Men often seek to tip the scales not through acquisition of a beer belly, but by gaining muscle. Muscle is made of protein and consequently a number of protein-packed eating tendencies (meals mainly comprised of massive serves of tuna and chicken) have arisen, but is this necessary or even safe?

Dietary protein is required to build skin, muscle, bones and hair and is also used for energy. Every cell in our body is formed from protein we have eaten and the building blocks of these are amino acids, of which 20.9 of these are essential and cannot be made in the body. For protein synthesis to occur, all 20 amino acids must be present; foods with an ample complement have a high Biological Value (BV). Animal proteins such as meat, fish, eggs, poultry and milk score well, whereas plant-based foods have low amounts of some essential amino acids and thus a lower BV. This shortcoming can be rectified with careful food combinations and this is the premise of a vegan diet. For example the limiting amino acid in pulses and beans is methionine, whereas in wheat-based foods it is lysine. By rustling up a meal with both wheat and pulses (such as baked beans on toast, pitta and hummus or wheat noodles and soy beans - zhajiang mian) you can ensure a complete amino acid intake.

Recommendations for protein intake vary according to gender, stage of development and training schedule. For those seeking to gain muscle an overall increase in energy intake is certainly required. Initially it is important to focus on increasing carbohydrate intake because this provides the energy necessary to train and so stimulate muscle growth. An increase in protein intake may be necessary but the majority of the population, certainly in Western countries, exceed their requirements on a daily basis anyway. A sedentary male or female requires 0.8-1.0g protein per kilogram body weight per day. For an 85kg male this would be met by having a large bowl of wholegrain cereal and milk (20g protein) for breakfast, a ham and cheese salad sandwich and a yoghurt for lunch (35g protein) and an evening meal of rice and a breast of chicken with cashew nuts (30g protein). This amount would also suffice for a recreational athlete (training 4-5 times/week for 30 minutes) however an elite male endurance athlete may require double this amount. Strength training athletes have high requirements only in the earlier stages of training but soon adapt.

Several studies have looked into the effect of a high-protein diet in healthy athletes and concluded that although it increases kidney size, it is not harmful to health. Excess protein intake has been shown to negatively affect kidney function in those with pre-existing kidney problems such as chronic kidney failure (CKD) which affects one in nine Americans.

One risk of excessive dietary protein is deficiency of vitamins, minerals and nutrients found in other typically plant-based food groups. High animal protein intake also tends to result in increased sodium and saturated fat intake and it is often expensive.

Gorging yourself on protein may increase calcium excretion in your urine which means that if genetically prone, you are more likely to develop calcium renal stones. This also has implications for osteoporosis risk. We know adequate protein intake is essential for healthy bones, but at really high intakes this could in fact encourage bone loss.

This nutrition-related column is written by Nina Lenton, a qualified dietitian living in Beijing and working at Bayley and Jackson Medical Center. Contact her at nina.lenton@bjhealthcare.com.

(China Daily 08/02/2007 page14)