Significance of milk lipids in human health OR Nutritive value of milk fat
Function of food lipids, in general, and milk fat, in particular, on human healthare as follows1. A source of energy.2. A supplier of structural components.3. Supplier of essential FAs.4. Supplier of fat soluble vitamins.5. Contribution to palatability of food: flavor, aroma & texture.6. Toxicity of lipids. disadvantages7. Role in diseases process.
1. A source of energy.• Fats primary source of energy that is a good fuel fuel for energy has high calorific value production• Fats supply 9.0K.cal/gm energy v/s 4.0K.cal –protein 3.8K.cal –CarbohydratesThus fats supply more than twice as much energy per unit weight as supplied by protein and sugar.• Fats being concentrated source of energy in the diet is particularly useful for the infants and children to meet their energy requirementBecause fats increase the energy devsity & decrease the bulk of diet.High calorific value of fat is of special significance because the fat stored in the body is available as source of energy during food shortage.
2. Lipids as supplier of structural components• Dietary fats supply structural components (i.e. the lipids used in the cell formation) in the form of FAs or cholesterol. Cholesterol• However, a dietary supply of is not essential because on body can synthesize its SFAs own lipids, if needed, to compensate for dietary MUFAs insufficiency.• The variety long chain PUFA which are also characteristics of structural components can be synthesized in our body if two essential PUFAs, provided by plants (linoleic & α-linoleic) are supplied in the diet.
Contd…• Principal function EFAs is to ensure as precursors of oxygenated compounds called “Eicosanoids”Like - leukotriens - PGs - ThromboxanesWhich function as local hormones• Milk fat has relatively low content of EFAs. As compared to Veg.oils & fats.Therefore milk fat would not be considered as good source of EFAs.• PUFA content of milk fat is about 3% of total FAs. but at least half of this 3% is considered as of isomeric FAs with no EFAs with no EFA activity.
4. Lipids as supplier of fat soluble vitamins.• Dietary fat/ milk fat contribute several fat soluble vitamins (like A, D, E and K)• Vit-A is found as such in animal fats.• However, green vegetables and veg.oils contains precursor called carotenoids such as β-carotene which gets converted into vit-A in the body.• Vit-A helps to initiate vision from light energy essential for growth & maintenance of epithelial tissue also essential for normal reproduction & growth.• Deficiency of vit-A causes night blindness, inflammation of cornea, retardation in normal growth, defects in teeth & disturbance in bone growth.• Milk fat is a good source of vit-A. Excessive intake of vit-A results in accumulation in the liver and result in toxicity.
Vitamin D: D3 (cholecalciferol) – Animal origin.• Two forms D2 (Ergocalciferol) – plant origin.• Helps in the increased absorption, longer retention & better utilization Ca & P in the body. Ultimately helps in normal bone formation & teeth formation.• Regulates the level of Ca &P in blood – by withdrawing it from bone as & when required in the blood.• Deficiency leads to rickets in children Osteomalcia in older people.Both these diseases characterized by soft bones & twisting of bones or deformed bonesLike vit-A, vit-D if consumed in excess causes toxicity.
Contd…Vitamin E:• Wide spread in foods• Stored in the body so that deficiency states are rarely seen.• Activity is exhibited by a family of compound – called tocopherols/tocotrienol. Most active is α-tocopherol.• Richest sources are veg.oils, cereal products & eggs.• It is a powerful antioxidant prevents peroxidation of UFAs. In living cells vit-E prevents oxidation of membrane FAs.• Requirement increases when diet rich in PUFAs.• Deficiency sterility in males missed abortion in females therefore, vit-E is called as anti-sterility factor.
Vitamin K :• Activity shown by group of compounds called Menaquinones• Two naturally occuring forms I. Vit-K1 – phytyl Menaquinones (plant origin) II. Vit-K2 - prynyl Menaquinones (animal & bacteral origin)• Vit-K3 synthetic compound called Menadione.• Our intestinal bacteria are capable of producing our entire needs.• Vit-K necessary for clotting of blood.• Deficiency causes delay(prolong time taken) for blood to clot, resulting in Haemrrhagic problem.
5. Contribution of lipids to palatability of food: flavor, aroma & texture• The presence of fats particularly milk fats contribute substantially to the palatability of foods.• Fat free diet would be extremly unplesant to eat. May lead to deficiency EFA/vitamin.• Milk lipids play a distinctive role in flavor & taste of milk products. give such a pleasing flavor which cannot be duplicated by any other fats.• The compound which contribute to flavor are low Mol.Wt.volatile FAs.• SFAs have a more intense taste & smell than LFAs(Because of their greater water solublity & volatility).• Chemical transformation of lipids (oxidative or enzymatic) may give rise to alcohol, ester, carbonyl compound & lactones. Each of there contribute to the unique flavor of different dairy product.
Contd…• Lipids also contributes towards body & texture (mouth feel) of product which are concerned with the consumer acceptability.• Softness & smoothness & rich tasting qualities are imparted by milk lipids.
6. Toxicity of lipidsToxicity of lipids can be due to the presence of following: a) Cyclopropene FAs. b) Branched chain FAs. c) Trans – FAs. d) Long chain monoenoic FAs. e) Oxidized fats.a) Toxicity due to Cyclopropene FAs: Cyclopropene FAs i.e. sterculic acid (19:1)& mlalvalic acid (18:1) CH2 CH3-(CH2)7- C=C-(CH2)7COOH Present in cottonseed oil (level 0.1 to 0.5 %in processed 0.6 to 1.2% in unprocessed cottonseed oil. Can causes toxicity effects inhibition of desaturation of steric acid to oleic acid. Thereby altering the permeability of membrane. However, fortunately dairy products contains – No cyclopropene FAs.
b) Toxicity due to Branched chain FAs• Some branched FAs i.e. phytanic acid (3 ,7, 11, 15-tetra methyl – hexadecanoic acid) are present in ruminants tissue & also in some dairy products.• Some people have some specific disorders. Such people cannot utilized theses branched FAs. For theses people thesese branched chain FAs can causes toxic effects like – Chronic neuropathy – Night blinness – Narrowing of the visual – Skeltal abnormality – Cardiac complication• On other hand, some branched chain FAs e.g. 14-methyl hexadecanoic acid may play an essential role is protein synthesis.
c) Toxicity due to trans FAs• Most UFAs found in nature contain double bonds is cis configuration.• FAs with TRANS configuration also found in nature but is much less abundance.• Bio-hydrogenation of PUFA in the rumen of ruminants produces trans FAs.• Chemical hydrogenation of oils also produces trans FAs.• Dairy products have 20% of MUFA as trans acids.
Ingestion of excessive amount of trans FAs result in the following metabolic disorder:I. Metabolism of available EFAs is disturbedII. A decrease in the concn. Of EFA in heart muscle take placeIII. Availability of EFAs for PGs formation is adversely affectedIV. Symptoms of EFAs deficiency are aggrated.V. In pigs, diet rich in trans – FAs causes atherosclerosis.
d) Toxicity due to long chain MUFA• Some naturally occuring edible oils contain appreciable quantities of MUFA(in addition to C18:1) having chain length of 22 carbons (22:1)e.g. rapeseed oils , mustard oils contain Erucic Acid(cis-13-docosaenoic acid)Diet rich in Erucic acid adversly affect the heart muscle• Fortunately dairy fats contain negligible quantities of these long chain MUFA
e) Toxicity due to oxidized fats• Normal level of autoxidation in food stuffs at room temp. may be imp. from toxicological point of view.• However, heating of unsaturated fats causes extensive chemical changes.• Heated fats contain a range of polymerized compounds extent of polymerization 10-20% under normal cooking practices up to 50% under frying conditions(when fat is severely abused) only is latter care toxic effect have been observed.
7) Role dietary lipids in diseases process• Diet play an imp. Role in the diseases like : a) Cardiovascular disease b) Cancer c) Diabetes d) Obesitya) Cardiovascular disease: It is a collective name for a number of disease which affect supply of blood to the heart. Ischaemic Heart Disease(IHD) Atherosclerosis (thickness of inner walls of arteries & loss of elasticity of walls of arteries) Due to deposition of cholesterolb) cancer Disease caused by irregular growth of cells. In this cell lose nearly all control & grow autonomously Cancer cells continue to grow & devide &vform a mass known as Malignant Tumor(it inavdes surrounding tissue & disrupt the structure & function of organs, leading to death of the oragnism. Information gained so far indicated that every fat & some protein contribute to cancer. Whereas, fiber , vit-A,C,E carotenoids, CLA, Ca and some protein may be protective.
Contd…c) Diabetes:• common disease of “ affluent countries”. It is gradually increasing.• It was once regarded as a disease of carbohydrates metabolism. But it is now reported that faulty lipid metabolism is equally imp.d) Obesity:• Means – excessive accumulation of fat in the adipose tissues - of the body• This also is one of the predominant health problem of different society,• Obesity occurs when the intake of energy is not precisely matched by energy expenditure.• We know dietary fats contain more than twice energy as compared to carbogydrates & proteins.Therefore high fat play imp. role in the development of obesity.Hence too much dietary fat should be avoided.