In Part I we examined the Ketogenic and Paleolithic diets. Here we examine the Vegan Diet, Intermittent Fasting and the Mediterranean Diet, and summarise which is the best diet for optimal brain health.
The vegan diet and the brain
What is it?
The vegan diet focuses on consuming a wide variety of plant foods, with no animal products. Honey may or may not be included depending on the strictness of the adherent.
Many of those following this dietary approach believe fresh produce is superior when it is eaten raw, which is an off-shoot of the vegan diet.
The vegan food movement has grown in leaps and bounds since the days where it was considered a fringe, ‘hippie’ approach to eating. Today it is estimated that there are approximately 79 million vegans globally.
Whether this is due to increased awareness regarding animal cruelty and/or a proliferation of influenceable young people using social media is challenging to identify.
A vegetarian diet, which includes some forms of animal products, such as cheese, eggs, and butter, is believed to be a better option than being vegan by some people, who prefer not to eat any animal flesh but still maintain there’s a need for animal-based protein.
Benefits?
The focus on unprocessed foods once again yields great brain benefits, as a wide variety of nutrients provide the brain with many of the building blocks it needs to function optimally.
The natural increase in fibre assists with digestive health, which supports optimal brain function too.
Challenges?
The brain needs B12 and iron to develop, and function optimally, across the lifespan, and case studies of children deprived of B12 and iron have revealed severe and irretrievable developmental delays, including death.
Adults who are deficient in these nutrients are also at risk of neurological challenges, although aging may lead to an accumulation of iron, which also needs to be addressed.
Although iron is present in a variety of plants, it is not as well absorbed as the form found in animal products, with genes and digestive health both believed to play a role in whether plant forms of iron are absorbed optimally or not.
Therefore, you may have a friend who can absorb enough iron from plants, but you may not have the same constitution.
Furthermore, B12 is not naturally found in plants. The only way to know what your status of these two critically essential nutrients is, is to have a blood test, and to supplement if required.
The idea that ‘anti-nutrients’ in plant foods, such as lectins and phytates, stop the body from absorbing other nutrients is a popular argument to support animal-based diets.
However, the evidence suggests that most people would have no challenges consuming more plant foods, while a few people may be susceptible to ’anti-nutrient’ effects of some plant foods.
Vegan and vegetarian diets do not necessarily eliminate processed foods and may also be low in omega 3 fats. If following either of these two diets, B12 and iron levels need to be checked and supplementation started if required. An increase in omega 3 fat consumption may also be required, along with eliminating dairy if you suspect an intolerance, and removing refined carbohydrates and refined, fake ‘meats.’
Excess gluten consumption may also be a challenge with any of these plant-based dietary approaches.
Evidence?
There are few long-term studies on vegan diets, supplemented with the required nutrients, or not, and their impact on brain health across the life span.
In relation to raw vegan diets, research suggests that the nutrients found in some forms of plants are better absorbed when they are lightly cooked, so consuming only raw plant foods may limit the optimal absorption of some nutrients, like beta-carotene.
Intermittent fasting
What is it?
Intermittent fasting is a way of eating where there is less of a focus on what to eat, versus when to eat.
There are three main categories in this approach, namely: alternate day fasting, whole-day fasting, and time-restricted eating, which involves only eating during certain hours and then skipping meals for the rest of the day. However, here is little evidence to suggest which approach is best.
The body naturally goes into a state of ketosis, similar to what happens when following a ketogenic diet, when food is not consumed for specific periods of time. However, what these periods of time are may differ per individual, and depend on a variety of factors.
Benefits?
There are some advantages to following this approach. For example, by eating nothing after dinner, say from 7pm, and then eating breakfast at 7am, while also eating foods which support brain health, the digestive tract gets to rest over the night fast.
However, ketosis will not be reached if intermittent fasting is only overnight, for example, and carbohydrates aren’t restricted, so weight loss won’t occur because of ketosis, but may occur due to less snacking after dinner!
There is evidence to suggest intermittent fasting isn’t any better at promoting weight loss than consistent energy restriction.
There is also some evidence to suggest improved mitochondrial health generally, and some neuroprotective benefits to intermittent fasting in the presence of ketosis in healthy people. However, most of this research has involved animals.
Challenges?
As the focus may be more on timing of eating, versus quality of food, there is a possibility that nutrient deficiencies may develop. And being hungry leads to the release of stress hormones, which would simply increase the physiological effects of stress for people already experiencing chronic stress.
Intermittent fasting that leads to long term ketosis can lead to adverse effects on health, such as revealed by a rigorous RCT in which participants following a strict fasting protocol over a three-month period lost lean muscle.
Evidence?
Overall, this approach to eating lacks the support of robust long-term studies among healthy humans and has not been examined in light of its effects on brain function and ageing across a diverse group of people. Whether chronic stress impacts its possible benefits has also not been examined.
The Mediterranean diet and the brain
What is it?
There isn’t one ‘Mediterranean’ diet. The different cultures within the region eat differently to each other but share many of the same principles in relation to food choices. For example, the focus is on whole, unprocessed, local fresh produce, a combination of fish and other animal flesh, in moderation, as well as nuts, seeds, legumes and grains, and extra virgin olive oil instead of refined vegetable oils.
Although meat and dairy have long been part of this style of eating, they are not dominant in the diet.
Benefits?
A wide variety of brain nutrients are consumed in this dietary approach, all of which combine to support optimal brain health. Furthermore, enjoying food in a relaxed environment with family and friends is also thought to contribute to its brain enhancing and mood supportive effects.
Challenges?
Although fish has always formed an integral part of the Mediterranean diet, offering essential omega 3 fats and other nutrients, ocean contamination and fishing unsustainability may pose a threat to this centuries-old diet, leading to the need to use a supplemental form of omega 3 fats.
In addition, the consumption of gluten in baked goods and pasta may be a challenge for people sensitive to gluten, which could impact brain health negatively. However, if consumed on rare occasions it may be tolerable.
Evidence?
The Mediterranean diet is the most well robustly researched diet. For many years it has been recognised as supporting mental wellbeing in relation to cognitive function, neurobiological aging, and mood in general.
Recently, a world first research project revealed that depression was lifted in a group of people who followed this diet.
The Mediterranean diet is also the most popular diet this year, probably because it is easy to follow and doesn’t focus on deprivation.
The MIND diet (Mediterranean-DASH Intervention for Neurodegenerative Delay), is the result of combining two well-researched diets, the Mediterranean Diet and the Dietary Approaches to Stop Hypertension (DASH) diet. Its creators aimed to combine the best aspects of each of these diets to produce a diet focused primarily on brain health.
Other dietary approaches
There are many more approaches to eating, with people calling themselves fruitarians, pescatarians, flexitarians and even pollotarians, who are semi-vegetarians who eat chicken but no beef or pork. However, none of them are ideal, with each approach possessing some challenges, including the potential for nutrient deficiencies and excesses, and/or pesticide accumulation.
‘Rules’ and how you ‘interpret’ your diet
Despite that fact that many people desire clear cut, definite, and simple rules to apply to their choice of foods, the evidence to support restricted diets is sparse, and the negative effects of ongoing restrictive dieting are plentiful.
Our genetic profile, coupled with our age, sex, stress levels, personality, activity level, and environment all combine to set the stage for specific nutrient needs, of which we may not be entirely aware.
Many of the above diets have been modified in a variety of ways by people selling the basic idea of a restricted diet, with some changes intended to make it healthier.
In addition, our interpretation of what a specific diet means, for example, how much meat should be consumed in a Paleo diet, or whether the focus is only on avoiding animal products while eating a lot of processed food, in a vegan or vegetarian diet, will also contribute to the nutrients a specific approach provides.
Furthermore, adopting a Mediterranean diet, but consuming mainly pasta, is another interpretation that won’t offer great brain benefits.
Keep in mind that any diet that restricts a specific food may lead to a sense of deprivation, either initially, or over time, and when exposed to it again, most people tend to overeat that food.
This can lead to yo-yo dieting, and worse, food disorders in those vulnerable to them.
In addition, very few people can sustain following a chart, weighing food, and/or eating and preparing different food from their family over long periods of time.
Non-negotiable nutrients
Research has revealed a few facts that we can rely on, and which don’t need any interpretation:
The brain needs unprocessed foods, that are nutrient-dense, and contain fibre.
The brain needs fresh, additive-free foods.
The brain needs certain nutrients for optimal development and functioning throughout life, including B12 and iron, and deficiencies in these nutrients during specific windows of development, and later, will leave lasting neurological damage.
Essential fatty acids (EFAs) are essential for both brain development and functioning, and without them the genetic potential of a child can’t be realised, neither can optimal brain functioning be maintained throughout life.
The brain needs a steady supply of unrefined carbohydrates to sustain its huge energy requirements and no long-term studies on the use of ketones for this purpose are yet available.
A large body of research suggests that the phytonutrients available in a variety of fresh produce, which includes carbohydrates, support optimal physical and mental health.
A simple blood test will reveal deficiencies in B12, iron, zinc, or omega 3, after which you can rectify the deficiencies if required.
In summary, following the framework that the Mediterranean diet suggests is supported by robust evidence for brain health across a lifetime.
Reconciling our dietary approach with our values and beliefs is a luxury that modern life has afforded us. However, our brain is an ancient structure and doesn’t care for philosophical arguments.
We know a lot more than we ever have about what our brain needs to function optimally, and what causes it harm. Your reward for providing it with what it needs are clear thinking, focus, learning and memory, as well as a stable mood across a lifetime, and a plethora of other health benefits. Neglect its needs and it will reward you with the opposite.
Please check the ‘Become a Lighter Brighter You! in 90 Days ’ Online Course if you want a focused, deep dive into nutrition and brain health where you will discover the facts behind feeding your brain optimally.
References
Athinarayanan, SJ, et al. (2019). Long-Term Effects of a Novel Continuous Remote Care Intervention Including Nutritional Ketosis for the Management of Type 2 Diabetes: A 2-year Non-randomized Clinical Trial. Front Endocrinol, 10:348.
Begdache, L. et al. (2021) Diet, Exercise, Lifestyle, and Mental Distress among Young and Mature Men and Women: A Repeated Cross-Sectional Study. Nutrients 2021, 13(1):24
Bolla, A.M, et al. (2019) Low-Carb and Ketogenic Diets in Type 1 and Type 2 Diabetes. Nutrients. 11(5), p. 962.
Bonnie B. et al. (2015) Vegans report less stress and anxiety than omnivores, Nutritional Neuroscience, 18:7, p. 289-296.
Brouns, F. (2018) Overweight and diabetes prevention: is a low-carbohydrate–high-fat diet recommendable? European Journal of Nutrition. 57:1301-12.
Collier, R. (2013) Intermittent fasting: the science of going without. CMAJ. 185(9), p. E363-4
De Cabo, R. & Mattson, M.P. (2019) Effects of Intermittent Fasting on Health, Aging, and Disease. N Engl J Med. 381:2541-2551.
Dobersek, U. et al.(2021) Meat and mental health: a systematic review of meat abstention and depression, anxiety, and related phenomena, Critical Reviews in Food Science and Nutrition, 61:4, p. 622-635.
Eur J Nutr. 2020 Aug;59(5):1845-1858
Genoini, A, et al (2020) Long-term Paleolithic diet is associated with lower resistant starch intake, different gut microbiota composition and increased serum TMAO concentrations. Eur J Nutr. 59(5):1845-1858.
Goldenberg, JZ. Et al. (2021) Efficacy and safety of low and very low carbohydrate diets for type 2 diabetes remission: systematic review and meta-analysis of published and unpublished randomized trial data. BMJ, 372:m4743.
Halyburton, A.K. et al. (2007) Low- and high-carbohydrate weight-loss diets have similar effects on mood but not cognitive performance. Am J Clin Nutr. 86(3), p. 580-7.
Hardman, R.J, et al. (2016) Adherence to a Mediterranean-Style Diet and Effects on Cognition in Adults: A Qualitative Evaluation and Systematic Review of Longitudinal and Prospective Trials. Front Nutr. 3(22).
Horne, B.D. (2015) Health effects of intermittent fasting: hormesis or harm? A systematic review. Am J Clin Nutr. 102(2), p. 464-470.
Kennedy D. O. (2016). B Vitamins and the Brain: Mechanisms, Dose and Efficacy--A Review. Nutrients, 8(2), 68.
Lowe, D.A. et al. (2020) Effects of Time-Restricted Eating on Weight Loss and Other Metabolic Parameters in Women and Men With Overweight and Obesity - The TREAT Randomized Clinical Trial. JAMA Intern Med. 180(11), p. 1491 – 1499.
Mazidi, M. et al (2019). Lower carbohydrate diets and all-cause and cause-specific mortality: a population-based cohort study and pooling of prospective studies. European Heart Journal, Volume 40, Issue 34, 7 September 2019, Pages 2870–2879.
Miller, D (MD) (2009) The Jungle Effect: Healthiest Diets from Around the World - Why They Work and How To Make Them Work for You. NYC: William Morrow Paperbacks, pp. 384.
McCabe, D. (2016) Feed Your Brain. 7 Steps to a Lighter, Brighter You! Sydney, Australia: Exisle, pp. 286.
McCabe, D. et al (2020) Specific Nutrient Intake Via Diet and/or Supplementation in Relation to Female Stress: A Cross-Sectional Study. Women’s Health reports. 1(1), p. 241-251.
Passos, J.A. (2020) Cycles of attention to fad diets and internet search trends by Google trends. SciELO. 25(7), p. 2615-2631.
Sanchez, H.P et al. (2012) Adherence to the Mediterranean diet and quality of life in the SUN Project. Eur J Clin Nutr. 66(3), p. 360-386.
Schmerling, R.H. (2019) Plant-based diets are best… or are they? Harvard Health Publishing. Available at:
Shannon, O.M, et al. (2020) Mediterranean Diet Increases Endothelial Function in Adults: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. J Nutr. 150(5), p. 1151-1159.
Snorgaard, O. et al (2017) Systematic review and meta-analysis of dietary carbohydrate restriction in patients with type 2 diabetes. BMJ, 5(1): e000354-e000354.
Tae Jung Oh, et al. (2018) Body-weight fluctuation and incident diabetes mellitus, cardiovascular disease, and mortality: a 16-year prospective cohort study. The Journal of Clinical Endocrinology & Metabolism, 104(3), pp. 639-646.
Tinsley, G.M & Horne, B.D. (2017) Intermittent fasting and cardiovascular disease: current evidence and unresolved questions. Future Cardiology. 14(1) Special Report.
Tinsley, G.M & La Bounty P.M. (2015) Effects of intermittent fasting on body composition and clinical health markers in humans. Nutr Reviews. 73(10), p. 661-674.
Tomiyama, A.J. et al. (2010) Low calorie dieting increases cortisol. Psychosomatic Medicine. 72(4), p. 357-64.
Wallis, C (2020). How Good a Diet Is Intermittent Fasting? Scientific American. The Body. Available at: https://www.scientificamerican.com/article/how-good-a-diet-is-intermittent-fasting/ (Accessed: 19 March 2021).
Zamroziewicz, M.K & Barbey, A.K. (2018) Chapter 2 - The Mediterranean Diet and Healthy Brain Aging: Innovations From Nutritional Cognitive Neuroscience. Role of the Mediterranean Diet in the Brain and Neurodegenerative Diseases. Academic Press: p. 17-33.