What is the Best Diet for People Living with Diabetes?

What we eat affects our blood sugar levels. There is strong evidence that interventions focusing on dietary change are beneficial in managing diabetes. It is common knowledge that weight loss and a reduced total calorie intake, are fundamental in helping to control blood glucose. The question that is often asked is in what proportions the three main nutrients (carbohydrates, fats, and proteins) should be recommended, for those living with diabetes. In this article, I am going to outline what you need to know about a few of the popular dietary approaches that can be taken by those living with diabetes.

MEDITERRANEAN DIET

The Mediterranean diet is one of the most popular and healthful styles of eating. It is based on traditional food, drink and preparation methods, from countries surrounding the Mediterranean Sea, including Greece, Crete and Southern Italy1. It is plant-based and focuses on the daily consumption of complex whole grain carbohydrates, legumes, seasonal fruits, vegetables, herbs and spices1,2,3. It is also high in healthy fats (olive oil, avocados, nuts, seeds and omega-3 rich fish), as well as dairy (feta cheese, mozzarella cheese and yoghurt)1,2,3. The protein sources are primarily fish, chicken and legumes and the consumption of red meat is limited to a few times a month1,2,3. There is often a low to moderate intake of red wine with meals1,2,3.

What does the research say?

There is strong evidence that adherence to the Mediterranean diet may have a beneficial role in glycaemic control, weight loss and controlling lipid parameters. A review published in 2013 looked at three studies and 1 397 subjects4. Authors found those following a Mediterranean diet showed improved Haemoglobin A1c (HbA1c) levels, reduced triglycerides levels, increased high-density lipoprotein (HDL) levels and weight loss4. Another review published in 2015 included seven studies and a total of 2 065 participants5. Authors concluded the Mediterranean diet played a “protective” role in glycaemic control, and resulted in reduced HbA1c levels and lower fasting glucose levels as well as decreased insulin resistance and lower mortality5.

Points to be considered for those living with diabetes

As this eating style includes carbohydrates, make sure to choose whole grain, high fibre options and practise portion control. Remember that dairy, starchy vegetables, legumes, fruits and whole grain starches all contain carbohydrates so consider the total carbohydrate content of a meal. This style of eating is non-restrictive, easy to adopt and follow and not linked with vitamin or mineral deficiencies.

There is strong evidence that this way of eating is beneficial for those living with diabetes. Research shows following a Mediterranean diet results in improvements in HbA1c, fasting glucose, triglyceride and HDL levels. This in addition to decreased insulin resistance and mortality. If you follow this diet, focus on whole grain, high fibre carbohydrates, practise portion control and consider the total carbohydrate content of your meals.

VEGETARIAN DIET

The vegetarian or plant-based diet has also become increasingly popular. This is not only because of its many health benefits but for ethical, religious and environmental sustainability reasons too1. This diet focuses on plant foods such as legumes (dried beans and peas), fruits, vegetables, nuts, seeds and grains4,6. There are variations of the vegetarian diet:

Lacto-ovo vegetarians include milk (Lacto) products such as yoghurt, milk and cheese as well as eggs (ovo), and exclude meat, poultry, fish and seafood1,6.

Lacto-vegetarians include milk products but exclude eggs, poultry, meat, fish and seafood.

Vegans only consume plant foods and exclude all meat and animal products1,6. They also do not use animal by-products, such as leather, silk, fur, honey, wool or cosmetics or soaps derived from animals1,6.

Pescatarians do not eat meat, however they will eat fish.

There are many variations of the above, with a new trend being the flexitarian or semi-vegetarian diet, which is mainly plant-based but does occasionally include meat6.

What does the research say?

Vegetarian diets are high in fibre, vitamins, minerals and phytochemicals and low in saturated fat (SFA) and cholesterol1,6. According to the American Dietetic Association (ADA) position paper, vegetarian diets lower your risk of developing diabetes and are beneficial in treating obesity, high blood pressure, coronary heart disease, diabetes mellitus and certain types of cancer6. Vegetarians generally have a lower Body Mass Index (BMI), lower blood cholesterol and lower low-density lipoprotein (LDL) than non-vegetarians6. Results from a review published in 2014 showed that a vegetarian dietary pattern significantly reduced HbA1c levels by 0.4% in patients with type 2 diabetes7. They also found that a vegetarian diet was characterised by decreased energy, protein, total fat and cholesterol intake while there were increases in the intake of carbohydrates and fibre7. These observations suggest several possible mechanisms that explain the beneficial effect of a vegetarian diet on improved glycaemic control. Higher intakes of vegetables, whole grain foods, legumes, and nuts (all associated with a vegetarian diet) result in a substantially lower risk of insulin resistance and type 2 diabetes as well as improved glycaemic control in normal and insulin-resistant individuals4,6.

Points to consider for those living with diabetes

As you can see, the vegetarian diet has many beneficial effects in the prevention and management of diabetes. However, as this diet is high in plant-based foods, consuming whole grain, high fibre carbohydrates, limiting the intake of fruits and counting the total carbohydrates in your meals becomes important to maintain normalised blood glucose levels. There is also a risk of lower intakes of certain vitamins and minerals which could lead to deficiencies. These include vitamin B-12, calcium, vitamin D, iron, zinc and long-chain omega-3 fatty acids – particularly in vegan or certain vegetarian diets6.

There is strong evidence that this way of eating is beneficial for those living with diabetes. Research shows following a vegetarian lowers your risk of developing diabetes and is beneficial in treating other chronic conditions. Vegetarians also tend to have a lower BMI, lower blood cholesterol, lower LDL and improved glycaemic control. If you follow this diet, monitor the total carbohydrate content of meals, limit the intake of fruit and be wary of possible vitamin and mineral deficiencies.

LOW CARBOHYDRATE DIETS OR LOW CARBOHYDRATE HIGH FAT DIETS (LCHF)

Low carbohydrate (low-CHO) diets have become popular over the last few years1. These diets focus on higher fat and protein intakes, the inclusion of whole, minimally processed foods and the total avoidance of sugar1. Many people believe that these diets are beneficial in treating obesity and other chronic diseases of lifestyle.

There are many variations of low-CHO diets. The first version (which is quite popular amongst those who can afford it) is LCHF or banting. This diet includes the total avoidance of sugar, fruit, starchy vegetables, whole grains, legumes and other carbohydrate-containing foods such as dairy products (in some cases). There is a high intake of non-starchy vegetables and fats from both animal and plants sources, with the avoidance of most plant-based oils and margarines e.g. canola and sunflower oil. There is a moderate to high intake of protein from animal sources.

Another popular variation of the low-CHO diet involves following similar guidelines, but including some carbohydrate-containing foods. Dairy, fruit, starchy vegetables and whole grains are incorporated but the quantity and quality (i.e. type and amount) are monitored. The same can be said for fats.

What does the research say?

In a review that looked at studies published from 2001 to 2015 on adult diabetics, researchers found there was a significant reduction in HbA1C across all studies8. The size of the decrease tended to depend on the amount of carbohydrates consumed per day. The reduction in HbA1C ranged from a 0.7 – 0.9 % with a daily carbohydrate intake of 75 – 120g. The greatest reduction was 2.2 %, with 30g of carbohydrates per day8. The studies also reported decreases in body weight, fasting glucose levels, triglycerides and medication needs and an increase in HDL4,8. Another review included 3 209 subjects from 19 random controlled trials. Results showed little to no difference in changes in weight, cardiovascular and diabetes risk factors between those on low-CHO weight loss diets and those on balanced weight loss diets, with an equal energy intake9. There is evidence that shows following a low-CHO diet often leads to a more drastic initial weight loss, but over a longer term (12 months) the weight loss is the same as on other diets10. The question that remains unanswered is around the safety of this diet as well as the long-term effects on your health.

Before you change to this style of eating, remember that you are cutting out or down on carbohydrate-containing foods, so there will be a higher intake of protein and fat, particularly SFA. There are numerous clinical trials showing that a high intake of SFA increases the risk of heart disease11. The new Dietary Guidelines for Americans (released every 5 years and based on the latest research) states that “fat should be included as part of a healthy diet, but should be limited as it is still a concentrated source of energy12,13. Trans-fat, cholesterol and saturated fat should be limited in the diet, with these being replaced with unsaturated fat such as mono and polyunsaturated fats found in plants and oily omega-3 rich fish12,13. A high intake of red meat also comes with various negative effects, not only on our health but also on the environment.

Points to consider for those living with diabetes

Those who are taking insulin still need to include carbohydrate-containing foods in their diet as they will experience hypoglycaemic episodes otherwise. Because people following low-CHO diets may replace calories from carbohydrates with fat or protein, it is important they monitor their blood lipid profile including cholesterol and triglycerides as well as kidney function14. Remember that eliminating carbohydrates takes a lot of discipline and long-term adherence can be difficult. It is also quite restrictive leading to a decrease in fibre and certain vitamins and minerals. This diet can get quite expensive as the quality of food is important and focuses on organic, grass fed, free range etc.

There is strong evidence that this way of eating is beneficial in the management of diabetes. Research shows following a low carbohydrate diet results in reduced body weight, fasting glucose levels, triglycerides and medication needs with an increase in HDL. Those taking insulin still need to consume some carbohydrates, exclusion could cause hypoglycaemic episodes. Health risks need to be considered and the pros and cons need to be weighed up. Chat to a healthcare professional before starting this diet and monitor your blood lipid profile including cholesterol and triglycerides as well as kidney function.

LOW FAT DIET

Low fat diets have been recommended for decades, by health organisations around the world. This diet is characterised by a total fat intake of less than or equal to 30% of your total energy. SFA is limited to less than 10%; polyunsaturated, 6 – 10% (5-8% of energy, with an additional 1-2% of energy coming from omega-3) and the remainder of the fat comes from monounsaturated fats. Trans fat intake should be less than 1% of your total energy and cholesterol intake is also limited1,15. The ADA guideline for diabetes states that the primary goal regarding dietary fat in individuals with diabetes is to limit saturated fatty acids, trans fatty acids and cholesterol16. It also goes on to state that dietary goals for individuals with diabetes are the same for individuals with pre-existing cardiovascular disease (CVD), since the two groups appear to have equivalent cardiovascular risk16. Thus, a saturated fatty acid intake of less than 7% of your total energy, minimal intake of trans fatty acids and a cholesterol intake  under 200 mg daily, is recommended16.

What does the research say?

A trial included 49 000 women who were assigned to receive either the low-fat, high-carbohydrate diet or the usual diet. After eight years of follow up, results showed that those in the low-fat diet group lost weight and had a small but significant reduction in LDL cholesterol and diastolic blood pressure17. Hooper et al. (2001) reviewed 27 studies on the effect of intake of dietary fats on CVD risk. They concluded that ‘reduction or modification of intake of dietary fat reduces the incidence of combined cardiovascular events by 16%’18. The type and amount of fat that influenced CVD risk factors was assessed by Schwab et al (2014). They found that ‘partial replacement of SFA with polyunsaturated fat or monounsaturated fat lowers fasting serum/plasma total and LDL cholesterol concentrations’11,15. This was further supported in the male population with partial replacement of SFA with polyunsaturated fat11,15. With regards to weight loss and a low-fat diet, in most cases weight loss is initially slower at 3 – 6 months than on other diets, but at one year results did not differ.

There has been new research regarding cholesterol in recent scientific research that found no substantial relationship between dietary cholesterol and that which is found in the blood or cardiovascular events in general populations12,13. Dietary advice should place emphasis on the types of fat consumed, as opposed to reducing total fat intake12,13. Researchers found that when total fat was restricted, the intake of good, health-promoting fats – i.e. monounsaturated and polyunsaturated fatty acids, which have many health benefits – was also decreased.

Points to consider for those living with diabetes

Fat has many roles in food and has a big influence on taste and mouth feel. When fat is removed, (e.g. in lower fat products), sugar and salt are often added to improve the taste and texture of the food. Therefore, care needs to be taken to ensure you aren’t eating too much added sugar or salt. Most of the research shows there should be a focus on reducing the intake of saturated and trans fats. These should both be replaced with poly- and mono- unsaturated fats such as omega-3 rich fish, nuts, seed, avocados, olives and plants oils but portion control should be practised. Remember fat has more than twice as much energy per gram, than protein and carbohydrates. This can lead to increased energy intake and thus weight gain if too much is eaten at once.

There is evidence for the beneficial effect of a low-fat diet on diabetes. Research shows that following a low-fat diet results in reduced LDL cholesterol, diastolic blood pressure and incidence of cardiovascular events as well as weight loss when compared to other diets. Evidence also shows that partial replacement of SFA with polyunsaturated fat or monounsaturated fat has further beneficial effects on fasting serum/plasma total and LDL cholesterol concentrations. Focus on reducing the intake of saturated and trans fats by replacing them with polyunsaturated and monounsaturated fats, such as omega-3 rich fish, nuts, seeds, avocados, olives and plants oils. Portion control of these fats should be practiced for weight management.

There you have it: Information on many of the popular diets that people living with diabetes hear about. When it comes to choosing something that works for you, make sure you chat to your dietician and read credible articles as there is a lot of incorrect information out there. Remember that everyone is different so what works for you might not work for your neighbour. Choose a way of eating that is affordable, sustainable and focuses on a lifestyle change rather than a diet. What most of the guidelines have in common is that they recommend a variety of foods from different food groups. If carbohydrates are included focus on high fibre, whole grain carbohydrates and consume less sources of added sugar. Include plenty of vegetables in your diet and limit fruit intake. Put an emphasis on the healthy fats. Drink plenty of clean, safe water and exercise regularly. When it comes to diet and health, there is no ‘magic bullet’ and no single food that causes disease. Remember balance is key and you need to take your whole lifestyle into account.

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REFERENCES

  1. Heart Healthy diets by Ashleigh Smith FUTURELIFE Available at: dietitian http://futurelife.co.za/heart-healthy-diets/
  2. Diabetes.co.uk. Mediterranean Diet. http://www.diabetes.co.uk/diet/mediterranean-diet.html (Accessed 31st July 2017)
  3. American Diabetic Association. The Basics of Mediterranean-Style Eating. Available at: http://www.diabetes.org/mfa-recipes/tips/2011-09/the-basics-of.html?referrer=https://www.google.co.za/? (Accessed 31st July 2017)
  4. Am J Clin Nutrition. (2013) Systematic review and meta-analysis of different dietary approaches to the management of type 2 diabetes. Available at: http://ajcn.nutrition.org/content/97/3/505.full.pdf+html (Accessed 31st July 2017)
  5. NCBI (2015). Effect of Mediterranean Diet in Diabetes Control and Cardiovascular Risk Modification: A Systematic Review. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4411995/ (Accessed: 31 July 2017)
  6. Position of the American Dietetic Association: Vegetarian Diets (2009). Available at: http://jandonline.org/article/S0002-8223(09)00700-7/fulltext (Accessed 31 July 2017)
  7. Cardiovasc Diagn Ther (2014). Vegetarian diets and glycaemic control in diabetes: a systematic review and meta-analysis. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4221319/ (Accessed 31 July 2017)
  8. Proceedings of the Nutrition Society (2017). Should a Low Carbohydrate Diet be recommended for Diabetes Management? Available at: https://www.cambridge.org/core/services/aop-cambridge-core/content/view/E5C2E3059142A9C4D5C2A73EB1DB8F09/S0029665117000192a.pdf/div-class-title-should-a-low-carbohydrate-diet-be-recommended-for-diabetes-management-div.pdf (Accessed 31 July 2017)
  9. PLOS One (2014) Low Carbohydrate versus Isoenergetic Balanced Diets for Reducing Weight and Cardiovascular Risk: A Systematic Review and Meta-Analysis. Available at: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0100652 (Accessed 1 August 2017)
  10. The New England Journal of Medicine. (2003) A Randomized Trial of a Low-Carbohydrate Diet for Obesity. Available at: http://www.nejm.org/doi/full/10.1056/NEJMoa022207 (Accessed 1 August 2017)
  11. NCBI (2014). The amount and type of dietary fat on cardiometabolic risk factors and risk of developing type 2 diabetes, cardiovascular diseases, and cancer: a systematic review. Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4095759/ (Accessed 31 July 2017)
  12. ODPHP (2015). 2015–2020 Dietary Guidelines for Americans Available at: https://health.gov/dietaryguidelines/2015/ (Accessed 31 July 2017)
  13. Fats & Heart Health: An Update by Nicola Wilkinson Available at: http://futurelife.co.za/fats-heart-health-update/ (Accessed 31 July 2017)
  14. American Dietetic Association. ADA Issues New Clinical Practice Recommendations. Available at: http://www.diabetes.org/newsroom/press-releases/2007/new-clinical-practice-recommendations-122807.html  (Accessed 31 July 2017)
  15. SAJCN (2013).The importance of the quality or type of fat in the diet: a food-based dietary guideline for South Africa. Available at: http://sajcn.co.za/index.php/SAJCN/article/view/750/1081. (Accessed 31 July 2017)
  16. Nutrition Recommendations and Interventions for Diabetes: A position statement of the American Diabetes Association (2008) Available at: http://care.diabetesjournals.org/content/31/Supplement_1/S61.full (Accessed 31 July 2017)
  17. The JAMA network (2006). Low-Fat Dietary Pattern and Risk of Cardiovascular Disease: The Women’s Health Initiative Randomized Controlled Dietary Modification Trial Available at: http://jamanetwork.com/journals/jama/fullarticle/202339 (Accessed: 31 July 2017)
  18. Pubmed.gov (2001). Dietary fat intake and prevention of cardiovascular disease: systematic review. Available at: https://www.ncbi.nlm.nih.gov/pubmed/11282859 (Accessed 31 July 2017)