Recently, the popular and engaging health influencer - the Glucose Goddess - has stoked concerns about oats and their negative effect on health. What is the problem that she has identified? That oats cause a glucose spike that can, in some way, harm us. I was recently served several online videos featuring her talking on this subject. But aren't oats healthy? Are the dietary recommendations for consuming whole grains, in particular oats, incorrect? Do they harm health and, should we avoid them as she suggests?
Below we review a short video where the Glucose Goddess discusses oats. We compare each statement with the evidence, primarily from meta-analyses (collections of multiple studies) from human randomised controlled trials. Studies that look at actual health outcomes from eating oats.
As ever, please talk to your doctor, or medical practitioner most familiar with your medical history before implementing any changes in diet, exercise or lifestyle; especially if you are under treatment. We provide links to the quoted and other relevant studies at bottom of page.
Oats and the Glucose Goddess
The key comments and the science:
Firstly, the Glucose Goddess' recommendation to enjoy "...a savoury breakfast is a breakfast built around protein... animal protein or plant protein..."
No argument here, there are valid reasons to consume protein in the first meal of the day.
Secondly, she states"Most importantly, nothing sweet in the morning, except - if you really want some, some whole fruits."
Here we really need to understand what is meant by 'sweet' and we'll come to that in a moment.
The Glucose Goddess also seems to suggest that we should perhaps avoid fruit (?) unless we 'really want' something sweet. Is there a problem with fruit for healthy people? Or what about fruit for those with glucose issues, with diabetes? For both groups, fruit is recommended as part of a healthy, balanced diet. In this article our focus is on the oats. We review the specific effects of fruit on blood glucose, spikes and health in detail here.
Thirdly, she shares"What you want to avoid is a breakfast that is pure starch and sugar. Oats with honey and a banana: pure starch and sugars; glucose, fructose: big glucose spike.
This is where the conversation gets nuanced. Whole oats, and here we will define them as the commonly consumed rolled oats, are healthy as long as they are minimally processed. This means enjoy thick oats - not the fast cooking 'quick' or 'instant' oats that behave more like simple sugars when digested. Unfortunately she has not specified the type of oat in her statement.
She goes on to say "If you really love sweet taste in the morning, have for example an omelette and then have an an apple, but a whole apple. Because when you transform a piece of fruit then a lot of problems start to happen, so no fruit juices, no jams, no cereal, no muesli, no granola etc no acai bowls, no smoothies, but if you really want something sweet, a piece of whole fruit."
So once we have some whole oats, with a banana and perhaps some honey... what will happen? I'll argue in favour of not having the honey as I don't have a sweet tooth. But a little honey - if it allows you to enjoy the health promoting oats - is no big deal for most people. In contrast to her advice, I will enjoy the oats with a banana - or any piece of whole fruit - for sweetness. But what does the science say?
As Wherli et al found in their recent meta-analysis on oats:
"We conducted a systematic review and meta-analysis using data from approximately 471,157 participants from 8 studies to help clarify available evidence on the associations of oat intake with the risk of type 2 diabetes (T2D), cardiovascular disease, and all-cause mortality. Overall, our findings show that a high oat consumption is associated with a lower risk of T2D and all-cause mortality, but not consistently with cardiovascular disease.
To date, this is the first meta-analysis to investigate the association between oat intake and risk of T2D cardiovascular disease and all-cause mortality. Our findings are in agreement with multiple published meta-analyses, reporting positive effects of oat intake on T2D risk factors, such as lowering HbA1c, fasting and postprandial glucose and fasting insulin. Since oats are considered to be a whole grain, our findings are consistent with the previously published data on beneficial effects of whole grains on the risk of coronary heart disease, coronary vascular disease, total cancer, and mortality from all causes. Moreover, whole grain oats appeared to be the most effective whole grain in terms of cholesterol reduction."
A similar positive finding, for the health benefits of oats, is common to many other studies. (shred at bottom of page)
Fourthly, the Glucose Goddess states"Have an apple, but a whole, apple. When you transform a piece of fruit a lot of problems start happening. So no fruit juices, no jams, no cereal, no muesli, no granola etc Acai bowl, smoothies. But if you really want something sweet, a piece of whole fruit."
From this list we would generally avoid sugary juices and jams, save them for an occasional treat. When it referencing 'cereal, muesli and granola' once again much depends on the specifics. Is she describing highly processed corn flakes or colourful fruit loops versus minimally processed whole grains; or something in between? Added sugars can be a problem for many seemingly healthy breakfast items, say granolas, often a whole grain covered in a sweetener.
When it comes to 'muesli' consumption, an advanced genetic based study (a Mendelian randomisation) from the UK found the following in relation to heart disease. Note that muesli was defined as "a mixture of oats, seeds, nuts, dried fruits and milk":
"Our results suggested genetic evidence for a potential causal relationship between muesli intake and reduced coronary artery disease risk... Secondary Mendelian randomisation analyses on plasma metabolite levels suggested this may be mediated by increased levels of acetate, a gut microbiota-derived short-chain fatty acid. These genetic data are consistent with previous observational findings of a negative association between muesli and heart disease. They also substantiate previous studies associating acetate with antihypertensive and immunoregulatory mechanisms. Lastly, they agree with the current guidelines for primary prevention of cardiovascular disease, which emphasizes a diet rich in fruits, vegetables, and whole grains." Joshua Park et al, 2024
Whole grains and the other components of muesli, feed the healthy gut bacteria that regulate and support our heart health, blood pressure and immunity.
Finally, on the subject of smoothies - blended fruit, what does the evidence show? When prepared simply (without the addition of sugars or juices) fruit smoothies do not cause glucose spikes greater than consuming whole fruit as the Glucose Goddess states. In fact, somewhat counter-intuitively, the opposite is found to be true. Learn more and see the evidence here.
So What Does This Mean?
The above studies - or rather studies on collections of multiple studies - have all found that consuming oats leads to positive health outcomes.
The fact that eating carbohydrates causes a rise in blood sugar that takes the form of a 'spike' - rising, then falling within a couple of hours - is irrelevant to actual health outcomes. Indeed, this 'spike shape' when plotted on a graph is the normal response to consuming sugars - a healthy response. Other responses, especially a prolonged high blood sugar state, indicates that there is a potential metabolic problem and should be investigated further.
After eating it is normal for blood glucose levels to rise and to fall in the hours afterward. Consistently high blood sugar can create increased risk of chronic conditions like cardiovascular disease and type 2 diabetes.
So what is going on? Is the Glucose Goddess right, wrong, making things up? It would appear that all three might be true at the same time.
Certainly for those concerned with weight management or metabolic illness: breads, jams, fruit juices should be consumed with caution. Some elements of the population will also be affected to a greater (or lesser) degree by blood sugar than others, either due to their genetics or, in the short term, a poor night's sleep. This can cause greater responses, both higher and lower, to blood sugar.
But should we avoid eating oats, for breakfast, or at any other time? The evidence clearly demonstrates that oats - whole oats - promote positive long-term health outcomes. Even for those with diabetes where blood sugar levels and glucose variability are a concern, dietary guidelines advise that oats - and fruit - should form part of a properly managed diet.
Perhaps her tight focus on mechanistic actions obscures the bigger health picture, unable to see the wood for the trees? At least when it comes to oats. Or could her continued messaging be part of a strategy to get people to buy her anti-glucose spike supplement?
It is surprising that there is so much to unpack from a short video. While I find the content engaging, there is a real danger that simple statements, easy soundbites, based on snapshots of health (like 'glucose spikes') hide the truth around health and nutrition. One of the key problems with modern eating practices is the lack of whole grain, fruit and fibre in our diets that drives poor health outcomes. Unfortunately, when it comes to ostracising oats, these easy to consume videos can be more harmful than healthful.
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Alastair
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Related Studies
Meta-analyses and systematic reviews in blue:
Mathews R, Chu Y. An encompassing review of meta-analyses and systematic reviews of the effect of oats on all-cause mortality, cardiovascular risk, diabetes risk, body weight/adiposity and gut health. Crit Rev Food Sci Nutr. 2024 Aug 13:1-22. doi: 10.1080/10408398.2024.2382352. Epub ahead of print. PMID: 39137936.
Park JK, Petrazzini BO, Bafna S, Duffy Á, Forrest IS, Vy HM, Marquez-Luna C, Verbanck M, Narula J, Rosenson RS, Jordan DM, Rocheleau G, Do R. Muesli Intake May Protect Against Coronary Artery Disease: Mendelian Randomization on 13 Dietary Traits. JACC Adv. 2024 Apr;3(4):100888. doi: 10.1016/j.jacadv.2024.100888. Epub 2024 Mar 6. PMID: 38737007; PMCID: PMC11087059.
Amerizadeh A, Ghaheh HS, Vaseghi G, Farajzadegan Z, Asgary S. Effect of Oat (Avena sativa L.) Consumption on Lipid Profile With Focus on Triglycerides and High-density Lipoprotein Cholesterol (HDL-C): An Updated Systematic Review. Curr Probl Cardiol. 2023 Jul;48(7):101153. doi: 10.1016/j.cpcardiol.2022.101153. Epub 2022 Feb 19. PMID: 35192870.
Llanaj E, Dejanovic GM, Valido E, Bano A, Gamba M, Kastrati L, Minder B, Stojic S, Voortman T, Marques-Vidal P, Stoyanov J, Metzger B, Glisic M, Kern H, Muka T. Effect of oat supplementation interventions on cardiovascular disease risk markers: a systematic review and meta-analysis of randomized controlled trials. Eur J Nutr. 2022 Jun;61(4):1749-1778. doi: 10.1007/s00394-021-02763-1. Epub 2022 Jan 3. PMID: 34977959; PMCID: PMC9106631.
Wehrli F, Taneri PE, Bano A, Bally L, Blekkenhorst LC, Bussler W, Metzger B, Minder B, Glisic M, Muka T, Kern H. Oat Intake and Risk of Type 2 Diabetes, Cardiovascular Disease and All-Cause Mortality: A Systematic Review and Meta-Analysis. Nutrients. 2021 Jul 26;13(8):2560. doi: 10.3390/nu13082560. PMID: 34444718; PMCID: PMC8398256.
Musa-Veloso K, Noori D, Venditti C, Poon T, Johnson J, Harkness LS, O'Shea M, Chu Y. A Systematic Review and Meta-Analysis of Randomized Controlled Trials on the Effects of Oats and Oat Processing on Postprandial Blood Glucose and Insulin Responses. J Nutr. 2021 Feb 1;151(2):341-351. doi: 10.1093/jn/nxaa349. PMID: 33296453.
Reynolds A, Mann J, Cummings J, Winter N, Mete E, Te Morenga L. Carbohydrate quality and human health: a series of systematic reviews and meta-analyses. Lancet. 2019 Feb 2;393(10170):434-445. doi: 10.1016/S0140-6736(18)31809-9. Epub 2019 Jan 10. Erratum in: Lancet. 2019 Feb 2;393(10170):406. doi: 10.1016/S0140-6736(19)30119-9. PMID: 30638909.
Du H, Li L, Bennett D, Guo Y, Turnbull I, Yang L, Bragg F, Bian Z, Chen Y, Chen J, Millwood IY, Sansome S, Ma L, Huang Y, Zhang N, Zheng X, Sun Q, Key TJ, Collins R, Peto R, Chen Z; China Kadoorie Biobank study. Fresh fruit consumption in relation to incident diabetes and diabetic vascular complications: A 7-y prospective study of 0.5 million Chinese adults. PLoS Med. 2017 Apr 11;14(4):e1002279. doi: 10.1371/journal.pmed.1002279. PMID: 28399126; PMCID: PMC5388466.
He LX, Zhao J, Huang YS, Li Y. The difference between oats and beta-glucan extract intake in the management of HbA1c, fasting glucose and insulin sensitivity: a meta-analysis of randomized controlled trials. Food Funct. 2016 Mar;7(3):1413-28. doi: 10.1039/c5fo01364j. PMID: 26840185.
Hou Q, Li Y, Li L, Cheng G, Sun X, Li S, Tian H. The Metabolic Effects of Oats Intake in Patients with Type 2 Diabetes: A Systematic Review and Meta-Analysis. Nutrients. 2015 Dec 10;7(12):10369-87. doi: 10.3390/nu7125536. PMID: 26690472; PMCID: PMC4690088.
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