The NHS website section which deals with Healthy Eating recommends that we should choose low fat dairy products in order to reduce our intake of saturated fats (SFA) which raise cholesterol levels and therefore increase in the risk of heart disease. This has contributed to the demonization of the fat in milk and milk products. In this post I will consider how this specific recommendation stands up to examination.
There are many studies which indicate that the consumption of milk and dairy products reduces the risks of diabetes and related conditions such as hypertension and obesity. In the CARDIA (Coronary Artery Risk Development in Young Adults) which was conducted at 4 different centres in the USA, 3157 young men and women were monitored for 10 years (from 1985 to 1995). It was found that there was a consistent reduction in the incidence of obesity, hypertension, abnormal glucose homeostasis and dyslipidaemia with increasing consumption of milk and dairy products in those who were overweight or obese as determined by BMI. When the results for these individual factors are combined an index of IRS (Insulin Resistance Syndrome) is obtained. Over the 10-year period the IRS was lower by more than two thirds among overweight individuals in the highest category of dairy consumption (?5/d) compared with those in the lowest category (<1.5/d). These associations were not confounded by other lifestyle factors or dietary variables that are correlated with dairy intake and did not differ materially by race or sex(1). Insulin resistance is a key characteristic of diabetes and a series of related conditions referred to as “Metabolic Syndrome” which includes obesity, hypertension and heart disease. This very substantial reduction in IRS strongly suggests that high consumption of dairy products is beneficial to health. It is also consistent with the conclusion that the alternatives to the milk and dairy products (such as sweetened soft drinks) are much more dangerous to health.
Essentially similar results have been obtained for colon cancer. In a meta-analysis based on 12 cohort studies which involved 1,170,942 men and women who developed 11,570 cases of colorectal cancer, it was reported that high intakes of milk and total dairy products were associated with a statistically significant reduction in colorectal cancer risk as compared with low intake. There were significant inverse associations both among men and women for colorectal cancer(2).
The importance of fat
Although the benefits of a diet which has a high content of dairy products are reasonably well established it is worthwhile to try to understand the role of the individual components involved. The Hoorn Study conducted in The Netherlands enabled a comparison to be made between the effects of the consumption of low-fat and high-fat dairy products. The participants were 2064 men and women aged between 50 and 75 years. The results showed that consumption of high-fat dairy was significantly inversely associated with BMI, waist circumference, triglycerides, and insulin and significantly positively associated with HDL-cholesterol concentrations after adjustment for confounders. On the other hand low-fat dairy was significantly positively associated with BMI, waist circumference, and fasting glucose concentrations. To exclude possible bias due to prescribed diets, these analyses were repeated after exclusion of subjects with known diabetes mellitus or cardiovascular disease and subjects who used antihypertensive or lipid-lowering medication. These exclusions did not materially change the results. These findings s are highly significant because the presence of fat in the dairy products appears to facilitate factors such as weight loss, a reduction in triglycerides coupled with an increase in the “good” HDL cholesterol whereas the absence of fat is having the opposite effect(3).
The role of the short and medium chain fatty acids
Cow’s milk contains about 10% of the short and medium chain length fatty acids, which have up to 12 carbon atoms. These fatty acids do not need to be emulsified by bile salts and so are rapidly absorbed into the blood stream from the small intestine. They are especially valuable because they boost the immune system and possess anti-microbial, anti-viral and anti-tumour properties. Lauric acid (C12) is particularly effective. It is only synthesised in the mammary gland and it has been advocated that it should be regarded as an essential fatty acid. The derivative monolaurin exerts its’ virucidal and bactericidal effects by solubilising the lipids and phospholipids in the envelop of the pathogen so that it disintegrates. Although milk fat contains only about 3% of lauric acid it is nevertheless a very important source as it is present in very few other foods apart from coconut oil. Milk fat is virtually the only source of butyric acid C4) which possesses anti-fungal and anti-tumour properties(4,5).
There absolutely no suggestion that there are risks to health from the evidence cited here. On the contrary there is a very convincing case building up that the fats in milk play a vital role in human nutrition and that those who have followed the official advice on Healthy Eating may actually be damaging their own personal health.
- M A Pereira et al (2002) Journal of the American Medical Association 287 (16) pp 2081-2089
- D Aune et al(2012) Annals of Oncology 23 (1) pp37-45
- M B Snijder et al (2007) American Journal of Clinical Nutrition 85 (4) pp 989-985
- Mary Enig(2000) “The Skinny on Fats” http://www.westonaprice.org/know-your-fats/skinny-on-fats?
- S Lieberman et al (2006) Alternative and Complementary Therapies December pp 310-314