Protein intake can be confusing and people ALWAYS have questions. Am I getting enough? Am I having too much? Is it bad for my health? I have answers (of course).
Protein is made up of amino acids which are essential components in cellular repair, hormone production, DNA, the immune system…generally everything. It is one of the three macro-nutrients (carbohydrates and fats being the other two…you knew that) and each gram of dietary protein provides 4kcal worth of energy.
I’ll get this out of the way first – higher intakes of protein will NOT be harmful to a healthy person.
The classic claim tends to relate to high protein intake and kidney function. The waste products of protein metabolism are filtered out of the blood by the kidneys, therefore when you eat more protein your kidneys are forced to work harder. But the truth is – the kidneys are incredibly complex and rarely run at, or near to, their full working capacity.
There is no difference in kidney function between athletes ingesting a high intake vs. moderate intake (Poortmans and Dellalieux, 2000).
Excessive protein intake may aggravate PRE-EXISTING kidney disease, but there is no research that suggests protein intake may INITIATE any sort of kidney problems (Martin et al. 2005).
For decades one of the main cases against a diet high in protein was that is caused the onset of osteoporosis. The protein-calcium-bone link is a long and tedious one (I wrote my post graduate dissertation on it so I know first hand), in summary – higher protein intakes lead to a higher level of calcium in the urine, traditional thinking led us to believe that this calcium was harvested from bone. Turns out this was a common case of assumptions being made about correlation and causation. Here’s the more up to date stuff;
High levels of protein are not detrimental to bone health – Kerstetter et al. (2005) showed a high protein intake (2g per kg of BW) is not detrimental to bone health in women.
Protein may have a positive effect on bone density- Dawson-Hughes et al. 2004 showed that exchanging protein for carbohydrates can have a favourable effect on bone density.
Overall calcium balance, and therefore bone density, is largely unaffected by protein intake (Bonjour, 2005)
We’ve all heard it – eat red meat and your heart will explode. Turns out it’s not so bad for the old ticker;
Lean meat intake has no effect on heart disease risk factors – Li et al. 2005 showed that lean red meat is associated with reductions in LDL-cholesterol in both healthy subjects and subjects with high cholesterol.
Red meat consumption has no link to heart disease or diabetes (processed meats aren’t so good); Micha (2010) found that consumption of processed meat is associated with the incidence of heart disease and diabetes, highlighting the importance of separate consideration of health effects, underlying mechanisms, and policy implications of different types of processed versus unprocessed meats.
Protein recommendations are normally made via grams per kilogram of LEAN bodyweight (LBW) i.e you should have at least a rough idea of your body fat percentage.
Your protein intake should be defined by your current goals or diet phase, as such I’ve separated my recommendations into 4 categories;
Strength Training/Muscle Gain (when combined with an overall daily caloric excess – i.e consuming more calories than you’re using)–
2.5-3g of protein per kg of LBW– Tipton and Wolfe (2004) concluded that high protein intakes can have benefits in strength athletes that are hard to monitor directly in a lab, and as we know it won’t be harmful it will most likely be beneficial to aim for the upper range.
Fat Loss (when combined with an overall, caloric deficit):
3g of protein per kg of LBW – Although there are no DIRECT references for a 3g/day intake, there are plenty to suggest a higher intake accelerates fat loss, through personal experience and generally my own opinion I would push it to 3g per kg of LBM.
Demli and DeSanti (2000), Layman (2009) and Layman et al. (2009) all concluded that high protein intakes can accelerate fat loss via increased satiety, thermogenesis and increased lean muscle mass.
Non-Training (sedentary – usually elderly)
1.5gof protein per kg of LBW– Vellas et al. 1997 did a 10 year study on the elderly (72 median age) and found that subjects with a higher protein intake 1.2-1.7g of protein per kg of LBW had fewer health complications. Houston et al. (2009) showed protein intake was a modifiable factor in regulating the loss of muscle in the elderly.
2g of protein per kg of LBW – Tipton and Wolfe (2004) concluded 2g/kg would be best to maintain lean muscle, while not gaining too much weight (which would be a disadvantage for an endurance athlete).
Here’s a little reference table for some popular protein sources. It’s hard to be exact with this type of thing due to varying quality and portion sizes, but I’ve done my best to give some useable estimates.
[table]Food,Serving Size,Protein (grams)
Chicken,1 breast (100g),30g
Pork,1 chop (100g),30g
Beef,1 steak (100g),30g
Turkey,1 breast (100g),30g
Fish,1 fillet (100-120g),20-30g
Greek Yoghurt,200g pot,18g
Whey Protein,1 x 70cc scoop,18-25g
Oats,100g (made with water),10g
Meat Substitute (e.g Quorn),100g,12-15g
Cashew Nuts,Handful (about 30g),5-7g
Milk,1 glass (200ml),7.2g[/table]