The Science of Lifestyle-Based Diets Blog

For LIVE with Scientists’ Diet and Nutrition month, we wanted to explore the science behind four lifestyle-based diets commonly mentioned in the media. Below we discuss some of the research and studies investigating the health benefits of a Mediterranean, Vegan, Ketogenic and Gluten-Free diet.

It is advisable to consult with a medical specialist before making drastic changes to your diet.

Mediterranean Diet

The Mediterranean diet is often mentioned in news articles and TV shows in association with healthy living, but what is a Mediterranean diet?

In short, the Mediterranean diet is based on the eating habits and traditional foods of the people who live in the regions surrounding the Mediterranean Sea [1]. With many different countries and populations located in this part of the world, there are a great variety of dishes and ingredients that can be enjoyed when following this diet.

Typically the food comprising the Mediterranean diet is rich in plant-based foods, such as fruit, vegetables, legumes, breads, potatoes, nuts and seeds. Olive oil, alongside moderate portions of fish, eggs and dairy products make up dietary fats [2]. Red meats, high sugar and processed foods are not included within the diet.

There has been a considerable amount of research into the health benefits of eating a Mediterranean diet. Multiple large-scale studies have identified significant decreases in the rates of heart disease [3], type 2 diabetes [4], and risk of Alzheimer’s disease [5] in participants who followed a Mediterranean-like diet. Another positive consideration of this diet is that participants in these studies were not asked to calorie count or increase their physical activity. This may explain why more study participants appeared to adhere to their Mediterranean-like diet plans, rather than the control diet groups [3].

The decreases in disease and mortality observed in people following a Mediterranean diet has been linked to the reduction of inflammation biomarkers that are associated with cardiovascular disease, as well as reduced measurements in blood pressure and blood sugar levels [6]. It is thought that the Mediterranean diet lifestyle as a whole – which combines a high consumption of non-processed grains and plant-based foods, alongside the low intake of meats, dairy and processed foods – is what creates these beneficial health changes [6].

Vegan Diet

The vegan diet is becoming increasingly popular as people choose not to consume animal products for ethical, environmental and health reasons. Whilst a few types of vegan diet exist, this article will focus primarily on the benefits of whole-food veganism [7], where the diet consists of a wide range of plant-based foods such as fruit, vegetables, legumes, grains nuts and seeds.

As with the Mediterranean diet, which is primarily plant-based, a vegan diet has been shown to reduce the risk of a number of diseases. Increased protection from heart disease and type 2 diabetes has been attributed to the lower rates of cholesterol [8] and blood sugar [9] that result from a vegan diet rich in fibre and low in fat. This high level of fibre intake is thought to cause a feeling of fullness, which may result in a natural tendency of vegans to consume fewer calories [7], assisting in weight-loss without calorie restricted eating. Further studies have also linked veganism to decreased risks of cancer [10], Alzheimer’s disease [11] and arthritis [12]. It is thought that the anti-inflammatory effects of a plant-based diet is a contributing mechanism by which these disease risks are reduced [12].

As with any diet, it is important to include a wide variety of nutrient-rich foods. Vegans can be particularly susceptible to developing nutrient deficiencies in vitamins such as B12 and D, as well as Iron and Calcium [7], which are often found in larger concentrations in animal products. Some plant-based products, such as cereals and alternative milks are now enriched in these vitamins and minerals; soy-based foods like tofu are a good source for all of these nutrients, whilst Marmite is rich in vitamin B12 [13]! As with most changes to your lifestyle, it is important to listen to your body and if you have any nutritional concerns seek advice from your GP.

Ketogenic Diet

The ketogenic, or keto diet is a low carbohydrate, high fat diet that shifts the body’s metabolism actions away from carbohydrates, towards fats and ketones [14] – ketones are produced by the breakdown of fats [15]. This new metabolic state is called ketosis. Ketosis is a state in which the body begins to burn fat more effectively, rather than carbohydrates, to produce energy.

The standard keto diet is high in fat (70% of diet), moderate in protein (20%), and low in carbohydrates (10%) [15]. First developed in 1921 for the treatment of epilepsy [16], the ketogenic diet is now studied and practiced widely. Whilst the significant reduction in carbohydrate intake has been attributed to rapid weight loss, lower blood sugar levels [17], and reduced inflammation [18], there are also a number of considerations that should be made before commencing a keto diet.

The state of ketosis that the body enters after exhausting carbohydrate-based glucose stores can create more physiological changes to the body than weight loss. Short-term effects such as muscle cramps, fatigue, bad breath and changes in bowel habits are commonly reported, often referred to as keto-flu [15]. Whilst long-term effects require further study, there are concerns that prolonged commitment to a keto diet may increase the risk of organ stored fat, kidney stones and vitamin and mineral deficiencies [16].

Most studies suggest that whilst this diet is effective for rapid weight loss and reduction of some disease risks [15], it is advisable that a strict ketogenic diet should only be followed for up to 12 months [16] with regular monitoring of bodily functions. Consult your GP if you plan to adhere to a long-term ketogenic diet plan and remember, ‘moderation is key’ [15]!

Gluten-Free Diet

A gluten-free diet avoids the consumption of the protein gluten, found in grains such as wheat, barley and rye. Maintaining a gluten-free diet is essential for people with coeliac disease, an immune response disorder triggered by gluten, symptoms of which include stomach cramps, bloating, weight loss, rashes and anaemia. Whilst only a small proportion of the population have diagnosed coeliac disease [19], many people choose to follow a gluten-free diet because of suspected gluten sensitivity [20], to achieve weight loss and to gain other health benefits. However, evidence to support some of these benefits can be limited.

Whilst some studies have suggested that a gluten-free diet can reduce cholesterol, blood pressure and blood sugar levels [21], it remains unclear as to whether these effects can be attributed to the removal of gluten from a persons’ diet, or whether people avoid consuming processed foods when following a gluten-free diet. Breads, cakes, cereals, pastas, biscuits, beer and processed meats all commonly contain gluten, and in general are high-calorie foods. Reducing or removing intake of these food types in your diet may cause a subsequent reduction in calorie-intake and therefore lead to weight loss [22].

It is estimated that up to 13% of the population may be affected by non-coeliac gluten sensitivity [23], where an individual feels stomach pain, discomfort or other features similar to those in coeliac disease after eating gluten containing foods. Some researchers debate as to whether it is the gluten protein that causes symptoms in these individuals, or a different molecule also contained in these types of carbohydrates [19]. Nevertheless, following a gluten-free diet has been shown to ease digestive symptoms in people with non-coeliac gluten sensitivity [24].

Conclusions

We hope this brief article has helped summarise some of the facts and figures behind a few popular diets often promoted by celebrities and other influential figures. Ultimately, a balanced diet high in fruit and vegetables is key to achieving good nutrition. If you want to improve your health through changing your diet, find ways of preparing fruit and veg in a way that you love, if you don’t enjoy eating the new foods in your diet then you won’t stick at it! Always listen to your body and talk to a health practitioner if you have any concerns over your diet, or the effects of a diet.

If you liked the looks of some of the dishes featured in this article keep an eye out on our social media as we’ll be releasing recipes for them soon! Thanks to Lily Kate Kitchen.

~This article was written by Katie Sadler on behalf of the LIVE with Scientists team. All views belong solely to the author. ~

References

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  3. Estruch et al. (2013) [https://www.nejm.org/doi/full/10.1056/NEJMoa1200303]
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  13. Anita Bean, The Vegetarian Athlete’s Cookbook (2016) [https://www.google.co.uk/books/edition/The_Vegetarian_Athlete_s_Cookbook/THK9DAAAQBAJ?hl=en&gbpv=1&printsec=frontcover] – accessed May 2021.
  14. Healthline, Ketogenic Diet [https://www.healthline.com/nutrition/ketogenic-diet-101] – accessed May 2021.
  15. Shilpa and Mohan (2018) [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6251269/]
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