Almost every client I see eats less protein than they should. When asked to bump up protein intake, frowns start to appear. ‘Aren’t high protein diets unhealthy?’ that’s the most common reaction I get. Well let us look at the different myths surrounding high protein diets and how they get debunked.

High Protein Diet Causes Colon cancer/Heart Disease
A large meat intake, especially red meat, is often believed to be involved in the development of some diseases, namely heart disease and colon cancer. A good deal of this research is based on observational work where individuals consuming a meat-based diet are more likely to get these diseases.

But you can’t simply isolate protein/meat intake from other aspects of the diet. This is crucial when looking at the research as most of it tends to be epidemiological in nature, looking at large populations of individuals and tries to draws correlations between different measured variables. This may lead scientific researchers to draw incorrect conclusions.

For eg, modern meat based diets are also normally very high in saturated fat, a known risk factor for many diseases. In comparison, lean red meats, trimmed of visible fat, have a drastically different impact on the risk of heart disease.

Diets high in meat are often low in fruits and vegetables and fiber and research suggests that it is the lack of those foods (fruits, vegetables) more so than the presence of red meat that is responsible for any greater cancer risk. High fat intakes have also been associated with low food variety and low intakes of fruits and vegetables; this would further contribute to the apparent link between consuming fatty meat and health risk.

Put differently, there is going to be a fairly large difference in the overall impact of a diet that is high in animal protein, high in fat, low in fruits and vegetables (and thus low in fiber and other important nutrients) which may be accompanied with other health risks such as inactivity, being obese, etc. This would be held in complete contrast to an athletic diet containing large amounts of lean meats along with a large fruit and vegetable intake, high levels of activity, maintenance of a low level of body fat, etc.

As I mentioned above with regards to bone health any diet high in animal protein must be accompanied by a high intake of fruits and vegetables. As well, leaner cuts of meat (especially red meat) should be chosen whenever possible.

High Protein Diet Causes Decreased Kidney function
A common criticism of high protein intakes/diets is the concern that they are damaging to the kidneys. This belief seems to stem from the fact that, in individuals with preexisting kidney damage, protein intake often has to be reduced to prevent further development of the disease. Incorrectly, this has been turned around to suggest that high-protein intakes are damaging to the kidneys.

There is at best a weak case to be made for a risk of high protein intakes on kidney function; quite in fact, some research suggesting a beneficial effect of higher protein intakes on kidney function. Simply put, the adaptations to kidney function that are often cited as indicating ‘strain’ or damage are more likely to simply be normal adaptive effects of varying protein intake.

Unfortunately, very little research has directly examined the impact of high protein intakes on kidney function in athletes. One study examined the impact of 2.8 g/kg protein on the kidney function of bodybuilders, no negative effect was seen. To my knowledge, higher intakes have not been studied.
Empirically, it’s worth considering that athletes have been habitually consuming large amounts of protein for at least several decades without any reported increase in the incidence of kidney problems. If such a problem were going to occur, it seems likely that it would have shown up by now. While this certainly doesn’t prove that high protein intakes aren’t potentially detrimental to kidney function, the data in support of that idea would seem to be lacking both from a scientific and real-world point of view.

Interestingly, while it’s always been stated that high dietary protein intakes increases fluid requirements, this idea appears to have originated from a military study examining nitrogen balance under conditions of water and energy restriction. There is no indication that individuals who are sufficiently hydrated need to go out of their way to increase fluid intake when they are consuming large amounts of protein.

High Protein Diet Causes Bone Loss
Perhaps one of the most pervasive criticisms of high protein intakes has to do with the impact of protein on bone health and calcium status. This goes back to early nutritional studies which gave purified protein diets and saw a loss of calcium from the body.

Later studies, using whole food proteins (which included other nutrients such as phosphorous) found very different effects. Frankly, the early studies on this topic are irrelevant to normal human nutrition since the consumption of protein in the total absence of other nutrients would be extremely rare; all whole food proteins and protein powders contain micronutrients.
The impact of protein on overall calcium status is more complex than having a simple positive or negative effect as dietary protein can impact on both calcium excretion as well as calcium absorption and utilization. It is the combined effect of these processes which determines the end result in terms of bone health.

In epidemiological studies, a high intake of animal protein increases the risk of bone fractures; as well, a high ratio of animal to vegetable protein intake has also been associated with an increased risk of bone loss. In contrast, high intakes of protein improve bone healing, following a fracture for example. This is mediated both by increased calcium absorption as well increased levels of insulin-like growth factor 1(IGF-1), a hormone involved in tissue growth. How can this contradiction be reconciled?

Fundamentally, it’s too simplistic to look at protein intake in isolation in terms of its effects on bone health as the protein content of food interacts with other nutrients in that food or in the total diet. For example, recent studies suggest an interaction between protein and calcium intake.

When calcium intake is low, high protein intakes appear to have negative effects on bone health. In contrast, when calcium and vitamin D intake are sufficient, protein intake has a beneficial effect on bone health. This suggests that ensuring adequate calcium intake (through a sufficient intake of dairy foods, or calcium supplements) is crucial for bone health when a high protein intake is being consumed.

This most likely serves to explain the above contradiction. In the studies where dietary protein intake was found to have a negative impact on bone health, there were other dietary factors playing a role. Calcium or Vitamin D intake may have been insufficient causing an overall negative effect. However, when sufficient calcium and Vitamin D are provided (as they typically are following bone injury), dietary protein has a beneficial impact.

In Conclusion. Eat your proteins and reap the multiple benefits that they bring!

Original article by Lyle Mcdonald

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