Protein for health and weight loss
By Elaine Magee, MPH, RD
WebMD Weight Loss Clinic - Expert Column
It seems that everywhere you turn you are bombarded with carb-bashing rhetoric. Stores and food companies are even selling only low-carb products. The anti-carb craze has everything to do with the recent resurgence in high-protein fad diets. So what should we know about protein if we are concerned with losing or maintaining weight? How much do we need? What happens if we don't get enough or if we get too much? And what does all of this have to do with successful weight loss?
How Much Protein Do You Need?
When you don't get enough protein in your diet, all your organs are affected -- from the kidneys to the heart. The immune system also suffers greatly, so you are more likely to get sick and get infections.
So how much protein do you really need? Well, it depends on your sex, age, and weight:
|Protein Recommendations for Men|
|19-30 years old||0.8 gram per kg per day (about 56 grams per day)|
|31-50 years old||0.8 gram per kg per day (about 56 grams per day)|
|51-70 years old||0.8 gram per kg per day (about 56 grams per day)|
|Protein Recommendations for Women|
|19-30 years old||0.8 gram per kg per day (about 46 grams per day)|
|31-50 years old||0.8 gram per kg per day (about 46 grams per day)|
|51-70 years old||0.8 gram per kg per day (about 46 grams per day)|
SOURCE: the Dietary Reference Intakes report by the Institute of Medicine, 2002
NOTE: The popular low-carb, high-protein diets can contain about 145 grams of protein or more.
Dangers of Eating Too Much Protein
* High protein can mean high fat
If you are getting a lot of your protein (as part of a high-protein diet) from fatty animal foods, you are not only eating a high-protein diet; you are most likely eating a high-fat diet, too. And higher fat means more calories and an increased risk for weight gain. According to the Institute of Medicine's Dietary Reference Intakes report, saturated fat, trans fats, and cholesterol in food increases the "bad" LDL cholesterol and total cholesterol levels; therefore, this type of diet increases your heart disease risk. Certainly eating less saturated fat is universally accepted sage dietary advice. The quickest way to minimize your intake of saturated fat is to:
- eat less animal fat (meat fat and butterfat) and certain oils (coconut, palm, and palm kernel oils)
- choose lean cuts of meat
- trim away any visible fat on meats
- eat smaller portions of meat
NOTE: The Atkins diet contains about 53% of total calories from fat and 20% from saturated fat alone.
*Higher protein means lower fiber
Fiber comes to us courtesy of plant foods, and plant foods are our main source of carbohydrates. So if you eat a very high-protein diet, chances are pretty good you are eating a lower-carb, lower-fiber diet, too. In its Dietary Reference Intakes report, the Institute of Medicine noted several adverse health effects associated with eating a lower-fiber diet:
- increased risk of cancer
- increased risk of obesity
- increased risk of heart disease
- increased risk of type 2 diabetes
Likewise, if you're eating a low-carb diet, you are also likely to be lacking important phytochemicals (that come from plant foods) and certain vitamins and minerals.
* Higher protein could mean low bone density
When your body breaks down the protein you eat, several types of acids are triggered. Your body neutralizes these acids with citrate and carbonate from the bone. Simply put, this means calcium loss increases as protein consumption increases. The Institute of Medicine's Dietary Reference Intakes suggests, although it is still considered to be controversial, that as you double the amount of protein in your diet, the amount of calcium lost through your urine increases by 50%. This not only increases the loss of bone calcium but also increases the risk of kidney stones by as much as 250%.
It doesn't matter whether you get your protein from animals or plants -- they have the same effect on calcium loss through urine, says Linda Massey, PhD, a researcher and calcium and protein expert with Washington State University in Spokane. But some plants, like grains and legumes (beans), have a little something going for them: They contain high amounts of potassium, and potassium helps decrease urinary calcium. Milk products can help lessen this effect, too. The high amounts of calcium in milk and milk products help compensate for the calcium that will be lost in the urine due to the digestion/absorption of the protein in milk.
Many health organizations, including the American Heart Association and the American Dietetic Association, caution against low-carb diets because of concerns that the diets lead to abnormal metabolic functioning in the body that can cause serious medical problems, particularly among people with heart disease and with heart disease risk factors, such as type 2 diabetes, high cholesterol, or high blood pressure.
What happens to bone when people eat very high-protein diets for a long time? This hasn't been studied, but it's likely to be associated with increased bone loss. But the answer isn't a very low-protein diet since the recommended amount of protein is needed to keep bones strong as well.
* Higher meat protein could mean higher colon cancer risk
Reviews of the literature on colon cancer suggest that though a high-protein diet, per se, doesn't l increase your colon cancer risk, a diet high in meat may be the ticket that does increase the risk. Following along these lines, a recent Japanese study concluded that as dietary animal protein and fats and oils increase, incidence of colorectal cancer increases as well, but colorectal cancer incidence decreases as dietary plant protein increases (along with amounts of carbohydrates and cereals).
* Don't regular exercisers need more?
The answer is "probably not." The Institute of Medicine's Dietary Reference Intakes report recently released concluded: "In view of the lack of compelling evidence to the contrary, no additional dietary protein is suggested for healthy adults undertaking resistance or enduring exercise."
But What About All That Weight Loss?
Is it the protein or the calorie cuts that lead to weight loss? The high-protein diet programs and gurus will most certainly tell you it's the protein. But two recent studies say it's the restriction of calories rather than the protein that is the most important determinant of weight loss. In an Australian study, 36 obese adults, mostly women, were assigned to a 12-week energy-restricted diet that was either moderately high in protein (27% calories from protein) or lower in protein (16% calories from protein). The weight loss was similar in both diets. Researchers at Stanford University analyzed all research published on low-carb or ketogenic diets over the past 37 years. They concluded that the successful weight loss from low-carb diets was "principally associated with decreased caloric intake and increased diet duration but NOT with reduced carbohydrate content."
One of the most popular features of the low-carb, high-protein diet is the quick weight loss. Don't be fooled here. You cannot physiologically lose more than 2 pounds of body fat a week. So what are all the pounds that people lose in the first few days of starting the diet? Water. To make up for the lack of dietary carbohydrates, the body uses its own carbohydrate stores in the liver and muscle tissue (called glycogen), which in the process also mobilizes water. Many of the early and rapid pounds lost are due to -- that's right -- excessive urination!
Can a Certain Type of Protein Lead to Weight Loss?
Apparently, it doesn't matter whether your protein primarily comes from lean beef or chicken. As long as you reduce your total calories by 500 a day and participate in an exercise program (in this study it was a walking fitness program), you will most likely enjoy some weight loss and improved cholesterol levels. This evidence comes from a recent study with overweight, sedentary, nonsmoking women conducted by the Rippe Lifestyle Institute in Shrewsbury, Mass.
A recent six-month trial demonstrated that replacing "some" dietary carbohydrate with protein improved weight loss -- but this was when the diet was still, overall, a reduced-fat diet.
Higher protein is in vogue these days because of the publicized success of quick weight loss. But studies also show that there might be long-term health consequences of such a diet, and slow but sure weight loss can take place with a healthy high-fiber, moderate-protein, and moderate-fat plan -- a way of eating that we can live with for the rest of our lives. Yes, we do need protein, but at levels of 15%, not 50%, of calories from fat. So when it comes to protein, it looks like moderation is the healthiest choice of all.
Published June 6, 2003
SOURCES: Institute of Medicine Dietary Reference Intakes report, 2002. International Journal of Obesity, (volume 27) 2003. The Journal of the American Medical Association, April 9, 2003. Nutrition, May 2003. Journal of Nutrition, March 2003. Asian Pacific Journal of Cancer Prevention, 2002. Journal of the American Dietetic Association, November 2002.