今天又看到有帖子说不敢吃鸡蛋，怕胆固醇高，这几年，胆固醇的争议特别多，我不是生物专家，但是有点nerdy，有问题就想研究一下，所以说说我掌握的知识吧！

几年前，我就被医生警告胆固醇高，那时候我刚刚30，吓了一条，酷爱吃海鲜的我有一段时间海鲜都不敢吃了，尤其是能吃螃蟹，简直要了我的命。当时，胆固醇的争论还没有那么多，但是最基本的知识首先应该是，什么是胆固醇？
What Is Cholesterol? （source: [url=http://www.pcrm.org/health/health-topics/cholesterol-and-heart-disease]http://www.pcrm.org/health/health-topics/cholesterol-and-heart-disease[/url])Cholesterol is not the same as fat. If you had a bit of cholesterol on the end of your finger, it would look like wax. The liver manufactures cholesterol and sends it out to other parts of the body for the production of hormones and cell membranes. Based on the results of the Framingham Heart Study and other research, the ideal cholesterol level is below 150 mg/dl. At that point, coronary artery disease is very unlikely. Unfortunately, nearly 107 million Americans have cholesterol levels more than 200 mg/dl,1 dangerously close to 225 mg/dl, which is the average cholesterol level of coronary artery disease victims.5
According to the 2010 USDA Dietary Guidelines, the federal government’s recommended maximum for dietary cholesterol intake is still as high as 300 mg. Both the American Heart Association and the National Cholesterol Education Program recommend less than 200 mg per day for [url=http://pcrm.org/health/heart/]people at risk for cardiovascular disease[/url].6 The amount of cholesterol in one egg exceeds this recommended maximum amount.


Heart Disease and Lowering Cholesterol

（source: [url=http://www.webmd.com/heart-disease/guide/heart-disease-lower-cholesterol-risk]http://www.webmd.com/heart-disease/guide/heart-disease-lower-cholesterol-risk[/url]）
What Numbers Should I Look For?
Here's how to interpret your cholesterol numbers:

Total Cholesterol	Category
Less than 200	Desirable
200 - 239	Borderline High
240 and above	High

[url=http://www.webmd.com/cholesterol-management/video/bernstein-ldl-cholesterol-level-strive]LDL Cholesterol[/url]	LDL-Cholesterol Category
Less than 100	Optimal
100 - 129	Near optimal/above optimal
130 - 159	Borderline high
160 - 189	High
190 and above	Very high

HDL*	HDL-Cholesterol Category
60 or more	Desirable - helps to lower risk of heart disease
Less than 40	Major risk factor -- increases the risk for developing heart disease

并不算胖的我，其实非常高的是HDL，中文名字是高密度胆固醇，其实是越高越好，高了反而降低心血管疾病的概率。但是我的primary care doctor却没有跟我这么说，反而是警告我，年纪轻轻已经这样，必须立刻注意。害得我白担心了很久，可见医生不可全信的！

还有一个甘油三酯，也是需要注意的：

Triglycerides	HDL-Cholesterol Category
Less than 150	Normal (desirable) heart disease
150-199	Borderline high
200-499 >500	High Very high

另外一个官网，国家的心肺功能协会：[url=http://www.nhlbi.nih.gov/health/resources/heart/heart-cholesterol-hbc-what-html]http://www.nhlbi.nih.gov/health/resources/heart/heart-cholesterol-hbc-what-html[/url]
Everyone age 20 and older should have their cholesterol measured at least once every 5 years. It is best to have a blood test called a "lipoprotein profile" to find out your cholesterol numbers. This blood test is done after a 9- to 12-hour fast and gives information about your:

Total cholesterol
LDL (bad) cholesterol--the main source of cholesterol buildup and blockage in the arteries
HDL (good) cholesterol--helps keep cholesterol from building up in the arteries
Triglycerides--another form of fat in your blood
If it is not possible to get a lipoprotein profile done, knowing your total cholesterol and HDL cholesterol can give you a general idea about your cholesterol levels. If your total cholesterol is 200 mg/dL* or more or if your HDL is less than 40 mg/dL, you will need to have a lipoprotein profile done. See how your cholesterol numbers compare to the tables below.

HDL (good) cholesterol protects against heart disease, so for HDL, higher numbers are better. A level less than 40 mg/dL is low and is considered a major risk factor because it increases your risk for developing heart disease. HDL levels of 60 mg/dL or more help to lower your risk for heart disease.
Triglycerides can also raise heart disease risk. Levels that are borderline high (150-199 mg/dL) or high (200 mg/dL or more) may need treatment in some people.

具体的，我们可以做什么？

What Affects [url=http://www.webmd.com/cholesterol-management/video/ldl-hdl-cholesterol-levels]Cholesterol Levels[/url]?
A variety of factors can affect your cholesterol levels. They include:

Diet. [url=http://www.webmd.com/cholesterol-management/features/truth-about-saturated-fats]Saturated fat[/url], trans fat, and cholesterol in the food you eat increase cholesterol levels. Reducing the amount of [url=http://www.webmd.com/food-recipes/rm-quiz-fats-and-oils]saturated fat[/url]and [url=http://www.webmd.com/diet/guide/understanding-trans-fats]trans fats[/url] in your diet helps lower your blood cholesterol level. Increasing the amount of fiber and plant-derived sterols can also help lower LDL cholesterol.
[url=http://www.webmd.com/diet/healthy-weight-what-is-a-healthy-weight]Weight[/url]. In addition to being a risk factor for heart disease, being [url=http://www.webmd.com/diet/am-i-obese]overweight[/url] can also increase your cholesterol. [url=http://www.webmd.com/diet/default.htm]Losing weight[/url] can help lower your LDL, total cholesterol levels, and [url=http://www.webmd.com/cholesterol-management/assessment-triglycerides/default.htm]triglyceride levels[/url], as well as raise your HDL.
[url=http://www.webmd.com/fitness-exercise/default.htm]Exercise[/url]. Regular [url=http://www.webmd.com/fitness-exercise/ss/slideshow-7-most-effective-exercises]exercise[/url] can lower LDL cholesterol and raise [url=http://www.webmd.com/cholesterol-management/hdl-cholesterol-the-good-cholesterol]HDL cholesterol[/url]. You should try to be physically active for 30 minutes every day.
Age and Gender. As we get older, cholesterol levels rise. Before [url=http://www.webmd.com/menopause/default.htm]menopause[/url], women tend to have lower total cholesterol levels than men of the same age. After [url=http://www.webmd.com/menopause/ss/slideshow-menopause-overview]menopause[/url], however, women's LDL levels tend to rise.
Heredity. Your genes partly determine how much cholesterol your body makes. High blood cholesterol can run in families.
Medical conditions. Occasionally, a medical condition may cause an elevation of cholesterol levels in the blood. These include [url=http://www.webmd.com/women/hypothyroidism-underactive-thyroid-symptoms-causes-treatments]hypothyroidism[/url] (an underactive [url=http://www.webmd.com/women/picture-of-the-thyroid]thyroid[/url] gland), [url=http://www.webmd.com/hepatitis/ss/slideshow-surprising-liver-damage]liver[/url] disease and[url=http://www.webmd.com/a-to-z-guides/understanding-kidney-disease-basic-information]kidney disease[/url].
[url=http://www.webmd.com/drugs/index-drugs.aspx]Medications[/url]. Some medicines, like [url=http://www.webmd.com/a-to-z-guides/ss/slideshow-steroids-101]steroids[/url] and progestins, may increase "bad" cholesterol and decrease the "good" cholesterol.


这些都是很传统的理论了，基本上应该说是过去十年的常识，可惜我不知道，我的医生居然知道的也不准确。简单分享一下。
这里讲一个最最重要的概念：When cholesterol is released from dead cells it is picked up for disposal by high-density lipoproteins (HDL), the “good cholesterol.” When doctors measure cholesterol levels, they first look at total cholesterol as a quick way to assess a person’s risk. For a more exact guide, they divide the total level by the HDL level. Heart attack risk is minimized by having a lower total cholesterol and a higher proportion of HDL cholesterol. The ratio of total cholesterol to HDL should be less than 4 to 1. Unfortunately, the average American male’s ratio is much higher than that, at 5 to 1. Vegetarians, on the other hand, average only about 2.8 to 1.3. Smoking and obesity lower HDL; however, vigorous exercise and foods rich in vitamin C may increase it.8


就是说，虽然教科书说得是总胆固醇含量，但是我们需要真正关注的，只是LDL，只要这个低于100，HDL其实越高越好。可悲的是，大多数人，包括有些医生，都忽略了其中的重要差别。

重要的事情再来两遍：
When cholesterol is released from dead cells it is picked up for disposal by high-density lipoproteins (HDL), the “good cholesterol.
When cholesterol is released from dead cells it is picked up for disposal by high-density lipoproteins (HDL), the “good cholesterol.
HDL是我们的好朋友！好朋友！好朋友！




下面说说大约从前年开始的一些关于胆固醇的争论：
首先，胆固醇为什么对健康不好？低密度胆固醇（LDL）容易引起动脉硬化 （Atherosclerosis ）。
What Is Atherosclerosis?
Atherosclerosis is not caused by old age. Examination of American casualties during the Korean and Vietnam wars showed significant atherosclerosis by age 18 or 20.2 Their Asian counterparts, raised on diets consisting mainly of rice and vegetables, had much healthier arteries. The elderly are more likely to have heart conditions not because of genetics, but because they may have indulged in unhealthful habits, like smoking and poor diet, for longer periods of time. Your doctor can tell you if you are one of only about 5 percent of the population with a genetic tendency toward [url=http://pcrm.org/health/heart/fact-sheets]heart disease[/url]. Many studies show the connection between lifestyle choices and heart health. An article published by Caldwell Esselstyn Jr., M.D., in the American Journal of Cardiology explains that stenting and bypass surgeries may only be a solution for a minority of patients, while a transition to a plant-based diet free of cholesterol proves to be a more effective treatment.3


In 1948, William Castelli, M.D., began to monitor the population of Framingham, Mass., to study what factors influenced the rate of heart disease.4 Castelli’s study showed that a cholesterol level exists, below where coronary artery disease does not occur. Framingham data show that only patients with cholesterol levels of less than 150 milligrams per deciliter (mg/dl) achieve the lowest coronary artery disease risk. In the first 50 years of the Framingham Heart Study, only five subjects with cholesterol levels of less than 150 mg/dl developed [url=http://www.pcrm.org/health/heart/breaking-medical-news]coronary artery disease[/url]. Rural residents in Asia, Africa, and Latin America typically have total cholesterol levels of about 125-140 mg/dl.

这个Mayo clinic的研究，我先给大家总结一下，你再慢慢看。
1. 推荐减少胆固醇的研究是1977年的老皇历了
2. 食物中的胆固醇过量，不是一个问题，但是您还是需要注意饱和脂肪，盐和糖。
3. 食用过多的饱和脂肪，会让你的肝脏产生大量的胆固醇，这是一个问题
4. HDL是个好东西，again!


http://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/expert-blog/new-cholesterol-guidelines/bgp-20127383
Cholesterol — the controversy continues
The headlines are saying cholesterol may not be a "nutrient of concern." To understand what that means, you have to look beyond the headlines.
What the 2015 Dietary Guidelines for Americans Committee meeting minutes actually say is that "cholesterol is not a nutrient of concern for overconsumption." Separating it from fat, sodium and added sugar — the nutrients that Americans do consume in amounts that are worrying.
What's changed? Some experts are saying that dietary cholesterol was mistakenly connected to heart disease. There was a rise in coronary artery disease leading up to the 1977 recommendation to reduce cholesterol intake. However, a closer look at the science reveals that there is more evidence to suggest that dietary cholesterol may not play a significant role for most healthy Americans and their risk of heart disease.
In addition, it appears that Americans are eating less cholesterol, approximately 80-100 mg less a day compared with the 1970s. This data comes from the National Health and Nutrition Examination Survey (NHANES), a series of studies that began in the 1960s to assess health and nutritional status in the U.S.
That perhaps provides more support for the argument that dietary cholesterol intake is not connected to blood (serum) cholesterol levels. But the reality is that heart disease is still a major health concern. Many people take medications to reduce their serum cholesterol levels.
Let's review what we know about cholesterol:

Cholesterol is an essential part of every cell in the body
Dietary cholesterol is the cholesterol we eat. It's found in foods of animal origin, such as meat, eggs, fish and dairy products.
Cholesterol is also produced by the body (in the liver). It's thought that a diet high in saturated fat signals the liver to make more cholesterol.
High serum levels of low-density lipoprotein (LDL) and very-low-density lipoprotein (VLDL) cholesterol are associated with increased risk of cardiovascular disease, whereas a high level of high-density lipoprotein (HDL) cholesterol is thought to be protective.
What does this mean for you? You should talk with your health care provider about your heart health. This conversation should include your serum cholesterol levels, your personal and family history of cardiovascular disease, and your weight and lifestyle habits, including your diet.
Your diet does matter. You can enjoy eggs, lean meats, shellfish and dairy products. However, it's still important to balance these foods with high-fiber, lower-calories foods like fruits and vegetables, which also help lower serum cholesterol levels. Whole grains and healthy fats, like nuts and seeds, should find their way to your plate as well.

希望大家家里的老人都健康！