Monday, 30 October 2017

Are you what you eat?

Circumstantial evidence has suggested an association between diet and MS, but hard evidence proving a causal link has been lacking. 

A new multicentre, prospective, longitudinal cohort study from the USA tried to crack this problem. They recruited children with MS from 11 centres. 


People were included if they met the following criteria:
  •           ‘high risk’ CIS or RRMS
  •           Disease onset < 18
  •           >= 2 silent MRI lesions
  •           Disease duration < 4 years

Dietary intake was assessed using a special questionnaire completed by the participant or a caregiver. The main outcome of interest was the time to the first relapse.

219 people were included in the final analysis. Over about 2 years of follow-up, (median 1.8 years), 42.5% experienced at least one relapse.

They adjusted for age, gender, race, ethnicity, disease duration, BMI, total energy intake and use of DMT. After all of these adjustments, they found a significantly increased hazard ratio for each 10% increase in the proportion of the diet made up by fat (overall) and saturated fats. Conversely, the hazard ratio was significantly decreased for each extra 10% of the diet made up by vegetables.

A brief note on hazard ratios…

Hazard ratios are used to compare the time taken to some kind of adverse event between two groups. Examples of adverse events used in MS studies include relapse and disability progression. The ‘hazard’ is the probability of the adverse event occurring at any given time point. You can work this out as the number of people who experience the event at that time divided by the number of people who are left in the study. The hazard ratio is equal to the hazard in one group divided by the hazard in the other. A hazard ratio of less than 1 implies a protective effect.

So in this study it appears that getting a higher proportion of daily calories from fats in general, and saturated fats in particular, increased the risk of having another relapse in paediatric MS. Vegetable calories, on the other hand, appear to decrease the risk of further relapse. This is biologically plausible as there is some data suggesting that contents of the diet can lead to alterations in gut bacteria which may promote inflammation in the CNS.

I do not think these data show that saturated fats cause more active MS. While there is a clear correlation between dietary saturated fat content and the hazard of relapse, I am doubtful that this supports a causal relationship between diet and MS activity. 

First, as the authors acknowledge, dietary data were collected as a one-off at baseline, often reported by the patients themselves. This not only carries the risk of recall bias, but as a snapshot is unlikely to capture accurately what the participants’ ‘average’ diet looked like over time. 

Second, there are lots of possible confounding factors that might explain the increased correlation between relapse risk and increased fat intake. Increased fat intake might be associated with, for example, increased smoking and decreased physical activity, which may be independently associated with disease activity. 

Third, there is the possibility of reverse causation; that the fact of having more active MS changes people’s behaviour and predisposes them to eat more saturated fat and fewer vegetables. It is plausible, for instance, that the parents or guardians of children with more active MS are more likely to let them eat more sweets. There is no evidence to suggest whether this is the case or not from this study. The point is that there are lots of plausible reasons for why dietary contents might be associated with MS activity while not having any causal bearing on the disease.

All in all this is a good paper that, to be fair to the authors, does not make any outlandish claims and merely makes some interesting observations about the link between diet and MS activity. While there is very little harm in recommending a healthy lifestyle with a well-balanced diet and regular exercise, there is not enough here to conclude that saturated fats influence the course of MS.

***
Abstract
Objective The role of diet in multiple sclerosis (MS) course remains largely unknown. Children with MS have a higher relapse rate compared with MS in adults. Thus, studying the effect of diet on relapse rate in this age group is likely to provide more robust answers.
Methods This is a multicentre study done at 11 paediatric MS centres in the USA. Patients with relapsing-remitting MS (RRMS) or clinically isolated syndrome (CIS) with disease onset before 18 years of age and duration of less than 4 years were included in this study. Dietary intake during the week before enrolment was assessed with the validated Block Kids Food Screener. The outcome of the study was time from enrolment to the next relapse. 219 patients with paediatric RRMS or CIS were enrolled. Each 10% increase in energy intake from fat increased the hazard of relapse by 56% (adjusted HR 1.56, 95% CI 1.05 to 2.31, p=0.027), and in particular each 10% increase in saturated fat tripled this hazard (adjusted HR: 3.37, 95% CI 1.34 to 8.43, p=0.009). In contrast, each additional one cup equivalent of vegetable decreased the hazard of relapse by 50% (adjusted HR: 0.50, 95% CI 0.27 to 0.91, p=0.024). These associations remained with mutual adjustment and persisted when adjusting for baseline 25(OH) vitamin D serum level. Other studied nutrients were not associated with relapse.
Conclusions This study suggests that in children with MS, high energy intake from fat, especially saturated fat, may increase the hazard to relapse, while vegetable intake may be independently protective.


13 comments:

  1. I thought you were talking about fasting and Ms?

    :(

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  2. Given the duel role the lymphatic system plays in draining inflammatory fluid from the brain, AND transporting / absorbing fat in the body... it seems entirely plausible that excessive fat intake can worsen MS.

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  3. No sorry if misleading - just talking about link between specific contents of the diet and MS activity.

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  4. Quite predictably this study has been leapt upon with cries of joy by those who are followers of the low sat fat dietary approaches to MS (i.e. Swank and Jelinek) - and equally predictably they are claiming it as "evidence" that high sat fat consumption is a contributing cause of MS and that the low sat fat Swank and OMS approaches work for people with MS - i.e. will reduce numbers or severity of relapses, and help limit progression (or even reverse it).

    Pointing out any of the shortcomings in the study (such as the small number of participants, or the lack of reliability of a one week self-recorded food diary as a basis for a two year long study) has no impact on the "low sat fat" mob's enthusiasm for this study. They just retreat to their "we know best, but the world doesn't want to listen to us" castles, and maintain that the Westernised diet is the cause of MS. Yes - a Westernised diet low in vegies but high in processed foods, sugar, and unhealthy fats has a lot to answer for in the disease stakes, but it is worrying to see the psychological harm being caused when followers of some of the diet/lifestyle approaches tell PwMS who have relapses or progression that the cause is falling off their Swank or OMS wagon (you only need to browse some of the forums to see this blaming in action - one person actually truly believed that they had caused a relapse by eating one meal of steak and chips!!!).

    There are in fact many good elements to the the Swank and OMS diets, but the claims made for them need to be viewed with caution, and many/most disciples have a problem with understanding the difference between correlation and causation. I suspect that the reality for many who adopt these approaches is that their lifestyle and diets were so appalling in the first place that any change would produce improvements.

    Fortunately, the couple of places where this study has been published have included some caveats around it, which have not diminished it's potential value as a pointer for an area for future research, but do warn against taking its findings as gospel.

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    1. Completely agree - the authors themselves are conservative about what their results mean and I would be very sceptical of anyone making strong claims for a low sat-fat diet on the basis of this to alleviate MS. That said, standard NHS recommendations - balanced diet, exercise, minimal alcohol - are definitely good for overall physical and mental health.

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    2. I complete agree with the psychological harm you mention. Equally academic 'floors' in studies aren't a meaningful rebuke, in a sense, it is unrelated to whether diet effects MS.

      In fact, nearly all sensible studies looking at diet and MS, show some relationship. And there has never been proof the diet doesn't effect MS.

      Btw - as someone with MS, who struggles with destructive diet - I'm the last person who wants to buy in to diet causing or effecting MS.

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  5. Definitely biologically plausible but not enough here to support a clear link I think

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    1. What do you think of the evidence regarding the links between smoking and disability progression in MS? I am not advocating smoking, of course, but I am trying to understand why smoking cessation is often recommended by neurologists, while a vegan or mediterranean diet is generally not recommended. It seems to me that the nature of the evidence for both recommendations is similar, being based on epidiomelogical studies, dietary intake studies, and in vivo research. What's more, we know from the broader landscape of medical research that both of these recommendations are very good for your health more generally and will lower your risk of developing other health conditions (cancer, heart disease, diabetes). I find it curious that so many neurologists advise their MS patients to stop smoking, but say nothing about the benefits of limiting intakes of red and processed meat.

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    2. I thought a mediterranean style diet was recommended by doctors and HCP's for MS,
      NHS Livewell website "You can make your diet more Mediterranean-style by:
      eating plenty of starchy foods, such as bread and pasta
      eating plenty of fruit and vegetables
      eating some fish
      eating less meat
      choosing products made from vegetable and plant oils, such as olive oil".

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    3. The advice on the NHS website is interesting though because the advice on nutrition provided by the UK MS Society does not mention limiting your intake of red or processed meat and does not mention the general health benefits of vegan, vegetarian or Mediterranean diets: https://www.mssociety.org.uk/sites/default/files/Diet%20and%20nutrition%20August%202016%20web.pdf.

      What we are lacking is a middle ground between overblown claims that a vegan or Mediterranean diet will "cure" you of MS and blanket dismissals of common-sense healthy eating patterns (vegan, vegetarian, or Mediterranean) as not relevant to MS... something that says: "a balanced vegan, vegetarian, or Mediterranean eating pattern is healthy, it is associated with lower rates of a range of diseases, conditions, and co-morbidities (that are typically found to lower quality of life in individuals with MS), and is associated with a lower lifetime risk for several cancers (which may be higher, if you are on a highly effective DMT). It might also hep you manage your MS, but the evidence at this stage is inconclusive and you should therefore stay or start a DMT."

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    4. Agreed - in the absence of good evidence suggesting that any particular diet is good or bad for MS I would always err on the side of recommending what we know is best for overall physical and mental health. There are some good evidence that med diet is good for overall cardiovascular health. Even if a diet has no direct effect on MS, maintaining a healthy weight, getting your calories from a balanced diet, not drinking too much alcohol etc will help boost energy levels and mood.

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  6. You are what you eat - literally.
    The potato you eat will be you in a few hours,the pig butt you eat will be you in few hours,so it's a choice what you wanna be.

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