There has been much debate on how much protein we can safely digest in one serving
or meal, supplement companies all recommend different serving sizes for their
products and most references seem to refer to a study done in the 1970's
on subjects with pre-existing health problems and how a high protein diet
put additional strain on their kidneys and renal system. The UK Food Standads
Agency state as a guideline on their website; "The daily recommendation
for adults (over the age of 19) is 55 g protein per day. But it’s the
balance of foods we eat over a few days that’s important, rather than
what we eat every day. So if you don’t manage to eat much protein on
one day, you should aim to eat a bit more over the next few days.
This is because the body contains a small reserve of protein so it can cope
with day-to-day variations. However, eating large amounts of protein is bad
for the
kidneys, so it’s important not to eat too much protein, and it’s
especially important to keep within twice the recommended amount." They
do not support any of the above with any evidence.
The American Heart Association (AHA) stated in 2001 "Individuals who
follow these (high protein) diets are risk for potential cardiac, renal, bone
and liver abnormalities overall." This sweeping statement must cause concern
and in turn deter many people from following an Atkins type high protein diet
plan which incorporates a reduction in carbohydrate intake.
The justification of such a statement is unclear as there is no scientific
evidence that high protein intake has adverse effects on liver function. Relative
to renel function there is no scientific ducumentation to support the theory
that healthy kidneys are damaged by the increased demands of protein consumed
at 2 - 3 times the Recommended Daily Allowance (RDA). A study by Portman Dellalieux
investigated bodybuilders and other highly trained athletes with medium to
high protein intakes. The athletes underwent a 7 day nutrition record analisys
as well as blood sample and urine collection to determine the potential consequences
of such a diet. The subsequent data showed despite higher uric acid and calcium
the athletes had renal clearances of creatinine, urea and albumin which were
al considered to be within a normal range. This admittedly short study was
done with protein ingestation of up to 2.8gr/kg of bodyweight, 3.5 times as
much as the recommended daily allowance.
In contrast to the theory that a high protein diet promotes osteoporosis,
there has been some epidemiological studies showing a positive effect of protein
intake and bone mineral density, further to that recent studies suggest over
a short period the RDA of 0.8gr/kg of protein does not support calcium homeostasis.
Finally a negative relationship has been found between protein intake and
blood pressure in several epidemiological surveys(Honolulu Heart Study 6406
cases studied, Chinese Study 2672 cases and MRFIT Study with 11342 adult males
studied), all these factors show there is little if any hard and fast scientific
evidence to support the above AHA statement. For healthy individuals with normal
renal function the risks of a high protein diet are minimal.
Dr. Eric L. Knight, a researcher at Brigham and Women's Hospital and Massachusetts
General Hospital in Boston concluded after studying the effects of protein
consumption vs kidney function that, "Based on this study,
I would say in individuals with normal kidney function, we have no reason to
believe that
a relatively high protein intake has a harmful effect on the kidneys." The
findings appear in the March 2003 issue of the Annals of Internal Medicine.
The following chart is one of recommedations by the Australian Institute of
Sport;
Protein requirements of different athlete groups:
| Type of Athlete |
Grams of protein per kg of body mass per day |
| Sedentary individual |
0.8 |
| Athlete undertaking general training program |
1.0 |
| Endurance athlete undertaking moderate to heavy training |
1.2 - 1.6 |
| Endurance athlete undertaking extreme training program or competition |
2.0 |
| Strength athlete undertaking heavy training program |
1.2 - 1.7 |
| Adolescent Athletes |
2.0 |
So what does this really mean to people concerned with increasing muscularity,
wanting to maintain a protein based diet to control fat levels or those involved
in an intense exercise program which stresses skeletal muscle? I think it shows
that anecdotal evidence relating to high protein intakes doesn't relate to
the people who are most likely to be consuming the most protein, almost all
studies are done on people with medical problems which a high protein intake
may effect negatively, the studies I have mentioned which were done on healthy
individuals who exercised to a degree found no problems.
This I believe shows the old 30gr of protein per seving theory to be not only
out dated but also incorrect, this figure was a conclusion drawn by an American
study done in the 1970's on recovering alcohilics who were suffering from a
degree of liver and renal failure. It was found that servings
of over 30gr protein at any one time was not fully digested and caused stress
to the subjects renal system as the demands put on the kidneys to process the
additional nitrogen and elevated urea production were increased.
Could someone like Ronnie Coleman build such a physique on 6 meals a day containing
30gr of protein? I think not, my own theory which is only my theory, is that
as a naturally skinny person who can eat large amounts of fat, carbohydrate
and protein without getting fatter or more muscular has a body whch process
nutrients without storing them. Where the narurally fat person is the exact
opposite, whatever they eat tends to be stored well, good or bad.
I believe as individuals with differing numbers of muscle fibers and muscle
density we can all digest differing amounts of protein, the demands we all
put on our bodies mentally and physically differ greatly so does our ability
to deal with them this alone will have an effect on our ability to digest protein.
Until a study is done on people who are pushing the boundaries of protein consumption
I think we must do what we feel to be right for ourselves and follow what seems
to allow us to recover from our chosen form of exercise swiftly and allow those
of us who want added muscle tissue to still have enough excess protein in our
diet to support this new tissue growth.
References: Manninen AH. Protein metabolism in exercising humans with special
reference to protein supplementation. Dept of Physiology, University of Kuopio,
Finland. 2002
St. Jeor ST, Howard BV, Prewitt E, Dietary protein and weight reduction: A
statement for health care professionals from the Nutrition Committee of the
Council of Nutrition, Physical Activity and Metabolism of the American Heasrt
Association. 2001
Australian Institute of Sport, Protein are you getting enough? (article)
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