Tag Archives: Diet

Gluten Sensitivity but no Antibodies?

Consider the case of my good friend who developed gluten sensitivity in midlife. Subsequently he went on a gluten-free diet – his wife found this a terrible nuisance. So she surreptitiously re-introduced wheat to his diet. Within no time my friend complained and that he had been wrong, his symptoms had reoccurred despite no apparent exposure to wheat. He was disappointed with his wife when she had to confess to her clandestine challenge to his physiology. But I think she behaved like a true scientist!

The single case represented by my friend has been repeated on a larger-scale many times. The results have been the same; many people with gluten sensitivity manifest symptoms when challenged in blind studies.[1] Furthermore, unlike many types of putative psychosomatic illness, people with gluten sensitivity do not manifest different responses on psychological testing for depression or anxiety compared with those of the general population.

So what is the cause of this somatopsychic condition? It turns out that there are two main theories each with some evidence in their favour.[2] The theory that I prefer is called FODMAPs, based on the idea that wheat is a potent source of fermentable, short chain carbohydrates. These carbohydrates are poorly absorbed and thus ferment in the gut causing the typical symptoms of bloating, distention and discomfort. The alternative theory is that wheat, perhaps in the presence of certain alterations in the microbiome, causes an inflammatory reaction in the liver that is associated with symptoms.

It will be important to discern the cause, since treatment of excessive fermentation would consist of a more general reduction of foods containing large proportions of fermentable carbohydrates.

— Richard Lilford, CLAHRC WM Director

References:

  1. Skodje GI, Sarna VK, Minelle IH, Rolfsen KL, Muir JG, Gibson PR, Veierød MB, Henriksen C, Lundin KEA. Fructan, Rather Than Gluten, Induces Symptoms in Patients With Self-Reported Non-Celiac Gluten Sensitivity. Gastroenterol. 2018; 154: 529-39.
  2. Servick K. The war on gluten. Science. 2018; 360: 848-51.
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Food Deserts: a Problem of Supply or Demand?

That poor people have a less healthy diet than rich people is not in doubt. That poor people have worse health because they have less healthy diets is also not in doubt. That poor people have less access to healthy food than rich people is, again, not in doubt. This series of observations has led to a predominant narrative: that the poor are denied the healthy foods that they would choose, where it only that they had equitable access to healthy options.

This does not follow, any more than the argument that low access to contraception is causative of high birth-rates. It is quite feasible that low demand is the cause of both low access and the corresponding outcomes, both in the case of the pill and low access to healthy food.

Allcott and colleagues addressed this issue with respect to diet and health.[1] They examined the possibility that observed differences in supply of healthy foods are a response to differences in the demand for those foods in different neighbourhoods. The authors examined this through a rich array of data sets, one of which covered nearly half of all US grocery purchases. They were able to examine how people of different socioeconomic group behave when supermarkets are established in new locations, or when people move into, or out of, food ‘deserts’. Effectively they treat these geographic changes as instrumental variables.

When they examined the effect of entry of a new supermarket in a given locality, they find that local supermarket entry does not materially increase healthy eating. Then they examined the converse – movement of a household to an environment where more healthy food is available. Again, behaviour does not converge towards the general eating pattern in the new location.

Could this be because the supermarkets charge more for healthy products in poor neighbourhoods than they do in rich neighbourhoods? The authors examined this possibility and were able to exclude it. What they found is that poorer households are willing to pay much less than wealthier households for healthy food. As a result they are provided with less healthy food.

The results are broadly consistent with studies on education and food preferences. Food deserts exist, but they are not the result of supply-side failure. Rather they reflect the role of culture and tastes in the United States, as they have been shown to do in so many other places. The effects observed in the study did not change over many years. Policy initiatives that simplistically target food deserts are thus unlikely to succeed.

— Richard Lilford, CLAHRC WM Director

Reference:

  1. Allcott H, Diamond R, Dubé J-P. The Geography of Poverty and Nutrition: Food Deserts and Food Choices Across the United States. NBER Working Paper No. 24094. 2018.

Dieting Does a Lot of Good, Even If You Don’t Lose Much Weight

Well this paper gave me pause for thought.[1] I have always been rather nihilistic about dieting. The effect sizes in terms of actual weight loss seem nugatory and transient – a couple of kilograms after three years would be fairly typical. Well I was prompted to change my mind as a result of a recent meta-analysis of 54 RCTs of diet vs. no-diet. Most of the diets stressed saturated fat reduction as part of the diet, and most advocated exercise as well as a diet (although in only half of these trials were patients referred to a specific exercise programme). As I would have predicted weight loss was small in the intervention group vs. control – 3.4kg at one year, and 2.5kg at two years. Despite these small effect sizes, all-cause mortality was reduced by 18% (0.7-0.95) in the diet group. This finding held good, even when only the 34 best quality RCTs were retained in the analysis. There was a borderline significant reduction in cancer death in the diet groups among the eight trails that recorded this outcome. In an earlier study of abnormal liver function tests [2] we noted improvement in fatty livers in people who lost only small amounts of weight. My conclusion – it is worth persuading people to lose weight through diet and exercise. Even if the effects on weight are small they are not, after all, nugatory.

— Richard Lilford, CLAHRC WM Director

References:

  1. Ma C, Avenell A, Bolland M, Hudson J, Stewart F, Robertson C, Sharma P, Fraser C, MacLennan G. Effects of weight loss interventions for adults who are obese on mortality, cardiovascular disease, and cancer: systematic review and meta-analysis. 2017; 359: j4849.
  2. Lilford RJ, Bentham L, Girling A, Litchfield I, Lancashire R, Armstrong D, Jones R, Marteau T, Neuberger J, Gill P, Cramb R, Olliff S, Arnold D, Khan K, Armstrong MJ, Houlihan DD, Newsome PN, Chilton PJ, Moons K, Altman D. Birmingham and Lambeth Liver Evaluation Testing Strategies (BALLETS): a prospective cohort study. Health Technol Assess. 2013; 17(28):1-307.

Corroboration of Previous Reports on Vitamin D and on Coffee

In recent News Blogs we have provided evidence that vitamin D and calcium are useless in preventing osteoporotic fractures in elderly people with no obvious risk factors.[1] [2] This is now powerfully corroborated in a paper in JAMA by Zhao, et al.,[3] who carried out a systematic review and meta-analysis involving over 50,000 participants. They found absolutely no beneficial or harmful effects of either vitamin D or calcium or a combination of the two compared to placebo in reducing the risk of either vertebral hip or other non-vertebral fractures. The absolute risk difference was zero with an upper confidence limit of 0.01. Hopefully this puts the matter to bed once and forever.

Likewise a recent umbrella review in the BMJ [4] corroborated previous news blogs on the generally health promoting effects of coffee.[5] It would appear that these benefits are also seen in equal measure with de-caffeinated coffee, suggesting that it is the other components of coffee that benefit health.

— Richard Lilford, CLAHRC WM Director

References:

  1. Lilford RJ. Effects of Vitamin D Supplements. NIHR CLAHRC West Midlands News Blog. 24 March 2017.
  2. Lilford RJ. Yet Another Null Result on Vitamin D and Calcium Supplementation in Older Women. NIHR CLAHRC West Midlands News Blog. 5 May 2017.
  3. Zhao J-G, Zeng X-T, Wang J, et al. Association Between Calcium or Vitamin D Supplementation and Fracture Incidence in Community-Dwelling Older Adults: A Systematic Review and Meta-analysis. JAMA. 2017; 318(24): 2466-82.
  4. Poole R, Kennedy OJ, Roderick P, Fallowfield JA, Hayes PC, Parkes J. Coffee consumption and health: umbrella review of meta-analyses of multiple health outcomes. BMJ. 2017; 359: j5024.
  5. Lilford RJ. Should You Keep Drinking Coffee? NIHR CLAHRC West Midlands News Blog. 1 September 2017.

Antioxidants and Age-Related Macular Degeneration

It is estimated that around 5% of the general population suffer from age-related macular degeneration (AMD),[1] where extracellular material known as drusen accumulate under the retina at the back of the eye and which can eventually lead to blurred or a loss of vision. It has been suggested that antioxidants may help prevent or delay development of AMD in people who do not suffer the condition by protecting the retina against oxidative stress, but it is unclear as to whether this is the case.

A systematic review in the Cochrane Database by Evans and Lawrenson looked at the effectiveness of antioxidant supplements as treatment in people who already had AMD,[2] and found that taking a multivitamin antioxidant vitamin may delay the progression of AMD when compared to a placebo or no treatment (odds ratio 0.72, 95% CI 0.58-0.90). The authors also conducted a systematic review looking at whether there was an association between taking antioxidant vitamins (carotenoids, vitamin C, vitamin E) or minerals (selenium, zinc) and the development of AMD in people without AMD.[3] Five RCTs were included, with a total of 76,756 individuals without AMD. These studies all looked at the use of various supplements against placebo. Generally, the various studies found that there was no effect of supplements on development of AMD, while in some cases there was evidence of an increased risk (see table below).

Comparison No. of studies Disease Risk Ratio (95% Confidence Interval)
Vitamin E vs. placebo 4 AMD 0.97 (0.90-1.06)
Late-stage AMD 1.22 (0.89-1.67)
Beta-carotene vs. placebo 2 AMD 1.00 (0.88-1.14)
Late-stage AMD 0.90 (0.65-1.24)
Vitamin C vs. placebo 1 AMD 0.96 (0.79-1.18)
Late-stage AMD 0.94 (0.61-1.46)
Multivitamin vs. placebo 1 AMD 1.21 (1.02-1.43)
Late-stage AMD 1.22 (0.88-1.69)

— Peter Chilton, Research Fellow

References:

  1. Owen CG, Jarrar Z, Wormald R, Cook DG, Fletcher AE, Rudnicka AR. The estimated prevalence and incidence of late stage age related macular degeneration in the UK. Br J Ophthalmol. 2012; 96(5): 752-6.
  2. Evans JR, Lawrenson JG. Antioxidant vitamin and mineral supplements for slowing the progression of age-related macular degeneration. Cochrane Database Sys Rev. 2017; 7: CD000254.
  3. Evans JR, Lawrenson JG. Antioxidant vitamin and mineral supplements for preventing age-related macular degeneration. Cochrane Database Sys Rev. 2017; 7: CD000253.

Improving Access to Fresh Food in Low-Income Areas

In a previous News Blog we looked at a paper that found an association between adherence to the Mediterranean diet (i.e. high consumption of fruit, vegetables, and legumes) and reduction in cardiovascular disease risk.[1] So, it can be argued, that for those in low-income areas there is a need to improve their access to fresh fruit and vegetables. But how best to achieve this? Breck and colleagues, on behalf of the CDC, looked at one possibility in a cross-sectional survey analysis.[2]

Previously, the city of New York had attempted to address the issue by granting new licenses for mobile fruit and vegetable carts in those neighbourhoods with poor availability of fresh food. However, only some of the carts (27%) had the capacity to accept the Supplemental Nutrition Assistance Program (SNAP) benefits (a federal aid program to provide food-purchasing assistance) through use of Electronic Benefit Transfer (EBT) machines.

The authors conducted a survey analysis of 779 adults shopping at four carts in the Bronx neighbourhood of New York over several time periods. After controlling for cofounders, they found that those shoppers who were able to pay using their SNAP benefits purchased significantly (p<0.001) more fruit and vegetables (an average of 5.4 more cup equivalents), than those who were only able to pay with cash. While there are promising results from providing consumers with more ways to pay, there are challenges that could prevent widespread roll out of EBT, chiefly the high initial, monthly, and transaction fees that the cart vendors need to pay. Even when provided with financial support, less than one-third of carts were equipped with EBT machines at the time of this study. Although the study has a number of limitations that means causal inferences cannot be drawn, it can be seen as a possible avenue for future research.

— Peter Chilton, Research Fellow

Reference:

  1. Chilton P. Diet and Socioeconomic Status. 18 August 2017.
  2. Breck A, Kiszko K, Martinez O, Abrams C, Elbel B. Could EBT Machines Increase Fruit and Vegetable Purchases at New York City Green Carts? Prev Chronic Dis. 2017; 170104.

How Much Fruit and Veg is Enough?

We are often told that we should be eating five (or is it now ten?) portions of fruit and vegetables each day to protect against, amongst other things, cardiovascular disease (CVD).[1] However, such recommendations are generally based on research conducted in people from Europe, the USA, Japan and China. There is little data from countries in the Middle East, South America, Africa or South Asia.

The PURE study (Prospective Urban Rural Epidemiology) set out to rectify this, recruiting 135,000 participants from 18 countries, ranging from high-income countries, such as Sweden, to low-income countries, such as India.[2] The research team documented the diet of these individuals at baseline (using questionnaires specific to each country), then followed them up for a median of 7.4 years, looking at cardiovascular-related clinical outcomes. As expected higher intakes of fruit, vegetables and legumes were associated with lower incidences of major CVD, myocardial infarction, and mortality (cardiovascular-related and all-cause). However, the hazard ratio for all-cause mortality was lowest for three to four servings (375-400g) per day (0.78, 95%CI 0.69-0.88), with no significant decrease with higher consumption.

It is more likely that consuming around 375g of fruit/vegetables/legumes per day will be within the financial reach of people living in poorer countries, compared to the various recommendations of 400-800g that are often seen in Europe and North America. Before we ditch that extra snack of carrot sticks, however, it is important to note that factors such as food type, nutritional quality, cultivation and preparation are likely to vary between countries, while other clinical outcomes, such as cancer, were not looked at in this study.

The authors are continuing to enrol more participants, and are hoping to re-examine their results in the future.

— Peter Chilton, Research Fellow

References:

  1. Oyebode O, Gordon-Dseagu V, Walker A, Mindell JS. Fruit and vegetable consumption and all-cause, cancer and CVD mortality: analysis of Health Survey for England data. J Epidemiol Community Health. 2014; 68(9): 856-62.
  2. Miller V, Mente A, Dehghen M, et al. Fruit, vegetable, and legume intake, and cardiovascular disease and deaths in 18 countries (PURE): a prospective cohort study. Lancet. 2017.

Should You Keep Drinking Coffee?

It is nice, at last, to find something that is it is really enjoyable and that is good for us. Recent News Blogs have carried articles on the harmful effects of red meat,[1] milk,[2] and alcohol.[3] But what about coffee? A recent article, based on over 500,000 people in ten European countries confirmed the already extensive literature showing that coffee is beneficial for health.[4] In fact, overall death rates were reduced by over 10%. There was a massive (over 50%) reduction in diseases of the digestive system, confirming the well-known beneficial effect of coffee on the liver. The trend was also favourable for heart disease and stroke. Many biochemical markers also moved in a favourable direction, including glycated haemoglobin, and C-reactive protein. The only bit of bad news pertained to ovarian cancer, where a 30% increased risk of death was noted. Reverse causality is always a possibility in non-experimental studies, even if, like this one, they are prospective. However, this is unlikely since the hazard ratios were unaltered if patients who died within eight years of recruitment were excluded.

— Richard Lilford, CLAHRC WM Director

References:

  1. Lilford RJ. An Issue of BMJ with Multiple Studies on Diet. NIHR CLAHRC West Midlands News Blog. 4 August 2017.
  2. Lilford RJ. Two Provocative Papers on Diet and Health. NIHR CLAHRC West Midlands News Blog. 12 December 2014.
  3. Lilford RJ. Alcohol and its Effects. NIHR CLAHRC West Midlands News Blog. 18 August 2017.
  4. Gunter MJ, Murphy N, Cross AJ, et al. Coffee Drinking and Mortality in 10 European Countries. Ann Intern Med. 2017; 167: 236-47.

Diet and Socioeconomic Status

People looking to lose weight and/or get healthy try a wide variety of diets, from fad diets with highly specific restrictions on what can be eaten, to general healthy eating plans. One such nutritional recommendation is the Mediterranean diet, based on the “food patterns typical of Crete… Greece and southern Italy…”,[1] and entails consumption of high amounts of plant foods (fruit, vegetables, cereals, legumes, etc.) and olive oil, moderate amounts of dairy, fish and wine, and low amounts of poultry and red meat. A number of observational studies have shown associations between such a diet and lower incidences of cardiovascular disease (CVD) and associated mortality, cancer, neuro-degenerative disorders, and overall mortality. However, there is uncertainty whether such benefits differ across different socioeconomic groups.

Bonaccio et al. carried out a prospective analysis of nearly 19,000 Italians to see the effect of the Mediterranean diet on CVD.[2] While there was an overall reduction in CVD risk associated with adherence to the diet (HR=0.85, 95% CI 0.73-0.99), this was not seen across all socioeconomic groups – only in those who were educated to a postgraduate or higher level (HR=0.43, 0.25-0.72) and in those with a high (>€40,000) household income (HR=0.39, 0.23-0.66). Those with less education (HR=0.94, 0.78-1.14) and lower income (HR=1.01, 0.79-1.29) had no significant association. Why such a difference? Subgroup analysis of people with similar adherence to the diet showed that there were a number of differences in the diet of those with high compared to low education, and those with high compared to low income. These included consumption of organic vegetables (which would have higher antioxidants and lower levels of pesticides), monounsaturated fatty acids (found in avocado, nuts, olives, etc.), micronutrients, and whole-grain bread, as well as greater dietary diversity.

So perhaps it is more important to make sure the food you are eating is of high quality and varied, than just simple healthy eating. Of course, access to high quality food of high nutritional value is not easy for poor people.

— Peter Chilton, Research Fellow

References:

  1. Willett WC, Sacks F, Trichopoulou A, Drescher G, Ferro-Luzzi A, Helsing E, Trichopoulos D. Mediterranean diet pyramid: a cultural model for healthy eating. Am J Clin Nutr. 1995; 61(6): 1402S–6S.
  2. Bonaccio M, Di Castelnuovo A, Pounis G, et al. High adherence to the Mediterranean diet is associated with cardiovascular protection in higher but not in lower socioeconomic groups: prospective findings from the Moli-sani study. Int J Epidemiol. 2017.

An Issue of BMJ with Multiple Studies on Diet

This News Blog often contains information about diet and health. For example, we have cited evidence that salt is enemy number one [1]; trans-fats are unremittingly bad news [2]; and large amounts of sugar are harmful.[3] After that the risks become really rather small – relative risks of about 20%. Fruit, and more especially vegetables, are good news. Milk is an unhealthy drink in adults (never intended for that purpose and galactose is harmful, unless removed during a fermentation process).[4] Three further studies of diet were included in a single recent issue of the BMJ.[5-7]

The first study by Etemadi, et al. looked at meat consumption in a large cohort of people (n= 536,969) who gave detailed dietary histories.[5] The evidence corroborates other studies in showing that red meat is harmful, increasing relative risk of death by about 20% in high meat eaters compared to moderate meat eaters. The difference is greater if the comparison is made with people who obtain almost all of their meat in the form of fish and chicken. The causes of death that showed greatest increases in risk with high red meat consumption were cancer, respiratory disease and liver disease. Surprisingly, perhaps, increased risk from stroke was nugatory. The increased risk in unprocessed meat is probably related to haem iron, and in processed meat to nitrates/nitrites – there are all pro-oxidant chemicals. Of course this is an association study, so some uncertainty remains. The main problem with meat, as the BMJ Editor points out,[8] is the harmful environmental effects; apparently animal husbandry contributes more to global warming than burning fossil fuels. I take the environmental effects seriously – perhaps we will one day vilify meat farmers more vociferously than we currently vilify tobacco farmers. After all, individuals don’t have to smoke, but cannot protect themselves from the harmful effects of pollution.

Meanwhile, for those who are interested, the other two relevant articles in this issue of the BMJ looked at avoiding gluten in people who do not have celiac disease (no benefit and evidence points towards harm),[6] and the beneficial effect of a low salt and fat diet on gout.[7]

— Richard Lilford, CLAHRC WM Director

References:

  1. Lilford RJ. Effects of Salt in Diet. NIHR CLAHRC West Midlands News Blog. 17 October 2014.
  2. Lilford RJ. On Diet Again. NIHR CLAHRC West Midlands News Blog. 23 October 2015.
  3. Lilford RJ. How Much Sugar is Too Much? NIHR CLAHRC West Midlands News Blog. 25 September 2015.
  4. Lilford RJ. Two Provocative Papers on Diet and Health. NIHR CLAHRC West Midlands News Blog. 12 December 2014.
  5. Etemadi A, Sinha R, Ward MH, Graubard BI, Inoue-Choi M, Dawsey SM, Abnet CC. Mortality from different causes associated with meat, heme iron, nitrates, and nitrites in the NIH-AARP Diet and Health Study: population based cohort study. BMJ. 2017; 357: j1957.
  6. Lebwohl B, Cao Y, Zong G, Hu FB, Green PHR, Neugut AI, Rimm EB, Sampson L, Dougherty LW, Giovannucci E, Willett WC, Sun Q, Chan AT. Long term gluten consumption in adults without celiac disease and risk of coronary heart disease: prospective cohort study. BMJ. 2017; 357: j1892.
  7. Rai SK, Fung TT. Lu N, Keller SF, Curhan GC, Choi HK. The Dietary Approaches to Stop Hypertension (DASH) diet, Western diet and risk of gout in men: prospective cohort study. BMJ. 2017; 357: j1794.
  8. Godlee F. Red meat: another inconvenient truth. BMJ. 2017; 357: j2278.