The good news is that coffee consumption seems safe. The study published last week in the BMJ indicates a reduction in the risk of various health outcomes at three to four cups a day. These results don't necessarily mean that coffee consumption is causal; i.e. in itself responsible for the reduction. Coffee drinkers may be different to non-coffee drinkers and this rather than the coffee per se may be the reason for the reduction in risk. The evidence suggests that coffee could be tested as an intervention without significant risk of causing harm in the disease studied. This analysis did not cover MS. Maybe MS is too uncommon to have been noticed by this research group?
However, a Swedish study has looked at coffee consumption and MS risk. If you are a coffee drinker it appears you reduce your risks of getting MS by ~30% compared to non-coffee drinkers. Again is this simply an association or causation? Is there something that coffee-drinkers do those non-coffee drinkers don't that protects them from getting MS (association)? Or, do the genetic factors that increase your risk of getting MS simply increase your affinity for coffee, and your chances of becoming addicted to coffee (association)? Or is there something in coffee that alters the immune system and reduces your risk of getting MS (causation)? If the observation is causal what is it in coffee that reduces your chances of getting MS? Could it be caffeine? If it is caffeine then other caffeinated drinks should also reduce your risks of getting MS; e.g. tea, energy drinks, cola, etc. Apart from being a stimulant, we know that caffeine has many biological effects including immunological and neuroprotective effects.
Coffee not only reduces your chances of getting MS but is protective for Parkinson's and Alzheimer's disease as well. The latter observations alone make it worthwhile taking up the habit. Which is the reason I give for my habit of drinking 6-8 espresso shots per day. Did you know that on a global level caffeine is the most prevalent human addiction? Could coffee be another lifestyle factor to take into account when optimising your brain health?
There are downsides to caffeine if you have MS. Too much can make anxiety worse and could exacerbate tremor. If you take too much caffeine, particularly late in the day, it can cause insomnia. This is why I have my last coffee no later than ~3pm. Caffeine is also a mild diuretic and causes increased urine production (see paper 3 below). This may exacerbate bladder problems. I have many patients who report that just one coffee affects their bladder function (urinary urgency and frequency).
How much coffee do you have? Does it help you?
Coffee and general health:
Poole et al. Coffee consumption and health: umbrella review of meta-analyses of multiple health outcomes. BMJ 2017;359:j5024.
Objectives: To evaluate the existing evidence for associations between coffee consumption and multiple health outcomes.
Design: Umbrella review of the evidence across meta-analyses of observational and interventional studies of coffee consumption and any health outcome.
Data sources: PubMed, Embase, CINAHL, Cochrane Database of Systematic Reviews, and screening of references.
Eligibility criteria for selecting studies: Meta-analyses of both observational and interventional studies that examined the associations between coffee consumption and any health outcome in any adult population in all countries and all settings. Studies of genetic polymorphisms for coffee metabolism were excluded.
Results: The umbrella review identified 201 meta-analyses of observational research with 67 unique health outcomes and 17 meta-analyses of interventional research with nine unique outcomes. Coffee consumption was more often associated with benefit than harm for a range of health outcomes across exposures including high versus low, any versus none, and one extra cup a day. There was evidence of a non-linear association between consumption and some outcomes, with summary estimates indicating largest relative risk reduction at intakes of three to four cups a day versus none, including all cause mortality (relative risk 0.83, 95% confidence interval 0.83 to 0.88), cardiovascular mortality (0.81, 0.72 to 0.90), and cardiovascular disease (0.85, 0.80 to 0.90). High versus low consumption was associated with an 18% lower risk of incident cancer (0.82, 0.74 to 0.89). Consumption was also associated with a lower risk of several specific cancers and neurological, metabolic, and liver conditions. Harmful associations were largely nullified by adequate adjustment for smoking, except in pregnancy, where high versus low/no consumption was associated with low birth weight (odds ratio 1.31, 95% confidence interval 1.03 to 1.67), preterm birth in the first (1.22, 1.00 to 1.49) and second (1.12, 1.02 to 1.22) trimester, and pregnancy loss (1.46, 1.06 to 1.99). There was also an association between coffee drinking and risk of fracture in women but not in men.
Conclusion: Coffee consumption seems generally safe within usual levels of intake, with summary estimates indicating largest risk reduction for various health outcomes at three to four cups a day, and more likely to benefit health than harm. Robust randomised controlled trials are needed to understand whether the observed associations are causal. Importantly, outside of pregnancy, existing evidence suggests that coffee could be tested as an intervention without significant risk of causing harm. Women at increased risk of fracture should possibly be excluded.
Coffee and MS Risk:
Hedström et al. High consumption of coffee is associated with decreased multiple sclerosis risk; results from two independent studies. J Neurol Neurosurg Psychiatry doi:10.1136/jnnp-2015-312176
Objective: Previous studies on consumption of caffeine and risk of multiple sclerosis (MS) have yielded inconclusive results. We aimed to investigate whether consumption of coffee is associated with risk of MS.
Methods: Using two population-representative case–control studies (a Swedish study comprising 1620 cases and 2788 controls, and a US study comprising 1159 cases and 1172 controls), participants with different habits of coffee consumption based on retrospective data collection were compared regarding risk of MS, by calculating ORs with 95% CIs. Logistic regression models were adjusted for a broad range of potential confounding factors.
Results: Compared with those who reported no coffee consumption, the risk of MS was substantially reduced among those who reported a high consumption of coffee exceeding 900 mL daily (OR 0.70 (95% CI 0.49 to 0.99) in the Swedish study, and OR 0.69 (95% CI 0.50 to 0.96) in the US study). Lower odds of MS with increasing consumption of coffee were observed, regardless of whether coffee consumption at disease onset or 5 or 10 years prior to disease onset was considered.
Conclusions: In accordance with studies in animal models of MS, high consumption of coffee may decrease the risk of developing MS. Caffeine, one component of coffee, has neuroprotective properties, and has been shown to suppress the production of proinflammatory cytokines, which may be mechanisms underlying the observed association. However, further investigations are needed to determine whether exposure to caffeine underlies the observed association and, if so, to evaluate its mechanisms of action.
Caffeine and urinary symptoms:
Bradley et al. Evidence of the Impact of Diet, Fluid Intake, Caffeine, Alcohol and Tobacco on Lower Urinary Tract Symptoms: A Systematic Review. J Urol. 2017 Nov;198(5):1010-1020.
PURPOSE: Diet, fluid intake and caffeine, alcohol and tobacco use may have effects on lower urinary tract symptoms. Constructive changes in these modifiable nonurological factors are suggested to improve lower urinary tract symptoms. To better understand the relationship between nonurological factors and lower urinary tract symptoms, we performed a systematic literature review to examine, grade and summarize reported associations between lower urinary tract symptoms and diet, fluid intake and caffeine, tobacco and alcohol use.
MATERIALS AND METHODS: We performed PubMed® searches for eligible articles providing evidence on associations between 1 or more nonurological factors and lower urinary tract symptoms. A modified Oxford scale was used to grade the evidence.
RESULTS: We reviewed 111 articles addressing diet (28 studies), fluid intake (21) and caffeine (21), alcohol (26) and tobacco use (44). The evidence grade was generally low (6% level 1, 24% level 2, 11% level 3 and 59% level 4). Fluid intake and caffeine use were associated with urinary frequency and urgency in men and women. Modest alcohol use was associated with decreased likelihood of benign prostatic hyperplasia diagnosis and reduced lower urinary tract symptoms in men. Associations between lower urinary tract symptoms and ingestion of certain foods and tobacco were inconsistent.
CONCLUSIONS: Evidence of associations between lower urinary tract symptoms and diet, fluid intake and caffeine, alcohol and tobacco use is sparse and mostly observational. However, there is evidence of associations between an increased fluid and caffeine intake and urinary frequency/urgency, and between modest alcohol intake and decreased benign prostatic hyperplasia diagnosis and lower urinary tract symptoms. Given the importance of these nonurological factors in daily life, and their perceived impact on lower urinary tract symptoms, higher quality evidence is needed.