What an article published in The Lancet said about nutritions role in psychiatry:
“the emerging and compelling evidence for nutrition as a crucial factor in the high prevalence and incidence of mental disorders suggests that diet is as important to psychiatry as it is to cardiology, endocrinology, and gastroenterology” (Sarris et al., 2015)
Major depression and anxiety in particular have been described as an impending global epidemic with up to one-third of all visits to primary care clinicians due to emotional disorders.
But why is this? What are we doing so wrong that is creating a global epidemic? It really upsets me when I think about these sorts of statistics – spending so much time among health professionals and those interested in nutrition, it is easy to forget that the majority of the population have little understanding of how their daily habits are effecting not only their current health, but their future health too.
Now there are obviously many reasons behind it but “the clear message is that in the midst of a looming global epidemic, we ignore nutrition at our peril” (Patrick & Ames, 2015)
“The very structure and function…of the brain is dependent upon amino acids, fats, vitamins and minerals and trace elements. The antioxidant defence system operates with the support of nutrient cofactors and phytochemicals and is of particular relevance to psychiatry. Similarly, the functioning of the immune system is of substantial importance to psychiatric disorders and profoundly influenced by diet and other lifestyle factors. Neuronal development and repair mechanisms…throughout life are also highly influenced by nutritional factors.”
Poor sleeping patterns has also been linked to depression.
The mismatch theory sums it up. This theory states that there is a discrepancy between our physiological and psychological requirements, as determined through millennia of adaptation to natural and social
environments, and the ability of the modern world to help fulfil those requirements.
Convincing data suggest that select nutrient-based supplements may be beneficial in the management of mental disorders. Examples of these include: omega-3 fatty acids, S-adenosyl methionine (SAMe), NAC, zinc, B vitamins and vitamin D.
Zinc is involved in cytokine modulation and hippocampal neurogenesis . Zinc deficiency has been linked to increased depressive symptoms, and evidence is emerging that zinc supplementation improves depressed mood, mainly as an adjunctive intervention with antidepressants.
B vitamins are needed for proper neuronal function, and a deficiency of folate has been reported in depressed populations, and in poor responders to antidepressants.
Vitamin D is a neurosteroid, with data suggesting that low maternal concentrations are implicated in schizophrenia risk, and deficiency is likewise linked to increased depressive symptoms.
I don’t recommend simply supplementing these nutrients are there are likely many others that may be of benefit and nutrients do not work in isolated ways. Ensuring a nutrient dense, diverse diet is the initial step that must be taken. A healthy digestive system that is able to efficiently digest and absorb the nutrients for the diet is also a pre-requisite for optimal cognitive function. Hence we must always take a systematic and personalised approach to each and every case.
Interestingly it may not only be our food choices but our cooking methods that are also contributing to our global health status. Baking, roasting, grilling, frying encourage the formation of advanced glycation end products (AGEs).
AGEs are highly oxidant compounds formed through the non-enzymatic reaction between reducing sugars and free amino acids. AGEs form in the body under normal metabolic circumstances; however, oxidative stress and inflammation are a well known consequence of AGE levels rising beyond normal limits.
The results of human studies have shown that a shift toward stewing, steaming, poaching and boiling of foods (lowering the AGE burden by approximately 50%) significantly reduces systemic inflammation and oxidative stress.
“Nutrition does not stand alone; it is intimately woven throughout social, cultural, economic, technological, behavioral and other (ancestral past vs present) environmental fabrics with which physiological anthropology concerns itself.”
A great way to cook, especially if you are a busy person with limited time to spend in the kitchen, is to use a slow cooker.
The Serotonin Pathway
“Multiple factors including micronutrient inadequacies, exercise, inflammation, and stress have all been shown to influence the serotonin pathway…and consequently, affect social behaviour.”
So it is clear our nutritional habits have a role to play in cognitive health and we need to ensure optimal micronutrient status.
But there are other factors downstream of nutrient intake that may have an impact on our cognitive health. Meaning, a nutrient dense diet doesn’t guarantee the body is able to utilise the nutrients to maintain/improve optimal health.
Many of you will have heard of serotonin – often mentioned as the neurotransmitter that helps regulate our mood and now widely understood to be largely found in the digestive system and to have a role in gut motility.
“Cognitive functioning involves billions of neurons working with numerous biochemical pathways and associated enzymes. Many of these enzymes require micronutrients, essential vitamins, and minerals as cofactors for optimal function. Thus, one expects that suboptimal function caused by micronutrient inadequacies could adversely affect the functions of proteins and enzymes involved in brain function.”
See my article on the gut-brain axis for more information on serotonin and how stress and inflammation can impact on its production.
Tryptophan, an amino acid we obtain from our diet, is transported across the blood-brain barrier where, in the presence of sufficient levels of vitamin D, it is converted to serotonin. Vitamin D is a key regulator of brain serotonin synthesis as it increases the expression of the serotonin producing gene, tryptophan hydroxylase 2 (TPH2).
The omega-3 fatty acid EPA increases serotonin release from presynaptic neurons by reducing E2 series prostaglandins and DHA influences serotonin action by increasing membrane fluidity and thus serotonin receptor accessibility in postsynaptic neurons.
Suboptimal intake of these micronutrients contribute to dysfunction of the serotonin pathway, and, in combination with genetic factors, exacerbate dysfunction in the serotonin system, resulting in defects in executive function, impulse control, sensory gating, and prosocial behaviour, and precipitate neuropsychiatric disorders
Other micronutrients that affect the serotonin pathway also appear relevant, such as vitamin B6 and iron.
BH4 can be depleted in chronic states of oxidative stress and inflammation.
“It is likely that relatively small dietary inadequacies in several micronutrients can precipitate a cumulative detrimental effect on the nervous system, thereby compromising cognitive function and behaviour”
Stress & Inflammation
Stress and inflammation activate the enzymes IDO and TDO, which metabolise tryptophan to kynurenine and thus shunt tryptophan away from being transported into the brain. As mentioned, to produce serotonin in the brain, tryptophan must first be transported across the blood-brain barrier and thus stress or/and inflammation can effect cognitive health and function via their effects on tryptophan.
The transport of tryptophan across the blood-bran barrier depends on the ratio of tryptophan to other amino acids called branch chain amino acids, which strongly outcompete tryptophan for transport across the blood-brain barrier.
An influential 2004 study reported that gene expression of a primary nerve growth factor, brain derived neurotrophic factor (BDNF), was lower in the hippocampus and the cortex of germ-free (GF) animals compared with conventionally- raised specific pathogen-free animals.
BDNF plays a critical role in the plasticity of nerves throughout life
This study demonstrates the importance of the gut in cognitive health. Check out my article on the gut-brain axis to understand this concept more.
Logan et al., (2016) published an article in Clinical Psychopharmacology and Neuroscience stating: “Since the western diet is relatively devoid of deeply- colored fruits, vegetables and other plant-derived culinary items (e.g., turmeric, ginger, seaweeds, purslane, wasabi, Brassica-family sprouts, and regional spices) this represents a loss of complex phytochemicals that would otherwise make their way into the gastrointestinal tract. These phytochemicals play crucial roles in support of the antioxidant defense system, and in their ability to reduce the low-grade inflammation. In experimental studies, dietary phytochemicals from turmeric, apples, grapes, plums, blueberries and cherries (to cite only a few examples) can improve behavioral aspects of stress, anxiety and depression. It is interesting to note that dietary items such as green tea, coffee, cocoa, curcumin, and other polyhenol-rich foods associated with fatigue reduction, positive mood and lowered risk of depression in humans can also influence the growth of beneficial bacteria, and/or prevent dysbiosis in pre-clinical settings. The transformation and structural alteration of many dietary phytochemicals by intestinal microbes may determine the extent of their benefits in the brain. Remarkably, it also appears that microbially-transformed phytochemicals (e.g., quercetin after it has been subjected to fermentation) can modify the gut microbiota in ways that are considered healthy (i.e., growth of bifidobacteria and decrease in the ratio of Firmicutes to Bacteroidetes.”
Remarkably, honey flavonoids have been shown to show significantly inhibit the release of pro-inflammatory cytokines such as tumor necrosis factor alpha and interleukin-1 beta from microglia when they are stimulated by LPS. It is no less noteworthy that honey and its constituents appear to have a beneficial influence on intestinal microbiota.
Patrick and Ames, (2015) Vitamin D and the omega-3 fatty acids control serotonin synthesis and action, part 2: relevance for ADHD, bipolar, schizophrenia, and impulsive behaviour, FASEB
Sarris et al., (2015) Nutritional medicine as mainstream in psychiatry, Lancet Psychiatry; 2: 271–74
Logan and Jacka, Journal of Physiological Anthropology 2014, 33:22