Carmen Castanada Sceppa, M.D, Ph.D., is a scientist working at the Jean Mayer USDA/Human Nutrition Research Center on Aging at Tufts University School of Medicine. Carmen's research emphasizes protein nutrition and physiological function of healthy older individuals and those with chronic illnesses.
How does the average intake in the United States measure up against the Recommended Dietary Allowance (RDA) for protein?
The typical American diet provides plenty of protein — more than the RDA in most instances. The RDA represents the minimum amount of protein needed to fulfill protein needs in 97.5% of the population. This value is equal to 0.8 g of protein per kg body weight per day. The average mixed American diet provides from one to two times the RDA for protein. You might think, then, based on this that protein deficiency is unlikely in the U.S. . However, the RDA for protein has been derived from research studies performed on healthy individuals. Growing children, pregnant and lactating women, the elderly, and anyone undergoing severe stress (trauma, hospitalization, surgery), disease or disability need more protein.
What if you exercise?
We have seen in our lab that individuals undergoing endurance training increase their protein needs to about 1 to 1.2 g per kg per day, well above the RDA. In contrast, for subjects performing resistance exercises or weight lifting, the RDA for protein seems to be adequate. In resistance training, you are building up muscle and protein is used more efficiently.
Muscles are built from protein. Unlike fat cells for fat and muscle or liver for glucose, there is no place in the body to store protein. We need to consume enough protein to allow our muscles to be healthy and perform work.
Carmen, we hear a lot in the media about balancing different types of proteins. What are the best sources of protein and what exactly is meant by complementary proteins?
Animal and plant or vegetable foods are the two major protein sources. Animal protein foods include meat, poultry, fish, dairy products and eggs and are said to be of high biological value. That is, they contain all nine essential amino acids that can not be synthesized in the body (histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine).
Plant protein sources, although good for certain essential amino acids, do not always offer all nine essential amino acids in a single given food. For example, legumes lack methionine, while grains lack lysine. What is needed are complementary proteins, various protein food sources that, eaten together, enable a person to meet the standards of a high biologic protein diet.
Do vegetarians and people on macrobiotic diets get into problems with protein malnutrition?
There are two types of vegetarians. Lacto-ovo vegetarians and strict vegetarians or "vegans". Lacto vegetarians eat animal protein of high biological value, eggs and dairy products. Vegans, however, eat a more limited diet and often must take amino acids supplements to make up for their not-so-high biological protein diet. If vegans eat a variety of plant foods — cereals, nuts, seeds, grains and legumes — they'll be fine. They don't have to eat all these food items at a given meal. However, they should consume most or all of them during the course of the day to insure a well balanced protein diet of high biological value.
NOTE: We regret that we cannot answer personal medical questions.
(46) Comments have been made
this is a good article about protien
Posted Mon, Feb. 27, 2012 at 10:21 am EST
We do answer selected, general questions through our "Ask a Question" function. See above left to submit one. We don't, nor should anyone, practice medicine on the Web.
Posted Thu, Sep. 22, 2011 at 1:55 pm EDT
Looks like nobody is reading the note: "We regret that we cannot answer personal medical questions." This is a place for comments not questions. They will not be answered!
Posted Thu, Sep. 22, 2011 at 12:43 pm EDT
Clarissa, you need to check with a doctor or registered dietician. Protein is especially important for you. See our article on Nutrition for Athletes.
Posted Tue, May. 3, 2011 at 1:28 am EDT
How much protein does a 13, turning 14 in June, female athlete need per day? Weighs 120 lbs 5'3 Details: Vegetarian What food diets do you recomend?
Posted Mon, May. 2, 2011 at 8:38 pm EDT
How do the amounts of protein you need differ throughout the different life stages?
Posted Thu, Mar. 24, 2011 at 8:16 am EDT
Written by an ignorant meat supporter who has no clue how animals are killed, what issues that can lead to and our body doesn't only exist on PROTEINS.
Posted Wed, Mar. 16, 2011 at 11:31 am EDT
Consider this. The most we ever grow is from when we are
born to age six months. During that time we double our birth weight.
You would think that a little person who is doubling in size
would need more protein than anyone. But breast milk, the perfect
food for the baby with just the right amount of protein,
carbohydrates, fats, and enzymes is only about 5-8 percent protein
(the number varies depending on the source). So a child that
has maximum protein needs gets enough when less than
10 percent of his daily caloric intake is protein.
Posted Wed, Mar. 16, 2011 at 11:19 am EDT
yeah its nice research about protein biological value we must take care about it i am masters in animal nutrition from pakistan.
Posted Sat, Feb. 26, 2011 at 5:42 pm EST
I am taking a protein supplement that is called for in the "no diet" diet.
where u take a tsp. full @bedtime to
help break down fat . Is this safe?
Posted Thu, Feb. 3, 2011 at 3:31 pm EST
My question has not been answered: how is protein stored in the body?
Posted Fri, Jan. 14, 2011 at 2:46 pm EST
I am doing a class project and I was wondering if you could just give me the answers...My Nutrient is Incomplete protein,#1 Does the Canadian public get too much or too little of this nutrient? #2 How much do we need to consume daily? #3 What food can provide us with this nutrient? Give examples of quantities and nutritional value? #4 What does it do for our bodies? #5What happens if you get too much? #6 what happens if you get too little? #7 Where can people get more information about incomplete protein?
Yeah... its due soon :P
Posted Thu, Jan. 6, 2011 at 1:06 pm EST
If a person wieghs 110 pounds, wrestles, and gets 98 grams of protien a day would it be unhealthy?
Posted Thu, Dec. 2, 2010 at 12:23 am EST
Exactly how much protein should a healthy person consume, per day? 15 grams, 20 grams. Could you give a general amount? Thank you.
Posted Tue, Nov. 2, 2010 at 4:02 pm EDT
What happens to the body if it doesn't get enough protein? Please answer this question ASAP! Thanks!
Posted Sun, Oct. 31, 2010 at 9:59 am EDT
deepa kumar behera
What is the amount of protein you need for growth?
Posted Mon, Sep. 27, 2010 at 3:33 am EDT
How much incomplete protein do you need each day?
Posted Tue, Sep. 21, 2010 at 12:51 pm EDT
Michael Tulloch, PhD
Of course the RDA has been found to be woefully incorrect in many instances. The RDA for Vitamin D, for example, is only a fraction of the amount needed for good health. There is no reason to believe that the RDA for protein is any more accurate. This is especially true for seniors who digest and absorb protein less efficiently than younger people.
Posted Thu, Aug. 12, 2010 at 11:44 am EDT
What about someone with pku? They can't have but so much protein. Does that mean they will have problems later in life with their muscles and bones?
Posted Mon, Aug. 9, 2010 at 12:08 am EDT
What is the average daily intake of protien a 35 yr old woman who exercises daily should have?
Posted Sun, Jul. 25, 2010 at 11:37 am EDT
My height is 5.4 feet & weight is 59kilo. I have been going to the gym for the last four months to lose weight and to keep fit. I am vegetarian, but have been eating 4 eggs per day for the last 20 days, along with legumes, cereals, 5 almond milk, vegetable, fruits in a day. My right knee has been in constant pain for the last 30 days. What should I do to relieve the pain?
Posted Thu, Jul. 22, 2010 at 2:36 am EDT
It would be helpful for a lot of us if you would give this information in ounces. I just don't know my weight in kg, or just what 1.2 g protein means, in a practical sense.
Posted Thu, Jul. 15, 2010 at 7:14 pm EDT
What is the best way to lose weight? How many calories a day and How much protein?
Posted Wed, Jul. 7, 2010 at 4:56 pm EDT
How do I find out about too much protein in the liver that will not leave?
Posted Sat, Jul. 3, 2010 at 2:11 pm EDT
I weigh 265 lbs. How much protein should I have daily. What is the best source of protein?
Posted Wed, Jun. 30, 2010 at 8:20 pm EDT
I need a list of foods to buy to stay healthy and lose weight. I want to lose 25 pounds.
Posted Mon, Jun. 28, 2010 at 12:52 pm EDT
I have problem. I am 12 and I weigh 120 lbs. Is that bad? I am very athletic too. Can you give me help please?
Posted Fri, Jun. 18, 2010 at 3:25 pm EDT
Do you have any info regarding salvia hispanica and the effects on the human body? I am a vegetarian because of high cholesterol and have found it to be a great source of protein and nutrition - any bad side effects?
Posted Tue, Jun. 1, 2010 at 6:38 pm EDT
Protein is the most important thing to be increased in your muscle work, It is also important for bone building because it is structural helper.
Posted Wed, Apr. 21, 2010 at 9:51 am EDT
What is the amount needed for children?
Posted Sat, Apr. 17, 2010 at 11:34 am EDT
I suffer from depression for several years could you recommend a good nutritious diet to improve my concentration and give me more energy as I am always in pain and have lost my thirst for life.
Posted Fri, Apr. 16, 2010 at 9:03 pm EDT
What will happen if I had a lack of protein?
What will happen if I had a lack of Valcalseyoum?
please answer, it's emergency !
Posted Sun, Apr. 4, 2010 at 11:00 am EDT
thank so much for all the help
Posted Thu, Mar. 18, 2010 at 11:05 pm EDT
GOod work, Robert and all. GC
I love it. GC
Posted Sun, Mar. 7, 2010 at 5:15 pm EST
Some may feel squeamish about eating it, but rabbit has a fan base that grows as cooks discover how easy they are to raise — and how good the meat tastes.
Posted Sat, Mar. 6, 2010 at 5:11 am EST
Hello! I really liked your forum, especially this section. I just signed up and immediately decided to introduce myself, if I'm wrong section, ask the moderators to move the topic to the right place, hopefully it will take me well... My name is Mary, me 29 years, humourist and serious woman in one person. I apologize for my English
Posted Sat, Feb. 27, 2010 at 2:13 pm EST
Can You put answers for kids please.!!
Posted Tue, Feb. 23, 2010 at 8:07 am EST
in nutritional view point, which is better, animal protein or plant protein?
Posted Sat, Feb. 20, 2010 at 4:02 am EST
Posted Tue, Feb. 16, 2010 at 1:15 am EST
you said that we need to consume enough protein to allow our muscles to be healthy. However,how much porcentage of protein as a energy source muscles need comparing to triglycerids and glycogen as another type of energy that they also use?
Posted Fri, Feb. 12, 2010 at 11:08 am EST
Is 200g of canned tuna for lunch too much protein? I am trying to lose weight
Posted Tue, Feb. 9, 2010 at 12:03 am EST
sufficient information available
Posted Sat, Jan. 30, 2010 at 1:30 am EST
i want to information abot the bak pane during the waight lifting and start leg pane and after going int under the pens right said bolse thanks
Posted Mon, Jan. 25, 2010 at 2:44 am EST
so is that enough protein? i mean this is computed right right? cuz when you work out to thin down you also burn your protein into energy so its not actually used by the muscles just for energy so it becomes waste, well not really but does this computation considers that?
Posted Thu, Jan. 7, 2010 at 11:41 am EST
Someone who is weight training doesn't need any more protein than .36g / lb of body weight, the RDA? How could that possibly be? That flies in the face of umpteen studies on the subject over the years.
Posted Wed, Jan. 6, 2010 at 4:51 pm EST
I have just started my journey as a vegetarian (not vegan) and now I have concerns about not receiving enough protein. I will continue to eat biological products such as eggs and milk, but unsure if this is enough. Is there something I can do to add to my protein intake or should I reconsider a vegetarian lifestyle?
Posted Sun, Jan. 3, 2010 at 8:37 pm EST