A review of Diabetes Prevention and Nutritional Interventions.
With over 180 million people affected by diabetes worldwide (5) Type 2 Diabetes is a major global health problem. In Ireland over 854,165 adults over 40 are at increased risk of developing (or have) Type 2 diabetes] .(16). There is however no universal agreement on which dietary approach is best for the management of Type 2 Diabetes. Guldbrand et al state “Traditionally, a low-fat diet (LFD) has been recommended to patients with type 2 diabetes as a means to lose weight ” (3). However recently low carbohydrate, high fat diets have become more popular due to the growing understanding of the benefits they may bring for glycemic (blood sugar) control .
Dietary advice given to patients with Diabetes Type 2 often recommends a Low carbohydrate diet. As a result, the benefits of low carbohydrate diets have become a widely researched topic, with many trials undertaken to understand the real benefits, as per the table above. For the purpose of this article I reviewed a number of studies to further understand the benefits of a low carbohydrate approach.
In the four studies reviewed, all were randomized control trials which are widely regarded as the gold standard (11). However, they do have limitations as there are many factors at play, when it comes to understanding the outcomes of diets, for example adherence to the diet as dietary intake is self -reported.
The interventions used across the four trial were broadly similar. Each trial included a low carbohydrate (LC) intervention and compared it with either:
high carbohydrate/low fat dietary plan (2,3,7) or in the case of Westman et al a low glycaemic intervention was compared with a low carbohydrate ketogenic diet.
All the trials included dietary/nutritional support but differed in term of lifestyle/behavioural intervention with some studies including supervised exercise programme and lifestyle coaching.
The prevailing outcome from the trials reviewed was that low carbohydrate diets have a more positive impact on the glycemic control of patients with Type 2 Diabetes, many of the trial participants who followed a low GI or low carbohydrate diet were in fact able to reduce their diabetes medication as a result. In their trial Tay et al concluded that “the LC diet consistently induced at least ∼2-fold greater reductions across several GV markers[HC5] ” (2). When Westman et al (15) compared the efficacy of very low carbohydrate ketogenic diet with low GI the low carbohydrate ketogenic diet proved more effective in reducing diabetes medications at the 6 month measurement point[ (15)
HBA1c levels are a primary outcome of all the trials reviewed in detail as they are a primary indicator of diabetes. According to the American Diabetes Association “The A1C test measures your average blood glucose for the past 2 to 3 months .” (13). Therefore, in order for the real impact of a dietary intervention on HBA1c levels a minimum of 4 months would be beneficial to measure the impact on HBA1c levels[HC8] . All trials reviewed met this requirement .
The regional Ethics Committee of Linköping requested a study duration of 24 months when overseeing the trial carried out by Guldbrand et al (3). The other three trials reviewed had duration of one year or less. A longer duration offers benefits as it enables studies to understand if the outcomes if the benefits of the diets are sustainable over a longer term and also if it is realistic for the diets to be followed over a longer time period.
The primary outcome measurements used on all trials were consistently:
- Weight Loss
- HBA1c levels .
In order to achieve remission from Type 2 Diabetes, for overweight and obese people, Diabetes UK recommend to “aim for weight loss of at least 15 kg, as soon as possible after diagnosis” and “to improve glycemic control and CVD risk aim for at least 5% weight loss[HC14] ” (11)
HBA1c levels are a primary indicator of diabetes. According to the American Diabetes Association “Diabetes is diagnosed at an A1C of greater than or equal to 6.5[ %.” (13)
Secondary outcomes varied in the tests to included other glycemic control measures such a fasting blood glucose, total diabetes medications Cholesterol, CVD Indicators and Triglycerides .
All outcomes were relevant and insightful .
As stated by Thomas and Elliot “The aim of diabetes management is to normalise blood glucose levels since improved blood glucose control is associated with a reduction in the development and progression of metabolic and other complications including retinopathy, nephropathy, neuropathy and CVD ” (5) .
The trials reviewed as part of the research for this article clearly demonstrate the benefits of a low glycaemic or low carbohydrate diet for Type 2 diabetes patients in terms of weight loss and glycaemic control. In the trials that compared low carbohydrate to low fat/high carbohydrate diets, in terms of weight loss results were similar but the real benefit of low carbohydrate dietary plans for diabetes patients was the positive impact on glycemic control indicators[HC19] . Wang et al in their trial concluded that “LCD can improve blood glucose more than LFD[HC20] ” (1). Similar conclusion was drawn by Tay et al in their study where the low carbohydrate diet showed greater improvements in the “lipid profile, blood glucose stability, and reductions in medications requirements ” (2)
Further to this, the impact of reducing carbohydrates in the diets of diabetes patients can be seen in the trial carried out by Saslow et al (4) and Westman et al (15). In both of these trials, the advantages of the ketogenic diet where carbohydrates are severely restricted are evident. “The lower carbohydrate, ketogenic diet, was more effective for improving glycemic control than the low glycemic[HC22] diet”. (15) However, the ketogenic diet requires significant dietary changes that may be too challenging for most diabetic patients without extensive behavioural and lifestyle interventions to support[HC23] it. Westman et al conducted 18 group meetings during their 6-month study. Saslow et al state that the strong retention and adherence rates see their trial “may have been due to the novel supportive psychological strategies ” (4)
Expanding this level of intervention to a community clinical setting would, in most countries be financially prohibitive .
In trials conducted by Guldbrand et al (4) and Iqbal et al (6) found that over time, compliance with the low carbohydrate diet dropped HBA1c levels fell back to baseline levels. “At month 6, the low-carbohydrate group had a clinically significant reduction in HbA1c of −0.5% (compared to −0.1% in the low-fat condition), but this was not sustained over time.” And “By month 24, mean HbA1c fell from baseline by 0.1 and 0.2% in each group ” (6).
Compliance with dietary plans is always going to be a challenge with changing in dietary plans, and evidence from the trials studied shows the benefits of an education and behavioral programmes to improve adherence to the plans. Saslow et al demonstrate the benefits of a programme “using behavioural techniques including goal setting, peer support, and behavioral self-monitoring” (10) to support carbohydrate restricted diet. The added benefit of this programme was that it was delivered online, so it was cost effective and had a wider reach than other trials reviewed[HC28] . Results were strong and attrition rate relatively low with 70% of participants reporting outcomes at 12 months, 52% of participants completed all modules. Saslow et al found that “participants with elevated baseline HbA1c (≥7.5%) who engaged with all 10 weekly modules reduced their HbA1c from 9.2% to 7.1% (P<.001) and lost an average of 6.9% of their body weight” (10).
It should be noted that diabetic patients following a low carbohydrate diet should have glycaemic indicators checked regularly as if taking diabetic medications concurrently it could result in hypoglycaemia.
Despite clear evidence of the benefits of low carbohydrate diets in management of diabetes, this approach, is often not the primary plan advised to type 2 diabetes patients. Research reviewed were small in terms of participants and also duration. There is a need for broader trial of low carbohydrate diets with a larger trial base and longer duration with behavioural support programmes that would be feasible in a community clinical practice. Until then the debate will continue as to which is the best macro nutrient composition of the diet .
Additional Dietary Recommendations for Type 2 Diabetes.
For clients diagnosed with diabetes type 2, without question, the most important advice to share with them is the importance of blood sugar balancing and ways they can achieve this. Eating a balanced wholefoods diet, exercising regularly, managing stress levels and also getting adequate sleep can support the body to manage blood sugar balancing. In addition to this there are different foods, nutrients and herbs that can further support glycemic balancing for patients with Type 2 Diabetes:
- Proteins: Ensure to eat a source of protein with every meal. Protein slows down the absorption of sugar into the bloodstream and improves satiety.
- Slow Releasing Foods: Maximise foods that release sugar content slowly such as wholegrains, oats, berries, quinoa, and lentils.
- Essential Fatty Acids: Foods rich in essential fatty acids include oily fish include mackerel, salmon as well flaxseed, chia seeds, olive oil, offer many benefits to type 2 diabetes clients including:
- Fatty acids within the phospholipid bilayer of the cell help to determine the biochemical properties of membranes and influences cellular functions, including cell’s responsiveness to insulin .
- Fatty acids help to reduce inflammation and promote insulin resistance .
- EFA’s can support the cellular healing process by repairing damage done to cells caused by high blood glucose levels .
- Recommended supplementation is 2 capsules of Fish Oil per day.
- Chromium is a mineral that the body uses to make Glucose Tolerance Factor (GTF). GTF is produced in the liver and helps transport glucose from blood into cells. When high blood sugar levels are sustained over a long time, as is the case with diabetes type 2, chromium levels in the body can be depleted. According to McKennon in a review of non-pharmaceutical options for Type 2 diabetes “There is an apparent association between low chromium levels and impaired glycaemic control.” (18) In his review McKennon shared results from a meta-analysis of 15 randomized control trials demonstrating that “chromium supplementation had favourable effects on HbA1c and fasting glucose in patients with diabetes .” (18)
- Cinnamon is often used as a replacement to sugar but it also has benefits beyond its sweet taste for clients with Type Two Diabetes. According to Crawford “Taking cinnamon could be useful for lowering serum HbA1C in type 2 diabetics with HbA1C >7.0 in addition to usual care .” (17). There is much evidence supporting the benefits of Cinnamon and in particular Ceylon Cinnamon in glycaemic control. In a review of 8 clinical trials David et Yokoyama conclude that “Cinnamon intake, either as whole cinnamon or as cinnamon extract, results in a statistically significant lowering in FBG (-0.49±0.2 mmol/L; n=8, P=.025) and intake of cinnamon extract only also lowered FBG (-0.48 mmol/L±0.17; n=5, P=.008). Thus cinnamon extract and/or cinnamon improves FBG in people with type 2 diabetes or prediabetes.” (19 ). Patrick Holford in his book Good Medicine recommends 1 teaspoon a day of cinnamon .(20)
- Antioxidants including Vitamin E can help repair damage caused to cells by overload blood sugar. (20). Sources of Vitamin E include wheatgerm, green leafy vegetables, nuts and seeds .
The American Diabetic Association in their position statement set out goals of Nutrition Therapy for treating diabetes, which include “A1C <7%. Blood pressure <140/80 mmHg. LDL cholesterol <100 mg/dL; triglycerides <150 mg/dL; HDL cholesterol >40 mg/dL for men; HDL cholesterol >50 mg/dL for women. Achieve and maintain body weight goals.” (9) The trials I have reviewed and presented in this article clearly demonstrate that these goals can be achieved through a low carbohydrate diet supported by lifestyle and behavioural improvement programmes.
The person with diabetes plays the most important role in the management of their diabetes. The path to overcoming diabetes type 2 requires some effort by each individual to make changes over time by looking at what they eat, their lifestyle and exercise levels as well as stress level
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