FACT: Although women are more likely to develop osteoporosis, it also affects men and even children. Osteoporosis is more common in white or Asian women older than 50 years of age, but osteoporosis can occur in almost any person at any age. At present it is estimated that 300,000 people in Ireland have Osteoporosis. One in 4 men and 1 in 2 women over 50 will develop a fracture due to Osteoporosis in their lifetime.
FACT: Whether you regularly and intentionally crack your knuckles (known medically as ‘crepitus’) or just do it occasionally by accident, you don't have to worry because it has not been shown to increase the risk of arthritis.
FACT: Countries with high rates of fractures tend to be countries with longer life expectancies (e.g. Nordic countries). Fracture rates are now rising in non-Western countries (e.g. China) as they see increasing longevity in parallel with sedentary lifestyles. Many factors determine whether a person will develop osteoporosis and be at increased fracture risk. Genetics (race, sex, family disposition) are major determinants of osteoporosis and fracture risk. Lifestyle habits such as physical activity, body weight, smoking, alcohol-use, as well as certain medications and diseases, are also important determinants of fracture risk. Vitamin D status has also been associated with bone health and this can be influenced by exposure to sunlight or a country’s latitude on the earth. Dairy intake is not responsible for higher fracture rates, nor does dairy consumption alone guarantee strong healthy bones. However, dairy provides an important source of nutrients such as protein, calcium and phosphorus which have scientifically substantiated roles in bone growth, development and maintenance. The inclusion of dairy foods as part of a bone-friendly lifestyle is recognised by leading Osteoporosis authorities both nationally and internationally. (https://www.iofbonehealth.org/data-publications/fact-sheets/milk-and-dairy-products-are-good-bone-health).
FACT: This is a misconception and the European Food Safety Authority have substantiated the fact that protein is needed for bone health (EU Register of Nutrition and Health Claims made on Foods). The ‘acid-base’ hypothesis has been debated in the scientific literature for some time and the most comprehensive evidence shows that overall, the effect of dietary protein on bone appears to be favourable, not harmful. During digestion, protein gets broken down into various metabolic acids but the body efficiently manages these by using them for various functions, excreting them via the kidneys or buffering them with other dietary components. Where the confusion lies is that a high protein diet can potentially increase urinary calcium excretion, but this is only when calcium intakes are inadequate (Dawson & Harris SS, 2002; Mangano et al. 2014). Dairy foods are nutritionally well placed to balance this as they provide high quality protein but are also among the best sources of dietary calcium. The human body is highly efficient at maintaining blood pH under tight control and can manage higher protein levels when they are consumed as part of a balanced diet, regardless of the source of protein. However, for those with impaired kidney function, high protein diets are not well tolerated. Furthermore, when looking at the effect on bone health, several studies have established that although a high-protein diet may increase urinary calcium excretion this does not result in a negative skeletal calcium balance, bone loss or the risk of an osteoporotic fracture (Bonjour, 2011, 2013; Kerstetter et al. 2011; Fenton et al. 2009, 2011). In fact, much of the research suggests that protein works synergistically with calcium to improve calcium retention and bone metabolism (Kerstetter et al. 2011; Thorpe & Evans, 2011; Bonjour, 2005).
FACT: Recommendations for calcium requirements for the population are devised by panels of leading Nutrition and Scientific experts. They are based on age and life stage needs, but not dietary pattern choice. Therefore, the official dietary guidelines do not suggest lower calcium requirements for those following plant-based or vegan diets. In addition, the presence of oxalic, phytic and uronic acids in some plant foods decreases the bioavailability of calcium, as these compounds inhibit calcium absorption.
FACT: There are many practices that are unique to humans, such as cooking meals, driving cars and writing books; but they are not the only species to consume the milk of another. All species instinctively seek out nutritious food. It is naturally innate and central to survival. Access to food for any animal is determined by their ability and intellect. For example, a vulture and a lion will both eat a gazelle but they use different skill sets to access it. Around 7,500 years ago, humans realised that they could milk certain animals to access a rich source of nutrients and this is how dairy farming began. Other animals don’t have the ability or intellect to milk another species but when they have access to milk, many will readily consume it. Typical examples of this are domestic cats and wild birds. Many people will remember when milk was delivered in glass bottles, birds used to peck through the top to steal the cream!
FACT: Throughout evolution, humans have made many discoveries and innovations which have altered our ability to preserve food or enhance our nutritional intake. Examples include marinating, pickling and cooking. Using cow’s milk as a food source beyond weaning is just another beneficial practice that humans discovered. The consumption of milk before and after weaning are two different scenarios. Like all mammals, new-born babies consume only milk, usually their own mother’s which they gradually give up, once they are fully weaned onto a mixed adult diet. Cow’s milk is not suitable for infants and is generally not introduced to the human diet until 1 year of age, where it serves as a nutritious food, along with other animal products such as meat, fish and eggs. The benefits of consuming dairy beyond weaning is evident in human evolution. It is estimated that milk drinking began around 7,500 years ago in central Europe and scientists have suggested that it was a survival advantage to be able to continue digesting milk for its rich nutrient content. It is referred to as ‘natural selection’, which resulted in a change in human gene expression that enabled people to continue producing the enzyme to digest milk. The gene to produce lactase, an enzyme involved in milk digestion, is generally ‘switched off’ in mammals shortly after weaning, when they stop consuming milk. However, this genetic adaption means that the gene could stay ‘switched on’ and the trait is seen in parts of the world where dairy farming evolved. Individuals without this genetic trait can still digest smaller amounts of dairy foods and there is a wealth of research which suggests that dairy is a valuable addition of the diet across the life stages.
TRUTH: It is important to note that the ‘Nurses study’ consists of a compilation of several pieces of research based on a single cohort. Therefore, there are several published papers based on the Nurses Study. In contrast to the original study published in 1997, the most recent study using the Nurses’ Health Study data in 2018 found that each serving of milk per day was associated with an 8% lower risk of hip fracture in men and women; with total dairy intake associated with a 6% lower risk of hip fracture per daily serving in men and women. Unlike the original study, this finding used both the Nurses’ study cohort as well as the Health Professional Follow-up Study, meaning that both genders were included; 123,000 participants were observed (compared to approx. 80,000 in the 1997 study); and follow up was over 32 years (compared to 12 years in 1997). A number of studies have been published by the same author (Feskanich et al.) looking at milk intake and the risk of fracture using the Nurses' Health Study, which report conflicting findings. Two earlier studies (1997, 2003) report no reduction in fracture risk with a higher consumption of milk or other food sources of calcium. However, although these studies boast of a large number of participants followed across many years, there are a number of important limitations to the data collection; with many of these identified by the authors themselves. Firstly, the study design was observational, meaning that no intervention was applied and that only associations can be identified, without cause and effect conclusions. In fact, the study highlights in its discussion that there is “no reason to believe that dairy calcium itself was responsible for the observed increase in risk of hip fracture, rather some other characteristic of women who consume dairy foods might have contributed to the elevated risk".
TRUTH: The China Study is a popular book that endorses a plant-based diet and includes a chapter on an observational study which was conducted throughout the 1980’s in China (known as the China-Cornell-Oxford Project). The book recommends a whole, unrefined plant-based diet and to avoid all animal-based products. However, this recommendation of the removal or limitation of entire food groups is questionable based on how the data has been presented in the book. For example, the book reports an association between casein and cancer, based on laboratory studies where rats were fed various doses of casein. However, these studies were conducted with isolated casein protein rather than milk or milk protein in its natural form and so tells us little about how milk in its natural state will affect human health. The finding from these questionable studies with casein is subsequently applied to all other animal proteins and their effect on health. We simply cannot conclude cause and effect based on studies from one research and a single lab using rodents and translate this into humans. We need to look at recommendations from leading authorities who base their recommendations on the totality of evidence. The World Cancer Research Fund, a leading authority on cancer prevention research related to diet, nutrition and physical activity, recently published their updated Cancer Prevention Recommendations (May 2018) and have not recommended the elimination nor the limitation of dairy foods. The main criticism of this book - which has been reported by a number of scientific and dietary experts - is that while numerous studies are cited, it cherry picks data and omits contradictory findings. The book has been accused of failing to address the totality of evidence and therefore its claims are largely unsubstantiated. The nature of the research reported is observational, meaning only associations can be drawn, without cause and effect certainty. For example, as cancer is a multifactorial disease, influenced by both genetic and environmental aspects, it is suggested that other influencing variables apart from diet were overlooked such as chemicals exposure, nutrient intake patters, sugar intake etc. Extrapolation of a plant-based diet of a rural Chinese community to the vegan diet of an affluent Western population is not scientifically comparable. In addition, not all regions studies adhered to a strict vegan diet, making it impossible to state that all animal products should be omitted. What is overlooked in this book is that there are many published studies which support a role for milk and dairy as part of a balanced diet and indicate positive roles for dairy across several areas of health and chronic diseases including bone health, body composition, type 2 diabetes, some cancers and cardiovascular disease [Thorning et al. 2016].
TRUTH: No, there is no plausible evidence to suggest that dairy could cause osteoporosis. Many factors determine whether a person will develop osteoporosis or be at increased fracture risk. Our bone health and strength are determined to a large extent by factors outside of our control such as genetics, gender and age. However, there are factors that we can control such as our diet and physical activity and these are particularly important during adolescence, when bones are still developing. A balanced diet which provides ‘bone-friendly’ nutrients such as calcium, phosphorus, protein, vitamin D, zinc and magnesium is important. Recommended as part of a balanced diet, dairy foods provide many of these nutrients.
Regular participation in ‘weight-bearing’ activities (any activities involving impact or resistance against a weight, such as our own body weight) is also needed. Examples include: brisk hill walking, running/jogging, tennis and most team sports. Other bone-friendly advice includes maintaining a healthy body weight, avoiding excessive alcohol intake and not smoking.