Just last week the NHS reported a study stating that there was insufficient evidence that probiotics were beneficial for healthy people. The trials analysed so far had not been well enough designed to be sure.
“Given the limitations of the studies – including the variety of probiotics examined – it is not possible to conclude with certainty that all probiotics are ineffective.
Absence of good-quality evidence is not evidence of there being no effect. Better-designed studies may yet find some benefit from taking probiotics.”
However, there is certainly some good evidence that particular probiotics do have a beneficial effect on depression, particularly where that depression is associated with cellular inflammation. Inflammation is the body’s immune response to illness or injury; the swelling around a cut or a bruise is part of this process. But inflammation also happens within and around the cell in response to other non-injury factors such as poor diet, prolonged stress or an imbalance of bacteria in the gut. Inflammatory diseases such as rheumatoid arthritis and inflammatory bowel disease are commonly associated with psychological and behavioural changes such as lack of energy or interest, loss of appetite, loss of appetite; and depression. This consistent relationship between inflammation and depression has led to the inflammation theory of depression; that is to say that for some sufferers inflammation may be contributing to the severity of their depressive symptoms.
A well-designed study of petrochemical workers published in 2015 showed that probiotic yogurt and supplements significantly improved scores of depression and anxiety. I have reported elsewhere that probiotics have been shown to alleviate the negative thoughts associated with low mood. A more recent controlled study showed that eight weeks of probiotic supplementation was associated with a significant reduction on depression scores in patients with a diagnosis of Major Depressive Disorder. It is thought that part of the mechanism underlying this effect are the by-products of the bacteria’s metabolism. When breaking down food in the gut (particularly fibre) gut bacteria produce a number of metabolites, many of them beneficial to the human body such as vitamin K and some B vitamins. They also produce short-chain fatty acids. One of these, butyric acid, in a potent anti-inflammatory. It also forms part of a neurotransmitter called GABA, which has a calming, tranquilizing effect on the brain.
There are a lot of probiotic products on the market and it can be difficult to know which is likely to be the most effective. There is very good research data supporting the anti-inflammatory properties of a highly concentrated probiotic supplement called VSL#3 in a number of different diseases. Whilst not necessarily a recommendation, this is the product that I use as well as ensuring regular consumption of fermented and high fibre foods.
Mohammadi, A. A., Jazayeri, S., Khosravi-Darani, K., Mohammadpour, N., Asemi, Z., Adab, Z., Djalali, M., Tehrai-Doost, M., Hosseini, M. & Eghtesadi, S. (2015). The effects of probiotics on mental health and hypothalamic–pituitary–adrenal axis: A randomized, double-blind, placebo-controlled trial in petrochemical workers. Nutritional Neuroscience. Published online April 16th.
Laura Steenbergen, Roberta Sellaro, Saskia van Hemert, Jos A. Bosch, and Lorenza S. Colzato. 2015. A randomized controlled trial to test the effect of multispecies probiotics on cognitive reactivity to sad mood. Brain, Behavior, and Immunity, 48, 258-264.
Akkasheh, G., Kashani-Poor, Z., Tajabadi-Ebrahimi, M., Jafari, P., Akbari, H., Taghizadeh, M., Memarzadeh, M. R., Asemi, Z., & Esmaillzadeh, A. (2016). Clinical and metabolic response to probiotic administration in patients with major depressive disorder: A randomized, double-blind, placebo-controlled trial. Nutrition, 32, 315-20.
D'Mello, C., Ronaghan, N., Zaheer, R., Dicay, M., Le, T., MacNaughton, W. K., Surrette, M. G. & Swain, M. G. (2015) Probiotics Improve Inflammation-Associated Sickness Behavior by Altering Communication between the Peripheral Immune System and the Brain. Journal of Neuroscience, 35, 10821-18030.
Mariman, R., Tielen, F., Koning, F. & Nagelkerken, L. (2014). The probiotic mixture VSL#3 dampens LPS-induced chemokine expression in human dendritic cells by inhibition of STAT-1 phosphorylation. PLoS One, 9: e11567.
This information is provided for information purposes only and should not be taken as advice or instruction. This information does not replace the advice of your doctor. Please consult an appropriate health professional if you believe you are experiencing a mental or physical health concern. Speak to your GP or a trainer before making any significant changes to your exercise routine.