This piece was written by one of our contributors; nutritional science graduate studying a MSc in nutrition and dietetics – James Bradfield.
As the old adage goes, you are what you eat. That said, when was the last time you saw an apple, a frozen pizza or a bagel sitting beside you at work or walking towards you in the street? Similarly, have you ever heard someone ask for some carbohydrates with a side of antioxidants at the deli counter?
We frequently hear discussions in which the merits of an individual nutrient or class of nutrients are debated in isolation. In reality, food exists as a complex matrix of near immeasurable numbers of compounds. By oversimplifying, we run the risk of making two mistakes; firstly we ignore other pressing issues in nutrition and secondly, we may forget that food plays a more central role in many of our lives than simply the nutrients that it supplies us with.
When we look at food in very simple terms there are four macronutrients: carbohydrates, proteins, fats/lipids and water. Like most things however, the further you dig, the more you realise that this is just the beginning.
Fats for example are largely broken into saturated and unsaturated fats based on their chemical structure. Saturated fat can be broken down to individual saturated fatty acids. The same is true of unsaturated fats though before that, they must be described as being either monounsaturated fatty acids or polyunsaturated fatty acids. Suddenly you can see why debating about individual macronutrients may seem easy, but in reality is fatally flawed.
Take saturated fat; since data from the Seven Countries Study was first published (1) suggesting that the amount of energy we obtain from saturated fat was correlated with coronary artery disease, saturated fats have had an uneasy time in both medicine and mainstream media. It is important to note that this is not without scientific merit or the support of trusted and respected sources. The World Health Organisation (WHO) and the UK Government’s Scientific Advisory Committee on Nutrition (SACN) both advise limiting intake of saturated fat to 10% of energy requirements. The European Food Safety Authority (EFSA) goes one further when advising that saturated fat intake should be as low as possible ‘within the context of a nutritionally adequate diet’.
Interestingly, a recent joint task force of the European Society of Cardiology and European Atherosclerosis Society agreed with the limit of 10% while also noting that “foods are mixtures of different nutrients and other components, it is not appropriate to attribute the health effects of a food to only one of its components.” However, if it is not appropriate to attribute all the health benefits of a food to one component, then surely the opposite is true and it is inappropriate to attribute all the disease-related contributory factors of a food to one component too? Even though saturated fat raises low density lipoprotein (LDL) levels in our blood (sometimes described as the ‘bad’ cholesterol), there may be cases where this doesn’t explain the whole picture.
Recently, many research groups around the world have shed light on something called the ‘milk-fat globule membrane’ (MFGM). Essentially this describes a sort of coating on the fat molecules in milk. The MFGM is altered in production of other dairy products such as yogurt, cream and butter and the degree to which it survives is determined by the level of processing. Of the fat naturally present in milk, approximately 60% is saturated fat which has led to the popularity of low fat, skimmed and semi-skimmed milks for their perceived health benefits when compared to full fat milk. However a 2015 study from Sweden (2), showed what some might describe as unexpected results.
In this study, overweight men and women consumed a diet with an equal number of calories including 40g of fat from two dairy products: whipping cream or butter oil. In whipping cream, the MFGM is better maintained while it is left less intact in butter. Interestingly, those who received milk fat in the form of whipping cream had a more favourable lipid profile after just 8 weeks. This led to the authors concluding that the food matrix needs to be considered in its entirety when it comes to evaluating cardiovascular disease risk.
This is but one example of how looking at an individual nutrient, in an individual food and an individual outcome can lead you down a rabbit hole of forgetting that we don’t actually eat nutrients; we eat food. This fact is often lost in the attempts to describe the ‘best diet’, the newest superfood (which, for the record, is a regular food item with a marketing department!) or the next wellness trend. We tend to celebrate achievements with a meal or a trip to a restaurant, mark milestones with a sweet treat and cheer ourselves up after a tough day at the office with our favourite comfort meal. While it is important to maintain balance in what we eat and try our best to eat a healthy diet, it shouldn’t be forgotten that we are emotional beings and that for many of us, food plays a central role in keeping us happy and healthy.
Apart from missing the importance that food plays in our lives, debating macronutrient profiles in tabloid newspapers and on social media masks, among other things, the burden of micronutrient deficiencies facing the UK. For example, humans can produce vitamin D endogenously by exposing pigments in our skin to the UV radiation found in sunshine. However in the UK there is less sunshine than in other parts of the world and we spend many hours each day indoors. This has increased the burden of nutritional Rickets, a condition that had previously been near-eradicated and more fitting with Dickensian Britain than that of the 21st century. Even in those with adequate vitamin D status, a deficiency of calcium can lead to similar problems, due to the complex interaction of vitamin D and calcium in the mineralisation of bones (3).
The National Diet and Nutrition Survey (NDNS) is an on-going cross-sectional survey conducted in the UK (4). It collects data on dietary intakes and nutritional status of the UK population as a whole. Most recent data released (5) showed that over the period 2008 – 2017 vitamin D levels were lower from January to March due to less sunshine in the winter months. In this time, 19% of children (4 – 10 years), 37% of children (11 – 18 years), 29% of adults (>18 years) and 27% of adults aged 65 years and over were considered vitamin D deficient based on the SACN recommended concentration of >25nmol/L.
Vitamin D status just tells one story. In addition, the NDNS (6) has highlighted that over half of girls (54%) and 27% of adult women had low iron intakes which may contribute to iron deficiency anaemia. Additionally, over 90% of women of child-bearing age were found to have suboptimal blood folate status which has been shown to be associated with an increased risk of life-threatening neural tube defects (NTDs). Clearly, despite living in a largely affluent country, there is plenty of work to do when it comes to nutritional status. Once again, should we focus on just one issue in nutrition, we may overlook many others which are highly relevant and pressing today. Especially today when there is so much talk about macronutrients, let’s not forget about their little cousins, the micronutrients!
On the surface, food and nutrition is very simple. The fact that we all eat on a daily basis makes it seem even simpler. The fact is, there is likely a lot more going on in the wrap, curry or yogurt sitting in your lunch box than you may give it credit for. It’s ok to admit that we don’t know everything about nutrition and important that we know where to look for reliable information. However an absence of clear information should not be used as an excuse to spread opinions as fact.
References
(1) Keys A, Aravanis C, Van Buchem F, Blackburn H, Buzina R, Djordjevic BS, Fidanza F, Karvonen MJ, Kimura N, Menotti A, Nedeljkovic S, Puddu V, Taylor HL. The diet and all causes death rate in the Seven Countries Study. Lancet 1981;2:58-61.
(2) Rosqvist F, Smedman A, Lindmark-Månsson H, Paulsson M, Petrus P, Straniero S et al. Potential role of milk fat globule membrane in modulating plasma lipoproteins, gene expression, and cholesterol metabolism in humans: a randomized study. The American Journal of Clinical Nutrition. 2015;102(1):20-30.
(3) Allgrove J, Mughal M. Calcium deficiency rickets: extending the spectrum of ‘nutritional’ rickets. Archives of Disease in Childhood. 2014;99(9):794-795.
(4) National Diet and Nutrition Survey [Internet]. GOV.UK. 2019 [cited 4 December 2019]. Available from: https://www.gov.uk/government/collections/national-diet-and-nutrition-survey
(5) National Diet and Nutrition Survey Years 1 to 9 of the Rolling Programme (2008/2009 – 2016/2017): Time trend and income analyses. [Internet]. GOV.UK. 2019 [cited 4 December 2019]. Available from: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/772434/NDNS_UK_Y1-9_report.pdf
(6) Statistical Summary: National Diet and Nutrition Survey: results from Years 7 and 8 (combined) of the Rolling Programme (2014/15 – 2015/16). [Internet]. GOV.UK. 2018 [cited 4 December 2019]. Available from: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/690748/NDNS_years_7_and_8_statistical_summary.pdf
