- Probiotics, foods which contain live culture of certain bacteria, improve digestive health, help in weight loss and treat stomach cramping, diarrhea.
- When you take curd or cultured milk alongside a balanced meal, it may impair certain aspects of memory.
- Probiotics work best in balancing the gut bacteria after a diet high in fat and sugar.
Probiotics are much less effective when taken alongside a balanced diet, and could even impair certain aspects of memory.
Researchers from UNSW Medicine studied the impact of a commonly used probiotic on the gut health and cognitive function of rats, which were fed either a healthy diet or a "cafeteria diet" high in saturated fat and sugar.
‘By increasing microbial diversity in the gut, probiotics could combat behavioral changes and prevent memory impairment linked to high fat, high sugar diet.’
In fat rats with "grossly dysregulated" gut health, thanks to being fed junk food, probiotics positively changed the bacterial make-up in their digestive tract and befitted brain function, preventing spatial memory loss.
The probiotics had little impact on microbial diversity and actually impaired recognition memory. "If you're eating really badly then probiotics might be helpful. But if you're already eating healthily, they may not be that beneficial," says Professor Margaret Morris, Head of Pharmacology at UNSW.
"We were surprised to find that, in the rats we were feeding a healthy diet, the probiotics actually resulted in some memory impairment with regards to object recognition. Although this study is looking at rats, I think the main takeaway message is that we need to exercise caution when we recommend that people take probiotics."
Probiotics may offer a great opportunity to improve health so long as they are replacing the correct bacteria - the challenge is accurately determining which beneficial microbes are absent.
Gut Health May Alter Brain Activity
Western-style diets high in saturated fat and sugar have been consistently shown to have detrimental effects on the brain and cognitive function, and can "rapidly alter the composition and metabolic activity" of microbes in the gut, the researchers say.
Furthermore, there is an emerging body of literature that suggests gut bacteria can impact brain function. Professor Morris and PhD student Jess Beilharz investigated the effects of Western-style diets on brain function and gut bacteria. They suspected that by increasing microbial diversity in the gut, probiotics could combat behavioral changes and prevent memory impairment linked to poor diet.
Probiotics Restores Gut health after High Fat Diet
The researchers pre-exposed groups of rats to either a low or high dose of the probiotic medicine for two weeks before their diet was changed from healthy "chow" to cafeteria-style food (including cookies, cakes and meat pies). This diet change lasted for 25 days.
In addition to being fatter, Professor Morris says the cafeteria diet "dramatically altered the microbiota" resulting in rats with much less microbial diversity in their gut.
"It also affected the expression of certain genes in the brain that are involved in 'neuroplasticity', which may be associated with memory impairment," says Morris. "And it turned down gut conversion of things that are known to be really beneficial to the brain, such as flavones and flavonoids, which are found in leafy green vegetables."
But these rats also saw the greatest health benefits from the probiotics. They increased the abundance of certain bacteria-types contained in the probiotic such as Streptococcus and Lactobacillus and other bacteria-types such as Butyrivibrio, which were decreased by the cafeteria diet. Furthermore, memory impairment was prevented.
- Margaret Morris et al., Probiotics may not always be a silver bullet for better health, Molecular Psychiatry (2017).