Type 1 diabetes mellitus (T1DM) — prevalence and incidence

The prevalence of T1DM accounts for about 10% of all cases of diabetes, occurs most commonly in people of European descent and affects more than 2 million people in Europe and North America.^{1, 2} A recent update reported that in the US the prevalence of diagnosed and undiagnosed diabetes (all forms in all ages as at 2007) totalled 23.6 million people — 7.8% of the population had some form of the disease. That is, those diagnosed accounted for 17.9 million people and undiagnosed 5.7 million people.²

There is also a wide variation in incidence of T1DM from country to country that is evident globally.³ For example, the marked geographic variation in incidence is clearly evident from data that show that a child in Finland has approximately 400 times the likelihood than does a child in Venezuela to acquire the disease.^{2, 3, 4} Moreover, the incidence of T1DM in children is increasing in Western countries.^{2, 5, 6} The global incidence of T1DM in children less than or equal to 14 years of age as calculated per 100 000 population has marked variation within ethnic and racial distribution in the world population, as summarised in Table 13.1. The incidence increases with age, highest at 10–14 years of age.

Table 13.1 Worldwide incidence of T1DM in children less than or equal to 14 years of age

It is not clear from these worldwide variations the factors contributing to the incidence of T1DM but it appears genetics, environmental, dietary and lifestyle factors all play an important role. The reporting of incidence data for T1DM is further affected by possible under-reporting in some regions due to the quality of the registration system used in poorer countries.

There are also further sub-group variations of T1DM incidence within populations.^{2, 3, 4} For instance, in the US, non-Hispanic white youth have a higher risk of T1DM.² A multiethnic, population-based study in the United States estimated the incidence of T1DM (per 100 000 person-years) was 24.3 in children (less than 19 years of age) with the highest rate observed in non-Hispanic white youth (18.6, 28.1, and 32.9 for age groups 0–4, 5–9, and 10–14 years, respectively).⁷

Type 2 diabetes mellitus (T2DM) — prevalence and incidence

As with T1DM the prevalence of T2DM also varies extensively for different populations from distinct geographical areas.⁸ At the end of the 20th century, it was estimated that 150 million people in the world had diabetes and the World Health Organization (WHO) predicts that, between 1997 and 2025, the number of patients with T2DM will double to reach about 300 million.^{9, 10} According to the WHO, T2DM affects up to 7% of Western populations and is increasing in newly industrialised and developing countries.¹¹

The ageing of populations and the effects of modernisation of lifestyle have led to a dramatic increase in the prevalence of diabetes globally with very high rates in developing nations, particularly in Asia and the Pacific.

The heightened susceptibility and high prevalence of T2DM of Micronesian and Polynesian Pacific Islanders,^{10, 12} Native Americans,¹³ Indigenous Australians and Torres Strait Islanders,^{10, 14} and Asian Indians¹⁴ has been well documented.

In Australia, the prevalence of T2DM has been reported to have doubled since 1981^{6, 10} (Table 13.2).

Table 13.2 Australian prevalence of T2DM

There are a number of risk factors that have been identified with the development of T1DM and T2DM (Table 13.3).

Table 13.3 Risk factors that have been reported to be associated with T1 and T2DM

(Source: adapted from Adamo, Tesson)¹⁵

The number of adolescents with T2DM diagnosed yearly is also increasing globally and has been attributed to factors such as weight gain, poor nutrition and lack of exercise.¹⁶

Dietary factors and T1DM

Dietary factors and T2DM

Obesity is the main cause of developing T2DM according to large scale studies. Whilst lack of physical activity also contributes, the risk of T2DM rises progressively with increasing Body Mass Index (BMI), increasing waist circumference, and obesity.²⁵

Epidemiologic studies suggest that greater consumption of fruit and vegetables reduces the risk of diabetes mellitus. In a population-based prospective cohort (European Prospective Investigation of Cancer–Norfolk) study, 21 831 individuals aged 40–75 years at baseline were assessed for plasma vitamin C level and habitual intake of fruit and vegetables over a 12-year follow-up period. The researchers found a strong inverse association between plasma vitamin C level and T2DM risk. High plasma vitamin C level and, to a lesser degree, fruit and vegetable intake was associated with a substantially decreased risk of T2DM.²⁶

Cultural factors and prevention

Minority ethnic groups found that upper-middle and high-income countries often suffer a higher prevalence of T2DM than the local population, due to cultural and communication barriers, being of lower socioeconomic backgrounds, and having less access to good quality health care.²⁷

Education about positive lifestyle and prevention strategies of T1 and T2DM is vital and needs to be tailored to suit cultural differences and racial sub-groups by understanding lay beliefs and attitudes, religious teachings and professional perceptions in relation to diabetes prevention.

For instance, a UK study of a Bangladeshi community found the Islam norms and teachings offers many opportunities for supporting diabetes prevention. The authors noted that interventions designed for the white population needed to be adapted to be meaningful to the Bangladeshi community. So religion may play an important role in supporting health promotion in any sub-community. Working collaboratively between health educators, health professionals and religious leaders should be explored to promote positive lifestyle changes within communities.²⁸

Breastfeeding and prevention

Women breastfeeding for over 6 months significantly reduces the woman’s risk of developing T2DM later in life. The longer the duration of breastfeeding, the greater the protection against T2DM.

A large scale prospective observational cohort study of 83 585 parous women identified a strong association of duration of breastfeeding and the incidence of T2DM. Whilst controlling for other relevant risk factors such as BMI, the study found that the longer the women breastfed the less likely they would develop T2DM. For each additional year of lactation, women with a birth in the prior 15 years had a decrease in the risk of diabetes of up to 15% amongst participants. Lactation improves glucose homeostasis.²⁹

Gender factors and prevention

Studies indicate, in general, women with risk factors and a family history of diabetes were more likely to obtain diabetes education, gain benefits of self-management and reported higher levels of social support from their diabetes health care team than men did. This highlights the special needs for men with respect to diabetes education, understanding risk factors, prevention, self-care and self-management of T2DM.³⁰

Genetics

Whilst studies suggest T1DM is associated with a wide spectrum of susceptibility and protective genotypes within the HLA class II system, it is likely that increasing environmental exposure is able to trigger these genes even in subjects who are less genetically susceptible.³¹

T2DM is the most common disease in the Western world today that has a genetic link.³² It is the phenotype for more than 150 genotypes.^{32, 33, 34} Each of these genotypes is characterised by impaired glucose tolerance and impairment of the control of intermediary metabolism.

Life stressors and/or depression

Stress may be a contributor to T1DM onset according to a prospective population-based study of almost 6000 children. The study demonstrated children had a threefold risk of developing autoimmunity T1DM if their parents divorced or experienced violence during the child’s infancy within 2.5 years of the event.³⁶ The authors concluded that ‘maternal experiences of serious life events…seem to be involved in the induction or progression of diabetes-related autoimmunity in children’.³⁶ Bullying, a form of stress for a child, is also known to adversely affect glycaemic control and self-management, and increase feelings of depression in T1DM children.³⁷

Research demonstrates that regular use of stress management techniques can significantly reduce blood glucose levels in T2DM. After 1 year, compared with control, stress management reduced HbA1c by up to 1% which is clinically significant. Stress management would be a useful addition to a lifestyle intervention program for diabetics.³⁸

Even daily hot baths for relaxation has been shown to lower fasting serum glucose in diabetics.³⁹ The researchers postulated the benefits could result from increased blood flow to skeletal muscles.

Stress and depression both influence hormonal levels.⁴⁰ Stress and depression increase cortisol, growth hormone and adrenaline. Cortisol and growth hormone increase insulin resistance, and adrenaline stimulate the breakdown of glycogen into glucose (glycogenolysis).⁴¹

Depression is associated with insulin resistance and with diabetes.³⁵ Low mood, mild and moderate depression is 2 to 3 times more common in diabetics than in non-diabetics, and is frequently not diagnosed or treated.⁴² Insulin resistance is positively associated with the development of diabetes.⁴³ A large prospective scale study of 4847 participants without depression symptoms at baseline, at 3 years, treated T2DM was significantly associated with depression with an odds ratio of 1.52, even after adjusting for BMI, socioeconomic status, lifestyle and diabetes severity, and after excluding T2DM patients on antidepressants possibly for diabetic neuropathy. It was felt that depression contributed to diabetes and diabetes also contributed to depression.⁴⁴

In another large scale study of more than 4600 patients over 65 years or older, depression symptoms over time was associated with a higher incidence of T2DM after adjusting for other diabetic risk factors.⁴⁵

In a study of patients with work-related depression, the authors found the presence of depression or depressive symptoms was associated with subsequent increased risk of developing T2DM. The relative risk was 1.25 (95% confidence interval [CI]:1.02–1.48) compared with workers not experiencing depression.⁴⁶

There is a positive correlation between insulin resistance and severity of depressive symptoms with impaired glucose tolerance before the outbreak of T2DM.⁴⁷

A recent study found that serotonin receptor agonists can improve glucose tolerance, and reduce plasma insulin levels.⁴⁸

Hence, the proper management of depression and stress are key factors in reducing the risk and progression of diabetes (see also Chapter 12).

T₁DM

There is a significant body of biologically plausible evidence that strongly suggests that vitamin D plays a role in the prevention of T1DM. Giving infants vitamin D supplementation could protect them from T1DM according to a systematic review of 5 observational studies that showed a reduced risk of T1DM by up to 30% compared with infants not supplemented.⁵²

T₂DM

In a recent meta-analysis of the literature, studies demonstrate a consistent association of low 25-OH vitamin D status, calcium or dairy intake and the prevalence of T2DM.^{49, 53}

Smoking

Researchers have combined the best available information from 25 studies in a systematic review which followed the health of 1.2 million people for several years.⁵⁸

There is an increased risk of T2DM of approximately 50% from smoking and the more a person smoked the higher the risk and vice-versa; smoking preceded the development of T2DM.⁵⁸ Smoking has an adverse effect on pancreatic function. It may cause internal inflammation and increase abdominal fat, even in thin smokers, which could then lead to an increase in insulin resistance. Smoking becomes even more of a problem when combined with T2DM risk-enhancing behaviours such as obesity and inactivity.⁵⁹

Further studies have confirmed this association. In a study of 906 participants free of DM at baseline and after multivariable adjustment, the researchers found of the current smokers, 25% developed T2DM at 5 years, compared with 14% of those who never smoked.⁶⁰

Arsenic exposure

Environmental exposure to low levels of inorganic arsenic in drinking water has been associated with diabetes development. Millions of people world-wide are exposed to inorganic arsenic in water from natural mineral deposits. A cross-sectional USA study of 788 adults aged 20 years or older based on a 2003–2004 survey, urine arsenic levels, and after adjustment for biomarkers such as seafood intake, total urine arsenic was associated with increased prevalence of T2DM. Participants with T2DM had a 26% higher level of total arsenic in their urine than participants without T2DM. After similar adjustment, the odds of developing T2DM led to a 3.6 fold increase risk associated with exposure of arsenic. The authors speculated that arsenic could induce diabetes through oxidative stress, inflammation or apoptosis.⁶¹

Tai chi

Tai chi is a Chinese system of slow meditative physical exercise designed for relaxation, balance and health. Tai chi has demonstrated improved balance, gait speed, muscle strength, cardiorespiratory fitness, and quality of life in older adults.^75–80

However, recent studies including a systematic review have demonstrated that there is some controversy as to its efficacy for patients with T2DM.⁸¹

Recently reported RCTs have demonstrated a change in fasting blood glucose levels.^79–82 One RCT demonstrated no significant intergroup differences in fasting blood glucose levels compared with a placebo intervention.⁸³

One Chinese clinical trial⁸⁴ reported superior effects of tai chi on fasting blood glucose levels compared with walking or running, while 2 other Chinese clinical trials^{85, 86} reported that there was no difference compared with a self-management program, or no treatment.

Three clinical trials reported assessing the effectiveness of tai chi on HbA1c.^{83, 84, 85} Of these only 1 RCT⁸⁵ suggested no effectiveness of tai chi on HbA1c compared with a sham exercise regimen whereas 2 Chinese clinical trials^{83, 84} failed to report intergroup differences compared with no treatment, self-management, walking or running exercise activities. One recent Chinese clinical trial with women diagnosed with T2DM reported that the tai chi group had significantly improved glycaemic control and serum triglyceride levels.⁸⁶

Qigong

Qigong is another Chinese health practice that is associated with a system of healing and energy medicine. Preliminary studies show positive effects for qigong and reflexology in T2DM.^{87, 88}

A recent review has concluded that although qigong has beneficial effects on some of the metabolic risk factors for T2DM, there exist methodologic limitations that hence make it difficult to draw firm conclusions about the purported benefits.⁸⁹ Further clinical trials are warranted.

Further, a recent clinical study adds significant strength to the role of tai chi and/or qigong in the management of the metabolic syndrome and glycaemic control in pre-T2DM.⁹⁰

Yoga

There are few studies that have investigated the efficacy of yoga in T2DM.

Three small studies from India have demonstrated and suggested that yoga asanas and pranayama can better manage glycaemic control and stabilise autonomic functions in T2DM cases.^{91, 92, 93} Moreover, in 1 of these studies it was reported that yoga improved sub-clinical neuropathy.⁹³

A recent community-based study of yoga classes for T2DM aimed to demonstrate benefits of yoga for diabetic patients but unfortunately experienced ‘recruitment challenges; practical and motivational barriers to class attendance; physical and motivational barriers to engaging in the exercises; inadequate intensity and/or duration of yoga intervention; and insufficient personalisation of exercises to individual needs’ and these factors need to be considered in any future research.⁹⁴ It also highlights how research in yoga can be difficult.

A systematic review of the literature identified 25 eligible studies, including 15 uncontrolled trials, 6 non-RCTs and 4 RCTs. Overall, the studies demonstrate yoga showing benefit in several risk indices, including ‘glucose tolerance and insulin sensitivity, lipid profiles, anthropometric characteristics, blood pressure, oxidative stress, coagulation profiles, sympathetic activation and pulmonary function, as well as improvement in specific clinical outcomes’.⁹⁵ Again, the authors acknowledge the limitations of these studies when drawing firm conclusions and encourage additional high-quality trials to confirm the benefits of yoga in diabetics.⁹⁵

T₁DM

It is clear from the extensive literature, high dietary GI food affects HbA1c and glycaemic control in patients with T1DM. Patients with T1DM should be under the care and supervision of a dietician and diabetes educator to help fine tune their diet.

A study of 1776 young children (less than 11.5 years of age) who were at increased risk of genetic type 1 diabetes demonstrated that high dietary GI (hazard ratio [HR]: 2.20, 95% CI: 1.17–4.15) and high glycaemic load (HR: 1.59, 95% CI: 0.96–2.64) were associated with rapid progression of islet autoimmunity (IA) to T1DM. Furthermore it was reported that this was possible due to an increased demand on pancreas beta-cell release of insulin and that the development of IA was not associated with high GI foods.⁹⁷

High fish consumption in the diet may also play an important role in the prevention of T1DM onset. A 12-year study reported a diet rich in omega-3 oils, primarily from fish and other seafood, can reduce the chances of high-risk children developing pancreatic islet beta cell autoimmunity and T1DM by up to 55%. The researchers speculated that omega-3 fatty acids may accentuate T-helper 1 activity associated with autoimmunity and its anti-inflammatory effects may contribute to its benefits.⁹⁸

A recent study of 532 people over a 5-year period demonstrated that diets high in fat, saturated fat and lower in carbohydrates were associated with worse glycaemic control in T1DM, independent of exercise and BMI.⁹⁹

T₂DM

A low GI diet is as effective as medication in improving glycaemic control in diabetics. Patients with T2DM should be under the care of a dietician or diabetic educator to continually monitor their diet. Dietary compliance is fundamental in the management of T2DM.¹⁰⁰

A recent study has reported that in those individuals that are at risk for developing T2DM a change in lifestyle that includes dietary manipulation with a significant decrease in fat intake and a concomitant increase in vegetable and fruit consumption resulted in marked inhibition of the transition from the pre-diabetic state to manifest T2DM.⁴⁰

It has been documented that a diet rich in wholegrains and seafood will be high in magnesium.^{41, 101}

There is a strong inverse relationship to T2DM with magnesium.¹⁰² Also, such diets may be protective against the development of T2DM.¹⁰³ Wholegrain intake is inversely associated with homocysteine and markers of glycaemic control, and studies suggest a lower risk of diabetes and heart disease in persons who consume diets high in wholegrains.¹⁰⁴

Foods rich in soluble fibre such as oats, legumes, guar gum and psyllium are more slowly absorbed and produce lower blood glucose levels.¹⁰⁵ Increasing dietary fibre up to 50g daily (such as raisins and oranges) can improve glycaemic control in patients with T2DM.¹⁰⁶ There is increasing evidence that inflammation plays an important role in the pathogenesis of diabetes, as obesity is associated with a pro-inflammatory state.¹⁰⁷

A Cochrane review that investigated the potential effects of wholegrain foods for the prevention of T2DM has concluded that studies have consistently demonstrated that a high intake of wholegrain foods or cereal fibre is associated with a lower risk of the development of T2DM.¹⁰⁸ However, the evidence for a protective effect coming from prospective cohort studies only has to be considered as weak as with this design no cause and effect relationship could be recognised. Hence, it was further concluded that well-designed RCTs are warranted that are able to draw definite conclusions about the preventive effects of wholegrain consumption on the development of T2DM.¹⁰⁸

Fish

Fish is protective towards the development of T2DM apart from having a number of health benefits by preventing cardiovascular disease. In a study of insulin-resistant participants, a high fish diet improved insulin sensitivity compared with participants not eating fish.¹⁰⁹ Greater fish intake was associated with a lower risk of macroalbuminuria in a self-defined diabetic population.¹⁰⁹

An anti-inflammatory diet can include fish, nuts, flaxseeds, fruits and vegetables, ginger and turmeric.^{110, 111} Partially hydrogenated oils, as in vegetable oils and margarines, are pro-inflammatory and can increase the risk of T2DM.¹¹²

Other protective foods

Garlic, green tea, chilli and onions have all been shown to have beneficial effects in DM. Onion and garlic can decrease blood glucose, cholesterol and blood pressure.^{113, 114}

Two RCTs have found that supplementation with soy protein in T2DM improves fasting insulin, insulin resistance, total and low-density lipoprotein (LDL) cholesterol,^{115, 116, 117} which also showed soy improved glucose control. They also found that regular consumption of chilli could attenuate postprandial hyperinsulinemia.¹¹⁸

Diets with low GI and glycaemic load will modulate swings in blood glucose levels and insulin secretion because of slower absorption and have been shown to improve haemoglobin A1c (HbA1c).¹¹⁵

Other food considerations

Body weight

Obesity is the main predisposing risk factor for the development of diabetes.¹²⁸

The prevalence of obesity varies among different racial groups and it is associated with approximately 30% of Chinese and Japanese patients with T2DM. Obesity is found in 60–70% of people in Western countries and, although estimates vary, it is thought that the prevalence of T2DM could be as high as 30% of aboriginal people.¹²⁹ Pima Indians, Pacific Islanders from Nauru or Samoa will all almost certainly develop T2DM with obesity.¹³⁰

In a study of 1079 participants, intensive lifestyle intervention for overweight patients with impaired glucose tolerance reduced the 3-year incidence of overt T2DM from 35% to 15% by losing 5 kg compared with the control intervention. Every 1 kg of weight loss resulted in a relative risk reduction of developing TSDM by 16%.¹³¹

A number of dietary regimes have been recently reported as alternatives for macronutrient intake and the prevention of chronic diseases.¹³² A comparative study that included the macronutrient contents of 7-day menu plans from the Omni-Heart Study, Dietary Approaches to Stop Hypertension (DASH), Zone, Atkins, Mediterranean, South Beach, and Ornish diets were evaluated for consistency with the US Food and Nutrition Board’s Acceptable Macronutrient Distribution Ranges and with the dietary recommendations of several health organisations for the prevention of cardiovascular disease, cancer and metabolic syndrome. The intent of the study/analysis was to evaluate the healthfulness of the 3 Omni-Heart Trial diets high-carbohydrate (Omni-Carb), high-protein (Omni-Protein), and high unsaturated fat (Omni-Unsat) diets — and were compared with that of the DASH diet and 5 other popular diets, namely the Atkins, Ornish, South Beach, Mediterranean, and Zone diets. The resultant analysis reported that all 3 Omni study diets were consistent with US national guidelines to reduce chronic disease risk. Further, that, popular diets vary in their nutritional adequacy and consistency with guidelines for risk reduction.¹³²

There is also significantly strong evidence that special diets can substantially reduce the risk of developing T2DM.

The Mediterranean diet

The Mediterranean diet with its emphasis on vegetables, grains, fish and olive oil has been shown to reduce the risk of atherosclerosis in diabetic patients.^{133, 134} There is a significant amount of evidence that strongly suggests that the Mediterranean diet could serve as an anti-inflammatory dietary pattern.¹³⁵ This could help prevent diseases that are related to chronic inflammations that include visceral obesity, T2DM and the metabolic syndrome.¹³⁵ The rationale for this evidence is further supported by a recent study that demonstrates that adherence to the Mediterranean diet is inversely associated with risk of developing diabetes and the clustering of hypertension, diabetes, obesity, and hypercholesterolemia among high-risk patients.^{136, 137}

Monounsaturated fatty acids (MUFA) — olive oil and nuts

The MUFA (especially olive oil) in the Mediterranean diet appear to play an important preventative role for T2DM, even in healthy subjects. Insulin sensitivity reduced in healthy subjects on diets high in MUFA compared with diets high in saturated fatty acid. Subjects with the Ala 54 allele of the fatty acid-binding protein 2 gene demonstrated improved insulin sensitivity when the saturated fats were replaced by the MUFA.¹³⁷

High content of MUFA found for instance in the Mediterranean diet may explain the preventative role in reducing insulin resistance leading to T2DM.

A large prospective cohort study involving over 83 000 university graduates without diabetes at baseline demonstrated high adherence to the Mediterranean diet with an 83% reduced risk of developing T2DM.¹³⁸

Consumption of nuts and peanuts is related inversely with diabetes risk.¹³⁹ Nuts may also confer cardiovascular benefit and improve lipid profile for patients with T2DM due to their high content of MUFA and nutritional value.¹⁴⁰

After 6 months of adding 30g of walnut to a low-fat diet of T2DM patients, compared with those on no walnuts, the LDL cholesterol dropped by 10% and HDL cholesterol increased.¹⁴¹

(Refer to Table 13.4.)¹⁴²

Table 13.4 Healthy fats for diabetics’ monounsaturated fats

(Source: adapted from Phillips & Carapetis.)¹⁴²

The Palaeolithic diet

A randomised control study of 29 patients with ischaemic heart disease plus either glucose intolerance or T2DM were randomised to receive (1) a Palaeolithic (‘Old Stone Age’) diet based on lean meat, fish, fruit, vegetables, root vegetables, eggs and nuts or (2) a Mediterranean-like diet based on wholegrains, low-fat dairy products, vegetables, fruits, fish, oils and margarines. The study demonstrated that the Palaeolithic diet — the basis of diet by humans before the introduction of grains, dairy, salt and refined fats and sugars — improved glucose tolerance with a 26% decrease of GI compared with 7% decrease in patients on the Mediterranean diet and independent of waist circumference.¹⁴³

The Ornish diet

The Ornish diet was originally designed as a therapy to reverse cardiovascular disease and is also applicable to patients with diabetes. The Ornish diet consists of a low fat, high fibre, basically vegetarian diet with 75% of the kilojoules (calories) obtained from carbohydrates.^144–146

Critical components of the Ornish dietary plan also include physical activity, yoga and relaxation therapy. In a group of T2DM patients requiring insulin who had adhered to the plan, 60% no longer required insulin at the end of the study.¹⁴⁴

Caffeine

A systematic review of the literature identified coffee consumption as being protective towards the development of T2DM, reducing the risk by up to 35%.¹⁴⁷

A large-scale longitudinal study demonstrated a significant reduction in incidence of glucose intolerance and T2DM of up to 64% in white middle-class people who drank regular coffee consumption compared with people who never drank coffee.¹⁴⁸ This benefit persisted in those even after ceasing coffee consumption.

Similarly, another large-scale population-based study of approximately 2400 subjects found that coffee consumption was found to be significantly and inversely associated with fasting glucose, 2-hour plasma glucose, and fasting insulin in both men and women compared with non-drinkers of coffee.¹⁴⁹

A prospective, community-based cohort of 12 204 non-diabetic, middle-aged men and women assessed risk of caffeine consumption as part of the Atherosclerosis Risk in Communities (ARIC) Study. After adjusting for potential confounders, increased coffee consumption was significantly associated with a decreased risk of diagnosed T2DM in community-based US adults.¹⁵⁰

Cocoa

Based on epidemiological data, diets rich in flavanols are associated with reduced cardiovascular risk and may play a role in reversing vascular dysfunction in diabetics. Cocoa is rich in flavanols. In a study of 41 medicated diabetic patients over a 30-day period, dietary intervention with flavanol-rich cocoa (321mg flavanols per dose) significantly increased circulating flavanols, vascular function and flow-mediated dilation of the brachial artery compared with a nutrient-matched control (25mg flavanols per dose). The benefits of flavanol-rich cocoa (321mg flavanols per dose) were dose dependent up to 3 times daily.¹⁵¹

Alcohol

A large-scale US cross-sectional study of 32 000 people found an inverse relationship between alcohol intake and glycaemic control. On average, T2DM patients who drank alcohol in moderate amounts had HbA1c levels 1.2 less than non-drinkers.¹⁵²

A multicenter trial randomly assigned 109 patients (41–74 years old) with T2DM who abstained from alcohol to receive 150 ml wine (13g alcohol) at dinner or non-alcoholic diet beer (control) each day during a 3-month period. The study found initiation of moderate daily alcohol consumption reduced fasting plasma glucose but not postprandial glucose and improved sleep in T2DM patients. The authors concluded alcohol may have a favourable glycaemic effect on HbA1c. There were no significant changes on liver function tests.¹⁵³

Vitamins

Antioxidant micronutrients may play a role in the prevention of diabetic complications.¹⁵⁴

Multivitamin/mineral supplements

Elevated C–reactive protein levels have been associated with the risk of cardiovascular disease and T2DM. An analysis of the data from a randomised, double-blind, placebo-controlled study was carried out at the end of the trial and it was reported that multivitamin use was associated with lower C–reactive protein levels.¹⁷² Recently, it was demonstrated in an RCT that the effects of vitamins C and E, and also when in combination with magnesium and zinc, were a significant improvement of glomerular, but not tubular, renal function in T2DM patients.¹⁷³ Furthermore, in randomised placebo-control trials after 3 months of using the combined multivitamin and mineral supplements, the treatment group had significant increased HDL cholesterol and apolipoproteins (apo) A1 enzyme levels, and reduced blood pressure in T2DM patients but no change in serum levels of total cholesterol, LDL cholesterol, triglyceride, and apo B levels. This suggests that the multivitamin and mineral supplements may have a favourable cardiovascular benefit by raising HDL levels and reducing blood pressure in T2DM. Supplementation with vitamin C and E and Zn when used alone did not show any benefit.^{174, 175}

Other studies have not been able to demonstrate any benefit of antioxidants on fasting blood glucose levels in T2DM.¹⁷⁶

Middle-aged and elderly patients with T2DM experienced a significant reduction of infections such as flu-like illnesses respiratory, gastrointestinal and urinary tract infections, and days off work (17% of diabetics) in those who took a daily multivitamin supplement compared with those who took placebo (90% of diabetics).¹⁷⁷ Researchers postulated patients with diabetes were more likely to have suboptimal intake of micronutrients which would explain the positive effect.

Diabetics should be educated about the importance of consuming adequate amounts of vitamins and minerals from natural food sources.

Minerals

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