Diet to diet, activated charcoal to superfood dust. Nobody knows what to eat anymore.
And the food industry would like it to stay that way, thanks very much. In this edited article from The Conversation, pharmacologist Professor Lisa Bero unveils the bias in nutrition science – and how big companies get away with it.
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Should we eat breakfast every day? How much dairy should we have? Should we use artificial sweeteners to replace sugar? If we had the answers to these questions, we could address some of today’s biggest public health problems such as heart disease, cancer, diabetes and obesity.
Consumer choice is often guided by recommendations about what we should eat, and these recommendations also play a role in the food that’s available for us. Recommendations take the form of dietary guidelines, food companies’ health claims, and clinical advice.
But there’s a problem. Recommendations are often conflicting and the source of advice not always transparent.
In September, a JAMA Internal Medicine study revealed that in the 1960s, the sugar industry paid scientists at Harvard University to minimise the link between sugar and heart disease. The historical papers the study was based on showed researchers were paid to shift the blame from sugar to fat as responsible for the heart disease epidemic.
In the 1960s, the sugar industry paid scientists at to minimise the link between sugar and heart disease.
The paper’s authors suggested many of today’s dietary recommendations may have been largely shaped by the sugar industry. And some experts have since questioned whether such misinformation can have led to today’s obesity crisis.
We’d like to think industry influence of this scale won’t happen again. We’d like to have enough systems in place to shine a spotlight on any potential bias, or risk of it, as soon as it happens. But the reason it took so long to expose the sugar industry’s tactics is bias can be well hidden. To avoid the potentially huge ramifications, we need much better systems in place when it comes to nutrition research.
Industry influence on nutrition research.
What we know is that food industry sponsorship is associated with researchers interpreting their findings to favour the sponsor’s products. Conclusions don’t always agree with results but can be spun to make readers’ interpretations more favourable.
For example, a study might find that a particular diet leads to weight loss and an increase in heart disease but the harmful effects of heart disease are omitted from the conclusion. Only the weight loss is mentioned. This spin on conclusions is a tactic in other industries and can influence how research is interpreted.
We need more rigorous investigation of the effects of industry sponsorship on the results of both primary nutrition studies and reviews. For example, our recent study examined 31 reviews of the effects of artificial sweeteners on weight loss. We found reviews funded by artificial sweetener companies were about 17 times as likely to have statistically significant results showing artificial sweeteners use is associated with weight loss, compared to reviews with other sponsors.
Reviews funded by artificial sweetener companies were 17 times as likely to show artificial sweeteners use is associated with weight loss.
Nutrition research agenda.
A research agenda focused on single ingredients (such as sugar) or foods (such as nuts) rather than their interactions or dietary patterns may favour food-industry interests. This is because it may provide a platform to market a certain type of food or processed foods containing or lacking specific ingredients, such as sugar-free drinks.
Most data sources used to study publication bias in other research areas are not available for nutrition research, which make it more difficult to detect.
Researchers have identified publication bias in pharmaceutical and tobacco research by comparing the full reports of drug studies submitted to regulatory agencies with publications in the scientific literature. Researchers have also compared data released in legal settlements with published research articles. There are no similar regulatory databases for foods or dietary products.
It is possible to use statistical methods to estimate publication bias in large samples of nutrition research, as in other research areas. Interviewing industry-funded researchers could be another way to identify publication bias.
Another obstacle to rigorously assessing bias in nutrition research is the lack of transparency about funding sources and conflicts of interest. Our review of artificial sweetener studies found authors of 42 per cent of them had conflicts of interest not disclosed in the published article.
42 per cent of artificial sweetener studies had conflicts of interest not disclosed in the article.
Also, about one-third of the reviews didn’t disclose their funding sources. Although disclosure in journals is improving over time, not all journals enforce disclosure guidelines for author conflicts of interest and research funding sources.
Reducing bias in nutrition research.
Studies on research bias related to pharmaceutical and tobacco industry sponsorship and conflicts of interest has led to international reforms. Similar reforms are needed in nutrition research.
Further studies will determine which mechanisms to reduce bias should be urgently implemented for nutrition research. Options include:
- refined methods for evaluating studies used in systematic reviews,
- enforced policies for disclosing, managing or eliminating financial conflicts of interest across all nutrition-related journals and professional associations,
- mechanisms to reduce publication bias, such as study registries that describe the methods of ongoing studies, or providing open access data,
- revised research agendas to address neglected topics and to produce studies relevant to population health, without corporate sponsors driving the agenda,
- independent sources of funding for nutrition research, or, at a minimum, industry sources pooling their funding with research funds administered by an independent party.
In the current economic climate, in which industry funding is encouraged by universities, studying bias is important and contentious research.
The full effects of industry sponsorship and financial conflicts of interest on nutrition research remain hidden. An evidence base as rigorous and extensive as the the one on bias in pharmaceutical and tobacco research is needed to illuminate how nutrition research is at risk of bias.
This article was originally published in The Conversation.
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