Diabetes

35^th World Vegetarian Congress
'Food for all our futures'
Heriot Watt University, Edinburgh, Scotland
July 8-14, 2002

by Sandra Hood, BSc (Hons), SRD

[ Vai alla traduzione in italiano ]

My talk this afternoon is going to be on diabetes and the vegan diet. Unfortunately there have been few studies that have looked at the vegan diet and diabetes although a few have suggested that a vegan diet can relieve symptoms and perhaps prevent diabetes. It has been suggested that approximately 80-95% of cases of type 2 diabetes could be prevented and in Finland last year, it was demonstrated that with lifestyle interventions, increased activity, low fat diet and weight loss, the risk of diabetes was reduced by 58%. (Tuomilehto et al 2001)

This afternoon I wish to highlight the benefits of the vegan diet and how it may prevent against diabetes. I believe that often as vegans we have to prove that we can be healthy and getting enough of this, that and the other but we forget to look at the other side of the coin, how protective the vegan diet can be. However, I also wish to raise the fact that vegans are not immune from western diseases and still need to examine their lifestyle. Over recent years the diet of vegans and vegetarians has changed considerably with many high fat, high salt, high sugar convenience foods being available and there are an increasing number of vegans and vegetarians eating poor diets, taking less activity and putting on weight. However, there is no doubt that a vegan diet can be protective and perhaps prevent many western diseases and one of these may be diabetes!

Brenda Davis who has written Becoming Vegan and Becoming Vegetarian commented that "health cannot be bought or sold, it does not come in pills or potions and it is the produce of many years of wise choices". In my talk this morning I hope I demonstrated that infants can be brought up healthily and happily on a vegan diet and I believe the foundation of diseases start in childhood and a vegan diet is the best start to life. However, it is never too late to make changes to a diet and as Brenda says in her latest book, "it is sad that many brilliant people do not grasp the value of health until it is snatched from them". I believe vegans and vegetarians have a head start in the health field but many still have health changes to make and again as Brenda comments "it should not be looked upon as a sacrifice but a privilege to be treasured".

So what is diabetes?

Diabetes results from lack of the hormone insulin, which is essential for the transfer of glucose from the blood to the tissues. Insulin is a naturally occurring hormone secreted by the beta cells of the islands of Langerhans in the pancreas in response to increased levels of glucose in the blood. Insulin lowers blood glucose levels and promotes transport and entry of glucose into the muscle cells and other tissues.

Insulin deficiency may result from inadequate insulin production or resistance to its action. Without sufficient insulin, the amount of glucose in the blood becomes abnormally high (hyperglycaemia) and if this level exceeds the renal threshold, it passes into the urine. This in turn increases the amount of urine which has to be produced. At the same time the effective lack of glucose as an energy substrate at the cellular level means that the body has to use its stores of fat and if necessary, muscle tissue as an alternative energy source. The combination produces the classic symptoms of diabetes - excessive urine production, thirst and unexplained weight loss.

There are 2 distinct forms of the disease.

Type 1 - insulin dependent diabetes, where there is a lack of insulin production by the pancreas and needs treatment by insulin injections. The factors which cause this are still poorly understood but certain viruses, autoimmune disease and genetic factors may contribute. The disease usually develops suddenly in children or adults under 40 years, although it can occur at any age.

Type 2 diabetes is where the body is still producing insulin but either not enough and or the body is resistant to it. It is more common than type 1 diabetes, accounting for at least 75% of cases. There are strong genetic links with this type of diabetes and its development is closely associated with obesity. It most commonly develops in middle age and later life but with rising obesity levels in the population, is increasingly being seen in younger adults and even children. Its onset is often insidious and its presence sometimes only discovered during routine health checks. Diet and lifestyle measures may be sufficient to control the disease but some patients will require hypoglycaemic drugs which increase insulin production or enhance its effectiveness to insulin.

Cow's milk has been implicated in the development of Type 1 diabetes

Cows milk is not recommended for children under 1 year of age because of its high protein and salt content. Breast milk is the perfect food for babies. It protects the newborn against infectious diseases and against gastrointestinal and respiratory tract diseases and eye diseases. It may also enhance intellectual development. It most probably contains substances needed by growing infants that are not even known to be essential.

It has been suggested that early exposure to cows milk and or lack of breast feeding predisposes to type 1 diabetes. This remains controversial and well planned prospective studies are essential in order to confirm these observations. I am now going to cite just a few studies which suggest the link with type 1 and type 2 diabetes.

Early exposure to cows milk and lack of breast feeding

Date	Authors	Subjects	Results
1997	Gimeno et al	346 Brazilian diabetic children <18 years of age	Short duration of exclusive breast feeding is a risk factor for Type 1. Introduction of cow's milk before 8 days is a risk factor
1998	Jones et al	160 boys & 150 girls with Type 1	Increased risks associated with not breast feeding but these were not statistically significant
2001	Samuelsson & Ludvigsson	297 Swedish diabetic children diagnosed <15 years of age & seasonal variation with disease	Seasonality was most pronounced in children who developed diabetes between the ages of 10 and 15 years. Indicated increased risk in those who had been exclusively breastfed for a shorter time
2001	Monetini et al	28 Italian non-diabetic children, 16 exclusively breast fed & 12 bottle fed with cow's milk	Breastfeeding within the first 4 months of life prevents the generation of antibody response to bovine beta-casein
1997	Pettitt et al	720 Pima Indians	Exclusive breast feeding for first 2/12 of life is associated with lower rate of T2
2002	Young et al	46 native Canadian type 2 patients <18 years of age	Breastfeeding reduces the risk of Type 2 diabetes

In 1984 Borch-Johnsen et al in Norway and Sweden first suggested there was an inverse correlation between type 1 and duration of breast feeding. This was not supported in 3 subsequent studies but in 1999 Elliott looked at the incidence of type 1 diabetes in children from 10 different countries which suggested that the consumption of specific milk proteins (beta-casein A and B) correlated with type 1 diabetes incidence. Different breeds of cows produce varying amounts of these proteins which produce a peptide called beta-casomorphin-7 which has immune suppressing activity. Chowdhury et al in 1999 and also Alting et al in 1999 hypothesised a "potential diabetogenic role" for cow's milk proteins and suggested further research. Sarugeri et al 1999 looked at cows milk beta-casein as a trigger of autoimmunity associated with type 1 and recently diagnosed type 1 children showed an immune response to cows milk but so did some of the control subjects. Cooper et al in 1999 were unable to find a connection nor did Thorsdottir et al 2000 when he looked at children in Scandinavia and Iceland. Further research is urgently needed.

Dahlquist & Mustonen (2000) report on the rapidly increasing incidence in childhood diabetes in Sweden and suggest the correlation to gross domestic product may suggest risk factors associated with wealth such as high growth rate, a known risk factor for childhood diabetes. So is it that cow's milk is harmful or breast milk is protective?

Is anyone aware of vegan children developing type 1 diabetes? How about vegetarian children?

Type 2 diabetes

The prevalence of type 2 diabetes is increasing rapidly in the UK and worldwide (King et al 1998). In February this year the first cases of adult-type diabetes, type 2, were found in 4 teenage children, triggered by a condition now reaching worrying proportions in the UK: obesity. Although diet and nutrition are widely believed to play an important part in the development of type 2 diabetes, specific dietary factors have not been clearly defined. Much controversy exists about the relation between the amount and types of dietary fat and carbohydrate and the risk of diabetes. Current dietary recommendations promote low fat, high carbohydrate diets for the prevention of diabetes, heart disease and other chronic diseases. However, neither dietary fats nor carbohydrates are homogeneous molecules and it is now increasingly appreciated that the types of fat and carbohydrate are important. I will be exploring the role of fat and carbohydrate later this afternoon.

Approximately 80% of people with type 2 diabetes are overweight. Excess body weight is the single most important risk factor for type 2 diabetes, particularly those whose fat is distributed round their middle (apple shaped) rather than those whose fat is distributed on their hips and thighs (pear shape). Risk of diabetes is approximately doubled for those who are moderately overweight and tripled for those with obesity.

Prolonged surplus energy intake increases endogenous glucose production and hence the body's need for insulin, while at the same time creating surplus fat stores which increase insulin resistance and diminish its effectiveness.

Childhood diabetes

Diabetes is an evolving disease with changing patterns seen in both type 1 and type 2 diabetes. A wide variation exists in worldwide incidence rates of type 1 with the highest occurring in Finland (over 45% per 100,000 under the age of 15 years) and the lowest in parts of China. In Europe the incidence of type 1 diabetes in children has risen by 2-5%. Diabetes is the most common endocrine disease of childhood.

In some countries, such as Japan, there are 4 times as many adolescents with type 2 diabetes as with type 1. The Japanese health authorities were among the first to realize the importance of type 2 diabetes in schoolchildren following the start of urinary glucose screening in schools in 1974. Their data now show the seriousness of type 2 diabetes in adolescence. Obesity, a high energy, high fat diet, reduced exercise, urbanization and other lifestyle changes seem to be the major aetiological factors in the type 2 diabetes epidemic. There is so much readily available food available to so many populations.

There is also suggestive evidence that poor maternal nutrition sufficient to cause intrauterine growth retardation may leave a legacy of reprogrammed fetal cells and an increased risk of future type 2 diabetes when nutrition becomes abundant in later life.

Why vegans may be at reduced risk

• Vegans have less obesity.
• Lower intakes of saturated fat
• High intake of fibre, especially soluble fibre
• High intakes of unrefined foods

OBESITY

The vegan diet generally promotes healthful weights. It is less calorie dense and more nutrient dense than the western diet. The advantages are well recognised. Obesity is fast moving to the top of the health agenda and Britain has overtaken Germany to become the fattest nation in Europe with 1 in 4 of our children now overweight. Treating obesity related illnesses such as diabetes costs the NHS around £1.7 billion a year - £200 million more than smoking related diseases. Obesity is the single most obvious risk factor for type 2 diabetes. Lifestyle modification programmes starting in childhood are urgently needed and society needs to change its attitude to childhood nutrition, play and exercise.

FATS

There is no physiological requirement for dietary fat, only for essential fatty acids which are the polyunsaturated fats - linoleic and alpha-linolenic which are principally from plant sources. Humans and other mammals lack the enzyme to synthesize them therefore they are essential in the diet. The two types of fat I will be exploring in relation to diabetes are saturated fats and trans fatty acids.

Saturated

Animal products are the great sources of saturated fat in the western diet.

Milk fat is over 60% saturated fat compared to plant fats that are about 6-25% saturated fat, most being the in 10-15% range

The exception is tropical oil. Coconut fat is over 85% saturated, palm kernel oil over 80% and palm oil about 50% but they usually only count for a small part of the diet. There are differing opinions on saturated fats in tropical oils as they may be less damaging because they are not packaged with cholesterol but rather with fibre and protective plant chemicals. It would appear that when moderate amounts of tropical oils are consumed as part of a high fibre plant based diet, moderate use of these fats do not increase heart attack risk. By contrast, adding tropical fats to an already high saturated fat diet is adding fuel to fire.

Saturated fats have consistently been linked to heart disease, various forms of cancer and may increase insulin secretion and possibly lead to insulin resistance (Snowdon et al 1985). Meat and saturated fat go hand in hand and Snowdon et al 1985 found that meat consumption was positively associated with diabetes. Saturated fat has been shown to alter faecal microbial enzyme activity and steroid production which might increase the synthesis of estrogens which could impair insulin sensitivity.

For people with diabetes, recommendations are no more than 10% of the diet. Snowdon et al in 1985

Trans fatty acids (hydrogenated oils)

TFA's are produced during the manufacture of margarines. People believe they are making healthier choices changing from butter to margarine but these fatty acids produced have been associated with an increased risk of Type 2

PROTEIN

Omnivores tend to have protein intakes above recommendations. High protein intakes do not seem to adversely effect blood glucose control but it has been shown to adversely affect kidney function. It has been suggested that vegetable protein may be protective to kidney function and it is definitely less toxic than animal protein. Nearly one third of people with diabetes will develop kidney problems.

A few small studies have been carried out looking at the vegan diet and renal function. In 1988 Crane et al showed that within 25 days the symptoms of diabetic neuropathy (damage to peripheral nerves) improved in 17 out of 21 patients when they converted to a vegan diet. Of the remaining 4 patients symptoms were only partially relieved

Date	Authors	Subjects	Results
1988	Crane et al	21 patients with diabetic neuropathy treated with vegan diet	Symptoms reduced in 17 patients within 25 days of changing to a vegan diet
1990, 1991 & 1996	Barsotti et al	Patients with nephrotic syndrome treated with low protein, supplemented vegan diet	Data suggested improvement in renal function

Barsotti also demonstrated the benefits of a vegan diet in relieve symptoms on 3 small groups of patients with kidney disease. Most people firmly believe that animal protein is necessary for human health and that plant protein is inferior. However, plants should be viewed as the primary source of protein, and the primary source of essential amino acids. Amino acids are the building blocks of protein and out of the 22 amino acids, 9 are essential as the human body cannot make these but can be supplied by plants. All animals get their essential amino acids directly by eating plants or indirectly by eating animals that ate plants. Combining amino acids is unnecessary as amino acids are stored in protein pools which we can draw upon as needed. Vegetable proteins should be viewed as the superior protein foods.

CARBOHYDRATES

The different types of carbohydrates can't be ignored. In refining, carbohydrates loose essential nutrients - 95% phytochemicals, 90% fibre and 75% of vitamins and minerals.

Sugar, like white flour, is a refined carbohydrate and at one time it was considered taboo for people with diabetes. This is no longer the case because clinical studies have shown that it has much the same effect on blood glucose levels as refined complex carbohydrates. However, just because sugar appears no worse than refined carbohydrate, does not make it innocuous. Therefore, rather than giving the stamp of approval to sugar, shouldn't we be cautioning against excessive use of refined complex carbohydrates and sugar?

It is important to remember that refining foods can dramatically diminish the nutrient content of food. While many people assume that cooking will damage plant nutrients, that is not necessarily so. In many cases cooking actually increases the availability of phytochemicals. For example lycopene is far better absorbed from cooked tomatoes than from raw tomatoes. Cooking can alter the structure of nutrients resulting in different health effects. There is little question that if you want to maximize the plant nutrients in your diet, it is best to include a variety of both raw and cooked foods

Refined carbohydrates affect glycaemic control and have adverse effects on blood lipids. They also provide little nutrition. Vegans generally have a high fibre diet with less reliance on refined carbohydrates.

FIBRE

This is the part of plants that cannot be digested. All plant foods contain fibre. Fibre is divided into 2 categories, soluble and insoluble. Most plants contain a mixture of the two. Insoluble fibre adds bulk to stools and ensures that food passes quickly and easily through the intestinal tract. Soluble fibre is especially valuable for people with diabetes because it has been shown to help with blood glucose control. Rich sources include oats, legumes and fruits. Vegans have been shown to consume 40-50g/day compared with vegetarians 30-40g/day and omnivores 10-20g/day. Recommended intakes are 18g/day. WHO recommend an upper limit of 54g/day. It has been suggested that intakes comparable to vegans would be beneficial for people with diabetes.

It has been suggested that excess fibre can be harmful as it can reduce the absorption of certain minerals. This may be true. However, high fibre whole foods provide enough extra minerals to more than compensate for any losses incurred and when fibre does bind with minerals they can be partly liberated during the fermentation of fibre by bacteria in the large bowel.

PHYTOCHEMICALS

People have known for a long time that fruits and vegetables, grains, seeds, nuts and pulses are good for you being rich in vitamins, minerals and fibre, but over the last few years there has been interest in the phytochemicals which have been shown to have many health benefits.

These phytochemicals are strong antioxidants which mop up free radicals, active harmful molecules circulating in the body.

A special group of phytochemicals are the plant oestrogens which block the destructive action of the potent form of oestrogen either by competing with oestrogen for receptor sites or by reducing the production of the potent form while increasing the production of the less potent form, possibly reducing the risk of osteoporosis and certain types of hormone dependent cancers. Just this last week studies have highlighted the benefits of soya and its role in the possible prevention of breast cancer

Another important group is the plant sterols. Sterols are a type of fat which have been shown to protect against heart disease. The functional foods Benecol and Flora pro-active are fortified with plant sterols and have been shown to be beneficial in lower cholesterol, large amounts of this type of fat can cause heart disease. The average western diet contains approximate 180-400mg plant sterols/day/ The vegan diet contains approx 600-800mg/day. There are no dietary recommendations for sterols.

ANTIOXIDANTS

For people with diabetes there is some convincing evidence that antioxidants may reduce the risk of complications including retinopathy and kidney failure. In 1998 Opara et al studied 50 people with type 2 diabetes and found that patients with poor blood sugar control and early signs of complications had depleted stores of antioxidants. The association between high blood sugar and low antioxidant level was striking. The ability to defend against free radical attack was approx half in people with poorly controlled diabetes and early signs of complications as it was in non-diabetic patients. This year he went on to review the literature on the therapeutic treatment of antioxidants in the treatment of diabetes and he highlighted the lack of studies. It is well known that vegan diets are rich in antioxidants and in 2000 Thane et al looked at the nutrient status of British pre-school vegetarian children and found that they had higher levels of anti-oxidants in the blood compared with omnivorous children.

VITAMIN C

Vitamin C is a powerful water soluble antioxidant, neutralizing harmful reactions in the blood and the fluid inside the surrounding cells. For people with diabetes vitamin c appears to protect against impaired glucose tolerance and possibly also against complications of diabetes, particularly eye damage.

A number of small studies have reported that people with diabetes have reduced vitamin C status when compared to non-diabetics. In 2001 Sargeant et al 2001 studied over 6000 British men and women and found that high fruit and vegetable intake may influence glucose metabolism and increased consumption may contribute to the prevention of diabetes. The study demonstrated an inverse association between plasma vitamin C and long term blood glucose control. This suggests that vitamin C may have a significant positive impact on both diabetes risk and management.

There are a number of other nutrients that appear to have a role in the cause and treatment of diabetes such as chromium and magnesium. However, we haven't time to discuss all these now. But I do hope I have raised your awareness of the epidemic of diabetes and how vegans and vegetarians lead the way but still need to be careful. Further studies on the health of vegans are desperately needed and I hope this conference demonstrates that vegans and vegetarians are at a distinct advantage and need to lead the way in the health revolution!!

Summary

• Limited saturated fat to no more than 8% of energy
• Avoid foods containing hydrogenated fats
• Consume a mixed vegan diet containing cooked and raw food
• Minimise refined carbohydrates
• Increase activity level

References

1. Dahlquist G, Mustonen L Analysis of 20 years of prospective registration of childhood onset diabetes time trends and birth cohort effects. Swedish Childhood Diabetes Study Group, Acta Paediatr 2000 Oct; 89(10):1231-7.
2. Fort P, Lanes R, Dahlem S, Recker B, Weyman-Daum M, Pugliese M, Lifshitz F Breast feeding and insulin-dependent diabetes mellitus in children, J Am Coll Nutr 1986 ; 5(5):439-41.
3. Gimeno SG, de Souza JM IDDM and milk consumption. A case-control study in Sao Paulo, Brazil, Diabetes Care 1997 Aug; 20(8):1256-60.
4. Golding J, Haslum M, Breast feeding and diabetes, Med Sci Res 1987 ; 15:1135 (letter).
5. Jones ME, Swerdlow AJ, Gill LE, Goldacre MJ Pre-natal and early life risk factors for childhood onset diabetes mellitus: a record linkage study, Int J Epidemiol 1998 Jun; 27(3):444-9.
6. King H, Aubert RE, Herman WH Global burden of diabetes, 1995-2025: prevalence, numerical estimates, and projections, Diabetes Care 1998 Sep; 21(9):1414-31.
7. Monetini L, Cavallo MG, Stefanini L, Ferrazzoli F, Bizzarri C, Marietti G, Curro V, Cervoni M, Pozzilli P; IMDIAB Group Bovine beta-casein antibodies in breast- and bottle-fed infants: their relevance in Type 1 diabetes, Diabetes Metab Res Rev 2001 Jan-Feb; 17(1):51-4.
8. Nigro G, Campea L, De Novellis A, Orsini M Breast-feeding and insulin-dependent diabetes mellitus, Lancet 1985 Feb 23; 1(8426):467.
9. Pettitt DJ, Forman MR, Hanson RL, Knowler WC, Bennett PH Breastfeeding and incidence of non-insulin-dependent diabetes mellitus in Pima Indians, Lancet 1997 Jul 19; 350(9072):166-8.
10. Samuelsson U, Ludvigsson J Seasonal variation of birth month and breastfeeding in children with diabetes mellitus, J Pediatr Endocrinol Metab 2001 Jan; 14(1):43-6.

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Published Online: 25 Aug 2002