Health Concerns about Dairy Products

PCRM

Many Americans, including some vegetarians, still consume substantial amounts of dairy products—and government policies still promote them—despite scientific evidence that questions their health benefits and indicates their potential health risks.

Bone Health

Calcium is an important mineral that helps to keep bones strong. Our bones are constantly remodeling, meaning the body takes small amounts of calcium from the bones and replaces it with new calcium. Therefore, it is essential to have enough calcium so that the body doesn’t decrease bone density in this remodeling process. Though calcium is necessary for ensuring bone health, the actual benefits of calcium intake do not exist after consumption passes a certain threshold. Consuming more than approximately 600 milligrams per day—easily achieved without dairy products or calcium supplements—does not improve bone integrity.1

dairy-products-and-health

Clinical research shows that dairy products have little or no benefit for bones. A 2005 review published in Pediatrics showed that milk consumption does not improve bone integrity in children.2 In a more recent study, researchers tracked the diets, physical activity, and stress fracture incidences of adolescent girls for seven years, and concluded that dairy products and calcium do not prevent stress fractures in adolescent girls.3 Similarly, the Harvard Nurses’ Health Study, which followed more than 72,000 women for 18 years, showed no protective effect of increased milk consumption on fracture risk.1

It is possible to decrease the risk of osteoporosis by reducing sodium intake in the diet,4,5 increasing intake of fruits and vegetables,5,6 and ensuring adequate calcium intake from plant foods such as kale, broccoli, and other leafy green vegetables and beans. You can also use calcium-fortified products such as breakfast cereals and juices. Soybeans and fortified orange juice are two examples of products which provide about the same amount of calcium per serving as milk or other dairy products.7

Exercise is one of the most effective ways to increase bone density and decrease the risk of osteoporosis,8,9 and its benefits have been observed in studies of both children and adults.8,10-11

Individuals often drink milk in order to obtain vitamin D in their diets, unaware that they can receive vitamin D through other sources. Without vitamin D, only 10-15 percent of dietary calcium is absorbed.12

The best natural source of vitamin D is sunlight. Five to 15 minutes of sun exposure to the arms and legs or the hands, face, and arms can be enough to meet the body’s requirements for vitamin D, depending on the individual’s skin tone.13 Darker skin requires longer exposure to the sun in order to obtain adequate levels of vitamin D. In colder climates during the winter months the sun may not be able to provide adequate vitamin D. During this time the diet must be able to provide vitamin D.

Few foods naturally contain vitamin D, and no dairy products naturally contain this vitamin. Therefore, fortified cereals, grains, bread, orange juice, and soy or rice milk exist as options for providing vitamin D through the diet.14Supplements are also available.

dairy-health-risks

Fat Content and Cardiovascular Disease

Dairy products—including cheese, ice cream, milk, butter, and yogurt—contribute significant amounts of cholesterol and saturated fat to the diet.15Diets high in fat and especially in saturated fat can increase the risk of heart disease and can cause other serious health problems.

A low-fat, plant-based diet that eliminates dairy products, in combination with exercise, smoking cessation, and stress management, can not only prevent heart disease, but may also reverse it.16,17

Dairy and Cancer

Consumption of dairy products has also been linked to higher risk for various cancers, especially to cancers of the reproductive system. Most significantly, dairy product consumption has been linked to increased risk for prostate18-20and breast cancers.21

The danger of dairy product consumption as it relates to prostate and breast cancers is most likely related to increases in insulin-like growth factor (IGF-1), which is found in cow’s milk.22 Consumption of milk and dairy products on a regular basis has been shown to increase circulating levels of IGF-1.23,24Perhaps the most convincing association between IGF-1 levels and cancer risk is seen in studies of prostate cancer. Case-control studies in diverse populations have shown a strong and consistent association between serum IGF-1 concentrations and prostate cancer risk.25 One study showed that men with the highest levels of IGF-1 had more than four times the risk of prostate cancer, compared with those who had the lowest levels.26 In the Physicians Health Study, tracking 21,660 participants for 28 years, researchers found an increased risk of prostate cancer for those who consumed ≥2.5 servings of dairy products per day as compared with those who consumed ≤0.5 servings a day.19 This study, which is supported by other findings,27,28 also shows that prostate cancer risk was elevated with increased consumption of low-fat milk, suggesting that too much dairy calcium, and not just the fat associated with dairy products, could be a potential threat to prostate health.

In addition to increased levels of IGF-1, estrogen metabolites are considered risk factors for cancers of the reproductive system, including cancers of the breasts, ovaries, and prostate. These metabolites can affect cellular proliferation such that cells grow rapidly and aberrantly,29 which can lead to cancer growth. Consumption of milk and dairy products contributes to the majority (60-70 percent) of estrogen intake in the human diet.

In a large study including 1,893 women from the Life After Cancer Epidemiology Study who had been diagnosed with early-stage invasive breast cancer, higher amounts of high-fat dairy product consumption were associated with higher mortality rates. As little as 0.5 servings a day increased risk significantly. This is probably due to the fact that estrogenic hormones reside primarily in fat, making the concern most pronounced for consumption of high-fat dairy products.

The consumption of dairy products may also contribute to development ofovarian cancer. The relation between dairy products and ovarian cancer may be caused by the breakdown of the milk sugar lactose into galactose, a sugar which may be toxic to ovarian cells.30 In a study conducted in Sweden, consumption of lactose and dairy products was positively linked to ovarian cancer.31 A similar study, the Iowa Women’s Health Study, found that women who consumed more than one glass of milk per day had a 73 percent greater chance of developing ovarian cancer than women who drank less than one glass per day.32

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Lactose Intolerance

Lactose intolerance is common among many populations, affecting approximately 95 percent of Asian-Americans, 74 percent of Native Americans, 70 percent of African-Americans, 53 percent of Mexican-Americans, and 15 percent of Caucasians.33 Symptoms, which include gastrointestinal distress, diarrhea, and flatulence, occur because these individuals do not have the enzyme lactase to digest the milk sugar lactose. When digested, the breakdown products of lactose are two simple sugars: glucose and galactose. Nursing children have active enzymes that break down galactose, but as we age, many of us lose much of this capacity.34 Due to the common nature of this condition, and in order to avoid these uncomfortable side effects, milk consumption is not recommended.

Dairy Contaminants

Milk contains contaminants that range from hormones to pesticides. Milk naturally contains hormones and growth factors produced within a cow’s body. In addition, synthetic hormones such as recombinant bovine growth hormone are commonly used in cows to increase the production of milk.35 Once introduced into the human body, these hormones may affect normal hormonal function.

When treating cows for conditions such as mastitis, or inflammation, of the mammary glands, antibiotics are used, and traces of these antibiotics have occasionally been found in samples of milk and dairy products. This treatment is used frequently, because mastitis is a very common condition in cows, due to dairy product practices which have cows producing more milk than nature intended.

Pesticides, polychlorinated biphenyls (PCBs), and dioxins are other examples of contaminants found in milk. Dairy products contribute to one-fourth to one-half of the dietary intake of total dioxins.36 All of these toxins do not readily leave the body and can eventually build to harmful levels that may affect the immune, reproductive, and the central nervous systems. Moreover, PCBs and dioxins have also been linked to cancer.37

Other contaminants often introduced during processing of milk products include melamine, often found in plastics, which negatively affects the kidneys and urinary tract due to their high nitrogen content,38 and carcinogenic toxins including aflatoxins. These are additionally dangerous because they are not destroyed in pasteurization.39

Milk Proteins and Diabetes

Insulin-dependent (type 1 or childhood-onset) diabetes is linked to consumption of dairy products in infancy.40 A 2001 Finnish study of 3,000 infants with genetically increased risk for developing diabetes showed that early introduction of cow’s milk increased susceptibility to type 1 diabetes.41In addition, the American Academy of Pediatrics observed up to a 30 percent reduction in the incidence of type 1 diabetes in infants who avoid exposure to cow’s milk protein for at least the first three months of their lives.42

Health Concerns about Milk for Children and Infants

Milk proteins, milk sugar, fat, and saturated fat in dairy products pose health risks for children and encourage the development of obesity, diabetes, and heart disease. While low-fat milk is often recommended for decreasing obesity risk, a study published in the Archives of Disease in Childhood showed that children who drank 1 percent or skim milk, compared with those who drank full-fat milk, were not any less likely to be obese.43 Moreover, a current meta-analysis found no support for the argument that increasing dairy product intake will decrease body fat and weight over the long term (>1 year).44

For infants, the consumption of cow’s milk is not recommended. The American Academy of Pediatrics recommends that infants below 1 year of age not be given whole cow’s milk,45 as iron deficiency is more likely due to the low amount of iron found in cow’s milk as compared with human breast milk.46 Colic is an additional concern with milk consumption. Up to 28 percent of infants suffer from colic during the first month of life.47 Pediatricians learned long ago that cow’s milk was often the reason. We now know that breastfeeding mothers can have colicky babies if the mothers consume cow’s milk. The cow’s antibodies can pass through the mother’s bloodstream, into her breast milk, and to the baby.48,49

Additionally, food allergies appear to be common results of cow’s milk consumption, particularly in children.50,51 Cow’s milk consumption has also been linked to chronic constipation in children.52

Conclusions

Milk and dairy products are not necessary in the diet and can, in fact, be harmful to health. It is best to consume a healthful diet of grains, fruits, vegetables, legumes, and fortified foods including cereals and juices. These nutrient-dense foods can help you meet your calcium, potassium, riboflavin, and vitamin D requirements with ease—and without facing the health risks associated with dairy product consumption.

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How is heart disease risk affected when saturated fat is replaced by other nutrients?

 Melted-Butter

SEP 29 2015

In the recent Harvard Gazette article “Butter’s benefits melt away,” researchers at Harvard T.H. Chan School of Public Health debunk the controversy surrounding saturated fat and heart health. In a new study appearing online in the Journal of the American College of Cardiology, senior author Frank Hu and colleagues found that people who replace saturated fat (primarily found in meats and dairy foods) with refined carbohydrates do not lower their risk of heart disease, whereas those who replace saturated fats with unsaturated fats or whole grains lower their heart disease risk.

“Our research does not exonerate saturated fat,” said Hu. “In terms of heart disease risk, saturated fat and refined carbohydrates appear to be similarly unhealthful.”

Butter is not back: Limiting saturated fat still best for heart health

Butter melting

For immediate release: September 28, 2015

Boston, MA ─ People who replace saturated fat (mainly found in meats and dairy foods) in their diets with refined carbohydrates do not lower their risk of heart disease, according to a new study led by researchers at Harvard T.H. Chan School of Public Health. On the other hand, those who replace saturated fats with unsaturated fats (found in vegetable oils and nuts) or whole grains lower their heart disease risk.

Many people fall back on carbs, especially refined carbs like white bread, when they reduce saturated fat in their diets, said senior author Frank Hu, professor of nutrition and epidemiology. This may in part explain findings from a controversial 2014 paper that called into question recommendations for limiting saturated fat for heart health, and led to headlines promoting the return of butter.

“Our research does not exonerate saturated fat,” said Hu. “In terms of heart disease risk, saturated fat and refined carbohydrates appear to be similarly unhealthful.”

The study appears online September 28, 2015 in the Journal of the American College of Cardiology.

This is the first prospective analysis to directly compare saturated fat with other types of fats and different types of carbohydrates in relation to heart disease risk.

Hu and colleagues looked at diet and health information from participants in two long-running observation studies, the Nurses’ Health Study (84,628 women) and the Health Professionals Follow-up Study (42,908 men), who were free of diabetes, cardiovascular disease, and cancer at baseline. Diet was assessed by food frequency questionnaires every four years. During follow-up, the researchers documented 7,667 cases of coronary heart disease (CHD).

They estimated that replacing 5% of energy intake from saturated fats with equivalent energy intake from either polyunsaturated fats, monounsaturated fats, or carbohydrates from whole grains was associated with 25%, 15%, and 9% lower risk of CHD, respectively. On the other hand, swapping 5% of saturated fat calories for the same amount of refined carbohydrates and sugars was not associated with CHD risk. These analyses took into account cardiovascular risk factors such as age, body mass index, smoking, and physical activity.

“Our findings suggest that the low-fat, high-carb trends of the 1980s and 1990s are not effective in reducing risk of CHD,” said Yanping Li, co-first author along with Adela Hruby, both researchers in the Department of Nutrition. “It means that individuals should not replace saturated fat with refined carbs or vice versa. Dietary recommendations to reduce saturated fats should specify their replacement with unsaturated fats or with healthy carbohydrates, such as whole grains,” said Li.

Other Harvard Chan School authors of the study included Sylvia Ley, Dong Wang, Stephanie Chiuve, Laura Sampson, Eric Rimm, and Walter Willett.

The study cohorts were supported by grants of UM1 CA186107, R01 HL034594, R01 HL35464, R01 HL60712 and UM1 CA167552 from the National Institutes of Health.

“Saturated fat as compared to unsaturated fats and sources of carbohydrates in relation to risk of coronary heart disease: A prospective cohort study,” Yanping Li, Adela Hruby, Adam M. Bernstein, Sylvia H. Ley, Dong D. Wang, Stephanie E. Chiuve, Laura Sampson, Kathryn M. Rexrode, Eric B. Rimm, Walter C. Willett, Frank B. Hu, Journal of the American College of Cardiology, online September 28, 2015, doi: 10.1016/j.jacc.2015.07.055

Visit the Harvard Chan School website for the latest newspress releases, and multimedia offerings.

Daily sugary drink habit increases risk of type 2 diabetes, heart attack, stroke

Drinking one or two daily sugar-sweetened beverages can lead to excess weightgain and a greater risk of developing type 2 diabetes and cardiovascular disease, according to a new study by researchers at Harvard T.H. Chan School of Public Health. In the most comprehensive review of the evidence on the health effects of sugar-sweetened beverages to date, the researchers also took a closer look at the unique role that the sweetener fructose may play in the development of these conditions.

The paper was published online September 30, 2015 in the Journal of theAmerican College of Cardiology.

Fructose is metabolized in the liver where it can be converted to fatty compounds called triglycerides, which may lead to fatty liver disease and insulin resistance, a key risk factor for developing diabetes and cardiovascular disease. The major source of fructose in the diet comes from fructose-containing sugars—sucrose and high fructose corn syrup—found in sugar-sweetened beverages, according to the researchers.

In the new paper, which reviewed recent epidemiological studies and meta-analyses of these studies, the researchers found that people who consumed one or two sugary drinks a day had a 35% increase in risk for heart attack or fatal heart disease, a 16% increase in risk for stroke, and a 26% increased risk for developing type 2 diabetes, when compared with people who drank fewer sugar-sweetened beverages.

“Our findings underscore the urgent need for public health strategies that reduce the consumption of these drinks,” said Frank Hu, professor of nutrition and epidemiology and lead author of the paper. Research scientist Vasanti Malik co-authored the study.

Read study abstract: Fructose and cardiometabolic health

Read American College of Cardiology press release: New research exposes the health risks of fructose and sugary drinks

Sugar-sweetened drinks increase risk for diabetes, heart disease, stroke (UPI)

Ground Beef Contains Dangerous Bacteria

Ground Beef
Getty Images

You may want to pay attention to the type of beef you buy

Store-bought ground beef often contains a variety of bacteria that can make humans sick and is resistant to the drugs used to treat it, according to new data from Consumer Reports.

While most bacteria in meat can be killed when cooked correctly, many Americans prefer to eat their meat rare, putting them at a greater risk for illness—especially when the meat comes from conventionally raised cows, which are treated with antibiotics and hormones, according to a new Consumer Reports study. The study found that nearly 20% of ground beef in the U.S. tested from conventionally raised cows had bacteria resistant to three or more classes of antibiotics. Only 9% of ground beef that was sustainably made had antibiotic-resistant bacteria.

For the report, Consumer Reports purchased and tested 300 packages of conventionally and sustainably produced ground beef sold in stores around the U.S. The meat was tested for five common types of bacteria that can be found in beef: Clostridium perfringens, E. coli, Enterococcus, Salmonella and Staphylococcus aureus. Bacteria of some kind was found in all of the beef samples, though sustainably produced beef was less likely to have harmful strains.

More than 80% of conventional ground beef had two types of bacteria and nearly 20% of the samples contained C. perfringens, which causes close to a million cases of food poisoning every year. “There’s no way to tell by looking at a package of meat or smelling it whether it has harmful bacteria or not,” Urvashi Rangan, executive director of the Center for Food Safety and Sustainability at Consumer Reports, said.“You have to be on guard every time.”

The research also found that 10% of the samples had a strain of S. aureus that produces a toxin that can make people ill and is not killed even when the meat is cooked properly. Still, cooking meat at 160 degrees Fahrenheit should kill most bacteria.

The findings suggest that consumers may want to look for ground beef that’s sustainably produced, with labels reading “no antibiotics,” “grass-fed,” and “organic,” according to Consumer Reports. Consumer Reports says “grass-fed organic” may be one of the best labels to go by since it means the cattle eat organic grass and forage and do not receive antibiotics or hormones.

United States Department of Agriculture (USDA) secretary Tom Vilsacksaid in a statement that the agency has put tight food safety standards in place over the last six years to avoid public health problems. “Measures taken to improve ground beef safety include a zero-tolerance policy for six dangerous strains of E. coli, better procedures for detecting the source of outbreaks, improved laboratory testing, and more. USDA’s food safety inspectors work in every meat facility, every day, to reduce illnesses across all products we regulate, and we’re proud to report that illnesses attributed to those items dropped by 10% from 2013 to 2014,” he said.

Virus Found in Dairy Linked to Breast Cancer

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Virus Found in Dairy Linked to Breast Cancer

A virus found in beef and dairy products may be a possible risk factor for breast cancer, according to a case-control study published in PLoS One. Researchers examined 239 donated breast tissue samples from the Cooperative Human Tissue Network archives for exposure to the bovine leukemia virus (BLV).

BLV in breast tissue was strongly associated with breast cancer diagnosis, as the virus appeared in 59 percent of those with cancer.

The researchers found 38 percent of cows used for beef and 84 percent of cows used for dairy were infected with BLV and hope these results may point to preventive techniques in the future.

Buehring GC, Shen HM, Jensen HM, Jin DL, Hudes M, Block G. Exposure to bovine leukemia virus is associated with breast cancer: a case-control study. PLoS One. 2015;10:e0134304.

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