On the origins of nutritional slogans II: Fibre

We can learn a lot about the basis for ubiquitous dietary slogans such as ‘eat more fibre’ by looking at how they became established in the first place. This is particularly true of the saturated fats slogan, as my recent post on its 50-year history summarises. That slogan started out as a campaign by a charismatic and influential individual, and went on to become lore well before the science was available.

Much the same can be said of dietary fibre. Lets go back to the beginning and meet Dr Burkitt, MBBS.

imagesDenis Parsons Burkitt (1911-1993) was an Irish surgeon with an evangelical calling that led him to move to Uganda (while it was still a British colony) as a medical missionary in 1946 (he described himself as a ‘simple bush surgeon’). Ultimately, he oversaw the country’s health-care system and was highly-regarded. A cancer research centre was established in Kampala that was dedicated to him. He relocated to the UK in 1966 when the Ugandan independence of 1962 degenerated into military rule.

He was an excellent clinical observer and successful surgeon, despite only having one eye (the other was lost in a playground accident). While in Uganda, he became aware of a striking cancer of the jaw in children that was relatively common in certain parts of the country. In 1958, based on his observations, he published a clinical report of the condition, which subsequently became known as Burkitt’s lymphoma.

images-2Thereafter, the pathologist/virologist M. Anthony Epstein (later Sir Anthony) heard Burkitt lecture on his findings (during a return visit to the UK) and wondered if the lymphoma might not be viral in origin (he was working on cancer viruses in chickens at the time). Working with a young Australian physician, Yvonne Barr, and using tumour samples provided by Burkitt, the pair eventually identified and isolated the virus in 1964. It is now known as Epstein-Barr virus (a variant of the herpes virus). It was the first discovery of a human cancer-causing virus. It has now been associated with some other forms of cancer, has been implicated in certain autoimmune-related diseases (such as rheumatoid arthritis or MS), and underlies some post-transplant cancers (where immuno-supressants are used to avoid rejection) and AIDS-related cancers.

27468__74021022_eb1The virus is remarkably common worldwide, with an estimated 9 in 10 adults in the US carrying it asymptomatically. The virus usually infects the host during childhood and causes only mild (or no) symptoms of fever, however, if infection occurs later in life (during adolescence) it can result in glandular fever. Our immune system does not defeat the virus completely, the virus retreats into certain immune cells (B cells) where it is safe from attack. While it stays there it is harmless, but if activated it can cause the B cells to divide uncontrollably leading to lymphoma.

image002Meanwhile, Burkitt wanted to better determine the geographical distribution of the cancer in Africa. He applied for and received a research grant of £25 which he used to send letters to hospitals throughout Africa describing his lymphoma and asking how often cases had been seen that matched the description. The results suggested to him that occurrence was temperature-dependent.

A subsequent£250 grant enabled him to set off in a second-hand station wagon with two missionary colleagues to better define the geographical conditions under which the lymphoma thrived. He spent months driving down the east of Africa to conclude that the occurrence of the lymphoma was both temperature and rainfall dependent. From this, it was a small step to surmise that the virus may have been distributed by an insect (mosquitos or ticks).

nri3906-i1In fact, we now know that the Epstein-Barr virus is not distributed by mosquitos, but rather person-to-person by saliva (glandular fever is sometimes known as the kissing disease). In poorer countries without access to pureed food, it was common for mothers to chew food before giving it to their babies during the weaning stage. However the link to mosquitos appears real – infection with the malaria parasite seems to be the co-factor that can enable the virus to multiply in B cells and cause cancer. The distribution of Burkitt’s lymphoma is an excellent match with the distribution of malaria.

Burkitt made one more significant contribution – treatment. The cancer is prolific and deadly, however he found that low-levels of chemotherapy could result in a complete cure in many cases. This discovery arose from pragmatism. There was no money for the chemicals and he relied on limited free supplies from pharmaceutical companies, meaning he could not administer the usual aggressive doses. As well, hospitals in Uganda were not equipped to manage the aftereffects of an aggressive treatment regime. So, he tried the low-dose approach, with success.

By now you may be wondering what all of this has to do with a food blog. Apart from the fact that it is an intriguing story, it makes clear that Burkitt was a thorough and thoughtful geographical epidemiologist who left a lasting legacy, both directly from his own work and indirectly from the work Epstein and Barr and those that came later. The Epstein-Barr virus continues to be studied to this day, and better targeted treatments for Burkitt’s lymphoma are getting closer.

Which makes what Burkitt did next somewhat understandable but mostly puzzling. He became the ‘Fibreman’.

_3452851On return to the UK he took up a position with the Medical Research Council to head a unit for the study of geographical epidemiology. In 1967 he was introduced to Surgeon-Captain TL Cleave (Royal Navy, retired) who had written a book extolling the virtues of fibre and postulating that many western illnesses were due to modern processed foods high in sugar, fat and calories. Burkitt immediately became interested. His background in epidemiology and pathology, combined with his first-hand experiences in Africa (high-fibre diet, low incidence of ‘western’ diseases), led him to develop and promote the fibre hypothesis. For Burkitt, this would now be his life’s work. He leveraged the prestige he had acquired from Burkitt’s lymphoma to campaign, as perhaps only a missionary could, in favour of dietary fibre for the rest of his life. He contributed no further to the study of Burkitt’s lymphoma.

In 1969 he visited a Dr Walker in Johannesburg, who had accumulated a large database of disease patterns and diets in native Africans, including such details as bowel transit times and stool weights. This further strengthened Burkitt’s resolve.

Resistant-starch-may-aid-in-IBD-and-cancer-resistance-Study_medium_vgaHe collaborated widely with like-minded colleagues, and began to publish regularly (sorry) in scientific journals to support his hypothesis. Burkitt seemed to turn away from his earlier thoroughness to offer anecdote and opinion not strongly founded in science. He ignored confounds (e.g. other differences in the African diet) and used simplistic measures of fibre. Even today, measurement of dietary fibre, and even its definition, is problematical. His methodologies were often criticised.

He made lists of diseases that were rare in Africa but common in the developed world, and ascribed them to fibre. The list is remarkable – in 1977 he ascribed all of the following conditions to fibre: ischaemic heart disease, diverticular disease of the colon, appendicitis, hiatus hernia, cancer of the large bowel, varicose veins, haemorrhoids, obesity, gallstones and diabetes.

None of these have since been proven to be linked to fibre. However, laboratory studies have revealed the importance of fibre in multiple biological processes in our bodies, and dietary manipulation of fibre may have a role in treating some diseases, but that is a medical decision. It does not follow that a higher fibre diet is warranted for the generally healthy population. That remains unproven.

label_high-in-fibreStill, health authorities exist to give dietary messages, and the fibre hypothesis appealed to them as it did to Burkitt. His credibility would have helped. Gastroenterologists carrying out better-controlled scientific and clinical studies were sceptical. But the lore was established, again before the science. The slogan was released and went forth, populating the minds of the health-conscious everywhere – Eat more fibre (whatever more means).

Multiple stage 3 prospective studies in large numbers of people have now been completed. The results are marginal and mixed. Most meta-analyses show no effect. Confounds are everywhere. For example, people who eat whole grains may exhibit other positive health behaviours such as more exercise, lower rates of smoking and lower alcohol consumption. While most large studies attempt to control for confounds, it is not always possible or as rigorous as desired.

Nevertheless, the high-fibre slogan is set to stay. As with other nutritional slogans, authorities are reluctant to withdraw their advice. They use a ‘guilty until proven innocent’ scenario – the advice stands until scientifically disproven. The foolishness of not needing scientific proof for the advice, but rather scientific proof against it, is lost on nearly everyone in authority. Given the complexities of the science, this slogan will not be easily defeated.

images-3And, industry is on its side – manufacturers love nutritional slogans. Suddenly there was a new market – the high fibre market (just as there was a low salt market, a low fat market, a low cholesterol market etc.). Fibre was seriously cheap, and just bulking a product with it became a successful marketing strategy. Of course, the net weight of a product high in fibre didn’t change, so adding fibre meant removing other (more expensive) macronutrients, thus creating a product less expensive to manufacture that could be sold for the same price or more.

Lastly, a better message might be to ‘eat more whole (real) food” and let the fibre take care of itself. This strategy seems likely to be better than fortifying highly processed and nutrient poor processed foods with fibre.

Burkitt kept faith with his hypothesis throughout his life, even as the evidence supporting it weakened. In a 1977 editorial, he concluded with a telling comment: “The importance of acting on observations in the absence of understanding requires emphasis”. Astonishingly, for a scientific publication, he then backed that statement up with a quote from the New Testament (the missionary was never far away).

The interpretation is: to Burkitt, science takes too long. It is an important attitude to be aware of because nutritional authorities exhibit the same philosophy. However, ‘act now and do the science later’ has risks: the dietary advice may do harm in other ways (see saturated fat); the advice could lead to dietary imbalances (see salt or animal fats or fish oil); it could deny us nutrient-rich sources of food (see cholesterol) and; it leads to misunderstanding of the real science and disempowers the consumer (see how nutritional science works).

So it is that my conclusion to the dietary fibre slogan is much the same as for saturated fat: ‘Our diet has been experimented on at a national level with an hypothesis that started out as a crusade by an influential individual, that went on to become lore, and that didn’t and doesn’t have scientific proof.’

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Further reading:

A biographical memoir of Burkitt by Epstein.

Burkitt’s Uganda legacy