According to Andrew M Prentice, PhD, from MRC International Nutrition Group, London School of Hygiene & Tropical Medicine, the intake of dairy produce shows enormous diversity between regions, cultures and individuals around the world. At the geographical level intake maps closely onto the distribution of lactase persistence (LP); a genetic trait that allows milk to be consumed beyond the weaning period without gastrointestinal side effects.

The LP trait has been independently selected at least 4 times and is under rapid positive selection showing that dairy consumption has very positive dietary benefits. For people lacking the LP trait and those with irritable bowel syndrome (IBD) the fermentation of milk into yogurt and related products (a process known for at least 8500y) aids milk digestion through the breakdown of lactose and the provision of bacterially-derived beta-galactosidase which remains active in the gastrointestinal tract.

Dietary recommendations

Despite concerns that the high saturated fat content of full-fat dairy produce would promote heart disease the latest meta-analyses show dairy consumption to be neutral or beneficial for weight control, coronary disease, diabetes, hypertension and most cancers.

In global ecological comparisons milk and dairy intake is strongly associated with adult height and many international advisory bodies recommend the consumption of 400-500ml milk equivalents per day, but few population groups meet these levels. Of 50 national food-based dietary guidelines (FBDG) surveyed two-thirds make reference to yogurt and either give guideline quantities or encourage an increase in consumption within the wider guideline to increase intakes of low-fat dairy produce.

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Further reading:

Brussow H. Nutrition, population growth and disease: A short history of lactose. Environmental Microbiology (2013) doi:10.1111/1462-2920.12117

Tishkoff SA, Reed FA, Ranciaro A, Voight BF, Babbitt CC, Silverman JS, Powell K, Mortensen HM, Hirbo JB, Osman M, Ibrahim M, Omar SA, Lema G, Nyambo TB, Ghori J, Bumpstead S, Pritchard JK, Wray GA, Deloukas P. Convergent adaptation of human lactase persistence in Africa and Europe. Nat Genet. 2007;39:31-40.

The Yogurt in Nutrition Initiative’s presentations on September 16 at the International Union of Nutritional Science’s 20th International Congress of Nutrition featured information from experts who spoke about the main science related to yogurt.

On her side, Nicole Darmon, PhD, Research Director at the National Research Institute of Agronomy (INRA), has examined how yogurt can fit into a nutritionally adequate diet.

Individual diet modeling with linear programming (2) was used to analyse and quantify the food changes needed to achieve a whole set of nutrient-based recommendations in a French adult population, with a focus on dairy products. From each individual weekly food intake (observed diets) of adults (n=1171) participating in the French national INCA (Enquête Individuelle et Nationale sur les Consommations Alimentaires) dietary survey, an isocaloric modelled diet was designed to simultaneously meet a whole set of nutrient recommendations (proteins, lipids, carbohydrates, fiber, essential fatty acids, 10 vitamins, 9 minerals, sodium, saturated fatty acids, cholesterol, and free sugars) while deviating the least from the observed food intakes.

The results indicated that, among seven main food groups, the quantities of three food groups had to be increased to reach nutritional adequacy, and the dairy group was one of them, together with fruit and vegetables (including nuts), and starches and grains. For all the food groups except the dairy one, their variation in energy contribution between the optimal diets and the observed ones followed their variation in weight.

Nutrient density

For instance, the contributions of fruits and vegetables to both total diet weight and total energy intake had to be increased by one third, and that of added fats had to be reduced by one third. The dairy group behave differently, as its weight increased by about 19% while its energy contribution decreased by 14%. This was explained by a heterogeneity within the dairy group, with an increase (in weight) of fresh dairy products (+ 60%) and milk (+17%), a decrease of cheese (-48%), without significant change of dairy desserts.

Lastly, Darmon and her team quantified the changes needed, within the dairy group, that were compatible with the fulfillment of all nutrient recommendations. Cheeses represented one out of two consumed portions of milk-based products in observed diets, whereas in modeled diets cheeses, milk, and yogurts each represented about one portion per day. Milk desserts were similar before and after optimization, at approximately one portion per week.

These results confirm that a large increase in intake of plant-based products is needed. They show that rebalancing the intake of milk-based products in favor of the least energy-dense ones (i.e., yogurts and milk) will help individuals in this population reach nutritional adequacy.

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Sources:

Clerfeuille E, Maillot M, Verger EO, Lluch A, Darmon N, Rolf-Pedersen N. Dairy products: how they fit in nutritionally adequate diets. J Acad Nutr Diet 2013;113:950-6.

Maillot M, Vieux F, Amiot J, Darmon N. Individual diet modeling translates nutrient recommendations into realistic and individual-specific food choices. Am J Clin Nutr 2010;91:421-30.

According to Arne Astrup (Department of Nutrition, Exercise and Sports, University of Copenhagen, Denmark), dairy products contribute important nutrients to our diet, including calcium, protein and other micro- and macro-nutrients.

Dairy products can be high in saturated fats, and dietary guidelines generally recommend reducing the intake of saturated fatty acids (SFAs) to reduce cardiovascular disease (CVD).

However, recent evidence question the role of SFAs in CVD, finding that substitution of SFAs in the diet with omega-6 (n-6) polyunsaturated fatty acids abundant in vegetable oils can, in fact, lead to an increased risk of death from coronary heart disease (CHD) and CVD, unless it is balanced with n-3 polyunsaturated fat. Replacing SFAs with carbohydrates of high glycemic index is also associated with a higher risk of CHD. Paradoxically, observational studies indicate that consumption of milk or dairy products is inversely related to incidence of CVD and diabetes.

Consumption of dairy products has been suggested to ameliorate characteristics of the metabolic syndrome, a cluster of risk factors including dyslipidemia, insulin resistance, increased blood pressure and abdominal obesity that together markedly increase the risk of diabetes and CVD.

Dairy products, like cheese, do not exert the negative effects on blood lipids as predicted solely by the content of saturated fat. Calcium, protein and other bioactive components may modify the effects on low-density lipoprotein cholesterol, triglycerides, blood pressure and energy balance. Apart from supplying valuable dairy nutrients, yogurt may also exert beneficial probiotic effects.

The consumption of yogurt, and other dairy products, in observational studies is associated with a reduced risk of weight gain and obesity, as well as CVD, and these findings are, in part, supported by randomized trials.

Yogurt is a nutrient-dense, tasty, handy and easily digested product to help people reach their daily dairy intake without excess calories. Replacing less healthy snacks and foods with yogurt is a simple way to re-establish healthier daily dietary habits.

Guidelines: the ‘Ideal’ healthy snacks

• Consuming products with a low energy density should be more satiating as, for the same number of calories, one would have to eat more of those foods (in volume).
• An ‘ideal’ healthy snack should have a high nutrient density and promote the feeling of satiation/satisfaction.
• Where weight control and obesity are a concern, an ideal snack should also have a low energy density.
• Yogurt is a nutrient-dense, tasty, handy and easily digested product to help people reach their daily dairy intake without excess calories.
• Replacing less healthy snacks and foods with yogurt is a simple way to re-establish healthier daily dietary habits.

A step further

Nutrient versus energy density: glossary (1,2)

• Nutrient density* describes the ratio of nutrients (in grams) to energy content (in joules or calories) of any particular food.
• Energy density* describes the amount of calories per gram of food. Its use helps consumers evaluate the energy provided by snacks through a given mass/volume ratio.

*calculation varies according to country

Snacking: what is a healthier alternative?

• An unhealthy snack can be described as having a low nutrient content and a high energy density, and failing to satiate, thus potentially promoting the craving for further consumption.
• An ‘ideal’ healthy snack would therefore have a high nutrient density and promote a feeling of satiation and satisfaction, which may limit its excessive consumption.

 Relevance of yogurt today

• According to the Nutrient Rich Foods (NRF) Index and the SAIN/LIM Index, 2 systems to rank foods according to their nutritional content validated in the USA and FRANCE, milk and yogurt are the second most nutrient-dense group of foods, behind vegetables and fruits (2, 7).

• Yogurt is a good source of protein, calcium and phosphorus, and also contains zinc and vitamin B2, B12, B5, B9 and A. The bioavailability of these nutrients in yogurt is also generally good (3).
• The proteins in yogurt contain all 9 essential amino acids and are of a higher quality than proteins from plant sources (4).
• Yogurt has a much lower energy density than most cheeses (5).
• The consumption of dairy, including yogurt but not cheese, is associated with a reduced incidence of type 2 diabetes and lower fasting blood glucose levels (6).

 Sources:

1. Dietary Guidelines for Americans, 2010. Available at www.dietaryguidelines.gov
2. Drewnowski A. Concept of a nutritious food: toward a nutrient density score. Am J Clin Nutr. Oct 2005; 82 (4) : 721-32
3. Gaucheron F. Milk and dairy products: a unique micronutrient combination. J Am Coll Nutr. 2011; 30 (5 Suppl1) : 400S-9S
4. Bos C et al. Nutritional and physiological criteria in the assessment of milk protein quality for humans. J Am Coll Nutr. 2000 ; 19 (2 Suppl) : 191S-205S
5. French food composition table, Table Ciqual 2008. Available at http://www.ansespro.fr/TableCIQUAL/
6. Fumeron F et al. Dairy consumption and the incidence of hyperglycemia and the metabolic syndrome: results from a French prospective study. Data from the Epidemiological Study on the Insulin Resistance Syndrome (DESIR). Diabetes Care 2011 ; 34 (4) : 813-7
7. Darmon N et al. Am J Clin Nutr April 2009 vol. 89 no. 4 1227-1236

Are the symptoms attributed to lactose intolerance really caused by lactose?

Researchers from Barcelona set out to ascertain this in 353 patients, who underwent a hydrogen test. The results show that the symptoms that the patients said they experienced following the consumption of dairy products at home were significantly more severe than those reported during the test, in which the participants were required to ingest 50 g of lactose.

Moreover, the test reveals an ‘over-perception’ of lactose intolerance at home, among both women and men. This study therefore shows that many symptoms are mistakenly attributed to lactose maldigestion.

Source: Casellas F et al. Clin Gastroenterol Hepatol. 2010 Jul;8(7):581-6. doi: 10.1016/j.cgh.2010.03.027. Epub 2010 Apr 10.

A team of researchers at the University of São Paulo in Brazil analysed the diagnosis, and genetic and clinical factors of lactose intolerance.

Their conclusion is that the symptoms of lactose intolerance may have been exaggerated and that persons with lactase non-persistence can tolerate up to 12 g of lactose. Consequently, they need not limit their consumption of dairy products to lactose-free milk and/or fermented milk, which could be beneficial to their bone mass density.

Source: Mattar R et al. Clin Exp Gastroenterol. 2012; 5: 113–121. Published online 2012 July 5. doi: 10.2147/CEG.S32368

This is the finding of a randomised double-blind controlled trial among institutionalised women with a mean age of 85.5 years. During the 56-day trial, the participants consumed two 125-g servings of yogurt – either fortified with calcium and vitamin D or not – as part of their daily diet. The two fortified yoghurts provided supplemental levels of vitamin D (10 mcg/day) and calcium (800 mg/day).

Source: Bonjour JP et al. The Journal of Clinical Endocrinology & Metabolism July 1, 2013 vol. 98 no. 7 2915-2921

However, the consumption of dairy products is often below the recommended intake. An Australian study assessed the impact of this low consumption of dairy products on healthcare costs in Australia and on the Disability Adjusted Life Year (DALY), which measures the number of years lost due to ill health.

In the financial year 2010-2012, costs linked to low consumption of dairy products were estimated at USD 1.6 billion, with a loss of 75,012 DALY. The authors concluded that the cost-efficiency of interventions using dairy products to reduce the costs associated with diet-induced diseases should be further developed and assessed.

Source: Doidge JC et al. J Nutr, 2012; 142: 1772-1780.

Scientists at Erasmus University in Rotterdam (Netherlands) have developed a model to estimate the potential impact of dairy foods on the costs linked to osteoporosis. Their model is based on the hip fractures that could potentially be prevented through a higher intake of dairy products.

The results show that an increased intake of dairy products by one portion a day could potentially reduce the costs associated with hip fractures by €129 million in France, €34 million in Sweden and €6 million in the Netherlands.

Source: Lötters FJ et al. Osteoporos Int. 2013 Jan;24(1):139-50. doi: 10.1007/s00198-012-1998-6. Epub 2012 Jun 16.

Many studies have identified a link between osteoporosis and hypertension. A cross-sectional study of 3,301 postmenopausal women reveals that the participants suffering from hypertension are more often also affected by osteoporosis, and that the prevalence of hypertension is higher among the women suffering from osteoporosis.

The proportion of women with hypertension, osteoporosis, and the two diseases combined rises significantly as their dairy intake decreases. A dairy intake in the lowest quartile was a significant predictor of osteoporosis and hypertension. The authors suggest that a low intake of dairy products may constitute a pathogenic link between these two conditions.

Source: Varenna M et al. Calcified Tissue International July 2013, Volume 93, Issue 1, pp 86-92