Healthy diets are known to reduce the risk of developing a host of chronic diseases, running the gamut from metabolic syndrome to cancer, and overall mortality (Esposito & Giugliano, 2005). Adherence to an anti-inflammatory diet like the Mediterranean, for example, is associated with a significant reduction of all-cause and cause-specific mortality (Mitrou et al., 2007). If there was a drug that was associated with a significant reduction of all-cause and cause-specific mortality, it would be worth billions, if not trillions. So, let’s consider the potent and medicinal quality of food. What makes it so special? And how can it impact your mood?
The answer has to do with inflammation.
Inflammation is the shared link among the leading causes of mortality (Aggarwal et al., 2006; Giugliano et al., 2006), and likely impacts behavior. There are three key players (also called cytokines) you need to know about.
High-fat diets induce insulin resistance and obesity via production of interleukin-1β (IL-1β) in multipotent stem cells (Cortez et al., 2013), interleukin-6 (IL-6) in fat (Matsubara et al., 2012) and tumor necrosis factor-alpha (TNF-α) in muscle, liver, and fat tissue (Borst & Conover, 2005).
IL-1β, IL-6, and TNF-α are all signaling cytokines produced by an activated immune system. All you need to know about cytokines is that they are secreted by certain immune cells and they have an effect on other body cells. They essentially keep the inflammatory processes going (Cameron & Kelvin, 2003); IL-6 and TNF-α are so powerful that they encourage breakdown of bone in vitro and in vivo (Yokota et al., 2014). Thus, it would be best to avoid letting cytokines hang around longer than they were designed to.
These immune-mediated cytokines likely influence personality traits, especially if diet-induced inflammation is habitual. Elevations in IL-6, TNF-α, and/or c-reactive protein (CRP, synthesized by the liver in response to general, non-specific inflammation), are more commonly found in hostile-prone individuals (Suarez et al., 2002; Coccaro, 2006; Ranjit et al., 2007; Brydon et al., 2010; Janicki-Deverts et al., 2010; Mwendwa et al., 2013). This means that if you are easily upset and angered, there might be a biological basis rooted in inflammation.
In a mouse model, administration of IL-1β elicits depression-like symptoms, noted by a decrease in positively motivated behaviors like exploration, social interaction, and in operant behaviors like food reward (Larson et al., 2002; Merali et al., 2013).
A Mediterranean diet, because of its anti-inflammatory nature, reduces IL-1β, IL-6, and TNF-α (Caughey et al., 1996; Chrysohoou et al., 2004), and is a therapeutic approach to decrease “sickness behaviors” like hostility/rage and/or depression-like symptoms.
However, inconsistent results have been reported, largely because of the dearth of research on diet-induced inflammatory cytokines that affect personality presentation. Additionally, human emotion is a complicated phenomenon, and is by no means completely dictated by what we eat.
It is possible that sample characteristics of a population—age, sex, and socioeconomic status—influence the association between hostility and the inflammation we see (Graham et al., 2006; Elovainio et al., 2011; Demarble et al., 2014). For example, individuals with hostile or aggressive behavior have enhanced cardiovascular reactivity to stress (Smith et al., 2004; Chida & Hamer, 2008), and this enhanced reactivity to stressful situations can contribute to higher concentrations of proinflammatory cytokines (Black & Garbutt, 2002).
Additionally, cytokines IL-1β, IL-6, and TNF-α are thought to activate the hypothalamic-pituitary-adrenal (HPA) axis, the central stress response system (Kunz-Ebrecht et al., 2003). With chronic activation of the stress response, people can become fatigued. Indeed, depression scores and CRP, IL-1β, and IL-6 are positively correlated (Howren et al., 2009).
Non-dietary stressors like marital discord also impacts the immune system, thereby influencing one’s emotional demeanor. Kiecolt-Glaser and colleagues (2005) found that couples who engaged in more hostile arguments had higher plasma concentrations of IL-6 and TNF-α following a conflict than couples who engaged in more non-reactive, supportive discussions. These authors suggest that more frequent and spiked increases in proinflammatory cytokines might accelerate a wide range of age-related illnesses. In other words, hostile relationships impact human physiology, setting the stage for disease later in life.
Three causal pathways are consistently shown:
- Inflammation impacts emotional state
- Emotional state impacts inflammation
- Bidirectional relationship between inflammation and emotional state
Three cytokines are thought to uniquely impact the following behavior:
- TNF-α → hostility
- IL-1β → depression
- IL-6 → anxiety
Anti-inflammatory diets, in combination with lessened reactivity to stress and supportive social interactions, likely reduce aggressive behaviors, depressive-like syndrome, and general anxiety.
- Diet is the single most influential determinant of human health and disease prevention.
- A central theme emerges: any diet that reduces inflammatory cytokines likely lessens aggressive or depressive-like behaviors.
- Age, sex, socioeconomic status, and marital conflict influence emotional states as well, but high-inflammatory diets have the potential to chronically activate the immune system, producing destructive cytokines that travel systemically.
Dr. Bhandari and the Advanced Health Team Are Here to Support Your Health
Dr. Bhandari and the Advanced Health team of experts work to help patients rid their body of inflammatory cytokines produced from the diet. They’re always ready to share their expertise on this commonly misunderstood disease. We collaborate closely together bringing the best in evidence-based Eastern and Western medicine. We believe that since each person is unique, their treatment plan should be personalized to them. To book an appointment, contact Advanced Health or call 1-415-506-9393.
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