Without a doubt, personalised nutrition is currently a hot topic. A brief scroll through social and mainstream media will bombard you with promising solutions claiming to help you discern precisely what YOU, and only YOU, should or shouldn’t eat. Diets tailored to blood types, eating plans based on body shapes, food intolerance testing, genetic testing, gut microbiome testing... the options seem endless. While some of these proposals are clearly too good to be true, others appear to have a more solid scientific foundation.
But is technology truly able to deliver personalised nutrition yet? The short answer, unfortunately, is no, not quite.
Currently, the most effective way to achieve truly personalised nutrition is still through consultation with a registered nutritionist or dietitian. These professionals take the time to understand your needs, objectives, concerns, and lifestyle, discussing the available strategies with you. Rarely do they require costly tests to be conducted.
There – I've saved you a lot of money already!
Unless... perhaps you are still tempted to enrol in a personalised nutrition programme promising to help you “understand how food affects your body.” Such programmes send a shiny box filled with state-of-the-art tools to assist you in determining precisely what you should eat. For the hesitant, let's delve a bit deeper into what personalised nutrition entails and what's on offer today.
Personalised nutrition: the promises
Research in the field of personalised nutrition began gaining momentum in the mid-noughties with the realisation that the ‘one-size-fits-all’ approach to nutrition had limited success in inspiring people to change their diet, coinciding with the rise of genomics and big data. These advances provided tools to deliver more tailored advice, considering individuals’ specific needs and potential health risks on a large scale [1, 2]. Unfortunately, this approach has been rather disappointing so far: incorporating genomics did not significantly improve health outcomes [3].
Additionally, genetics failed to explain why individuals with the same genetic makeup – such as identical twins – could react differently to similar diets [4]. This prompted the emergence of the gut microbiome as route to better tailored advice: if our genetic makeup does not predict our response to food, could it be influenced by our gut microbiome? By understanding and manipulating our gut microbiota, our hope is to improve health markers and prevent the onset of certain chronic diseases [5]. That’s the latest frontier for personalised nutrition.
So, let’s look at a few tests that are popular at the moment in the field of personalised nutrition.
A stool test to harness your gut microbiome?
It’s amazing what we can find within a stool sample: it’s packed with trillions of microorganisms. And it offers a simple and fairly cost-effective way to get an insight into the complex ecosystem that is our gut (although, its use as a proxy for the whole gut microbiome has been challenged [6, 7]).
By getting a stool test, you will get a detailed list of all these micro-organisms that were identified in it, some of which have been associated with health benefits. But can this stool test help us make informed, personalised advice on what to eat? The short answer is no.
The gut microbiota is an elusive and complex organ, and we are only beginning to comprehend its connection with our health. Understanding what constitutes a desirable gut microbiome for an individual and how to attain it remains akin to science fiction at this stage of research [8].
The only recommendation we can give people is to take care of their gut microbiota by consuming a diet rich in plants, dietary fibres, and phytochemicals [9, 10, 11] and to consider fermented foods.
Hard to describe this as personalised nutrition yet.
How about monitoring your glucose response?
A recent trend is the use of continuous glucose monitors (CGM). While crucial for those with type 1 diabetes [12] and potentially useful for raising awareness of glucose spikes in individuals with type 2 diabetes, they are unlikely to be significantly helpful for the general population. In fact, they may even pose problems.
The underlying assumption of these tests is that all glucose spikes are unhealthy and should be avoided at all costs. However, this is incorrect for healthy people. A rise in glucose after a meal containing carbohydrates is a normal response. What truly matters is not the spike itself but the body's response to it: can your body effectively clear the glucose within two hours? If so, there is no cause for concern.
An analogy to consider is comparing blood glucose to heart rate (bear with me, as I am not a cardiologist!): when you exercise, it is normal for your heart rate to increase and then return to your resting heart rate. Should you be concerned about the increase in heart rate? Of course not. However, if you take an exceptionally long time to recover from exercise or if your resting heart rate is high, these may be signs of an underlying issue requiring medical investigation. It is the response that is significant, not the spike itself.
If your body struggles to clear glucose effectively on a regular basis, showing signs of glucose intolerance, then you probably need to investigate and address the underlying cause and that can’t be done with a CGM nor through avoiding carbs. It requires medical input, which these testings cannot provide.
(If you want to explore further whether glucose spikes should be of concern, I highly recommend Dr Nicola Guess’s Substack [13].)
Caution required when interpreting your ‘glucose score’
Finally, I would also question the value of scoring systems used by some companies. To interpret the glucose response, they do not use the usual cut-off thresholds for glucose levels as we would for individuals at risk of diabetes [14] since these products are designed for general wellness, and not to diagnose, prevent, or treat any disease. So, instead, they rate your glucose response against that of other participants, of similar age and gender.
But here is the issue: this scoring system may wrongly flag some entirely normal responses as problematic.
Let’s take my own score as evidence. I signed up for one of these test packages when researching their value and my glucose score was ‘POOR,’ which intrigued me – there is no history of glucose intolerance in my family, I’m at a healthy weight and metabolically healthy, fairly physically active… I wasn’t expecting such a score. So I went back to the actual CGM data. And although my responses may have been higher than those of people with a similar profile, they were entirely within the normal range, and therefore by no means cause for concern.
What is concerning is that these tests run the risk of pathologising normal phenomena, causing unnecessary worry and leading people to restrict their diet without valid reason.
In my professional opinion, monitoring your blood glucose is unnecessary if you are otherwise healthy, even when attempting to optimise your nutrition. Instead, I recommend ensuring you consume a balanced and varied diet, incorporating fibre-rich foods, an adequate amount of protein, and healthy fats. Once again, the test itself does not deliver personalised nutrition!
Stool tests, blood glucose monitors – these tools are not bogus. They are regularly used in medical and research settings. They will give you some valid information on how your body may respond to diet to a certain extent. But what I am questioning here is the value of this information. What can you do with it? Sadly, not much at this stage.
At the end you will be given the same recommendations: eat a balanced and varied diet that is meeting your energy requirement, rich in all kinds of plant-based foods, with some proteins and healthy fat, and limit alcohol, refined sugars and saturated fat.
Conclusion: these tests are fun, but they cannot help you make better educated food choices.
Towards a more holistic approach to personalised nutrition
So, what truly constitutes personalised nutrition today? This, I believe, is the most interesting question, and to answer it, let's slightly reframe it: what prevents people from adopting the best eating patterns for them in the long term? Is it a lack of knowledge about what they should eat, or is it the difficulty of maintaining a healthy diet?
My years of experience working with people is that it is the latter. Which is, let’s face it, a far more complex challenge.
Our environment: What food is available? What is our budget? Who do we eat with?
Our lifestyle: Do we have time to cook or even take a break to eat? Do we mainly eat at home?
Our preferences and psychology: Which foods do we enjoy? What motivates our food choices? What role does food play in our lives?
I argue that the most potent personalised nutrition advice considers not only your health needs but also your environment, lifestyle, and preferences. This can only be achieved through human connections: by collaborating with an expert, such as a registered nutritionist or dietitian, who you trust to empower and assist you on your health journey, facilitating sustainable and effective changes to your diet.
My professional opinion is that no app or test can currently provide true meaningful personalised nutrition.
Hello, my name is Clem.
I’m an evidence-based, award-winning nutritionist (MSc, RNutr) and workplace wellbeing specialist.
I help organisations and individuals make sense of nutrition to nurture their health and wellbeing.
If you want to know more about nutrition and health, subscribe to my newsletter or get in touch with me
References:
[1] Gibney, M. J., McNulty, B. A., Ryan, M. F., et al. Nutritional phenotype databases and integrated nutrition: from molecules to populations. Advances in nutrition (Bethesda, Md.), 5(3), 352S–7S (2014). https://doi.org/10.3945/an.113.005496
[2] Ordovas, J. M., Ferguson, L. R., Tai, E. S., et al. Personalised nutrition and health. BMJ (Clinical research ed.), 361, bmj.k2173 (2018). https://doi.org/10.1136/bmj.k2173
[3] Celis-Morales, C., Marsaux, C. F., Livingstone, et al. Can genetic-based advice help you lose weight? Findings from the Food4Me European randomized controlled trial. The American journal of clinical nutrition, 105(5), 1204–1213 (2017). https://doi.org/10.3945/ajcn.116.145680
[4] Berry, S.E., Valdes, A.M., Drew, D.A. et al. Human postprandial responses to food and potential for precision nutrition. Nat Med 26, 964–973 (2020). https://doi.org/10.1038/s41591-020-0934-0
[5] Turnbaugh, P. J., Ridaura, V. K., Faith, et al. The effect of diet on the human gut microbiome: a metagenomic analysis in humanized gnotobiotic mice. Science translational medicine, 1(6), 6ra14 (2009). https://doi.org/10.1126/scitranslmed.3000322
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[7] Shalon, D., Culver, R.N., Grembi, J.A. et al. Profiling the human intestinal environment under physiological conditions. Nature 617, 581–591 (2023). https://doi.org/10.1038/s41586-023-05989-7
[8] Gebrayel, P., Nicco, C., Al Khodor, S. et al. Microbiota medicine: towards clinical revolution. J Transl Med 20, 111 (2022). https://doi.org/10.1186/s12967-022-03296-9
[9] Graf, D., Di Cagno, R., Fåk, F., et al. Contribution of diet to the composition of the human gut microbiota. Microbial ecology in health and disease, 26, 26164 (2015). https://doi.org/10.3402/mehd.v26.26164
[10] Singh, R.K., Chang, HW., Yan, D. et al. Influence of diet on the gut microbiome and implications for human health. J Transl Med 15, 73 (2017). https://doi.org/10.1186/s12967-017-1175-y
[11] Frame, L. A., Costa, E., & Jackson, S. A. Current explorations of nutrition and the gut microbiome: a comprehensive evaluation of the review literature. Nutrition reviews, 78(10), 798–812 (2020). https://doi.org/10.1093/nutrit/nuz106
[12] NHS website – Type 1 diabetes https://www.nhs.uk/conditions/type-1-diabetes/managing-blood-glucose-levels/continuous-glucose-monitoring-cgm-and-flash/
[13] Dr Nicola Guess’s substack https://substack.com/@drguess
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[16] Chen, P. J., & Antonelli, M. Conceptual Models of Food Choice: Influential Factors Related to Foods, Individual Differences, and Society. Foods (Basel, Switzerland), 9(12), 1898 (2020). https://doi.org/10.3390/foods9121898