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My friend was making tea with dry milk, I asked to him to let me eat some dry milk (it is delicious) and he said that alone it is harmful.

I searched for that and found this link, http://nutritiondiva.quickanddirtytips.com/is-powdered-milk-bad-for-you.aspx

It is true that in the process of turning fresh milk into a powder, the cholesterol in the milk is likely to get oxidized. And it is true that oxidized cholesterol appears to be a particularly dangerous form of cholesterol of all.

[...]

Oxidized cholesterol is cholesterol that’s been sort of roughed up around the edges, which makes it particularly irritating to your blood vessels. To make a long story short, that irritation is what triggers the formation of plaques, which are the beginning of heart disease. What’s worse, oxidized cholesterol molecules can in turn oxidize other cholesterol molecules, setting off a sort of chain reaction.

Is dry milk really harmful? Could eating it alone be more harmful?

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    Suppose that eating powdered milk is harmful. From where do we obtain the assurance that tea neutralizes its harm? I'm not able to rationalize this away like your friend. – Kaz Apr 24 '12 at 5:24
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    Eating anything can be harmful in the proper quantities. :) – Flimzy Apr 24 '12 at 5:27
  • @Flimzy: I can prove you wrong with chocolate. :) – user unknown Apr 26 '12 at 17:47
  • Technically speaking, oxydized cholesterol is not cholesterol anymore (but rather compounds like 7-hydroperoxycholesterols that form hydroxycholesterols) :) – nico Apr 30 '12 at 14:42
  • One more thing, is tea whitener not the dry milk? – LifeH2O Apr 30 '12 at 22:53
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Summary

Dry Milk contains higher levels of some chemicals than regular milk (but lower than, say, eggs). There is some evidence that these chemicals may cause heart disease, although the link is not clearly established.

Definitions

Some definitions, which might be useful later:

Oxysterols in Dry Milk

The Wikipedia page on Dry Milk reports:

Commercial milk powders are reported to contain oxysterols (oxidized cholesterol) in higher amounts than in fresh milk (up to 30 μg/g, versus trace amounts in fresh milk). Oxysterols are derivatives of cholesterol that are produced either by free radicals or by enzymes. Certain free radicals-derived oxysterols have been suspected of being initiators of atherosclerotic plaques. For comparison, powdered eggs contain even more oxysterols, up to 200 μg/g.

To support the oxysterol levels, it references:

  • "Advanced Dairy Chemistry: Volume 2 - Lipids" by P.F. Fox and P. McSweeney, Birkhäuser, 2006 ISBN 978-0-387-26364-9

To support the idea that dry-milk-based oxysterols are dangerous, they cite:

The abstract of this paper makes only weak claims of suspected/possible danger:

Cholesterol under certain in vitro and possibly in vivo conditions may be oxidized to oxysterols, which are suspected of being initiators of atherosclerotic plaques. Oxysterols inhibit HMG-CoA reductase activity resulting in a decreased cholesterol concentration in the cell membrane, which leads to endothelial membrane injury and probable premature cell death. Exogenous oxidation of cholesterol in human tissues under certain unusual conditions is highly probable. Dietary oxysterols are absorbed in the gastrointestinal tract and are selectively transported by the athrogenic lipoproteins LDL and VLDL. The oxysterols cholestanetriol and 25-OH cholesterol have been shown to be atherogenic. Oxysterols are commonly found in dried egg products, powdered milk, cheeses and in a variety of high temperature dried animal products.


Searching further, I found:

They showed that guinea-pig cells, in a dish, dosed with Ox-LDL:

induced cell damage and irregular electrical activity in ventricular myocytes. [...] The observed effects may play a role for functional cardiac abnormalities in patients with increased ox-LDL levels.

Another source cast further doubts:

According to current concepts, oxysterols are physiological mediators in connection with a number of cholesterol-induced metabolic effects. However, most of the evidence for this is still indirect, and there is a discrepancy between the documented potent effects of oxysterols under in vitro conditions and the studies demonstrating that they are of physiological importance in vivo. [...] The present review is a critical evaluation of the literature on oxysterols, in particular, the in vivo evidence for a role of oxysterols as physiological regulators of cholesterol homeostasis and as atherogenic factors

[...]

As judged from the results of animal experiments, the normal dietary intake of oxysterols is probably of little or no importance in the development of atherosclerosis.

In 2003, a Chilean paper repeated (but did not test) the claims that milk powder contains oxidized cholesterol, and that it is potentially harmful.

Several dairy products and milk powder are reported to contain oxidized cholesterol after processing (Dionisi et al., 1998). The oxysterols found in these products are the same as those in processed eggs. However, fresh milk contains 0 or only trace amounts of cholesterol oxides, which means that processing (e.g high temperature) is the main source of oxysterols (Angulo et al., 1997). Other milk-derived products such as cheeses, yogurt, and evaporated milk, contain very low amounts of cholesterol oxides. The oxysterol content of milk powder is in the range 1.0-2.5 ug/g. Dehydrated cheese has 8-15 ug/g; skimmed milk powder, 0.01-0.1 ug/g; and whole milk powder, 0.2-0.8 ug/g (Paniangvait et al., 1995). The amount of oxysterols present in these products depends on the processing temperature and the length of the storage period (Nourooz-Zadeh & Appelqvist, 1988).

[...]

The cytotoxic, mutagenic and probably carcinogenic effects described for some oxysterols have been observed in in vitro models. However, the atherogenic action of oxysterols has been demonstrated in both in vitro and in vivo study models, to be the best-characterized pathological expression of cholesterol oxidation (Staprans et al., 1998; Leonarduzzi et al., 2002) and comparable to the atherogenic action of trans fatty acid isomers (Valenzuela & Morgado, 1999).

This paper supports the idea that some oxidized LDL could cause harm, based on experiments in dishes:

At this link also Cole Watts have mentions of oxysterols and their possible relation to Alzheimer's disease:

Oxysterols are substances that are created as our bodies use and break down the elements in cholesterol. We’ve all heard how it’s important to keep our cholesterol levels down, and that our “good” cholesterol number, or HDL, should be normal or above normal, for better health. But it plays a more important role than that. Oxysterols that are produced from our bodies using cholesterol are meant to be broken down by the liver. However, people with a number of diseases like Hardened Arteries and Multiple Sclerosis have been found to have extremely high level of Oxysterols in their bodies. This has been found in some patients with Alzheimer’s Disease, as well.

[...]

The reason science is taking a hard look at the link between Oxysterols and Alzheimer’s is that our central nervous system contains the highest concentration of cholesterol in our bodies. Our brains need cholesterol to function properly. Many people believe that cholesterol is simply something to be watched in the diet to avoid heart disease and arteriosclerosis, but it’s something that’s vital for life.

[...]

While cholesterol itself doesn’t actually cross the blood-brain barrier, some of its by-products do. So any cholesterol-related processes that take place will affect the brain and nervous system heavily, most likely more than any other bodily system.

[...]

Only about a dozen of the known Oxysterols have been studied, and much more research is needed for the many that we haven’t explored. Scientists do say that since the Oxysterols are created when our bodies utilize cholesterol, and that a great deal of the cholesterol we have is produced by our bodies and not thanks to diet, a change in diet won’t affect the levels that might be linked to Alzheimer’s and other diseases.

Finally, this article looks at the types of Low Density Lipoproteins (LDL)and shows that Oxidized Low Density Lipoproteins (ox-LDL) causes cell damage.


Briefly: Oxysterols are produced in our body already. Dry Milk contains oxysterols in a low amount, but enough to increase the natural levels. Research on diseased bodies shown that they also contain high oxysterol levels. This shows us oxysterols might be playing a bigger role than we know and that Dry Milk ma be harmful for long term usage, but the research is not yet clear.

  • 80% of this answer is irrelevant. It all boils down to the last quote. The last quote needs references. I assume by "Wiki" you mean "Wikipedia"; Wikipedia is good enough to give general background, but when it comes to an actual medical claim, please link to a higher-quality, peer-reviewed source. Wikipedia is often a good place to start to find one. – Oddthinking Apr 27 '12 at 13:16
  • @Oddthinking here we are.. I added as much source as i can and how come its irrelevant? I putted those in order to make people understand each part of it. This is not an easy question to answer and its answer should contain as much knowledge as it can. I've given the info about Atherosclerosis and Cardiovascular Diseases cause DryMilk makes those by Oxysterols which are smaller piece of Cholesterol and more dangerous than their papa LDL. Also when you read those PDF's you will understand these are not the only Health issues it causes.. Alzheimer is one of them too.. – Berker Yüceer Apr 27 '12 at 14:50
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    I made a major edit, using only the research you found. I started out doing a simple copy-edit (i.e. tidying up the English, etc.), but as I went through the papers, I found they were not nearly as strong and clear-cut as the conclusion would suggest. I have softened the conclusion significantly. That's more of a change than I would normally care to do in an edit of someone else's work. Please check over it and ensure that you are still happy. There's still more work to do, but it is very late. – Oddthinking Apr 27 '12 at 16:28
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    Berker, the reason it was irrelevant is that, in the original, you spent most of the page defining related terms, and very little words actually showing any evidence for the claim. I still left a (much shorter) glossary in this answer, but normally I would just link to Wikipedia on the first instance of any unusual word, and let the people who have never heard of "cholesterol" follow the link themselves. – Oddthinking Apr 27 '12 at 16:33
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    @Oddthinking oh got your point now! I'm looking at the changes you made and yea i ve been a baad boy. I guess i understand now how to give an answer properly. Thanks for correcting me. – Berker Yüceer Apr 30 '12 at 6:07
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No, dry milk is not harmful.

It certainly isn't harmful because of Cholesterol, Oxidized or not.

the American Heart Association in its latest Guidelines for Cardiovascular Disease Prevention in Women when it decided that all women were at “high risk” for heart disease — because nearly all heart attacks occur in women without risk factors. Rather than admit that the risk factors themselves are poor measures for predicting heart disease, the guidelines called for treating the risk factors in nearly all women.

As covered in-depth here, none of the clinical trials the AHA used to support its new guidelines for women made their case at all. Multiple cardiologists examining the evidence, as well as several major studies published since the AHA guidelines, concluded cholesterol and, except for age, the traditional risk factors are next to worthless for predicting risks for heart disease,

... In other words, the people who end up hospitalized for heart problems have average LDL-cholesterol levels that are lower than the general population (104 versus 123 mg/dl).

Dry Milk does have a tendency to stick to the roof of your mouth, or tongue when eaten dry. This might cause a person to choke, but likely isn't life threatening.

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    Sorry, this reference isn’t notable. They actually make a compelling case and I’m inclined to agree with the reasoning, in particular since there there have been other indications recently exonerating cholesterol (to some extent). Nevertheless, this is not a valid resource to base an answer on here. – Konrad Rudolph Apr 23 '12 at 9:30
  • I'm also curious why this is an invalid source. The relevant meta post says "References should have credibility in the domain and should preferably be peer-reviewed literature." This source isn't peer-reviewed, but that's only a preference. Is the AHA not considered credible in the appropriate domain? – Flimzy Apr 24 '12 at 5:33
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    @Flimzy Yes but the AHA actually says the opposite of what the blog article claims, namely that a further reduction of cholesterol level could have prevented the risks. The blog article takes the claim and turns it on its head, and while the inference sounds convincing, this is just one of the dangers of “common” sense in skeptic reasoning and I’m unhappy with it. If the blog article had just echoed or explained the AHA’s claim that would be a completely different situation. – Konrad Rudolph Apr 24 '12 at 7:00
  • @KonradRudolph: IMHO, your complaint is justified, but does not make the reference "invalid" in the sense that it cannot be used in an answer here. But certainly it's worth a down vote if you disagree with the reasoning in the answer. – Flimzy Apr 26 '12 at 3:10
  • That is convincing enough for me. – Konrad Rudolph Apr 26 '12 at 6:57

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