I haven’t seen any new research on the biome and eating disorders recently (I first wrote about this topic in November of 2017, but have seen precious little since), so was very pleased to spot an article[i] yesterday on Gut Microbiota for Health which covers a paper just published by Australian researchers. The scientists reviewed 10 human studies on microbiota alterations in those with eating disorders, all of which agree that there are major bacterial differences between those affected and controls. And while there are differences in what various scientists found in terms of specifics, generally speaking all the papers agree that there is a loss of diversity in the biome, i.e. biome depletion is a factor.
Unfortunately, whether the biome alterations are the cause of the anorexia, or the result of food deprivation, are currently unknown.
Specifically, the authors of this paper note that there seems to be a general pattern found in those with anorexia: “…a depletion of Lactobacillus and butyrate-producing Roseburia. In contrast, the relative abundance of Bifidobacteria, Proteobacteria, Akkermansia muciniphila and archaeon Methanobrevibacter smithii increases.” This last species, one I am not at all familiar with, apparently is thought to optimize the body’s ability to extract calories from food.
A couple of other interesting points. The typical treatment for anorexia is restoration of normal weight with a high calorie via high fat diet. However, the researchers note that “…there is accumulating evidence suggesting the importance of balanced, high-fibre diets on the gut microbiome.” We know that fiber is a critical element in restoring a healthy bacterial microbiome. Thus, they call for combining the two diets (i.e. high calorie and high fiber) – although fiber should be introduced and increased slowly, as it tends to be filling – for optimal nutritional rehabilitation.
After all, they state, achieving a normal body weight with the current high fat approach does not seem to resolve the microbiota alterations.
“Future nutritional rehabilitation protocols in AN [anorexia nervosa] are encouraged to include higher and more diverse fibre content and prebiotic foods. This may provide benefits on intestinal microbes and their metabolites and prevent gastrointestinal sequelae, especially constipation. Similarly, studies to investigate the potential role of probiotic foods or supplementations as a part of nutritional rehabilitation procedures are needed in the future. For example, butyrate-producing bacteria, namely Roseburia spp, have been suggested as candidates for probiotic intervention studies in AN.”[ii]
I wrote about Roseburia last month, if you remember, and its potential importance in cardiovascular health, improving gut barrier integrity (i.e. leaky gut), treating inflammatory bowel disease, and type 2 diabetes. As a known producer of anti-inflammatory short chain fatty acids, it seems like it’s going to have wide application once it becomes commercially available as a probiotic. (Remember though: it may only have its beneficial effect combined with a diet high in plant based food, according to current research.)
By the way, in one of those coincidences I love so much, the same day that I found this article, I also spotted new research[iii] into the effects of a high fat diet on the gut microbiota. This was published in one of, if not THE, most eminent scientific journals in the field, Gut. 217 healthy, normal weight people in China were broken up into three dietary groups. Each cohort ate the same amounts of fiber and protein, but different ratios of carbs and fat: one group ate low fat (20% of calorie intake), one ate moderate fat (30% total calorie intake) and one ate high fat (40% of total calorie intake). (Please note: the main fat used was soybean oil, which is among the most used fats in the world.) The participants followed the diet for 6 months, while having their gut bacteria and inflammatory blood markers tested before the diet and after.
The total amount of gut bacteria remained the same in all 3 groups, but the low fat group had a significant increase in the amounts of beneficial, short chain fatty acid (anti-inflammatory) bacteria. A noticeable decrease in these bacteria were found in the high fat group, which also showed a significant increase in inflammatory bacteria such as are found in those with type 2 diabetes. The low fat group also had an increase in species like Blautia, which are associated with healthier cholesterol levels; conversely, higher levels of species associated with high (bad) cholesterol were found in the high fat group. Another important finding: the high fat diet group showed changes in long chain fatty acid metabolism, which led to higher levels of inflammatory chemicals in their bodies – and the opposite was found in the low fat diet group. They conclude that, “…compared with a lower-fat diet, long-term consumption of a higher-fat diet appears to be undesirable owing to changes in gut microbiota, faecal metabolomic profiles and proinflammatory factors for healthy young adults….”[iv]
Obviously a huge amount of research is needed in this area, considering that at least 30 million people suffer from eating disorders in the USA alone.[v] On the bright side, doesn’t it feel, more and more, that research is moving toward optimal diet combined with pro- and pre-biotics as treatment modalities of the future?
[iv] Wan Y, Wang F, Yuan J, et al.Effects of dietary fat on gut microbiota and faecal metabolites, and their relationship with cardiometabolic risk factors: a 6-month randomised controlled-feeding trial. Gut Published Online First: 19 February 2019. doi: 10.1136/gutjnl-2018-317609