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Protein S deficiency

Protein S deficiency is a disorder associated with increased risk of thrombosis. more...

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Decreased levels or impaired function of protein S, a vitamin K-dependant physiological anticoagulant, leads to decreased degradation of factor Va and factor VIIIa and an increased propensity to venous thrombosis.


There are three types of hereditary protein S deficiency:

  • Type I - decreased protein S activity: low levels of free protein S, normal levels of bound protein S
  • Type IIa - decreased protein S activity: low levels of free protein S, low levels of bound protein S
  • Type IIb - decreased protein S activity: normal levels of free protein S, normal levels of bound protein S

Decreased activity is present in an acquired form in vitamin K deficiency or treatment with warfarin. This generally also impairs the coagulation system itself (factors II, VII, IX and X), and therefore predisposes to bleeding rather than thrombosis. Protein S levels are also lower in pregnancy and liver disease.

Protein S deficiency is the underlying cause of a small proportion of cases of disseminated intravascular coagulation (DIC), deep venous thrombosis (DVT) and pulmonary embolism (PE).

Hereditary PSD is an autosomal dominant condition, resulting in a 50 precent chance of passing the disease to offspring. Less than half of those diagnosed with PSD will experience thrombosis, and those who do usually are affected only from the age of the late teens onwards. A positive blood test can lead to the loss of health insurance benefits and/or employment, and the social downsides need to be balanced against the actual medical benefit of accurate diagnosis. Screening of young children is usually deferred because early testing is often inaccurate, and it is better to wait until they are old enough to decide for themselves whether they want to be tested.


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Shattering the myth of protein
From Vegetarian Times, 3/1/95 by Debra Blake Weisenthal

Ever since Francis Moore Lappe wrote her 1971 manifesto Diet for a Small Planet (Ballantine Books), in which she warned that vegetarians need to eat plant-based foods in certain combinations, vegetarians have worried needlessly about getting "complete" protein. But Lappe' doesn't deserve all the blame for our apprehension, and vegetarians certainly aren't the only group concerned about protein.

Since its discovery in the late 19th century, protein has had a stronghold on American culture and cuisine. Parents worry that their children may not be getting enough, as do many teenage boys and body-builders who are interested in "beefing up." Getting enough protein is still the main worry new vegetarians have. It's even a concern of longtime, relatively knowledgeable vegetarians like me.

Twenty years ago, I diligently combined beans with grains to make sure I was getting enough protein. When study after study finally convinced me that obsessing over protein was unwarranted, I stopped being such a kitchen chemist. Still, from time to time I had misgivings. I was healthy, but sometimes I felt I wasn't as energetic as I ought to be. Other vegetarians I knew also feared they weren't getting enough protein. Some even went back to eating meat on occasion to boost their protein intake and up their energy levels.

But protein wasn't what any of us needed. "Loss of energy isn't a symptom of protein deficiency," says Anne Shaw, Ph.D., a nutritionist with the U.S. Department of Agriculture's Agricultural Research Service. In fact, protein deficiency is so rare in this country that Shaw says she'd have to look up its symptoms because it's been so long since she's had to think about them. She reminds me that all of the recent research on the topic of protein indicates that if you're getting enough calories - just about no matter what you're eating - you're also getting sufficient protein. It's not just a claim made by defensive vegetarians; it's a subject of broad scientific agreement.

Still, there's a lot of confusion about protein - or to be more precise, the tiny amino acids that make up the long strands of protein - especially as it pertains to vegetarians. In fact, Lappe was right about protein combining to a certain extent. All plant-based foods are low in at least one of the nine amino acids our bodies need to get from foods. But the only foods that are truly protein-deficient are fruits, fats and sugars. And you need to obtain all nine amino acids over the course of a day or two, not within an hour of each other.

Even if you ate nothing but rice, which is low in the amino acid lysine, you'd still get enough of all the essential amino acids; if you ate nothing but beans, which are low in methionine, you wouldn't be courting a protein deficiency. But since you do not (and should not) eat just one food all day, every day, the foods that are relatively low in an amino acid are naturally complemented by those that are abundant in that amino acid. It's simply not necessary to think about what combines with what, especially if you naturally eat a variety of foods within a 24- to 48-hour time span.

Moreover, in the mid- 1980s, researchers discovered that what had been considered the ideal balance of essential amino adds was not correct. Until then, all proteins were assessed according to a system called the protein efficiency ratio (PER). On the PER scale, the egg was considered the "perfect" protein source, an assumption based on tests done with rats. Beef and milk also rated very high, while vegetables were low, in part because they are low in the sulfur-containing amino acids that animal foods tend to have, and which rats need more of than do humans. Rats, which differ from humans in many ways, also have different nutritional needs. The egg's amino acid pattern happens to suit them perfectly.

Protein research conducted on people resulted in a change in the way proteins are rated. The current standard for humans is known as the protein digestibility corrected amino acid score (PDCAAS). The system still involve a food's amino acid pattern and its digestibility, but it also throws in the amino acid requirements of human beings.

Using the PDCAAS scale, soy protein receives a top rating, along with eggs, dairy products and meats. But since no one-vegetarian or non-vegetarian needs to optimize the quality of their protein in order to get enough of it, it's unnecessary to consider such ratings in deciding what foods to eat.

The fact is, protein deficiency simply is not a concern for anyone in the developed world. "We never talk about protein anymore, because it's absolutely not an issue, even among children," says Marion Nestle, Ph.D., chair of the Department of Nutrition, Food and Hotel Management at New York University. "If anything, we talk about the dangers of high-protein diets. Getting enough is simply a matter of getting enough calories."


Try to answer this question: What does protein do for you? Did you say it gives you energy? Sorry; carbohydrates do that. Builds muscles? Nope, that's what exercise is for. Protein does have a variety of very important functions, just not the ones most people associate with it. Protein helps you think and see, makes up and repairs muscle and bone tissue, regulates hormones and enzymes, helps fight infections and heal wounds, affects the way you digest foods and affects your genes and chromosomes.

Fortunately, our bodies manufacture the bulk of the amino acids we need; of the 20 that have been identified as important to the human system, only nine are not manufactured by the body. These nine are called "essential amino acids." If we do not take in enough of them on a regular basis, the bodily systems mentioned above, plus many others, start to deteriorate. on the other hand, more is not better. We don't need nearly the amount of protein that most Americans - vegetarians and non-vegetarians - eat. We only need enough.

How much is enough? "For once I'd love to see my patients follow their government's recommendation," says Michael Klaper, M.D., a vegan physician who often finds himself at odds with conventional nutritional wisdom. He's not alone. Just about everyone with a hand in protein research or nutritional counseling agrees with the U.S. recommended dietary allowance (RDA) for protein.

The RDAs are actually rather low compared to what we get, and they change very little according to a person's age, with the exception of a significant increase just before a boy's teen years. The RDA for children of either gender between ages 11 and 14 is about 45 grams (g.) of protein per day; for girls between 15 and 18 it is 44 g., and for boys the same age it is 59 g. Women over 18 should get about 50 g. daily, and men about 63 g. Keep in mind that these figures deliberately exaggerate the amount of protein most individuals need. They include a built-in safety factor to account for individuals who, for whatever reason, require more protein than others. Regard the RDAs as the recommendations they are, not as minimum requirements.

Because protein is found in all foods except fruits, fats and sugars, it's practically impossible to not meet or exceed these numbers. To see how easy it is, consider the amount of protein in some common foods (see "Packing Protein," above right). A couple of things are obvious from looking at the chart: If you're a vegetarian with a varied grain, bean and vegetable-based diet and a decent appetite, you can easily meet the RDA for protein (remember, it's more than you actually need). If you eat dairy foods or eggs, it may be hard to not substantially exceed the RDA. These observations are borne out by studies done on American protein intake. According to the U.S. Department of Health and Human Services, the average protein consumption of American boys between the ages of 15 and 18 is a whopping 122 g., more than twice the RDA. Men through the age of 60 average almost 100 g. daily. Women tend to keep their protein consumption lower (probably because they eat fewer calories in general). Even so, they average about 65 g. daily through the age of 50, rather than the recommended 50 g.

Too much protein doesn't do more of what the "right" amount of protein does; it causes problems. The least serious effect of excessive protein consumption is waste. Your body either excretes it or converts it to fat. But recent research suggests a less benign side effect of excessive protein consumption: Too much protein in the blood may contribute to some of the most serious and chronic health conditions plaguing developed countries.


Various studies have established a connection between excessive consumption of protein - animal-derived protein in particular - and calcium loss and kidney disease. World research clearly shows that populations that eat the most protein suffer more from osteoporosis, a disease in which calcium is leached from the bones, leaving them weakened. This is true even among populations that consume plenty of calcium. (When protein intake is very high, about 142 g. per day, it becomes impossible to maintain the body's calcium balance.) Americans are a high-protein intake/high calcium-loss population. In countries where protein intake is low and where most of the protein consumed is plant-derived, osteoporosis is rare. Soy protein, for example, when eaten in the same quantities as animal protein, causes only half the calcium loss.

Even though there's a connection between protein intake and calcium loss, the relationship isn't necessarily one of cause and effect. Other factors may be involved. Vernon Young, Ph.D., a protein specialist at the Massachusetts Institute of Technology in Cambridge, Mass., notes that hormone levels, exercise and smoking are all implicated in calcium loss, and that these factors may also distinguish some of the populations in question. And even though patients with kidney disease tend to benefit from a low-protein diet, no studies have been conclusive enough definitively to blame too much protein as the cause of most kidney disease, though some studies have directly related high-protein intake with kidney stone formation.

There is a direct relationship between high protein consumption and increased blood cholesterol levels, but again, cause and effect is hard to establish. High-protein diets are typically meat based. Klaper says that animal proteins generally are accompanied by "hitchhikers" such as cholesterol, collagen, hemoglobin, antibiotics and certain essential fatty acids. "These may create various inflammations and set off immune responses that may be major contributors to chronic disease," he says. On average, Americans take in two-thirds of their protein from meat, fish, dairy, poultry and eggs; the other third comes from plants.

Even so, says Mark Messina, Ph.D, a former researcher at the National Cancer Institute's Diet and Cancer branch in Rockville, Md., "It is very hard to make the case that eating animal protein causes cancer or other chronic U.S. diseases." As a vegan, Messina admits this reluctantly. "I did a lot of research and [expected] to find something related to animal proteins and disease, but I didn't." What about vegetable protein? Could an excessive consumption of vegetable protein cause the same problems? That's really a moot point because vegetarians would be hard pressed to achieve the kind of protein surplus that meat eaters do. A vegetarian who eats the same number of calories as a non-vegetarian automatically gets less protein because vegetarian foods are less protein-dense.

Even if you were to go through a phase in which meat analogs (such as gluten-based hot dogs and burgers) and other high-protein vegetarian foods (such as tofu and beans) made up a substantial part of your diet, you'd probably be fine because plant proteins don't have the same effect on the body's systems as animal-based proteins. For example, they don't seem to cause calcium loss in the way excessive animal protein does. Messina explains that sulfur - found in abundance in animal proteins - indirectly keeps the kidneys from reabsorbing calcium into the blood. Instead, the calcium is filtered into the urine and excreted. Because plant proteins are low in sulfur-containing amino acids, they don't cause this calcium loss. And, of course, plant proteins don't keep company with the fat and cholesterol that accompany animal proteins.


Despite the evidence that too much protein is bad for you and that it's almost impossible to get too little, the protein myth persists. Many people diagnose themselves as having protein deficiencies. These people may be lacking any of a number of things, but they aren't lacking protein. "People are afraid of vegetarian diets, even when they themselves choose to be vegetarian, " says Virginia Messina, M.P.H., R.D. "When they start feeling tired, they blame it on protein. But people can be tired for a lot of reasons."

Klaper agrees. "The vast majority of people who switch to vegetarianism not only do well, but experience dramatic improvements in their health," he says. "The protein issue is a non-issue, just as it is for most people in the world whose diets contain much less protein than ours." Klaper doesn't deny that some people feel worse when they stop eating meat, complaining, among other things, of a lack of energy. This is not due to a protein deficiency, he says. "It's probably because their systems have adjusted to their old diets, which were typically high in fat and low in fiber and carbohydrates. There may be a dozen reasons why they don't feel well, including the fact that the mucus lining in their intestines hasn't yet adjusted to the new diet. If it hasn't, the magnesium or riboflavin from plant foods may have a hard time getting through it and into the blood stream; then they might feel a bit low."

These people typically try eating meat again to see if it will solve their problems. Sometimes it does. Then, says Klaper, "they'll think it's because of the protein. But it isn't; it's because they're getting the nutrient they were missing. I'm not against people taking their time in switching to vegetarian diets," he says. "Sudden transitions can be problematic. The thing to remember is that the body will absolutely adapt within weeks or months. Who cares how much time you take to do it?"

It's not only vegetarian proponents who make these claims. Remember, the USDA's Anne Shaw couldn't even recall the symptoms of protein deficiency. Those who know the symptoms well - extreme abdominal bloating, pain, nausea and an overall breakdown in hormonal and other physiological systems - see these symptoms among people who are severely malnourished in places like Ethiopia and Rwanda, not among well-fed American vegetarians.


The likely truth is that no matter how much the researchers write and no matter how extensively nutritionists counsel that protein isn't an issue, people will continue to worry. The people who will likely worry the most are pregnant women and the parents of teenagers.

Nestle's blanket statement that protein is "absolutely not an issue" applies even in these cases. There's no question that pregnant women need more protein, but they don't need to consume protein for two. Rather, the RDA for pregnant and nursing women is about 15 g. more than for other women. Therefore, a woman who meets the RDA for protein before becoming pregnant needs to add only one glass of milk or soymilk (8 g.) to her diet, plus either a serving of peanut butter (8 g.), a cup of yogurt (8 g.), a four-ounce serving of tofu (10 g.) or a serving of plain pasta (7 g.). But because most women already exceed the RDA, even most vegetarian women, it's more than likely she may not need to add anything.

As for teenagers, they need more of everything - calories and all nutrients - and they're typically not the best meal planners. Even so, says Virginia Messina, "I know of no evidence that there are any special protein issues among teens, if they're meeting their calorie needs." (This does mean that parents of weight-conscious teenage girls may need to be somewhat more vigilant than they might have been when their daughters were younger, but this caution applies to all nutrients, not just protein, and to all teenage girls, not just vegetarians.)

Most of the time, Virginia Messina advises parents to relax. The key to a teenager's dietary health, she says, is trusting their appetite; during growth spurts it's likely that they will automatically eat more thereby increasing their calorie (and protein) intake. Messina also notes that refined grains have just as much protein as whole grains. Because refined grains are less bulky, eating up to three servings of them a day, she suggests, can make getting enough calories easier for teens. Stock the refrigerator with healthful snacks and serve plenty of whole grains, beans and vegetables at meal times. Teenagers have a remarkable ability to survive their diets and go on to better eating habits in later years.

And when you feel tempted to worry about protein - for yourself, a teenager, a pregnant friend or anyone else - remember this: The protein issue is simply a calorie issue. As long as you're eating enough calories to maintain a healthy weight and are taking in a variety of foods, and don't suffer from a rare inborn disease that affects your protein metabolism (such as albinism and phenylketonuria) you won't have a problem.

Even professional bodybuilders, says Mark Messina, probably only need an extra 7 g. a day to account for the half-pound of new muscle they add weekly. Those of us who sometimes feel less energetic than we'd like may need more sleep or less stress. But we don't need more protein.

COPYRIGHT 1995 Vegetarian Times, Inc. All rights reserved.
COPYRIGHT 2000 Gale Group

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