to the same food, in this case bread. “The reason is due to the individual differences in our gut microbes and this is important,” said Tim Spector, professor of genetic epidemiology at King’s College London and author of The Diet Myth. “While glucose spikes are controversial as to whether they matter in most people, [the study] shows us that our healthy metabolism is best controlled by looking inside our guts and not at the food label.” 
 
 The findings tie in to other work from the same team at the Weizmann Institute of Science that has suggested that personalised diets, tailored to individuals’ gut microbes could offer health benefits. 
 
 “If you are of the type that responds in terms of [blood glucose levels] much more strongly to the sourdough bread then maybe you might want to consider getting these other fibres and mineral and nutrients not from sourdough bread but by other means,” said Segal.
– Is it better to eat whole-grain sourdough bread made traditionally, or a slice of industrially mass-produced white bread? The answer arrived at by a recent study might surprise you: Researchers looked at major metabolic markers, with most of them related to the risk of type 2 diabetes, and found no significant differences between people who ate the artisan sourdough and people who ate the factory-manufactured white bread, New Scientist reports. "The really shocking result was that on everything that we looked at, we didn’t find any difference between the effects of the two breads," a co-author says, per the Guardian. The white bread studied contained refined wheat flour, preservatives, and emulsifiers. Whether sourdough (which was fresh) or white (which was packaged), participants ate more bread (25% of their total calories compared to a normal 10%) than usual, per a press release. The study looked at the gut microbiomes plus clinical measures including cholesterol, blood sugar, fat, and mineral levels in 20 participants prior to its start. The subjects were then randomly assigned to either eat the sourdough or the white bread for one week, then take a two-week break and switch breads. Participants' gut microbiomes did not appear to be changed based on the bread they ate and researchers found no measurable differences when looking at most markers, but they did find that while half the group had a higher blood glucose response to the white bread, the other half had a higher response to the sourdough. Based on subjects' microbiomes, researchers could actually predict which half a participant would fall under. "The 'one-size-fits-all' diets that are given to the population as a whole, without personalization, are probably not optimal for everyone," a co-author says, per CBS. (This trick may help you eat more veggies.)