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What You Should Know About Your Let Down Reflex

Written by WebMD Editorial Contributors

In this Article

• How Does the Let Down Reflex Work?
• What Are Signs of a Good Let Down?
• Complications of the Let Down Reflex

When your baby first latches on to nurse, they don’t actually get much milk at first. Instead, their suckling sends a message to your body to release the milk stored in your breasts. The strength and timing of the let down reflex, also called the milk ejection reflex, varies from mother to mother. 

How Does the Let Down Reflex Work?

If milk came out of your breasts instantly when your baby latched on, you’d probably leak constantly. Instead, your breasts store the milk until it’s needed. Most often, your let down reflex is triggered by a particular suckling motion your baby makes to stimulate milk production.

The let down reflex is a physiological response to your baby’s sucking. They stimulate small nerves in the nipple, which causes prolactin and oxytocin to produce milk and let down milk, respectively. The reflex is often accompanied by a tingling sensation in the nipple, but not all women experience that.‌

If you pay attention to your baby’s nursing patterns, at first their suckling will be faster and shallower to stimulate the release of milk. Once your milk lets down and your baby is drinking, their suckles will be deeper and longer. If they nurse longer and need more milk, they may adjust how they suck to stimulate more milk flow. 

Other let down triggers. Since your brain is wired to care for a newborn, other things may trigger the let down reflex. If your baby cries, or if you hear any baby cry, your milk may let down in response. If you go too long without nursing and your breasts get too full, your let down reflex may trigger to relieve the pressure.

Strong emotions may also trigger a let down of milk. If you are feeling intensely stressed, angry, or sad, your body may take that as a sign that you need to nurse your baby or release milk to alleviate pressure.

If your milk is not letting down, you can physically stimulate the nipple to allow let down. Try gently rolling your hand down your breast toward the nipple, then massage gently. It can also help to relax and think about your baby.

What Are Signs of a Good Let Down?

Breastfeeding is wonderful for your baby, but it is often full of doubts and questions. Are you producing enough milk? Are you doing it right? This extends to the let down reflex, too. You may wonder if your let down is strong enough or too strong. 

Here are signs of a healthy, functioning let down response:

Uterine cramps. You may notice that your uterus cramps during a let down in the days following birth. This is natural and nothing to be concerned about. As with menstrual cramps, for some the cramps are mild and barely noticeable, while for others the contractions can be more painful.

Change in sucking pattern. You may notice a change in your baby’s sucking pattern during a nursing session. Their suckle will go from being short and fast to long and slow once milk lets down. If they need more milk, their sucking may change again to encourage another let down.

Your feelings. Moms often report that they feel very relaxed and even sleepy when their milk lets down. This is a side effect of the oxytocin released during let down. You may also feel suddenly thirsty, which is your body’s way of preparing to replace the milk being removed during a nursing session.

Complications of the Let Down Reflex

Oversupply milk ejection reflex. A powerful let down is often accompanied by an oversupply of milk, sometimes called oversupply milk ejection reflex (O-MER). When your let down happens, you may notice that your baby sputters, coughs, and even chokes on your milk. Your baby may bite down to slow the milk flow. You may leak when not nursing or notice that your baby has more frequent but short feedings if you have an oversupply.

If this happens, keep a bib or cloth handy to catch your milk when it first lets down so that your baby doesn’t choke. After a moment when the let down slows, you can try latching your baby again. You can also restrict your milk flow by squeezing your areola during breastfeeding.

Talk to your doctor about safe ways to decrease your oversupply so that your let down is less strong.

Dysphoric milk ejection reflex. In some women, breastfeeding can create a negative physiological response, leading to negative emotions like guilt, anxiety, depression, and sadness. It is usually an isolated response that occurs only when you first let down your milk and into the first few minutes of breastfeeding. This is called dysphoric milk ejection reflex (D-MER) and is different from postpartum depression. 

There is still more research needed on the causes and effects of D-MER. Talk to your doctor if you are struggling with negative emotions during breastfeeding. 

Weak let down. You may have a weak let down if your baby seems frustrated while nursing. They may not be getting enough milk, or they may not be getting milk as fast as they want it. Using a breast pump can supplement less successful nursing sessions.‌

When pumping, look at photos and videos of your baby to try and encourage a let down. And just as you do when breastfeeding, try to relax. Take deep breaths and think about your little one, letting go of any stress.

What is milk? The great physiologist I. P. Pavlov said about milk: “How amazingly food prepared by nature itself stands out from a number of other varieties.”

Milk is a normal secret (excretion) of the mammary glands, which appears after childbirth in all mammals. Everyone knows cow's milk. Less common on the globe is the milk of a goat, sheep, camel, mare, as well as yak, zebu, and reindeer.

Milk contains everything that is necessary for the nutrition of humans and young mammals. Milk requires the least amount of juice to digest and is easy to digest.

Cow's milk contains only 12-16 percent dry matter. The rest is water and those substances that evaporate if milk is dried at a temperature of 102-105 degrees.

Milk has a complex chemical composition. It contains over 100 different substances. It consists of two phases (parts) - water and fat. Milk sugar, minerals and vitamins are dissolved in the aqueous phase; at a very strong magnification (under an electron microscope), even the smallest protein bodies can be found in it. In the fatty phase, in addition to fat globules, there are fat-like substances, pigments, as well as fat-soluble vitamins.

Summer milk or milk from cows receiving good silage is yellowish. Such milk contains the pigment carotene, a significant part of which is converted in the body into vitamin A. The composition of milk also includes chemical agents of life processes common in wildlife - enzymes and hormones. When milk is dried, gases (carbon dioxide, oxygen, etc.) escape, and the milk no longer has a characteristic odor.

The quality of milk, its nutritional value, of course, is determined by the content of solids in it. The dry residue value is determined by the presence of fat, which is 2.8-6 percent in cow's milk, sometimes even more, as well as proteins, milk sugar and minerals. A cow with a milk yield of 20 liters excretes with milk at least 660 grams of proteins, 760 grams of fat, 940 grams of milk sugar, as well as 28 grams of calcium, 22 grams of phosphorus and 1 gram of sodium chloride (table salt). Most of all, the amount of fat in milk changes, the other components change much less. This is why the quality of milk is usually measured by dry skimmed milk residue - abbreviated as SOMO.

Milk proteins - casein, milk albumin and globulin - are among the most complete protein substances and are well absorbed by the body. In the milk of cows, goats and other artiodactyl herbivores, there is much more casein than in one-hoofed, omnivorous and carnivorous animals (for example, dogs, cats), in whose milk there is a lot of albumin. Albumin contains sulfur, and casein also contains phosphorus. Unlike casein, albumin is soluble in water; when heated to 70-75 degrees, it precipitates. The least in milk is globulin (only 0.1 percent), but its value is high, since it has immune properties, that is, it kills bacteria or delays their development.

Milk also contains other nitrogenous substances - urea, ammonia.

Fat in milk is in the form of fat globules with a diameter of 2-5 microns, however, they can be much larger and smaller. In one milliliter of milk, there are from 2 to 5 billion fat globules of different diameters. The larger they are, the smaller they are in a certain volume. The size of fat globules is of great importance in buttermaking. Larger fat globules are found in the milk of high-fat cows, they settle faster than small ones (Fig. 1). The special and complex structure of the shell of fat globules prevents them from merging in fresh milk and at the same time does not prevent them from grouping together in cream.

The color of milk depends on the number of fat globules and a special chemical compound of casein with calcium. When milk coagulates, this compound decomposes and casein precipitates.

There is quite a lot of milk sugar in milk. It is able to quickly decompose under the influence of bacteria and other microorganisms. Milk can turn sour, ferment. These processes are used for the manufacture of lactic acid products - kefir, curdled milk, etc.

Milk is rich in vitamins. It contains fat-soluble vitamins A, E, D, K and all water-soluble vitamins of group B. Unlike water-soluble vitamins, the amount of fat-soluble vitamins depends on: feeding conditions and animal welfare. A kilogram of cow's milk contains from 130 to 350 gamma of vitamin A and a small amount of carotene. It contains significantly less anti-rachitic vitamin D. In mountainous areas, there is twice as much of it in the milk of cows, since hay and animals are exposed here to increased action of ultraviolet rays. Vitamin B milk is much richer in summer than at the end of winter.

For newborn calves, the content of vitamin A in milk is of great importance. The placenta (afterbirth) is almost impermeable to this vitamin, as well as to carotene. Large doses of carotene (and vitamin A) to a pregnant cow do not lower this barrier. A calf is born with a very small supply of vitamin A in the liver and therefore needs to be supplied with milk.

B vitamins are synthesized in the rumen of a cow and then pass into milk.

Fresh milk can also serve as an anti-scurvy agent - it contains vitamin C.

As already mentioned, there are a lot of enzymes in milk. Some of them enter it from the cells of the mammary gland, others are formed as a result of the activity of milk bacteria. Milk always contains a certain amount of microorganisms that enter it already at the time of milking. They secrete enzymes that affect the chemical composition and properties of milk. Cow's milk is especially rich in calcium, potassium, and phosphorus. Salts of inorganic and organic acids were found in it. Most of all salts are found in combination with casein, phosphoric and citric acids. The weight ratio of phosphorus and calcium, despite the large differences in their content, is the same in the milk of almost all animal species and is 1: 1.2, that is, 1.2 parts of calcium account for one part of phosphorus. This ratio is very favorable for the absorption of calcium when eating milk.

It is curious that the ratio of salts in milk is quite close to the ratio of salts in the body of the young of this animal species.

A cow with every 10 kilograms of milk loses 12-14 grams of calcium and 10-11 grams of phosphorus, which cannot always be replenished with feed.

Citric acid in milk 0.1-0.2 percent. Its quantity depends not only on the breed of the animal, but also on the nature of feeding and even the season of the year. This is an important component of milk, because the stability during its processing (boiling, pasteurization, etc.) depends on the balance between citric acid and mineral salts. The flavor of dairy products such as butter, sour cream, kefir, etc., depends on a chemical formed from citric acid.

Milk always contains a small amount of trace elements: copper, zinc, iodine, manganese, cobalt, iron, etc. There is very little iron in cow's milk (only 1 milligram in one kilogram), and even less in pig's milk. A piglet is born with a small amount of iron in the liver, which is only enough for about 2 weeks. If piglets are not fed with iron salts in a timely manner, they develop severe anemia (anemia). The addition of chemical compounds of cobalt, iron, copper to the diet of dairy cows not only improves hematopoiesis, but also increases the percentage of fat in milk and the content of water-soluble vitamins. A liter of milk contains up to 70 milligrams of iodine. As Professor R. B. Davidov showed, the amount of iodine varies depending on the lactation period: the least of this element is in milk before starting a cow and the largest amount is observed in colostrum during the first two days after calving, iodine is an essential element in the nutrition of people and animals , since it is necessary for the normal functioning of such an organ as the thyroid gland (p. 83).

The milk in the udder is different from the milk produced. There is an even bigger difference between freshly milked milk and milk that has been stored for some time. Shortly after milking, within a few hours, the number of bacteria in milk does not increase, but even decreases. This is due to the fact that together with milk, the animal secretes immune substances that kill the bacteria that have entered it. This remarkable ability of freshly milked milk is sometimes used for medicinal purposes. If it is introduced through the nipple into the udder cavity, it is often possible to significantly reduce the inflammatory process in the mammary gland and cure some forms of mastitis.

Sanitary conditions for obtaining milk are of great importance. If these conditions are strictly observed, milk retains the properties of freshly milked milk much longer. In general, the faster and deeper the milk is cooled, the longer it does not spoil, does not turn sour.

Let us now note some physical properties of milk.

If we take the density of water as a unit, then the density of milk will be in the range of 1.029-1.032. The density of stored milk increases somewhat, as the fat in it passes from a liquid state to a somewhat solidified one. When diluted with water, the density decreases.

The osmotic pressure of milk varies within very narrow limits: it depends on the ratio of sugar and salts in the solution. An indicator of the normal chemical composition of milk is also its electrical conductivity, which decreases when diluted with water and increases when soured. The viscosity of milk depends on proteins. Therefore, the viscosity of colostrum, which contains many proteins, is especially increased. It also increases when milk is sour. Viscosity is determined by comparing the rate of passage through narrow (capillary) tubes of milk and water. The slower the liquid passes through the tube, the greater its viscosity.

The composition of milk varies

The chemical composition and nutritional properties of milk are not constant: they are influenced by the breed of the animal and feed, conditions of keeping and care of livestock, age, lactation period, season and other reasons.

Milk yield, as well as the chemical composition of milk, depends primarily on the feeding of animals. However, there are other reasons that invariably affect the amount of milk produced and its quality. It is known, for example, that the quantity and quality of a cow's milk to a certain extent change not only from day to day, but also within one and the same day. First of all, the fat content changes. So, the evening milk is richer in fat than the morning. More stable milk sugar content. When a cow for some reason noticeably and suddenly reduces milk yield, then the fat content in such milk often decreases. Apparently, the cow in these cases does not “give” milk well. The milk left in the udder, as we will see later, always contains a lot of fat. When the milk yield returns to the previous level, the fat content of the milk is restored.

It has been noted that when milk is milked, the first streams are less rich in fat than the last ones.

The chemical composition of milk in different breeds of cattle is not the same. Research by scientists from the Moscow Agricultural Academy named after K. A. Timiryazev found that the milk of cows of the Black-and-White breed contains up to 12 percent of dry matter, of which 3.41 percent is fat, 3.22 percent is protein, and the Jersey breed has up to 16 percent dry matter, of which 6.09 percent fat, 4.4 percent protein.

After calving for l, 5-2 months, the cow produces more milk every day than in the next time. Milk yield gradually decreases, up to transfer to dead wood (Fig. 2). Interestingly, the fat content of milk changes as follows: at the beginning of lactation, it is lower, then it gradually increases. The size of fat globules, on the contrary, is smaller at the beginning of lactation than at the end. By the end of lactation, the amount of protein in milk also increases.

A well-prepared (well-fed) cow produces not only more milk, but also a higher fat content.

Pregnancy affects milk yield and milk composition. From about the 4th-5th month of pregnancy, the cow begins to noticeably reduce milk yield, right up to the launch. Different cows have different milk yields. This is due to the fact that during pregnancy, various hormones and other chemicals enter the bloodstream, which to a certain extent delay the formation of milk. The same is observed when a cow comes to hunt.

The quantity and quality of milk depend to a large extent on the age of the cow. The highest annual milk yield, as a rule, occurs during the 6-7th lactation. After the calving of a two-year-old cow, the milk yield sometimes does not reach even three-quarters of this value. The annual productivity of a cow at the age of 10 years is usually already markedly reduced compared to productivity after the 6th-7th calving. In old cows, the fat content of milk also decreases to some extent.

Certain changes in milk production are also noted depending on the season. It is known that in hot weather, milk yield and fat content of milk decrease; on the contrary, in the cold (of course, up to a certain limit), the fat content in milk increases. In the same way, air humidity is reflected in milk yields. High humidity, preventing the evaporation of water from the skin, adversely affects the body temperature of the animal and indirectly - on the formation of milk, as it causes some overheating of the body.

Colostrum

Milk obtained from a cow during the first 3-7 days after calving is called colostrum. It is very different from regular milk.

Colostrum has a straw-yellow color with a brown tint, a salty taste, a special smell and, unlike milk, coagulates when heated as a result of its high content of globulin, which is less stable than casein. As can be seen from Table 2, there are much more dry substances in colostrum, in particular proteins - albumin and globulin, as well as mineral salts (especially iron).

In terms of protein composition, colostrum is closer to blood than milk, since colostrum contains many proteins such as globulin and albumin. Albumin is absorbed by the calf better than casein; together with globulin, it also receives enough immune bodies.

Table 2. Chemical composition of colostrum and cow's milk (in percent)

There are a lot of vitamins and enzymes in colostrum. The content of vitamins in it depends on how well the cow was prepared for calving. The colostrum of cows poorly prepared for calving lacks not only vitamins, but also globulin, albumin and some other substances. Feeding pregnant cows every day at least 10 kilograms of good silage entails the accumulation in colostrum of large amounts of the most important vitamin A for the animal.

If a cow is started to be milked before calving, then the milk of the first milk after calving does not seem to differ in appearance from normal milk, however, like colostrum, it coagulates when heated. Therefore, only 2 weeks after calving, cow's milk becomes suitable for cheese making.

For a newborn calf, colostrum is an indispensable food, a gradual change in its composition allows the suckling to adapt to extrauterine nutrition. The laxative properties of colostrum help to free the intestines from original feces. Due to the characteristics of colostrum fat, colostrum continues to have a beneficial effect on digestion in the following days, and also helps the calf's body to fight pathogenic microbes that enter it in the very first hours of the animal's life. This is why feeding colostrum to young animals is so important.

From the fifth day after calving, the amount of proteins and minerals in colostrum begins to decrease, the content of milk sugar increases, and gradually colostrum turns into milk.

Milk production (lactation) in females is regulated by hormones, primarily prolactin. When the nipples are stimulated, this hormone is released, and the mother's body secretes milk for the entire time that she feeds the offspring - whether it be weeks or months. In wild animals, after the transition of the cub to solid food, lactation gradually fades away. However, in pets, constant milking, which mimics suckling, maintains prolactin release. It is the same with breastfeeding women: in some cultures, children were breastfed until the age of 5-6, and all this time the mothers had milk, and professional nurses could give milk for decades.

What is milk, what is bad - Vlast - Kommersant

With the adoption of special technical regulations, buyers will be able to better understand what they are buying.

From the technical regulation for milk and dairy products

Milk is a product of normal physiological secretion of the mammary glands of agricultural animals obtained from one or more animals during lactation with one or more milkings without any additions to this product or any extractions substances from it.

Dairy product - a food product that is made from milk and (or) its components without the use of non-dairy fat and protein and which may contain components that are functionally necessary for milk processing.

Dairy compound product - a food product made from milk and (or) dairy products without or with the addition of by-products of milk processing and non-dairy components that are not added to replace milk constituents. At the same time, in this finished product, the components of milk should be more than 50%.

In the names of products that are not milk or dairy products or dairy composite products, it is not allowed to use the concepts established by this Federal Law, including the words that make up these names, their various combinations in the brand names of manufacturers when labeling such products, on their labels, for advertising or other purposes that may mislead consumers.

Signed by the President of Russia on June 16, 2008, will enter into force six months after publication.

From the technical regulation for fruit and vegetable juice products (draft)

For reconstituted fruit (vegetable) juices, the name of the product or close to it must indicate "made from concentrated juice (puree)" or "reconstituted".

The use of ascorbic acid as an antioxidant is not a reason to label consumer packaging "with vitamin C".

If sweeteners are used in the production of the nectar or juice drink, the name of the nectar or juice drink must be supplemented by the label "with sweetener(s)". In the case of aspartame content in nectar or juice-containing drink, the following inscription should be placed on the consumer packaging: "Contains a source of phenylalanine".

The second reading in the State Duma is scheduled for June 25, 2008.

From the technical regulation for tobacco products (draft)

The content of tar, nicotine (mg/sig) in the smoke of one cigarette cannot exceed:

For a cigarette with a filter: tar - 14 mg/sig; nicotine - 1. 2 mg/cig.

For unfiltered cigarette: tar 16 mg/cig; nicotine -1.3 mg/sig.

Four years after the publication of this Technical Regulation regarding the production and import of cigarettes, the content of tar, nicotine and carbon monoxide (CO) in the smoke of one cigarette may not exceed:

For a filter cigarette: tar 10 mg/cig; nicotine - 1.0 mg/sig; CO - 10 mg/sig.

For unfiltered cigarette: tar 13 mg/cig; nicotine - 1.1 mg/sig; CO — 14 mg/sig.

The second reading in the State Duma is scheduled for June 25, 2008.

From the technical regulation for confectionery products (draft)

Chocolate is a confectionery product that contains at least 35% cocoa solids, including at least 18% cocoa butter and at least 14% dry fat-free substances in cocoa products. In the production of chocolate, it is allowed to use, without changing the minimum amount of cocoa butter, up to 5% of the total weight of the chocolate mass (without large additives) of vegetable fats - cocoa butter equivalents and (or) cocoa butter improvers.

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