Dairy products contain nutrients and bioactive components that act synergistically as well as independently. It is an integrated food system of structure specific proteins, lipids, and carbohydrates that have beneficial physiological properties beyond the content of essential vitamins, minerals and macronutrients.

The facts

• Various studies have confirmed a blood pressure (BP) lowering effect of calcium consumption through dairy products and supplements; however the effect tends to be more consistent when dairy products, rather than calcium supplements are ingested.
• Mindful that calcium-channel-blockers are often used in controlling hypertension, dairy products have a beneficial impact on BP regulation.
• The observed beneficial effect of consumption of dairy products on BP appears not to be derived solely from calcium, but from the complete nutritional profile of dairy products, which include the synergy of minerals, vitamins, proteins and essential fatty acids.

The evidence

• The DASH (Dietary Approaches to Stop Hypertension) clinical trail, performed on 459 adults over 11 weeks, found the most dramatic decreases in BP when diets rich in dairy, fruits and vegetables were consumed (-5.5 mmHg diabolic blood pressure (DBP) and -11.4 mmHg systolic blood pressure (SBP)), compared to diets only high in fruits and vegetables (-2.8 mmHg DBP and -1.1 mmHg SBP)
• A South African cross-sectional study, with 325 adult subjects from various cultural groups, reported that dietary calcium intake was inversely associated with SBP as well as DBP

The MONICA cross-sectional survey on 912 men aged 45-64 yrs, found significant associations between low SBP and dairy consumption as well as total calcium intake

Bioactive peptides in dairy

In contrast to the high cost of hypertensive drug therapy which could have possible side effects, three servings of dairy products per day can be recommended as part of a healthy, preventative and antihypertensive diet

Apart from their basic nutritional role as sources of essential amino-acids, many food proteins contain encrypted peptide sequences with specific physiological functions. Both milk proteins (casein and whey) are rich sources of bioactive peptides that have been shown to inhibit the activity of angiotensin-I-converting enzyme (ACE). ACE is a key regulator in the rennin-angiotensin system which is a primary regulator of BP as well as fluid and electrolyte balance in the body. ACE converts the inactive angiotensin-I-hormone into angiotensin-II, which increased BP by constricting the vascular smooth muscle. Inhibition of ACE results in decreasing blood pressure, with a 5mmHg decrease relating to a 16% decrease in cardiovascular disease.

These ACE inhibitory peptides present in dairy, are released by enzymatic hydrolyses either during gastrointestinal digestion or during processing. During the fermentation of milk and maturation of cheese, the milk proteins are hydrolyzed into a number of ACE inhibiting peptides due to the action of indigenous milk enzymes (proteases), added coagulants and microbial enzymes e.g. lactic acid bacteria added during the production of yoghurt.

Dairy-protein-derived functional products, hydrolyzed for optimal ACE activity, have also been developed for commercial purposes. The proteins in which some potent ACE inhibiting peptides are found include αS1-casein, αS2-casein, β-casein, κ-casein, α-lactalbumin, β-lactalbumin and bovine serum albumin.

Reported hypotensive effects of fermented milks and dairy-protein-derived products in humans

References

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