We all know that most people could improve the quality of their diet. Most of us do not eat the recommended five-a-day portions of fruit and vegetables – let alone seven or even ten, as some have suggested. Nor do we consume adequate amounts of oily fish.
Instead, intakes are often too high in saturated fats and sugars added to foods and fruit juice, and too low in fibre and some key vitamins and minerals, including vitamin A and iron. A significant proportion of adults in both the UK and the US are obese or overweight. Intake of red and processed meat is too high, and meat consumption continues to rise in the US, the European Union and the developed world. Despite a shift toward higher poultry consumption, the largest proportion of meat consumed in the US is still red meat (58%).
There are serious implications for long-term health as a result of this disordered way of eating. To improve the situation we need to know how much energy and nutrients are being provided by our food. To help do this, we developed myfood24, an online dietary assessment tool that can support accurate, detailed recording of food and nutrient intake by researchers, but which can also support patients with diet-related conditions, sports enthusiasts, families with “picky” eaters and others. With data on 40,000 nutrients, it includes the largest and most complete food composition table in the UK, and possibly the world.
The size of portions and packaging has increased over the past 50 years, as has the number of products on supermarket shelves. This variety of choice makes it hard for consumers to even start to estimate how many calories or nutrients they might be consuming.
A new generation of smartphone apps offer users a chance to monitor their intake. However, there isn’t strong evidence that most of these are effective. Twenty-eight of the top 200 rated health and fitness category apps from Google Play and iTunes focused on both weight management and self-monitoring diets. When these apps were compared to people using a standard record of weighed food that they ate, the apps over- or underestimated energy intake by 10-14%.
But it’s not just consumers who are affected by inaccurate monitoring. Researchers, who base their studies on this kind of data, also encounter problems.
A major limitation of nutrition research is getting an objective measure of dietary intake. Misreporting is a big problem when people self-report their diet and is particularly common in overweight or obese people. Misreporting generally tends towards under-reporting of unhealthy foods and over-reporting of fruits and vegetables.
Metabolic profiling, which involves testing urine for the hundreds of metabolites that provide chemical signatures of food and nutrient intakes, doesn’t require self-reporting and may be a useful addition to self-reporting. A highly controlled study of 19 people fed four different diets found differences in metabolite concentrations. While this approach cannot replace the need to determine what actual food and nutrients have been consumed, it could be used as an objective measure to validate self-reports.
Understanding what nutrients are in the food we eat also relies on having comprehensive and up-to-date food composition tables – standardised national databases with accurate measures of many nutrients in typical foods. Standard food composition tables in the UK list around 3,000 food items, the majority of which are generic rather than branded (which more of us are likely to consume). While they include the full range of nutrients, they only include a limited selection of foods which are available for purchase.