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.
Individuals who drink three glasses of milk a day decrease their risk of cardiovascular disease by 18 percent, according to new research published in the American Journal of Clinical Nutrition.Researchers at Wageningen University and Harvard University examined 17 studies from the United States, Europe and Japan and found no link between the consumption of regular or low fat dairy and any increased risk of heart disease, stroke or total mortality. “Milk and dairy are the most nutritious and healthy foods available and loaded with naturally occurring nutrients, such as calcium, potassium and protein, to name a few,” said Cindy Schweitzer, technical director of the Global Dairy Platform. “It's about going back to the basics; maintaining a healthy lifestyle doesn't have to be a scientific equation.”
Schweitzer said during the past three decades as research sought to understand influencers of cardiovascular disease, simplified dietary advice including consuming only low fat dairy products emerged. However, in 2010 alone, a significant amount of new research was published from all over the world, supporting the health benefits of dairy. From dispelling the myth that dairy causes heart disease, to revealing dairy's weight loss-benefits, the following is a roundup of select dairy research conducted in 2010:
- U.S. researchers examined 21 studies that included data from nearly 350,000 and concluded that dietary intakes of saturated fats are not associated with increases in the risk of either coronary heart disease or cardiovascular disease. The study was published in the American Journal of Clinical Nutrition.
- A study published in the American Journal of Epidemiology examined 23,366 Swedish men and revealed that intakes of calcium above the recommended daily levels may reduce the risk of mortality from heart disease and cancer by 25 percent.
- An Australian study published in the European Journal of Clinical Nutrition concluded that overall intake of dairy products was not associated with mortality. The 16-year prospective study of 1,529 Australian adults found that people who ate the most full-fat dairy had a 69-percent lower risk of cardiovascular death than those who ate the least.
- A Danish study published in Physiology & Behavior concluded that an inadequate calcium intake during an energy restricted weight-loss program may trigger hunger and impair compliance to the diet.
- An Israeli study published in the American Journal of Clinical Nutrition showed that a higher dairy calcium intake is related to greater diet-induced weight loss. The study sampled more than 300 overweight men and women during two years and found those with the highest dairy calcium intake lost 38-percent more weight than those with the lowest dairy calcium intake.
The amount of dairy recommended per day varies by country and is generally based on nutrition needs and food availability. “In the US and some European countries, three servings of dairy foods are recommended daily, said Dr. Schweitzer.”
Supplementing diet with whey-based protein may help reduce high blood pressure, a U.S. researcher says.
Nutritional biochemist Susan Fluegel of Washington State University in Spokane says daily doses of commonly available whey brought a more than 6-point reduction in the average blood pressure of men and women with elevated systolic and diastolic blood pressures. Whey is a by-product of cheese-making. “One of the things I like about this is it is low-cost,” Fluegel says in a statement. “Not only that, whey protein has not been shown to be harmful in any way.”
The study, published in International Dairy Journal, finds not everyone drinking the whey-supplemented drink has changes in blood pressure.
The supplement did not lower the blood pressure of subjects who did not have elevated pressure to begin with. That's good, says Fluegel, since low blood pressure can also be a problem. However, blood-pressure reductions — as seen in those with elevated pressure in this study — can bring a 35 percent to 40 percent reduction in fatal strokes, says Fluegel.
Fluegel and colleagues looked at 71 student subjects ages 18-26, but Fluegel says older people with blood pressure issues would likely get similar results. The supplement was delivered in fruit-flavored drinks developed at the university's creamery.
To tackle immunosenescene the team targeted the gastrointestinal tract, which is the main entry for bacteria cells into the body through food and drink and is also the site where 70% of vital immunoglobulin cells are created.
The team asked volunteers aged between 72 and 103, all of which lived in the same care home, to eat one slice of either placebo or probiotic Gouda cheese with their breakfast for four weeks. Blood tests where then carried out to discover the effect of probiotic bacteria contained within the cheese on the immune system.
The results revealed a clear enhancement of natural and acquired immunity through the activation of NK blood cells and an increase in phagocytic activity.
“The aim of our study was to see if specific probiotic bacteria in cheese would have immune enhancing effects on healthy older individuals in a nursing home setting,” concluded Ibrahim. “We have demonstrated that the regular intake of probiotic cheese can help to boost the immune system and that including it in a regular diet may help to improve an elderly person's immune response to external challenges.
The randomized, double-blind, placebo-controlled study, which was funded by The Dannon Company, Inc., involved 638 healthy children aged three to six, all of whom attended school five days a week. Parents were asked to give their child a strawberry yogurt-like drink every day. Some of the drinks contained the probiotic strain Lactobacillus casei (L. casei) and the others did not. Parents were also asked to record how many yogurt drinks their child consumed and to keep notes on their child's health.
At the end of the study, there was a 19 percent decrease in the number of common infections—e.g., ear infections, flu, diarrhea, sinusitis–among children who had consumed the yogurt drink with the probiotics than those who had the drink without the beneficial bacteria. When the researchers broke out the individual types of illness, they found that children who had the probiotic beverage had 24 percent fewer gastrointestinal infections (e.g., diarrhea, nausea, vomiting), and 18 percent fewer upper respiratory tract infections (e.g., ear, sinusitis, strep).
The reduction in infections did not, however, result in fewer days lost from school. Merenstein commented that “It is my hope that safe and tolerable ways to reduce illnesses could eventually result in fewer missed school days which means fewer work days missed by parents.”
The finding that the probiotic yogurt drink reduced infections in children, however, is significant. This joins results from other studies demonstrating benefits of probiotics in children, including one published in Pediatrics in which they reduced cold and flu symptoms, another in which they eased diarrhea, and one showing they helped prevent eczema in infants. Generally, probiotics have also been shown to benefit people who have celiac disease, irritable bowel, colitis, and possibly autism.
Georgetown University Medical Center
All had reported on their diet at the beginning of the study. During follow-up, about 2,358 died.
The top calcium consumers had a 25 percent lower risk of dying from any cause and a 23 percent lower risk of dying from heart disease during follow-up relative to men that had the least amount of calcium in their diet. Calcium intake didn't significantly influence the risk of dying from cancer.
Men in the top third based on their calcium intake were getting nearly 2,000 milligrams a day, on average, compared to about 1,000 milligrams for men in the bottom third. The US Recommended Dietary Allowance (RDA) for calcium intake is 1,000 milligrams for men 19 to 50 years old and 1,200 milligrams for men 50 and over. “Intake of calcium above that recommended daily may reduce all-cause mortality,” Kaluza and her colleagues conclude.
Calcium could influence mortality risk in many ways, they note, for example by reducing blood pressure, cholesterol, or blood sugar levels. For the men in the study, the main sources of calcium in the diet were milk and milk products and cereal products. In contrast to calcium, there was no relationship between magnesium consumption and overall mortality or deaths from cancer or heart disease. Study participants' intakes ranged from around 400 milligrams per day to around 525 milligrams; the RDA for magnesium is 420 milligrams for men 31 and older.
This analysis, the researchers say, may have found no effect for magnesium because all of the men in the study seemed to be getting enough of the mineral in their diet. “Further studies are needed in other populations with lower dietary magnesium intakes to address this issue,” they say. Future research should also look into calcium and magnesium intake from drinking water, they add, which can be a significant source of these minerals.
SOURCE: American Journal of Epidemiology