Those with either type of diabetes will benefit from this approach but unlike type 2 diabetics, those with type 1 will always need to take insulin. Nevertheless, type 1 diabetics can use the D-Diet to keep insulin doses to a minimum and markedly reduce their risk of further health complications.
This approach is based on what you eat, not on counting how much you eat because, perhaps surprisingly, what you eat actually regulates how much you eat (see page 20).
Research has shown that with the right diet it is possible to decrease blood sugar, limit medication, cut the risk of complications and even reverse type 2 diabetes.
One of the first studies to test the effects of a plant-based, low-fat diet and exercise on a
group of 40 type 2 diabetic patients, had outstanding results – 36 of the patients were able to
discontinue all medication after only 26 days (Barnard et al., 1982). The same research group later demonstrated that the benefits of this diet are long-term and last for years, if the diet is adhered to (Barnard et al., 1983).
In one of the groundbreaking studies that followed, researchers employed a combination of
diet change and exercise (Barnard et al., 1994). The subjects were 197 men with type 2 diabetes and after just three weeks, 140 of them were able to discontinue their medication. A further study, conducted around the same time, involved 21 diabetics with diabetic neuropathy (characterised by numbness and shooting or burning pains in the lower limbs), who volunteered to follow a vegan, whole food diet and exercise programme for 25 days. Within 16 days, 17 of the patients reported that the neuropathic pain had been completely alleviated. Although the numbness persisted, it was noticeably improved within the 25 days of the programme (Crane and Sample, 1994).
A 2006 study, conducted by the Physicians Committee for Responsible Medicine with the George Washington University and the University of Toronto, tested health benefits of a low-fat vegan diet emphasising foods with a low glycemic index value and excluding all animal products on people with type 2 diabetes. It was compared to a diet based on the American
Diabetes Association (ADA) guidelines which restricted calorie intake and limited carbohydrates (Barnard et al., 2006). Portions of vegetables, grains, fruits and pulses were unlimited.
Over the 22-week study, 43 per cent of the vegan group and 26 per cent of the ADA group reduced their diabetes medications. Furthermore, the vegan group lost an average of almost one stone (13 pounds), compared with just over half a stone (9 pounds) in the ADA group.
Overall quality of this vegan diet was compared to the ADA diet on the basis of the Alternate Healthy Eating Index (AHEI), which is used to estimate the risk of chronic diseases (Turner-McGrievy et al., 2008). It employs a scoring system which assesses several dietary behaviours and rates food and nutrient intakes. The vegan group improved in every AHEI food category (vegetables, fruit, nuts and soya protein, ratio of white to red meat, cereal fibre, trans fat, polyunsaturated to saturated fat ratio) and significantly improved the overall AHEI score. The ADA group improved in only two categories (nuts and soya protein, polyunsaturated to saturated fat ratio) and did not improve the overall AHEI score of the
group. An increase in AHEI score was also associated with decreases in HbA1c value (which measures blood sugar levels over time) and weight.
Following the success of the previous studies, a 74- week clinical trial using a low-fat vegan diet was conducted (Barnard et al., 2009a). Participants were type 2 diabetics and they were randomly assigned a low-fat vegan diet or a diet following ADA guidelines. HbA1c changes from the beginning of the study to 74 weeks, or to the last available value before any medication adjustment, were -0.40 points for the vegan group and +0.01points for the conventional diet group. In patients whose medication did not need to be adjusted, HbA1c fell 1.23 points over the initial 22 weeks, compared to 0.38 points in the ADA group. Glycemic control, therefore, improved more in the vegan group.
The reduction in triglycerides (fats in blood) in the vegan group was also remarkable as was the decrease in cholesterol levels (-20.4mg/dl in contrast to just -6.8mg/dl in the conventional group). Both groups managed to lose weight but unlike the vegan participants, volunteers on conventional (ADA) diet had restricted calorie intake whilst the vegan group did not.
Parallel to these intervention studies, another research group focused on analyzing dietary patterns of 2,875 volunteers without diabetes and determined their risk of diabetes by repeated measurements of basic indicators – blood glucose, insulin concentrations, cholesterol levels, and waist circumference (Liu et al., 2009). Their findings were clear: consumption of a diet based mainly on plant foods protects against insulin resistance, while refined grains, high-fat dairy, sweet baked foods, sweets and sugary soft drinks promote insulin resistance.
A similar study from 2011 (Rizzo et al., 2011) focused on the risk or presence of metabolic syndrome (which often precedes diabetes) and dietary patterns of middle aged and elderly people. The study concluded that vegetarians had significantly lower values for all risk factors apart from one (HDL cholesterol – which can be explained by the participants’ consumption of
dairy and eggs) and much lower occurrence of the metabolic syndrome than semi-vegetarians (eating meat occasionally) and meat-eaters.
Volunteers participating in some of the above studies preferred the vegan diet (Barnard, 2007) not only because it was effective but also because they found it better than the diet previously recommended. Participants in the 74-week study were repeatedly asked to rate the acceptability of their diets (Barnard et al., 2009b) and the results showed that patients initially felt more restricted by the ADA diet and at the end of the study reported that the vegan diet was as acceptable as the conventional diet. These findings suggest that following a diet that reverses diabetes is no harder than following a conventionally recommended diet which produces only minor changes in metabolism.
The usefulness of vegan diets was eventually endorsed even by the American Diabetes Association when in 2010, their Clinical Practice Guidelines stated that plant-based diets had been shown to improve metabolic control in persons with diabetes (American Diabetes Association, 2010).
Basic principles of the D-Diet
In summary, the D-Diet should contain only foods from plant sources, a minimum of oils and should be rich in foods with a low glycemic index. For these reasons, the D-Diet is based on whole grains, pulses, vegetables, fruit and nuts and seeds (see the D-Diet nutrition basics, page 22, for more information on plant-based nutrition). Whilst limiting the types of food eaten, this diet does not limit the amount of food consumed. Being high in fibre and digested gradually, the recommended foods make the consumer feel full sooner and for longer, while calorie intake is reduced by the minimal amount of fat it contains (per volume of food eaten).
In this section, the basic principles of a diet used for preventing, treating and reversing diabetes are described together with explanations of each of them. The next section (‘Why and how it works’ on page 20) then provides a more detailed insight into how this diet influences the body’s processes. Anyone switching to the D-Diet should remain in close touch with their doctor as glucose control and insulin sensitivity can improve relatively quickly and there might be need for medication adjustment – a decision that needs to be made by a doctor, never by the patient.
1st principle: no to animal products
By eliminating all animal products (meat, fish, dairy, eggs) diabetics avoid eating substantial amounts of fat and their cholesterol intake will be zero. Even lean, white meat and fish contain surprisingly high amounts of fat. For example, 38 per cent of calories from roast chicken and 40 per cent of calories from salmon come from fat (Food Standards Agency, 2002).
Although promoted as a source of omega-3 fats, fish oils also contain cholesterol and a significant proportion of their fat is saturated fat – between 15 and 30 per cent, depending upon the species (Barnard, 2007). Dairy products, even low-fat varieties, inevitably contain fat and most of it is saturated fat. There is no requirement for saturated fats in our diet.
Reducing fat intake is vital for many reasons – in order to reduce the amount of intramyocellular lipid (which interferes with muscle cells’ insulin sensitivity), for cardiovascular health and for general weight loss.
This diet excludes all animal products also because animal protein from meat, fish, dairy or eggs places an additional strain on the kidneys and can damage them (Knight et al., 2003; Barclay et al., 2010). Plant proteins do not appear to cause the same problem (see pages 16 and 21). Protecting the kidneys is another key issue on the way to better health.
All foods should be of plant origin and unrefined wherever possible, which means they will be naturally high in fibre and complex carbohydrates, and low in fat (except oils, nuts and seeds). Animal products contain no fibre or healthy carbohydrates while plant foods contain all the essential nutrients we need.
It has been found that avoiding certain foods entirely is easier than attempting to moderate their intake (Trapp et al., 2010). Reducing the intake of problem foods may not have the desired effect and cravings for them may never be lost. Avoiding them entirely, on the other hand, enables the taste to adjust to the new way of eating and problem foods are likely to lose
2nd principle: low-fat
Even though vegetable oils are better for the body than animal fats because they contain essential fatty acids, less saturated fat and no cholesterol, it is important to keep them to a minimum. In order to reverse or improve the diabetic condition, it is essential to eliminate intracellular fats (Barnard, 2007) but this can only happen if excessive fat consumption is avoided. By eating low-fat foods, the body is still likely to obtain the essential amount of fat
it needs, but not more.
One of the pilot studies on the effects of a vegan diet showed that there are important differences between types of fat in a low-fat regime (Nicholson et al., 1999). Researchers compared the potential of a lowfat vegan diet with a conventional low-fat diet. Participants were all type 2 diabetics and they followed the assigned diet for 12 weeks. At the end of
the study period, the vegan group had 28 per cent reduction in fasting plasma glucose levels (tests carried out after approximately 12 hours without eating). The reduction in the conventional group was significantly lower – only 12 per cent. The average weight loss was 7.2kg in the vegan group compared to 3.8kg in the conventional group. Medication was
reduced in all vegan participants, in one of them completely, whilst there were no reductions in medication in the conventional group.
When individuals with impaired glucose tolerance were tested repeatedly for diabetes and their eating habits were examined (Marshall, et al., 1994), it was found that excessive fat consumption significantly increased the risk of developing diabetes. A recent review of studies on bariatric surgery (a surgical procedure reducing the size of the stomach and gut available for nutrient absorption, performed on severely obese people) (Andreelli et al., 2009) revealed a startling result. Type 2 diabetes can be reversed within days of the surgery, even before any
significant weight loss is achieved. The main mechanism for this dramatic change is the sudden decrease of triglycerides and free fatty acids in the blood and rapid reduction of fats in liver and muscle cells. Such drastic changes are obviously not achievable immediately through diet but the effects of this surgery clearly illustrate the efficacy and importance of a low-fat diet.
The amount of fat per serving should not exceed three grams (or ten per cent of calories from fat). Apart from added oils, diabetics should also limit their consumption of nuts and seeds.
3rd principle: low glycemic index (GI)
Glycemic index, or GI, is a measure of the effects of carbohydrates on blood sugar levels. Carbohydrates that break down quickly during digestion and rapidly release glucose into the blood have a high GI. Carbohydrates that break down more slowly, releasing glucose gradually into the bloodstream, have a low GI.
To help the body deal effectively with the carbohydrate content of different foods, those that release their energy slowly should be preferred. Low GI means that after ingestion, blood glucose will not reach high levels, which is exactly what people with diabetes need. It allows them to better control their blood sugar and reduces the likelihood of complications caused by hyperglycaemia, such as retinopathy, neuropathy and nephropathy (kidney disease).
Glycemic index of selected foods (from Glycemic Index Database and The GI Diet Guide)
55 or less
Most fruits and vegetables, pulses (beans, soya, peas, lentils, chickpeas), barley, buckwheat, hummus, pasta, nuts and seeds, sweet potatoes, dried apricots and prunes, rolled oats, all-bran cereals, wholegrain pumpernickel bread, soya yoghurt and products low in carbohydrates
wholewheat bread, rye bread, crisp bread, brown rice, basmati rice, corn, porridge oats, shredded wheat, pineapple, cantaloupe melon, figs, raisins, beans in tomato sauce
70 and above
potatoes, watermelon, pumpkin, white bread, French baguette, white rice, rice cakes, corn flakes, processed breakfast cereals, dates, sugary foods
Results from 14 studies on glycemic index show that choosing low GI foods alone reduces HbA1c (for both types of diabetes) by 0.3 to 0.4 percentage points. In some of the studies, the difference was even higher – 0.6 points (Brand-Miller, 2003). The authors concluded that the benefit of low GI food consumption is similar to that offered by medication targeting postprandial (after eating) hyperglycaemia. Another review (Willett et al., 2002) came to a similar conclusion and the authors suggested that low GI foods improve glycemic control and reduce hypoglycaemic episodes in people treated with insulin.
Why and how it works
What we eat has an enormous effect on our metabolism. As we have shown, the accumulation of fat in body cells can seriously damage our health and trigger a whole range of other problems. The D-Diet – a plant-based, wholesome and low-fat diet – works on many levels and for both types of diabetes.
This is why:
1) It eliminates intramyocellular lipids and thus improves cell metabolism, enabling mitochondria to work properly by removing the fatty obstacles which stand in the way of
A study comparing intramyocellular lipids in muscle cells of vegans and non-vegans, matched for age and body weight, revealed that vegans had 31 per cent less fat in their muscles (Goff et al., 2005). Another study of morbidly obese people who had to undergo gastric bypass
surgery (Greco et al., 2002) – which reduced the size of their stomach and shortened the length of intestine available for the absorption of nutrients – showed that the drastic weight-loss that followed had a striking effect on their cells. After the first six months, their intramyocellular lipid levels dropped by 87 per cent and their insulin resistance had largely disappeared.
Obviously, we do not recommend taking such extreme measures but these findings
illustrate an important point: insulin resistance is reversible.
As a part of the same study, researchers tested whether a low-calorie diet can also deplete intramyocellular lipids. They found that although weight loss was slower, the effects were equally significant. Nevertheless, the diet focused only on restriction of calories, not on types of food eaten. As other studies have shown, plant-based, low-fat and low GI diets can produce better results in terms of intracellular fat elimination (Barnard, 2007) and improved insulin sensitivity (Lovejoy et al., 1998).
2) When refined carbohydrates and fats are avoided and animal products are eliminated from the diet, the risk of heart and circulation-related problems (high blood pressure, raised
cholesterol and triglycerides and atherosclerosis) plummets. There is no cholesterol in plant foods. A recent review of studies (Ferdowsian and Barnard, 2009) on vegetarian and vegan diets concluded that a plant-based diet, including nuts, soya and soluble fibre, can reduce LDL (bad) cholesterol by 25-30 per cent – a figure comparable to the effects of statin drugs.
3) The kidneys can cope with plant protein much more easily than animal protein. By switching to a vegan diet, the kidneys are less stressed. Research has shown that among people with any degree of kidney damage, consumption of animal protein increases the risk of further kidney deterioration (Knight et al., 2003), while a vegan diet has a protective effect
(Kontessis et al., 1990; Soroka et al., 1998). Anderson et al. (2004) also suggested that
substituting soya protein for animal protein significantly reduces renal hyperfiltration, a
condition that may develop into diabetic nephropathy (kidney disease).
4) Many diabetes-associated complications are caused by damage to blood vessels of all sizes by poor blood sugar control (resulting in high glucose levels) and by raised cholesterol levels, which can harm artery walls. A diet based on starchy, high-fibre foods can protect blood vessels by reducing excess cholesterol, and enables the body to digest carbohydrates
gradually, therefore preventing peaks in blood glucose levels (Chandalia et al., 2000). This is
extremely important especially for the eyes, kidneys and the heart itself because these organs tend to suffer most as the result of diabetes. An investigation into the links between nutrition and retinopathy in diabetics (Roy et al., 1989) found that patients without retinopathy had a significantly higher daily intake of carbohydrates and fibre, and a lower intake of protein, than diabetics with retinopathy.
5) The D-Diet also induces the desired effect of weight loss without portion restriction, ensuring that those who follow it need never feel hungry. This is of particular importance as
too many dietary restrictions, limitations and a lack of positive results have the potential to
induce depression in many diabetics (Diabetes UK, 2010b). An increased intake of fibre
slightly decreases the intake of calories. It was suggested that every 14 grams of fibre reduce
the calorie intake by approximately 10 per cent (Howarth et al., 2001).