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Will whole grains make you live longer?

Three! journal articles were published on whole grains in the past couple of weeks; not sure how that happened. Zong et al had this article published in Circulation: “Whole Grain Intake and Mortality From All Causes, Cardiovascular Disease, and Cancer. A Meta-Analysis of Prospective Cohort Studies.” Aune et al had this article published in the BMJ: “Whole grain consumption and risk of cardiovascular disease, cancer, and all cause and cause specific mortality: systematic review and dose-response meta-analysis of prospective studies.” Chen et al had this one published in the AJCN “Whole-grain intake and total, cardiovascular, and cancer mortality: a systematic review and meta-analysis of prospective studies.”

The US Circulation/Harvard team study was the one that dominated the media headlines, not only in the US, but also in the UK, where we were misinformed: “Three slices of wholemeal bread a day slash risk of dying from heart disease by 25%”.

All three studies were meta-analyses of prospective cohort studies. Just to make sense of this – a meta-analysis is generally seen as the highest level of evidence possible. It is a statistical technique to pool together many similar studies, working on the principle that looking at several studies together is more powerful than looking at just one. Prospective cohort studies are also called population studies, or epidemiological studies. These types of studies follow populations over a period of time. At the start of the study they record as many things as possible about the participants’ lifestyle (smoking/alcohol/diet/exercise etc) and they record as many things as possible about the participants’ characteristics (age/gender/education etc) and then they see what happens to the people over the following years. The goal with prospective cohort studies is simply to spot patterns (associations) – do people who drink alcohol get liver disease? Do people who do yoga get fewer diagnoses of stress?

The standard issues

Every time a study hits the headline – e.g. “wearing red socks will reduce your risk of dying from boredom by 25%” – there are two standard issues: association is not causation and relative risk is not absolute risk…

1) Association is not causation.

Observational studies can only establish associations. They cannot say that A causes B. They can only say that A and B are associated. For example, observational studies are good ways of establishing that smoking and getting lung cancer are associated. The next question to ask is – does this have a plausible mechanism? The answer is yes – we have evidence of the ways in which substances in cigarettes damage lungs. We could then test the hypothesis “Smoking causes lung cancer” by conducting a randomised controlled trial where the intervention is smoking vs. not smoking and nothing else changes.

The two studies from last week have shown an association between consuming whole grains and mortality and that’s it. Is there a plausible mechanism? The BMJ article tries to suggest a few (are people who eat whole grains slimmer? Are whole grains anti-inflammatory? Read Dr William Davis’s Wheat Belly book and you’ll conclude the opposite.) There is nothing intrinsically healthy about whole grains, so there is no obvious plausible mechanism. I will suggest below an explanation for the observed association – the marker vs. maker argument.

2) Relative risk is not absolute risk.

I don’t blame the media for this one – I blame the press releases from the journals. These should know better than to put “25% reduced risk” in a press release – knowing that this is misleading relative risk hysteria and not scientific absolute risk information.

European heart data tell us that 33 in every 100,000 men died from coronary heart disease in 2009 and 8 in every 100,000 women died from CHD in 2009. IF eating whole grains were causal and IF eating whole grains could reduce this by 25%, then – taking the women – approximately 7 in 100,000 women in the top whole grain consumption category would be likely to die from CHD and 9 in 100,000 women in the never/hardly ever eat whole grains category would be likely to die from CHD (the difference between 7.1 and 8.9 being just over 25%, while maintaining 8 as the average/mean).

7 vs. 9 in 100,000. Hardly hold the front page now is it?!

The other key points

1) Dietary advice to eat whole grains is not evidence based.

For something to be evidence based, it needs to be based in evidence, If something is based in evidence, the evidence comes first. Advice to consume whole grains dates back to the 1980 Dietary Guidelines for Americans (if not earlier). If you can see the full BMJ article you will notice that only one study that appears in all the meta-analysis results even comes from the last century. This one study, Liu et al, dates back to 1999. All other studies used as evidence are from the year 2000 onwards (a high proportion are from the past couple of years).

Dietary Guidelines have been under serious attack from real food proponents for the past few years. I can understand wanting to try to find retrospective evidence for guidelines in this climate, but it will never make the guidelines evidence based. The evidence didn’t come first and it never will.

2) The comparator group is Jekyll & Hyde.

These studies claim to have found an association between whole grain consumption and reduced mortality (i.e. living longer). The groups that they compared were those in the highest intake of whole grain consumption (more than 3oz per day) vs. those in the lowest intake group. People in the lowest intake group were those who (self) reported “rarely or never” eating whole grains.

The 2010 Dietary Guidelines for Americans tell us: “Less than 5 percent of Americans consume the minimum recommended amount of whole grains, which for many is about 3 ounce-equivalents per day. On average, Americans eat less than 1 ounce-equivalent of whole grains per day.” (p.36)[Ref 1]

Hence – both studies have used a very small section of the population as the comparator group (<5%). There are two polarised groups of people in the “never/rare consumers of whole grains”: i) people who avoid all grains and ii) people who eat refined grains instead of whole grains. I would expect whole grain eaters to be healthier than refined grain eaters. The comparison that has not been done is the whole grain eaters vs. the no grains-at-all eaters (the latter, virtually guaranteed, also avoid sugar).

3) Whole grain consumption is a marker, not maker, of a healthy lifestyle.

I would expect people who consume whole grains regularly (the <5%) to: not smoke; not drink; be affluent; do yoga; be slim; shop at Whole Foods/Waitrose; eat at restaurants, not takeaways; have children called Olivia and Tarquin and so on. The whole grain consumption is a marker of good health, not the maker of good health.

The BMJ study noted this as one of the limitations of their research: “People with a high intake of whole grains might have different lifestyles, diets, or socioeconomic status than those with a low intake, thus confounding by other lifestyle factors is a potential source of bias.”

That’s journal speak for “Whole grain consumption is a marker, not maker, of a healthy lifestyle.”

The headlines imply that people just need to up their intake of whole grains and they will “slash their risk of dying from heart disease by 25%!” This could not be further from the truth. It’s not causal, the absolute difference is tiny and it’s a whole lifestyle being depicted in these studies – not a whole grain.

To prove me wrong, the authors of these studies need to give 3oz of whole grains daily to the smoking, drinking, obese, sedentary, aimless, fourth generation unemployed, living-on-benefits, deprived populations in the Welsh valleys and change nothing else. Do you think that will “slash their risk of dying from heart disease by 25%”?!

Me neither.

Ref 1: Department of Health and Human Services (HHS). Dietary Guidelines for Americans. In: Department of Health and Human Services (HHS), ed., 2010.

19 thoughts on “Will whole grains make you live longer?

  • Glad to learn about red sox – getting rid of mine tonight

    Makes as much sense as my research and article uncovered!

    Carrots finally fingered, as cause of most fatal auto accidents!

    After a massive 12-year painstaking US government study involving fatal automobile accidents, costing $31 Billion in taxpayer dollars, it was determined that carrots were at the “root” cause (pun intended) of 96.34% of fatal auto accidents. Autopsies, and extensive surviving family member interviews prove beyond a doubt these innocent victims had all eaten carrots within the last 30 days prior to the tragedies. Some drivers had even consumed these deadly vegetables as recently as within 2 hours or less, just prior to the accidents.

    New nationwide government study will be launched to determine if these killer carrots were consumed raw or cooked, and if cooked by which method: steamed, boiled, roasted, microwaved or some other clandestine family recipe passed down through the ages was used.

    Pharmaceutical companies now rush to formulate new drugs that would negate the dangerous effects of eating carrots.

    USDA and other government agencies push to put regulations in place to prohibit growing, importing, transporting or selling carrots until agriculture researchers can develop safe varieties. (Government will subsidize this research)

    Delmonte and Green Giant layoff thousands as they hurriedly close packing and canning facilities as they file for bankruptcy protection. Food manufactures rush to find and patent new artificial carrot replacement foods made from insects, worms, and tree bark. Billions of dollars in profits expected to be made on these new products. Shortage of orange colored dies expected as newly manufactured carrot products and substitutes hit the market.

    Food manufacturer stocks skyrocket as new highs unfold.

    Public demands answers – how could this have gone on so long and harmed so many people? Marshall Law and curfews invoked as police and National Guard called up to help quell the massive demonstrations as angry millions flock to streets and storm government facilities to protest.

    Trial lawyers have been suddenly bombarded with requests for new class action lawsuits against farmers, growers, and grocery stores – after all they must have known the problem with carrots all along.

    Justice department will investigate conspiracy allegations of massive bribes and payoffs to elected officials and government employees by the growers (taken over the years from their enormous carrot government subsidies).

    Researchers were shocked at just how dangerous carrots really were, and asked for more US taxpayer funds to study how carrots may also be involved in bicycle accidents with children ages between 4-14 years old.

    Congress and the Senate quickly approved (within 6 hours) the requested $27 Billion with only 1 descending vote (which came from a California Senator who’s family owned a small carrot farm), after all, this new research was necessary to help protect the children.

    This just in: countless thousands of dieticians and nutritionists file massive class action law suits against colleges – demanding refunds on tuitions (with interest) for there now worthless degrees.
    (Government considering program to reimburse colleges for these tuition refunds)

    More requests urgently needed for research to determine just exactly how the carrots react in the digestive system to enable them to cause so many accidents. It is also suspected carrots might also be the cause of most industrial accidents as well. New government studies will be needed to validate this suspicion.

    Congress also considering legislation requiring all citizens (over 16 with drivers licenses) to keep a detailed electronic food diary to be kept on their person at all times. A new electronic smart card would be created and issued that records ALL food purchases both at grocery and convenience stores, as well as restaurants, bars, ball parks, theaters, street vendors etc., where ever food is sold or consumed. This will help facilitate desperately needed research. There may be more killers lurking in what we eat. (Ice cream and water also now beginning to look very suspicious)

    Food police could stop anyone at any time, swipe the electronic food diary card to see if suspects have consumed carrots with in the last 30 days. This would be similar to the breath analyzers in use today for alcohol consumption.

    Government officials assure us that all this new spending would be completely paid for by savings from the outdated seat belts, shoulder restraints and air bags no longer necessary as auto accidents are dramatically finally reduced and/or eliminated in America.

    Zoe I really enjoy your work – keep it up

    You have my permission to use this any way you see fit
    hope you get a laugh out of it. [email protected]

    • Ha ha very good! Carrots it is then :-)

  • My glucometer tells me that there is a marginal difference between “whole grains” and refined grains – and a huge difference with “no grains at all”. My lipid panels agree. Current policy is like saying that since arsenic is less toxic than cyanide we should eat more arsenic . . .

  • Apologies for repeating my comment from your Eatwell thread. This is in light of the current discussion of differing definitions of whole grains:
    My Summer 2016 Osteoporosis news mag just arrived from the National Osteoporosis society, who had also just sent me a reminder to renew my NOS membership. I am planning to write to them, saying why I am hesitating to renew, when they have a big feature endorsing and recommending the Eatwell Plate. (and sending them the link to your article and blogpost.) The article writes: Public Health England recommends ..2 whole wheat cereal biscuits, 2 thick slices of wholemeal bread.. And refers to the Eatwell guide to eat lower fat milks. It quotes Ailsa Welch, Reader in Nutrional Epidiomology at University of East Anglia, as welcoming the revised recommendations.

    Alongside the Eatwell feature is a report of a study by MRC Human Nutrition Research (Zoe, have you heard of them- Cambridge institute of some repute, it seems) who have examined records stretching back to 1946 and found women with a diet high in low fat milk.. wholegrain bread, breakfast cereals, fruit and veg and low in added sugars, sweets, processed foods and animal fats, will have stronger bones over age 60. The next page says the Med diet may be good for bones, which it defines as “rich in fruit, veb, fish and whole grains..”

  • So true. There should be regulation for setting up food studies and analysis. Set a standard for low and high intake for instance, and mandatory inclusion of other known contributors of health. There are studies who take more into consideration, like the well known Potsdam study.

  • Brilliant post, as er usual Zoe!

    BTW a meta-analysis of rubbish studies results in meta-rubbish, so the meta whatsit is not much of a gold standard, is it?

  • Apart from the questionable ‘evidence’ about the wondrous health benefits of eating whole grains, what exactly is the definition of ‘wholegrains’? From memory, the FDA definition is different from the Canadian definition, and different again from how the word is used in other countries, such as Australia. Journal articles started appearing using the word ‘wholegrain’, where ‘cereal’ had been used previously. Dietary guidelines started using ‘wholegrain’, but the foods stayed the same, just the quantities might have changed. Odd that the graphics and words stayed the same – pasta was still referred to as pasta, not wholemeal/wholegrain pasta, etc. How did pasta, rice, bread and other carbohydrates became ‘wholegrain’, without actually changing their composition or meeting the FDA criteria?

    • Good point! There’s a definition here:

      The SACN report ( defines them as:
      Whole grains
      8.126 The definitions of whole grains vary between studies. The term ‘whole grains’
      can have several meanings from ‘whole of the grain’ through to physically intact
      structures. Whole grains include whole wheat, whole-wheat flour, wheat flakes,
      bulgar wheat, whole and rolled oats, oatmeal, oat flakes, brown rice, whole rye
      and rye flour and whole barley. The definition of whole grains is discussed further
      in Chapter 2, paragraphs 2.39 to 2.41. Any associations indicated for whole grain
      may be related to its cereal fibre component. In one study cereal fibre intake was
      shown to be strongly correlated with consumption of whole-grain bread (r = 0.71)
      (Schulze et al., 2007a).

      And probably a few more elsewhere.

      Each study included in meta-analysis probably had it’s own definition. Having been involved in the EPIC study (as a participant), the questionnaire is here ( Look for P4 – presumably brown bread counts as whole grain even if it doesn’t really! Is readybrek whole grain? It’s lumped together with porridge…

      Nice one!
      Best wishes – Zoe

  • Great stuff Zoe! It seems we can always rely on you and Dr Kendrick & Nina Teicholz to expose the garbage that masquerades as medical news. Oh that there were more like you.

    One point though regarding Wales. I’m afraid those you describe have escaped and are now living all over the country!

    Kind regards,


  • I would like to know if whole grains really boost serotonin levels in the brain…for support in mild/major depression including bipolar. One “expert” suggested three servings of whole grains per day for bipolar. Or is this an unsubstantiated myth?

  • Me niether,
    in fact it’s been done, in DASH and WHI, and probably in other long-term experiments I don’t know about, and advice that increased wholegrain consumption didn’t produce marvellous effects.

  • Nicely done, Zoe. Take this post: rinse and repeat for the next slew of over-hyped observational findings with weak relative risks. Here is my favorite line in your piece, which suggests the magnitude of the wrong-headedness of contemporary dietary policy: “For something to be evidence based, it needs to be based in evidence.” Oh, it does? How is it that all of nutrition policy in the US and UK exists to the contrary?

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