This is one of the most common queries when it comes to protein intake. Instead of going for one source of recommendation, I have chosen seven different authorities on the subject and given their respective figures for daily protein recommendation or better understanding and consensus on the subject:
Dietary requirement is the amount of proteins or amino acids, that must be supplied in the diet in order to satisfy the metabolic demand and achieve nitrogen balance. So, the recommended dietary allowance is given to ensure that the diet supplies adequate protein. The protein recommendations differ according to the requirements of an individual, at different stages of life, physical activity, medical conditions, body composition, goal etc.
The method of assessing the protein requirement of an individual can be in terms of loss of nitrogen through feces, urine and skin. This loss of nitrogen is assessed by maintaining an individual on a protein-free diet and estimating the fecal and urinary excretion of nitrogen. There is formula for calculating that, but we won’t be discussing that here.
DRI (Dietary Reference Intake) values as per the 2005 report, by the Food & Nutrition Board, Institute of Medicine, National Academy of Sciences, US, established a set of reference values for dietary energy, carbohydrate, fibre, fat, fatty acids, cholesterol, protein, and amino acids to expand and replace previously published Recommended Dietary Allowances (RDAs) and Recommended Nutrient Intakes (RNIs) for the United States and Canada, respectively.
Acc. to the report, Dietary Reference Intakes (DRIs) comprise a set of reference values for specific nutrients, each category of which has special uses. The development of DRIs expands on the periodic reports called Recommended Dietary Allowances, published from 1941 to 1989 by the National Academy of Sciences, and Recommended Nutrient Intakes, published by the Canadian government.
The reference values, collectively called the Dietary Reference Intakes (DRIs), include the Estimated Average Requirement (EAR), Recommended Dietary Allowance (RDA), Adequate Intake (AI), and Tolerable Upper Intake Level (UL). Establishment of these reference values requires that a criterion of nutritional adequacy be carefully chosen for each nutrient, and that the population for whom these values apply be carefully defined.
A requirement is defined as the lowest continuing intake level of a nutrient that, for a specific indicator of adequacy, will maintain a defined level of nutrition in an individual.
Recommended Dietary Allowance (RDA): the average daily dietary nutrient intake level sufficient to meet the nutrient requirement of nearly all (97 to 98 percent) healthy individuals in a particular life stage and gender group. The RDA is intended to be used as a goal for daily intake by individuals as this value estimates an intake level that has a high probability of meeting the requirement of a randomly chosen individual.
Adequate Intake (AI): the recommended average daily intake level based on observed or experimentally determined approximations or estimates of nutrient intake by a group (or groups) of apparently healthy people that are assumed to be adequate—used when an RDA cannot be determined.
Tolerable Upper Intake Level (UL): the highest average daily nutrient intake level that is likely to pose no risk of adverse health effects to almost all individuals in the general population. As intake increases above the UL, the potential risk of adverse effects may increase.
Estimated Average Requirement (EAR): the average daily nutrient intake level estimated to meet the requirement of half the healthy individuals in a particular life stage and gender group.
In the case of energy, an Estimated Energy Requirement (EER) is provided. The EER is the average dietary energy intake that is predicted to maintain energy balance in a healthy adult of a defined age, gender, weight, height, and level of physical activity consistent with good health. In children and pregnant and lactating women, the EER is taken to include the needs associated with the deposition of tissues or the secretion of milk at rates consistent with good health.
There is much less certainty about an AI value than about an RDA value. Because AIs depend on a greater degree of judgment than is applied in estimating an EAR and subsequently an RDA, an AI may deviate significantly from, and may be numerically higher than, an RDA. For this reason, AIs must be used with greater care than is the case for RDAs. Also, an RDA is usually calculated from an EAR by using a formula that takes into account the expected variation in the requirement for the nutrient.
Tolerable Upper Intake Limit (UL): is the highest level of daily nutrient intake that is likely to pose no risk of adverse health effects for almost all individuals in the specified life stage group. As intake increases above the UL, there is the potential for an increased risk of adverse effects. The UL is not intended to be a recommended level of intake, as there is no established benefit for healthy individuals if they consume a nutrient in amounts exceeding the recommended intake (the RDA or AI).
The need for setting ULs has arisen as a result of the increased fortification of foods with nutrients and the use of dietary supplements by more people and in larger doses. The UL applies to chronic daily use and is usually based on the total intake of a nutrient from food, water, and supplements if adverse effects have been associated with total intake. For some nutrients, data may not be sufficient for developing a UL. This indicates the need for caution in consuming amounts greater than the recommended intake; it does not mean that high intake poses no potential risk of adverse effects.
Acceptable Macronutrient Distribution Ranges (AMDR): is defined as a range of intakes for a particular energy source that is associated with reduced risk of chronic diseases while providing adequate intakes of essential nutrients. The AMDR is expressed as a percentage of total energy intake because its requirement, is not independent of other energy fuel sources or of the total energy requirement of the individual. Each must be expressed in terms relative to each other.
Because much of this evidence is based on clinical endpoints (e.g., coronary heart disease, diabetes, cancer, and obesity), which point to trends rather than distinct endpoints, and because there may be factors other than diet that may contribute to chronic disease, it is not possible to determine a defined level of intake at which chronic disease may be pre- vented or may develop. Therefore, an AMDR is not considered to be a Dietary Reference Intake (DRI) that provides a defined intake level. An AMDR is provided to give guidance in dietary planning by taking into account the trends related to decreased risk of disease identified in epidemiological and clinical studies.
A key feature of each AMDR is that it has a lower and upper boundary, some determined mainly by the lowest or highest value judged to have an expected impact on health. If an individual consumes below or above this range, there is a potential for increasing the risk of chronic diseases shown to affect long-term health, as well as increasing the risk of insufficient intakes of essential nutrients.
[Each type of Dietary Reference Intake (DRI) refers to the average daily nutrient intake of individuals over time. The amount consumed may vary substantially from day-to-day without ill effects in most cases. More- over, unless otherwise stated, all values given for Estimated Average Requirements (EARs), Recommended Dietary Allowances (RDAs), Adequate Intakes (AIs), or Acceptable Macronutrient Distribution Ranges (AMDRs) represent the quantity of the nutrient or food component to be supplied by foods from diets similar to those consumed in Canada and the United States. Healthy subgroups of the population often have different requirements, so special attention has been given to the differences due to gender and age, and often separate reference intakes are estimated for specified subgroups.
For some nutrients (e.g., trace elements), a higher intake may be needed for healthy people if the degree of absorption of the nutrient is unusually low on a chronic basis (e.g., because of very high fibre intake). If the primary source of a nutrient is a supplement, a higher or lower percentage may be absorbed and so a smaller or greater intake may be required, or an adverse effect may be demonstrated at a lower level of intake.
The DRIs apply to the apparently healthy population, and while the RDAs and AIs are levels of intake recommended for individuals, meeting these levels would not necessarily be sufficient for individuals who are already malnourished. People with diseases that result in malabsorption syndrome or who are undergoing treatment such as dialysis may have increased requirements for some nutrients. Special guidance should be provided for those with greatly increased nutrient needs or for those with decreased needs such as energy due to disability or decreased mobility. Although the RDA or AI may serve as the basis for such guidance, qualified medical and nutrition personnel should make necessary adaptations for specific situations.]
World Health Organization, Food and Agriculture Organization, and International Atomic Energy Agency (WHO/FAO/IAEA) Expert Consultation on Trace Elements in Human Nutrition and Health. That publication uses the term basal requirement to indicate the level of intake needed to prevent pathologically relevant and clinically detectable signs of a dietary inadequacy. The term normative requirement indicates the level of intake sufficient to maintain a desirable body store, or reserve. In developing an RDA, emphasis is placed instead on the reasons underlying the choice of the criterion of nutritional adequacy used to establish the requirement. It is not designated as basal or normative.
RDA for Protein by the Institute of Medicine:
Infants Aged 0-6 Months: 1.52 g/kg/d
Human milk is recognized as the optimal source of nutrients for infants throughout at least the first year of life and is recommended as the sole nutritional source for infants during the first 4 to 6 months of life. There are no reports of apparently healthy, full-term infants, exclusively fed human milk, who manifest any signs of protein deficiency.
Although protein intakes have been reported to be 66 to 70 percent higher in infants fed formula compared with those fed human milk for up to 12 months of age, there is no evidence that the lower protein intakes in the breast-fed infants were associated with adverse outcomes. In fact, despite their lower protein intakes, some studies have demonstrated that infants fed human milk have better immune function and behavioural development than formula-fed infants. As expected, gains in weight and lean body mass are higher in the formula-fed than breast-fed infants, but when controlled for energy intake, protein intake is not associated with weight or length gain within the breast-fed infants.
Infants Aged 7-12 Months: 1.0-1.2 g/kg/d
During the second 6 months of life, solid foods become a more important part of the diet of infants and add a significant amount of protein to the diet.
Children Aged 1-13 Years:
1–3 years – 1.05 g/kg/d
4–8 years – 0.95 g/kg/d
9–13 years – 0.95 g/kg/d
Ages 14-18 Years:
RDA for Boys 14–18 years – 0. 85 g/kg/d
RDA for Girls 14–18 years – 0. 85 g/kg/d
Ages 19-50 Years:
RDA for Men
19–30 years: 0.80 g/kg/d
31–50 years: 0.80 g/kg/d
RDA for Women
19–30 years: 0.80 g/kg/d
31–50 years: 0.80 g/kg/d
Ages 51 Years & Older:
RDA for Men
51–70 years: 0.80 g/kg/d
> 70 years: 0.80 g/kg/d
RDA for Women
51–70 years: 0.80 g/kg/d
> 70 years: 0.80 g/kg/d
RDA for Pregnancy
All age groups: 1.1 g/kg/d
RDA for Lactation
All age groups: 1.3 g/kg/d
Acc. to the Institute of Medicine, athletes may need a higher than normal protein to maintain optimum physical performance. Whether or not this is true has significance not only for athletes, but also for those with muscle wasting who wish to preserve muscle mass by training, such as elderly or immobile adults, or those suffering from muscle-wasting diseases.
However, acc. to the Institute of Medicine, gave a controversial recommendation in regards to endurance and strength athletes, which were debated in a number of studies subsequently. Acc. to the Institute of Medicine: “In view of the lack of compelling evidence to the contrary, no additional dietary protein is suggested for healthy adults undertaking resistance or endurance exercise.”
Similar recommendations were given for vegetarians: “available evidence does not support recommending a separate protein requirement for vegetarians who consume complementary mixtures of plant proteins.”
Acc. to NIN, in normal healthy individuals, the RDA for protein is expressed as ‘per kilogram of body weight’. On an average, an adult can maintain health at an intake of 0.8-1.0g of protein per kg or body weight. But the requirements change according to individual’s needs. 0.8g/kg body weight is basic protein required for daily protein turnover. As a general rule, people training at less than 50% VO2 max for 20-60min/day do not need much increase in protein intake beyond basic RDA requirements.
Individuals involved in resistance training, such as weightlifters, bodybuilders, powerlifters, sprinters, football players, rugby players, boxers, wrestlers etc. strive for increased muscle mass and strength. This type of training increases protein synthesis in the body, thus increasing the need for protein. During such high intensity training the recommendations can increase to about 1.5-2.0g/kg body weight. However, the need for protein in endurance runners is also increased, though not to an extent of strength athletes. For them 1.2-1.4g/kg body weight is recommended.
Below is the chart given by the National Institute of Nutrition, India, for various macros and micros, though our focus will be on the protein recommendations:
Acc. to the 2017 report, in the Journal of the International Society of Sports Nutrition, by a large US research team, with researchers in the likes of Alan Aragon, Brad Schoenfeld, Dr. Jose Antonio, gave a position statement, on intake of protein for healthy, exercising individuals.
In a 2016 report in the Journal of the American Academy of Nutrition and Dietetics, by researchers D. Travis Thomas & Louise M. Burke, gave the position of the Academy of Nutrition and Dietetics (Academy), Dietitians of Canada (DC), and the American College of Sports Medicine (ACSM). For proteins, the recommendations are:
Acc. to a 2010 study in the journal Current Opinion in Clinical Nutrition & Metabolic Care, by a Canadian research team, led by R. Elango, the Dietary Reference Intake recommendations for population-safe intake of 0.8g/kg/day, respectively, was considered to be inadequate. Using a better method of analysis, the researchers found the new values to be 1-1.2g/kg/day.
Also, as we saw above, that RDA has various limitations, based on many factors. It doesn’t give you ideal intake, rather it gives the minimum intake to prevent malnutrition. Acc. to examine.com report, unfortunately, the RDA for protein was determined from nitrogen balance studies, which require that people eat experimental diets for weeks before measurements are taken. This provides ample time for the body to adapt to low protein intakes by down-regulating processes that are not necessary for survival but are necessary for optimal health, such as protein turnover and immune function.
An alternative method for determining protein requirements, called the Indicator Amino Acid Oxidation (IAAO) technique, overcomes many of the shortcomings of nitrogen balance studies.For example, it allows for the assessment of protein requirements within 24 hours, thereby not leaving the body enough time to adapt. Studies using the IAAO method have suggested that about 1.2g/kg is a more appropriate RDA for healthy young men, older men, and older women.
As we discussed in the controversial and debatable guidelines of Institute of Medicine, regarding endurance and resistance training athletes, as well as vegetarians, there are various studies which proved the higher need for proteins for athletes later.
In a 2011 study in the Journal of Sports Science, researchers S.M. Phillips & L.J. Loon Van, suggested that, athletes seeking to gain muscle mass and strength are likely to consume higher amounts of dietary protein than their endurance-trained counterparts. The main belief behind the large quantities of dietary protein consumption in resistance-trained athletes is that it is needed to generate more muscle protein. Athletes may require protein for more than just alleviation of the risk for deficiency, inherent in the dietary guidelines, but also to aid in an elevated level of functioning and possibly adaptation to the exercise stimulus. It does appear, however, that there is a good rationale for recommending to athletes protein intakes that are higher than the RDA. Elevated protein consumption, as high as 1.8-2.0g/kg/day depending on the caloric deficit, may be advantageous in preventing lean mass losses during periods of energy restriction to promote fat loss.
In a 2019 study in the American Journal of Physiology, Endocrinology & Metabolism, Canadian researcher A. Bandegan & team, debated the Institute of Medicine protein recommendations for athletes, and determined the dietary protein requirement of healthy young endurance training men, 24h post exercise. The data suggested that the protein EAR for endurance training men 24h post-exercise exceeds the Institute of Medicine EAR and established athlete guidelines by 1.3 to 3.5 times, respectively.
Canadian researcher A. Bandegan & team, in an earlier 2017 study in the Journal of Nutrition, assessed the dietary protein requirement of healthy young male bodybuilders. Eight men were studied at rest on a non-training day, on several occasions (4-8 times) each with protein intakes ranging from 0.1 to 3.5g/kg/d, for a total of 42 experiments.
Researchers found that, the Estimated Average Requirement (EAR) of protein and the upper 95% RDA for these young male bodybuilders were 1.7 and 2.2g/kg/d, respectively. The data suggest that the protein EAR and recommended intake for male bodybuilders at rest on a non-training day exceed the current recommendations of the Institute of Medicine by app. 2.6 fold.
In a 2014 study in the International Journal of Sports Nutrition & Exercise Metabolism, a New Zealand research team, led by E.R. Helms, evaluated the effects of dietary protein on body composition in energy-restricted resistance-trained athletes and to provide protein recommendations for these athletes. They reviewed six different studies and found that, protein needs for energy-restricted resistance-trained athletes are likely 2.3-3.1g/kg body weight.
Dr. Jose Antonio & team, in a 2015 study in the Journal of International Society of Sports Nutrition, determined if a high protein diet in conjunction with a periodized heavy resistance training program would affect indices of body composition, performance and health. Forty-eight healthy resistance-trained men and women completed this study. Subjects were divided into two groups, normal protein (app. 2g/kg/d) and high protein (>3g/kg/d).
Subjects in the normal protein and high protein groups consumed 2.3 and 3.4g/kg/day of dietary protein during the treatment period. The normal protein group consumed significantly more protein during the treatment period compared to their baseline intake. The high protein group consumed more total energy and protein during the treatment period compared to their baseline intake. Furthermore, the high protein group consumed significantly more total calories and protein compared to the normal protein group.
There were significant group changes in body weight, fat mass, and % body fat. The normal protein group gained significantly more body weight than the high protein group; however, the high protein group experienced a greater decrease in fat mass and % body fat. Thus, the researchers concluded that, consuming a high protein diet (3.4g/kg/d) in conjunction with a heavy resistance-training program may confer benefits with regards to body composition. Furthermore, there is no evidence that consuming a high protein diet has any deleterious effects.
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