Originally published April 22 2015
MSM claims new study shows dietary fat leads to depression - here's what they aren't telling you about their flawed conclusion
by David Gutierrez, staff writer
(NaturalNews) In response to a recent study in Biological Psychiatry, news media have been making claims like "diets high in fat can lead to... depression and behavior changes."
These claims are inaccurate for two reasons: 1) not all fats are the same, and 2) the researchers found no such thing.
The study, by researchers from Louisiana State University, was actually designed to examine how mood might be affected by the composition of the gut microbiome -- the trillions of microorganisms that naturally inhabit the gut and play a role in metabolic, immune and cognitive processes.
Antibiotic-based experimentThe researchers fed mice one of two diets: normal rat chow (13 percent of calories from fat), or a high-fat diet (60 percent of calories from fat). After 10 weeks, the mice were killed, and their microbiota harvested.
Meanwhile, the scientists had placed another group of mice on a cocktail of five separate antibiotics in order to kill off their microbiomes. These mice were then implanted with the harvested microbiota of either the "rat chow" or "high-fat" groups of euthanized mice.
The researchers found that mice who received microbiota transplants from the "high-fat" group were more prone to anxiety, repetitive behaviors and impaired memory. They also showed increased intestinal permeability and increased inflammation, including in the brain.
"This paper suggests that high-fat diets impair brain health, in part, by disrupting the symbiotic relationship between humans and the microorganisms that occupy our gastrointestinal tracks," wrote Biological Psychiatry editor John Krystal in an accompanying commentary.
But is that really what the results show?
The researchers actually acknowledge the possibility that the antibiotics used did not actually remove the original microbiome, and that the results were consequently invalid.
"[T]here are limitations of the antibiotic-based model that could have affected the outcome," they wrote.
Which fats are being studied?A more fundamental problem is that the comparison between "rat chow" and "high-fat" is not a single-variable comparison. The rat chow's ingredients were dehulled soybean meal, ground corn, dried beet pulp, fish meal, ground oats, dehydrated alfalfa meal, cane molasses, brewer's dried yeast, wheat germ, whey, porcine animal fat preserved with BHA and citric acid, wheat middlings, porcine meat and bone meal, plus vitamins and minerals. In contrast, the "high-fat" diet contained casein, L-cystine, corn starch, maltodextrin 10, sucrose, cellulose, soybean oil, lard and FD&C red dye #40, plus vitamins and minerals.
The diets contained essentially none of the same ingredients, including fat sources. Notably, the
high-fat diet also contained red #40, which has been linked with behavioral changes.
The producers of the high-fat diet actually warn against comparing the diet with normal rat chow: "We recommend that you use a matched, purified ingredient diet and not a grain-based 'chow' diet," the product literature reads. "There are many, many differences between purified diets and chow diets and these variables make it difficult to interpret your data from a study in which one group was fed a purified ingredient high-fat and the other a low-fat chow diet."
It is also questionable whether a diet that is 60 percent fat has much relevance to real-world nutrition.
Finally, the researchers note a paradox in their findings.
"[R]eports have shown that high-fat diet consumption can allay anxiety and depressive-like behaviors in mice subjected to chronic social stress," they wrote.
This paradox may be partially explained by the fact that not all fats are the same. Indeed, monounsaturated fats (like those found in nuts and olive oil) and omega-3 polyunsaturated fats have been linked to improved metabolic and heart health, while omega-3s and saturated fats have also been linked with improved brain health and mood. The fats to avoid? Trans fats, which increase the risk of heart disease and death, and which the body cannot even metabolize for energy.
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