Dairy Products Consumption: Benefits and Beliefs

 Dairy Products Consumption: Benefits and Beliefs

Dairy products provide a package of essential nutrients that is difficult to obtain in low-dairy or dairy-free diets, and for many people it is not possible to achieve recommended daily calcium intakes with a dairy-free diet. Despite the established benefits for bone health, some people avoid dairy in their diet due to beliefs that dairy may be detrimental to health, especially in those with weight management issues, lactose intolerance, osteoarthritis, rheumatoid arthritis, or trying to avoid cardiovascular disease. This article provides information for health professionals to enable them to help their patients make informed decisions about consuming dairy products as part of a balanced diet. There may be a weak association between dairy consumption and a possible small weight reduction, with decreases in fat mass and waist circumference and increases in lean body mass. Lactose intolerant individuals may not need to completely eliminate dairy products from their diet, as both yogurt and hard cheese are well tolerated. Among people with arthritis, there is no evidence for a benefit to avoid dairy consumption. Dairy products do not increase the risk of cardiovascular disease, particularly if low fat. Intake of up to three servings of dairy products per day appears to be safe and may confer a favourable benefit with regard to bone health.

Dairy products have been an important part of the human diet for some 8000 years and are part of the official nutritional recommendations in many countries worldwide. They provide a package of key nutrients that are difficult to obtain in diets with limited or no dairy products, such as vegan or dairy restrictive diets. Indeed, dairy products are rich in calcium, protein, potassium and phosphorus. They contribute around 52–65 % of the dietary reference intake (DRI) of calcium and 20–28 % of the protein requirement, depending on the age of the consumer . The contribution of dairy products to providing recommended calcium intakes has largely driven the dietary recommendations for dairy intake in most guidelines.

Dairy Products as a Source of Key Nutrients

Worldwide, many people fail to achieve an adequate dietary calcium intake. The adequacy of dietary calcium consumption varies geographically and reflects milk consumption.

To meet the daily dietary calcium requirement, dairy products, green vegetables and mineral waters are important, easily available, sources of calcium. Indeed, dairy products represent good dietary sources of calcium due to their high calcium and nutrient contents, high absorptive rate, availability and relatively low cost, which makes the regular consumption of dairy products feasible. They provide more calcium, protein, magnesium, potassium, zinc and phosphorus per calorie than any other typical food found in the adult diet . Many dietary recommendations include the consumption of 3 servings of dairy products per day (for example, 1 glass of milk, 1 portion of cheese, 1 yogurt)—an amount that provides most of the DRI of calcium for the general population. For example, 250 mg of calcium may be obtained from a 200 ml glass of milk, a 125 g serving of yogurt or 35 g of hard cheese. The nutrients most at risk if dairy products are excluded are calcium, potassium and magnesium. For women of 19–50 years of age who do not consume dairy products, only 44 % of calcium and 57 % of magnesium and potassium recommendations are met .

Under normal dietary conditions, about 30–40 % of the calcium contained in milk and cheese is absorbed in the gut either through vitamin D-dependent transport across the duodenum, facilitated diffusion or under the influence of lactose in the distal small intestine via the paracellular route . Calcium is found in green leafy vegetables in reasonable quantity , however, a high proportion of the calcium is made insoluble by the presence of fibres, phytic acid and oxalic acid, which reduce the bioavailability of calcium. For example, cooked spinach contains 115 mg of calcium per serving but only 5 % of spinach calcium is absorbed, as spinach contains a high proportion of oxalates and phytates, which bind calcium and form insoluble salt compounds . Thus, while consumption of 1 cup of milk per day may be considered feasible to provide 100 mg of absorbed calcium, the consumption of 16 servings of spinach per day to provide the same amount of bioavailable calcium may be considered unpalatable.

Head-to-head intervention trials show bone-health benefits for dairy foods over non dairy calcium supplements. In postmenopausal women, those randomised to dairy (low-fat milk and yogurt products, fortified with concentrated milk protein) had greater improvements in arm, pelvis, total spine and total-body bone mineral density (BMD) than those receiving calcium supplements  In studies cheese has been found beneficial than other non dairy calcium supplements for tibia cortical bone mass accrual in children. This may be a result of better absorption of dairy calcium, differences in the distribution of intake over the day (small regular amounts of dairy versus two large doses from the supplement) and differences in protein or micronutrient intakes. Greater increases in insulin-like growth factor-I (IGF-I), which favours bone formation, have also been reported for dairy compared with calcium supplements

Dairy foods also contain protein, with a 200 ml glass of milk also providing around 6–7 g of mostly casein and whey proteins . The casein phosphor-peptides (CPP) and lactose in dairy foods can facilitate intestinal calcium absorption . For example, the enzymatic hydrolysis of casein protein leads to the formation of CPP. These molecular species have been shown to bind calcium and therefore protect it against precipitation with anions such as phosphates in the small intestine. The net result is an increase of passive calcium absorption in the ileum .

Phosphorus (P) ions are also present in milk, generally combined with proteins and peptides. At the kidney level, increased inorganic phosphate intake leads to decreased urinary calcium and increased calcium retention. During growth and adulthood, the administration of calcium and inorganic phosphate in a ratio close to that found in dairy products leads to positive effects on bone health . Calcium and inorganic phosphate interact at both the intestinal and renal levels and impact on bone maintenance and osteoporosis management. Interactions between calcium, inorganic phosphate, protein and vitamin D reduce bone resorption, attenuating age-related bone loss.

Conclusion

Human beings are the only mammals that continue to consume milk after the period of breastfeeding, and this is because milk provides calcium and vitamins tothe  body.  Milk is an excellent combination of all macronutrients, such as  carbohydrates,  proteins  and

fat together, in excellent proportion to each other, but it also offers several vitamins and minerals important for the body is an invaluable and irreplaceable liquid that offers considerable long-term benefits to both people of all ages and society.