August 2010 Issue

Nutrition and Type 1 Diabetes — Can Diet Reduce Risk?
By Janice H. Dada, MPH, RD, CSSD, CDE, CHES
Today’s Dietitian
Vol. 12 No. 8 P. 36

Although science has yet to prove a way to prevent the disease, some research suggest factors such as breast-feeding and vitamin D supplementation may have risk-reducing effects.

Type 1 diabetes mellitus (T1DM) accounts for approximately 5% to 10% of all diabetes cases. Unlike type 2 diabetes, T1DM is an autoimmune condition—that is, the immune system has “attacked” the insulin-producing beta cells of the pancreas, creating a total insulin deficiency. Various environmental factors may trigger this attack, including several dietary factors, which this article will discuss. Based on studies of monozygotic twins, experts believe that genetics account for 30% to 40% of the risk for T1DM and that a person’s environment (including diet) makes up 60% to 70% of the risk, based on temporal trends and migrant studies.1

Breast-Feeding vs. Early Introduction of Cow’s Milk
The hypothesis that early exposure to cow’s milk or a lack of breast-feeding may predispose a child to T1DM dates to the 1980s.2 In 1994, the American Academy of Pediatrics (AAP) began recommending that infants with a strong family history of T1DM be breast-fed and that the introduction of cow’s milk be delayed.3 Since then, many researchers have examined this proposed mechanism.

Ecologic Studies
Ecologic studies have made several associations between early cow’s milk exposure and an increased incidence of T1DM. Several investigations have revealed a high correlation between the per capita consumption of cow’s milk and the prevalence of T1DM between and within countries.4-6 Scott evaluated milk consumption data from 13 countries and found a significant positive correlation with T1DM incidence.4 This research also found an inverse relationship between breast-feeding and avoidance of cow’s milk until the age of 3 months and diabetes risk among data from 18 countries.

Case-Control Studies
A meta-analysis of 13 case-control studies by Gerstein revealed a 1.5 times higher risk of developing diabetes with cow’s milk exposure before the age of 4 months.7 Additionally, a separate meta-analysis of 17 studies by Norris and Scott revealed a similar relationship between early infant diet and T1DM risk.8 When researchers in Finland set out to determine whether breast milk is protective or cow’s milk is causative, they found that cow’s milk exposure was more closely linked with causation than breast milk was with protection from diabetes development.9

However, there is evidence that calls the causal implications of cow’s milk and T1DM into question. The negative correlation between the frequency and the duration of breast-feeding and T1DM was not seen in some studies.1 Some study authors have concluded that the increased incidence of T1DM was due to early introduction of solid foods within the first four months of life.

Cohort Studies
A Finnish population-based prospective birth-cohort study analyzed the development of insulin-binding antibodies in relation to cow’s milk exposure in 200 infants.10 The researchers found that the amount of immunoglobulin G antibodies binding to bovine insulin was higher at the age of 3 months in infants who were exposed to cow’s milk formula than in those who were exclusively breast-fed. Vaarala et al concluded that “cow’s milk feeding is an environmental trigger to insulin in infancy that may explain the epidemiological link between the risk of T1DM and early exposure to cow’s milk formulas.”

According to the research team, the possibility that insulin-specific lymphocytes induced by cow’s milk feeding may be later activated in some children needs to be considered as a possible mechanism leading to the autoimmune destruction of beta cells and subsequent progression to clinical T1DM.

In the German BABYDIAB study, researchers followed offspring from mothers with T1DM and collected data prospectively from questionnaires completed at birth, 9 months, and 2 years of age.11 This study aimed to assess the influence of breast-feeding, vaccinations, and childhood viral illnesses on the initiation of islet autoimmunity in early childhood. In regard to breast-feeding, the study results showed that breast-feeding for three months or longer did not confer protection from antibody development or diabetes onset in the first two years of life in offspring of parents with T1DM.11

Vitamin D
Vitamin D has long been recognized for its role in bone and mineral metabolism. It is now also widely considered a regulator of growth and differentiation in many target tissues and an immune system modulator.12 Population studies have suggested that supplementation with vitamin D in early childhood may decrease incidence of T1DM.

A Deficiency Epidemic
It is well known that individuals living in the very northern parts of the world or in places with little sunshine are more prone to vitamin D deficiency. Vitamin D deficiency is an underrecognized epidemic in both children and adults throughout the world, even in some of the sunniest climates.13,14

One research team observed that 32% of healthy adults between the ages of 18 and 29 were vitamin D deficient at the end of the winter in Boston.13,14 Results of a U.S. survey of vitamin D intake, published in 2004, revealed that neither children nor adults were receiving the recommended Adequate Intakes for vitamin D.13,14 According to Holick, the public health consequences of vitamin D deficiency are incalculable, especially for people who are more prone to the condition, including people with darker skin color. In addition, obesity is often associated with vitamin D deficiency.13,14

Experts now recognize that whether vitamin D is obtained from diet or exposure to sunlight, it is efficiently deposited in the large body fat stores and is not bioavailable. Furthermore, infants who are breast-fed will not receive a good source of vitamin D, as breast milk contains low amounts of the vitamin. Holick suggests that without exposure to sunlight, people require a minimum of 1,000 IU of vitamin D daily.13,14

Animal Studies
Experiments in nonobese diabetic (NOD) mice have provided strong evidence of a vitamin D effect on T1DM risk. Researchers say NOD mice experience disease pathogenesis similar to that of humans, including autoimmune destruction of the beta cells. A 1994 study by Mathieu et al found that T1DM was prevented when the researchers administered 1,25-dihydroxyvitamin D to NOD mice in pharmacologic doses. A 2004 study by Giulietti et al found that NOD mice raised in a vitamin D-deficient state developed diabetes at an earlier age than nondeficient NOD mice.

Case-Control Studies
The EURODIAB Substudy 2 Study Group published data from a large case-control study conducted in seven European countries in 1999. This study involved the parents of 820 children with T1DM and 2,335 population-based controls. The groups were interviewed to ascertain whether the children received supplemental vitamin D during their first year of life. If given, the type and amount of vitamin D were not determined. The researchers found that those who received supplemental vitamin D had a one-third reduced risk of developing T1DM by the age of 15.

Stene et al conducted another large case-control study, published in 2003 in the American Journal of Clinical Nutrition. In this study, surveys including questions about vitamin D supplement and cod liver-oil intake during the first year of life were mailed. Cod liver oil administered to infants at least five times per week was associated with a significant reduction in T1DM risk compared with no supplementation. Interestingly, there was no evidence of a protective effect from other vitamin D supplements, even when taken five or more times per week. The reason for this difference is unknown; however, researchers speculate that the vitamin D in cod liver oil may be more bioavailable or that there are other components in the cod liver oil exerting influence.

Cohort Studies
In 2001, Hyppönen et al published the first prospective study examining T1DM and vitamin D supplementation in infants.15 More than 12,000 pregnant women from Finland were enrolled in the study. Infants received vitamin D at the age of 1, and the researchers followed them for 25 years. The researchers found that infants who were given vitamin D supplements in amounts greater than 2,000 IU/day regularly had an 80% decreased risk of developing T1DM than those infants given vitamin D in doses less than 2,000 IU/day. Children who were vitamin D deficient had a fourfold increased risk of developing the disease later in life.

In a review, Harris concluded that this large, well-designed study provides compelling evidence that vitamin D supplementation of 2,000 IU/day or more during infancy may reduce the risk of T1DM, at least in areas where sunlight is limited.16 This is almost 10 times the amount used in the Stene study discussed previously. Harris speculates that this drastic difference in dosage may be the reason for the somewhat contradictory findings between the studies. It may be that vitamin D prevents T1DM only in relatively large doses.

Current Recommendations
In 1997, the Institute of Medicine set a Tolerable Upper Intake Level of 1,000 IU/day for infants aged 0 to 12 months and 2,000 IU/day for children. However, the data used to set these levels were very limited.16

Holick suggests that vitamin D intake from fortified foods and supplements, in combination with sensible sun exposure, should maximize a person’s vitamin D status to promote good health.13,14 Estimates indicate that exposure to sunlight for usually no more than five to 15 minutes daily (between 10 am and 3 pm) on arms and legs or hands, face, and arms during the spring, summer, and fall provides the body with 1,000 IU of cholecalciferol. After people achieve minimum sun exposure, Holick suggests they apply a broad-spectrum sunscreen with at least SPF 15 to prevent sun damage.13,14

Dietary Protocols
Based on the available research, RDs should consider recommending a few dietary protocols to help clients potentially reduce risk for T1DM.

First, RDs counseling pregnant women should discuss breast-feeding and its benefits. Breast-feeding may help not only reduce acute illness, such as the common cold and ear infections but also prevent chronic illness, such as T1DM. RDs should convey the message that breast milk is the most biologically appropriate infant food. The AAP recommends exclusive breast-feeding for the first six months of life, continued with supplemental foods for the first year or more of life. The World Health Organization recommends that women continue breast-feeding with supplementary foods through the second year of an infant’s life.

Second, aside from encouraging women to breast-feed, RDs should advise parents to wait until an infant is at least 1 year old before introducing cow’s milk. Much research supports cow’s milk as being the antagonist rather than breast milk being solely preventative. Some women may find it challenging to continue providing ample breast milk for their infant when they return to work. RDs can assist working mothers by brainstorming ideas for pumping and storing breast milk.

Third, the available research suggests that all infants and children should receive a vitamin D supplement. Some research has indicated that children, especially those living in a northern area, who are exclusively breast-fed, who are dark skinned, or who have limited sun exposure, should be given between 200 and 1,000 IU/day of supplemental vitamin D.16 Additionally, when reviewing a client’s lab results, RDs should determine whether the vitamin D level has been checked; if it hasn’t, they should recommend that the physician order it for the next blood draw. Vitamin D status has such important health implications that a measurement should be part of a routine physical examination for children and adults of all ages.13,14

— Janice H. Dada, MPH, RD, CSSD, CDE, CHES, is a dietitian in private practice, college nutrition instructor, and freelance writer based in southern California.


Future T1DM Prevention Research
To keep up-to-date on the research surrounding T1DM, visit


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