The study was carried out by researchers from University of Otago Medical School, New Zealand. Funding was provided by Genesis Oncology Trust, the Dean’s Bequest Funds of the Dunedin School of Medicine, the Gisborne East Coast Cancer Research Trust and the Director’s Cancer Research Trust. The research was published in the peer-reviewed American Journal of Epidemiology. This was a case-control study in New Zealand that compared a group of adults with bowel cancer, and a group without bowel cancer, and looked at whether they drank milk at school. School milk was freely available in most schools in New Zealand until 1967 when the government programme was stopped. Many schools in the Southland region stopped free milk as long ago as 1950.
Case-control studies are appropriate for looking at whether people with and without a disease have had a particular exposure (milk in this case). The difficulty is in accounting for all potential confounding factors, particularly other health and lifestyle factors, which could be related to both diet and bowel cancer risk, for example regular childhood milk consumption could be a reflection of a ‘healthy’ diet and other healthy lifestyle behaviours that may reduce risk of cancer. In addition, when examining such a specific dietary factor – ie milk consumed in school – it is difficult to account for all possible milk or other dairy products consumed outside of school.
In this case-control study, 562 adults (aged 30 to 69) with newly diagnosed bowel cancer were identified from the New Zealand Cancer Registry in 2007. For a control group, 571 age-matched adults without cancer were randomly selected from the electoral register. All participants were mailed a questionnaire that asked about any previous illness, use of aspirin or dietary supplements in childhood, participation in school milk programmes, other childhood milk consumption, childhood diet (including other milk and dairy), smoking, alcohol consumption prior to 25 years of age, screening tests for bowel cancer, family history of cancer, education and sociodemographic characteristics. Childhood weight and height were not questioned. For school milk consumption they were specifically asked:
- Whether they drank school milk
- How many half-pint bottles they drank a week
- What age they first drank school milk
- When they stopped drinking school milk
Statistical risk associations between school milk participation and cancer were calculated. The calculations took into account several risk factors for bowel cancer risk including age, sex, ethnicity and family history.
What were the basic results?
Data on school milk consumption was available for 552 cases and 569 controls. As expected, people who started school before 1967 were more likely to have had free school milk than those who began school after 1968. Seventy-eight percent of cases participated in the school milk programme compared with 82% of controls. School milk consumption was associated with a 30% reduced risk of developing bowel cancer (odds ratio 0.70, 95% confidence interval 0.51 to 0.96).
When looking at the effect of number of bottles consumed per week they found that compared with no bottles, five bottles per week was associated with 32% significantly decreased risk, and 10 or more bottles with 61% significantly decreased risk. However, there was no significant association with one to four bottles or six to nine bottles. The researchers found a similar trend when the total school consumption of milk was compared with no consumption: 1,200-1,599 bottles was associated with 38% significantly decreased risk; 1,600-1,799 with 43% decreased risk; and 1,800 or more bottles associated with 38% significantly decreased risk. There was no significant association with fewer than 1,200 bottles. The researchers calculated that for every 100 half-pint bottles consumed at school there was a 2.1% reduction in the risk of bowel cancer. Outside of school, there was a significantly reduced risk of bowel cancer with more than 20 dairy products a week compared with none to nine dairy products a week.
The researchers conclude that their national case-control study ‘provides evidence that school milk consumption was associated with a reduction in the risk of adult colorectal cancer in New Zealand. Furthermore, a dose-dependent relation was evident’. This study has strengths in its relatively large size, its reliable and nationally representative identification of cases and controls, and its thorough data collection. However, the conclusion that school milk consumption is associated with a reduced risk of bowel cancer in adulthood must be interpreted in light of a number of considerations:
The analysis took into account established risk factors for bowel cancer including age, sex, ethnicity and family history. However, many other potential confounders were not considered, including diet, physical activity, overweight and obesity, smoking or alcohol consumption. Diet in particular has been implicated in bowel cancer risk, with diets high in saturated fat, red meat and processed foods and low in fibre, fruit and vegetables thought to increase risk. Potentially, any of these lifestyle behaviours could be confounding the relationship between school milk consumption and bowel cancer and regular childhood milk consumption could be a reflection of a ‘healthy’ diet and other healthy lifestyle behaviours that reduce risk of cancer. When looking at the effect of number of bottles consumed per week, the researchers found that, compared with no bottles, five bottles were associated with 32% significantly decreased risk and 10 or more bottles with 61% significantly decreased risk. However, there was no significant association with one to four bottles or six to nine bottles. Therefore, the trend here is not very clear. Particularly as only 16 cases and 31 controls drank 10 or more bottles a week, statistical comparison between such small numbers should be viewed with caution. With many food questionnaires there is the potential for recall bias. For example, adults may have difficulty remembering how many bottles of school milk they drank many years before. When estimating their average weekly amount, it is highly possible that this could be inaccurate or that their consumption varied slightly from week to week and year to year. Particularly when researchers were using this response and combining it with the number of weeks in the school year and their total years at school to give a total number of bottles consumed at school (figures in 100s or 1,000s), there is the possibility of being incorrectly categorised. Hence, there may be less reliability when calculating risk according to the category of total milk bottles consumed. Cancer prevalence, and particularly environmental and lifestyle risk factors for cancer, can vary between countries. These findings in New Zealand may not be represented elsewhere. Of note, the researchers acknowledge that a cohort study in the UK found the opposite: increased childhood dairy consumption was associated with increased risk of bowel cancer. Case-control studies are most appropriate for looking at rare diseases, where you would expect there to be only a small number of cases developing among a large number of people. In the case of bowel cancer, which is common, the slightly more reliable cohort design could have also been used, where children who drank milk at school and those who didn’t were followed over time to see if they developed cancer. However, such a cohort would consequently need extensive long-term follow-up.
The possible association between milk/dairy consumption, or calcium intake, in childhood, or in later years, is worthy of further study. However, from this study alone, it cannot be concluded that school milk prevents bowel cancer later in life.
The link between obesity and cardiac disease is not merely anecdotal, there is proof for that. Now, there is further proof that even overweight causes a clustering of risk factors for cardio vascular abnormalities. A recent publication in Heart Asia, a British Medical Journal, has showed that there is not much difference between the cardio vascular risk factors in obese and overweight people. “The clutch of risk factors – glucose intolerance, hyper tension, high cholesterol – are all significantly higher among overweight and obese subjects than among normal subjects,” Vijay Viswanathan, MV Hospital for Diabetes and Prof. M.Viswanthan Diabetes Research Center said. He co-authored the article with Shabana Tharkar, also from the Indian hospital.
The study, conducted among two groups – 2021 subjects aged over 20 years, and 1289 subjects aged 8-19 years – indicated that even among overweight, 'non-obese' people, the presence of major cardiovascular risk factors was not significantly different. While the total diabetes prevalence among the obese population is 28.4 per cent, among the overweight population is 25 per cent. Again, with hypertension, the value for the obese group is 34.2 per cent, while for the overweight population it is 27.6 per cent. In contrast, the corresponding values are 16.2 per cent (diabetes) and 20.2 (hypertension).
Similarly, the study showed higher values for triglycerides and high HDL cholesterol for both these groups.
Overweight was defined as a Body Mass Index, equal to, or in excess of 25 kg/m2 and obesity, a BMI of 30 kg/m2 or above. Further worrisome is the increasing rate of overweight and obesity among both men and women from 1995 to 2008, across all age groups. Dr. Viswanathan added that this is the result of rapid urbanisation. “Obesity has already hit the Western world and it is time for Indians to wake up to the alarm bells,” according to the article. Results from previous studies show a lower risk of developing diabetes with just a five per cent initial reduction in weight, Dr. Viswanathan said.
The findings highlight the urgent need for framing direct and indirect strategies to control the rising levels of obesity in the population, in order to substantially reduce the country's non communicable diseases burden, he added. Regulating the diet, reducing intake of fast foods and high-calorie meals, and upping physical activity and exercise on a regular basis would go a long way in keeping weight under control, diabetologists advise.
Could the Mediterranean diet actually help prevent diabetes? The Mediterranean Diet, which is rich in vegetables, fruits, whole grains, healthy fats from nuts and olive oil, with moderate amounts of fish, low-fat dairy, and wine, and minimal red meat and processed meats, is considered to be an especially healthy eating plan.
Previous research conducted on newly diagnosed diabetic participants showed the diet did indeed help control the sugar spikes. The previous study found the mediterranean diet eating diabetics had better glycemic control. Furthermore, they had less needs for diabetes medications when adhering to the Mediterranean diet as opposed to a simple low-fat diet.
Recently, a team of researchers in Spain conducted a study using data from a large clinical trial to determine the effects of the Mediterranean Diet on preventing the onset of Type-2 diabetes. Participants were followed for an average of 4 years. Upon completion of the study, 54 participants had developed diabetes–but the split varied significantly among groups. The researchers found that the risk of developing diabetes was reduced by 52% among both groups of people who followed the Mediterranean Diet plans compared to the low-fat control group. In analyzing diet adherence, the researchers further noted that the closer an individual followed the Med-Diet plan, the lower their risk of developing diabetes. Interestingly, the weight of all participants did not change significantly throughout the study, nor did it vary significantly among the three groups.
The participants were divided in one of three groups: adherence to the Med-Diet with 1 liter per week of extra virgin olive oil, adherence to the Med-Diet with 1 oz per day of mixed nuts, or a standard low-fat diet as a control. No calorie restrictions were imposed on any of the groups. The two Med-Diet groups were instructed to increase fruit and vegetable intake, decrease meat intake, stay away from refined sweets and unhealthy fats such as butter, and consume red wine in moderation, if desired. The control group was given general instructions to lower overall fat intake. Baseline measurements and annual follow-up involved an oral glucose tolerance test and interviews to assess diet adherence.
Interestingly, the weight of all participants did not change significantly throughout the study, nor did it vary significantly among the three groups.
This study reinforces prior study results suggesting that the Mediterranean Diet – even without weight loss – may be protective against Type-2 diabetes. The researchers suggest that future studies should focus on the Med-Diet’s effects on younger people, and point out the possible benefits of the Mediterranean Diet as an effective intervention against complications of Type-2 diabetes.
“Fruit and vegetables are all good, but the data significantly show that green leafy vegetables are particularly interesting, so further investigation is warranted,” Carter said. “Green leafy vegetables contain antioxidants, magnesium and omega 3 fatty acids — all of which have been shown to have health benefits”, she added.
Each of the studies that Carter and her colleagues analyzed followed a group of adults over periods of 4-and-a-half to 23 years, recording how many servings of fruits and vegetables each participant ate on a daily basis then examining who was diagnosed with type 2 diabetes.
The researchers found no significant difference in diabetes risk with higher intake of vegetables in general, fruits in general, or combinations of vegetables and fruits.
Green leafy vegetables stood out, however, with an increase of 1.15 servings a day producing a 14 percent decrease in an individual's risk of developing diabetes. Type 2 diabetes is caused by the body's inability to adequately use insulin, a hormone produced by the pancreas, to regulate levels of glucose produced from food. Uncontrolled, the sugar levels rise and can damage the eyes, kidneys, nerves, heart and major arteries.
An estimated 180 million people worldwide have diabetes. The costs of caring for those with the disease are soaring in wealthy nations and becoming an increasing burden in developing countries too. Although there is no cure for diabetes, people with the condition can minimize their chances of getting sicker by being more active and losing weight.
Of the participants, 15.5%, 29.7%, 28.1%, and 21.1% reported being physically inactive at teenage, at 30 years, at 50 years, and in late life respectively; the increase in cognitive impairment for those who were inactive was between 50% and 100% at each time point. When physical activity measures for all four ages were entered into a single model and adjusted for variables such as age, education, marital status, diabetes, hypertension, depressive symptoms, smoking, and BMI, only teenage physical activity status remained significantly associated with cognitive performance in old age.
Middleton added, “As a result, to minimize the risk of dementia, physical activity should be encouraged from early life. Not to be without hope, people who were inactive at teenage can reduce their risk of cognitive impairment by becoming active in later life.”
The researchers concluded that the mechanisms by which physical activity across the life course is related to late life cognition are likely to be multi-factorial. There is evidence to suggest that physical activity has a positive effect on brain plasticity and cognition and in addition, physical activity reduces the rates and severity of vascular risk factors, such as hypertension, obesity, and type II diabetes, which are each associated with increased risk of cognitive impairment.
“Low physical activity levels in today's youth may mean increased dementia rates in the future. Dementia prevention programs and other health promotion programs encouraging physical activity should target people starting at very young ages, not just in mid- and late life,” said Middleton.
Home-cooked meals are at the heart of a healthy diet. Keep the food you prepare at home both delicious and safe by taking control of home food safety. If you handle food properly, you can significantly reduce your risk for foodborne illness.