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Protein - What about the health risks?

By Matt O'Neill, MSc(Nut&Diet), APD

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In my last article about protein I explained how higher protein diets may prove a useful option for helping people lose weight. But are there safety issues, particularly associated with diets high in red meat?

Health authorities recommend a protein intake of around 15% of daily calories. This level is sufficient to meet needs for growth and repair for almost all people. Individuals with higher protein requirements can generally meet their needs at an intake of 15% protein because they simply eat more food.

Boosting protein to around 30% of daily calories in energy-restricted diets has been found to assist with weight loss, mainly due to curbing of hunger and a resulting reduction in energy consumption. It appears that more protein may help you feel full enabling you to eat less, at least in the short term.

Anecdotally, body builders have known this for years. Their typical “cutting up” phase diet contains large amounts of protein from chicken breast, tuna and protein supplements. Some Atkins' low-carb dieters may also find themselves better able to adhere to their diet due the high-satiety value of animal protein.

So, should we be advocating higher protein diets? Neither the bodybuilding nor Atkins' eating plans can be regarded as healthy.

For a higher protein diet to become an acceptable option for weight management, it needs to provide adequate amounts of key vitamins, minerals and other nutrients. It also should not pose any health risks.

Adequate nutrition

The Atkins' Diet clearly falls short on key nutrients. With only 20 grams of carbohydrate (about 4 per cent of daily energy) allowed in the two-week induction phase it provides inadequate amounts of fibre, calcium and B vitamins.

Clearly, a diet that dramatically restricts the intake of bread, cereals, pasta, rice, beans and starchy vegetables such as potatoes and corn does not provide the variety that is needed to meet nutritional needs.

Health risks

Most of the controversy over higher-protein diets surrounds the potentially negative impact on heart, bowel, kidney and bone health. Here is a summary of research findings:

Heart disease: Weight loss tends to reduce blood cholesterol levels, which explains why studies of slimming diets high in animal protein have reported neutral or beneficial affects on blood lipids. But as long term data is lacking, it is still wise to minimise the intake of fatty meats and dairy products high in saturated fat and cholesterol.

A comprehensive review of protein and cardiovascular health in the July 2005 issue of the American Journal of Clinical Nutrition cautioned that diets containing substantial amounts of red meat, and products made from red meats, appear to increase the risk of coronary heart disease (CHD).

For other protein sources, the review suggested:

  • Substituting poultry or fish for red meat can reduce risk of CHD.
  • Egg consumption may only be of concern for people with existing high cholesterol levels or type 2 diabetes.
  • Nuts protect against CHD.
  • Soy may have a modest protective effect.
Bowel cancer: In June 2005, a large European study linking meat consumption and bowel cancer reported that eating more than 160g of red meat each day increased the risk of colorectal cancer by 35 per cent compared to people who ate very little meat (less than 20g a day or one portion a week). Note that the researchers combined fresh and processed red meats (salamis, sausages, corned beef, etc). Lean red meat would be expected to have a lesser association with bowel cancer risk, but we can't tell what level of risk from this research.

This study also revealed:

  • Those who ate more fish in place of red meat had a lower risk.
  • Poultry consumption had no affect on relative risk.
  • Fibre intake offered some protection against the risk of a high meat intake.
Kidney function: Diets high in animal protein, but not plant protein, appear to reduce renal function in people whose kidneys are already compromised. Although this suggests that people with healthy kidneys may not be affected, Dr Neal Barnard, MD from the US Physicians Committee for Responsible Medicine points out that people, particularly those with diabetes, may not be aware that that they suffer from kidney impairment.

Osteoporosis: There is evidence that high-protein diets enhance calcium excretion and increase bone loss. Research on low carbohydrate diets have shown this, with one study from the University of Texas finding calcium loss was 55 per cent higher than normal in the maintenance phase of the diet. No studies have followed these diets for long enough to fully evaluate risk of osteoporosis.

Healthy advice

Many questions still remain about the long term health impact of higher protein diets. Current Federal Government recommendations for red meat consumption are around three to four serves (65 to 100g serve size) a week.

Some diets promote greater consumption, including the CSIRO's Total Wellbeing Diet which recommends around 200g lean red meat per day. If weight loss can be achieved within the lower limit, it provides, on balance, a healthier option than higher intakes of red meat.

There is little research on the effects of non-meat protein supplements on the health parameters discussed in this article. So, we don't really know the health impact of diets high in protein from sources such as vegetarian foods, protein bars or shakes. One real risk is eating a 'high protein junk food diet'. Consuming protein bars or shakes as snacks, rather than fruits, yoghurt or whole grains will compromise nutritional status. Even if supplements are fortified with vitamins and minerals, they are no substitute for the synergistic benefits of whole foods.

Another closely related risk is the over-emphasis on dietary macronutrient ratio as the solution to all our weight woes. Striving to achieve the correct balance of fats, carbohydrates and proteins can distract people from making more productive changes in their lifestyle, like planning meals, managing hunger and dealing with eating triggers.


  • If you have experienced little success with a low-fat / high-carbohydrate, energy restricted diet and appear to consume little animal protein, you may benefit from additional lean protein serves at lunch and dinner.
  • The potential health benefits of weight loss with a higher red meat diet should be weighed up against the potential risks on an individual basis. If your weight is putting your health at risk, this risk may be greater than the risk from eating larger quantities of red meat.
  • Choose protein from a range of sources, including lean red meat, chicken, fish, low fat dairy or soy, beans, lentils and other non-meat protein foods.
  • Ensure an adequate intake of fruits (2 to 3 serves a day) and vegetables (4 to 5 serves a day) to provide vitamins, minerals, fibre and other beneficial plant chemicals.
  • Aim for three serves of dairy or calcium-enriched dairy alternatives such as soy milk each day to promote calcium status.
  • Choose whole grain and low-glycaemic index (GI) carbohydrates, rather than highly processed forms from sugar, white breads, refined breakfast cereals or bars.
  • Consume fewer calories than you expend. Any diet that creates a negative energy imbalance will promote weight loss.



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