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Dietary Protein - health effects related to protein intake as described by food- and health-related organisations

Health Promotion Knowledge Gateway

Effect of protein intake on cardiovascular health

Cardiovascular disease
  • 'No consensus has been reached about whether such associations showing protective effect of protein for cardiovascular disease are causal and no convincing potential mechanisms have been proposed'.
  • 'For cardiovascular diseases, the association between protein intake and coronary heart disease and stroke was statistically non-significant in six cohort studies, and the evidence was regarded as inconclusive'.
Blood Pressure
  • 'Overall, while it seems certain that protein intakes are not harmful for blood pressure, with cross-sectional population studies clearly showing benefit of increasing protein intakes, some caution is probably still justified since dietary associations can be confounded by highly correlated nutrients for which no adjustment has been made'.
  • 'The evidence for an association between protein intake and blood pres­sure was assessed as inconclusive for total and animal protein, but an in­verse association with vegetable protein intake was assessed as suggestive'.
  • 'Evidence is suggestive for an inverse association between hypertension and intake of vegetable protein'.
Blood lipids
  • 'The evidence was assessed as probable to convincing in regard to the effect of soya protein on LDL-cholesterol concentration'.

Effect of protein intake on type 2 diabetes mellitus

  • Evidence was assessed as suggestive regarding the relation of total and animal protein intake to increased risk of type-2 diabetes.

Effect of protein intake on cancer

  • 'The evidence indicates that there is little effect of total protein intake on the incidence of cancer, but that specific foods, such as red or processed meat, might increase the risk relative to vegetable protein sources'.
  • 'The evidence from the systematic literature reviews did not suggest that proteins specifically modify the risk of cancers of any sites'.
  • 'The overall association between cancer and protein intake was assessed as inconclusive'.

Effect of protein intake on body weight/ energy intake

  • 'Evidence for an association between the dietary macronutrient composition in prevention of weight gain after prior weight loss was inconclusive. The results suggested that the proportion of macronutrients in the diet was not important in predicting changes in weight or waist circumference'.
  • Based on studies in individuals with healthy weight, evidence for an association between protein intake and energy intake was assessed as inconclusive.
  • 'The evidence for an association between protein intake and body weight change was also assessed as inconclusive'.
  • 'In shorter-term studies, low-calorie, high-protein diets may result in greater weight loss, but these differences are not sustained over time'.
  • 'A moderate amount of evidence demonstrates that intake of dietary patterns with less than 45% calories from carbohydrate or more than 35% calories from protein are not more effective than other diets for weight loss or weight maintenance, are difficult to maintain over the long term, and may be less safe'.

Effect of protein intake on bone health
  • 'Taken together, it does appear that dietary protein as part of a well-balanced diet is most likely to be beneficial for bone, possibly at dietary levels in excess of the recommended intake'.
  • 'The fact that our current models of protein and energy requirements identify sedentary elderly people as most likely to be at risk from protein deficiency (…), together with the evidence of a beneficial effect of dietary protein on bone in elderly people, suggests that attention should be given to the provision of protein-dense foods to this particular population group'.
  • 'Evidence for beneficial or adverse effects of higher protein intake in relation to bone health was assessed as inconclusive'.
  • 'The association between bone health and protein intake was assessed as inconclusive. However, there seems to be an interaction with the intake level of calcium. Under conditions of low calcium intake an increased risk of fractures was found to be related to high animal-protein intake, but under conditions of high calcium intake (>800 mg) a decreased risk of fractures was related to high animal-protein intake'.
  • 'Evidence for an association between vegetable protein intake and fracture risk was inconclusive'.
  • In the elderly, evidence was assessed as suggestive 'in regard to a positive association between protein intake and bone mineral density'.
  • 'Evidence was assessed as inconclusive regarding the relation of protein intake to bone loss and risk of fractures'.
  • 'A favourable effect on bones seems to be likely: studies reveal a positive association between the level of protein intake and bone mineral density, without, however, indicating any reduction in the risk of fractures'.
Effect of protein intake on kidney health
Kidney disease
  • 'There is clear evidence that high intakes of protein by patients with renal disease contribute to the deterioration of kidney function'.
  • 'Chronic protein intake is a determinant of glomerular filtration rate, but does not suggest a role for protein intake in the deterioration of kidney function'.
  • 'Protein restriction on the grounds of renal function is justifiable and prudent only in subjects who are likely to develop kidney failure owing to diabetes, hypertension, or polycystic kidney disease'.
  • 'The evidence for associations between protein intake and kidney function and kidney stones was regarded as inconclusive'.
Kidney stones
  • 'Although some studies suggest that high animal protein intake might increase the risk of kidney stones, particularly in those subjects who are classified as idiopathic calcium stone formers, as yet no clear conclusions can be drawn since dietary effects are apparent only in studies with very large differences in protein intakes (i.e. >185 g/day compared with 80 g/day)'.
  • 'it is not yet clear whether there is a difference between proteins of animal versus plant origin'.
  • 'in order to minimize the risk of kidney stones in patients who are at risk, the diet should ideally provide at least the safe level (0.83 g/kg per day), but not excessive amounts (i.e. less than 1.4 g/kg per day), preferably from vegetable sources'.
  • 'The evidence for associations between protein intake and kidney function and kidney stones was regarded as inconclusive'.

Effect of protein intake on exercise

  • 'evidence was assessed as suggestive with regard to a positive relation between muscle mass and a total protein intake in the range of 13 E% to 20 E%'.
  • 'The evidence was assessed as suggestive for the effect of training on whole-body protein retention'.
  • Evidence on dietary protein intake for the optimal effect of physical exercise in older adults have been assessed as inconclusive.
  • 'repetition of strength exercises leads to an increase in protein requirements, but, generally speaking, the protein requirements necessary for nitrogen balance equilibrium are covered by a balanced diet. The dietary habits of strength athletes mean that their protein intakes far exceed the quantities that can be recommended. It is training that explains the increase in muscle mass, and the protein intakes are justified by the necessary availability of amino acids to ensure increased synthesis of structural and functional proteins'.
Muscle mass  in elderly
  • Based on studies on elderly populations, the evidence on the relationship between muscle mass and total protein intake (in the range of 13 E% to 20 E%) was assessed as limited-suggestive.
Effect of protein intake on mortality
  • '…the evidence was assessed as suggestive regarding an increased risk of all-cause mortality' in relation to an low carbohydrate/high protein diet (LC/HP), with total protein intakes of at least 20–23 E%.
  • 'For cardiovascular mortality, the evidence was assessed as suggestive for an inverse relation to vegetable protein intake based on three studies in which the protein intake was expressed in E% and on one study with an LC/HP diet score based on vegetable protein'.
  • 'Generally, the use of an LC/HP score makes it uncertain whether the effects result from reduced carbohydrate or increased protein and/or fat, and thus the effect of protein per se cannot be assessed from LC/HP diets'.

a The statements provided here originally come from the 2010 DGAC study; the 2015 update refers to them and states that 'The published literature since that review does not provide sufficient evidence to change these conclusions'.