TL:DR Use protein to calorie ratios for an efficient way to work out what foods are good sources of protein.
So protein foods are having a bit of a moment right now. We have protein bars on every corner, protein cheese, protein bread, even protein mars bars. Many want to eat more protein to build muscle to burn their fat, some because it supposedly keeps you fuller for longer than other macros, and some probably just because they have no idea whether carbs or fat are the enemy anymore so just want to avoid both. It seems every product is proudly declaring that it is a ‘source of protein’.
But when we say “high in protein” or “source of protein” what do we mean? One definition might be:
- A good source of protein has many grams of protein in it, let’s say 10g.
But in my view, this definition doesn’t really help most regular people. These people want protein to feel fuller, lose weight, build muscle. I’m don’t think anyone in the western world is protein deficient, and the average person isn’t trying to put on slabs of muscle, so it’s mainly weight loss and appetite control that draws them to protein.
If you’re looking to lose weight, the amount of g of protein in food doesn’t actually matter that much: you could get 100g of protein just from brown bread if you ate 37 odd slices of it. The obvious problem that jumps out here is that you would take in tons of calories too, ~2700 actually, which isn’t a good number for people trying to lose weight. Point is, for the most people, you can meet your protein needs with any food if you forget about calories. But that would be stupid.
One definition I see used a lot is:
- A good source of protein is one that packs in most grams of protein in least grams of food. If I can’t get my daily protein requirements on this food without busting my stomach, it’s not a very good source of protein. We might measure this by how many grams of protein per 100g of overall food.
This definition is most useful for people who have large protein needs and/or small stomachs because they don’t want to eat kilos of food all day. This is probably why it’s popular, as the main group of people who care loads about protein are bodybuilders, who often have to (or so they claim) eat far, far more protein than the average person. However, the average person (who may require as little as 46/56g a day) does not need such efficiency. So for most people this definition is not useful.
This is the problem I have with modern foods labelling themselves as “sources of protein”. If a cereal bar has 10g of protein, is that a good source? If i told you it had 50 calories, you’d say that’s a great source: that’s 1/5th or 1/6 of your daily total, but leaves you the vast majority of your daily calories for things that you like far more than cereal bars. But if i told you it had 500 calories, you might not think it was worth it. If this makes sense to you, then what you really want are foods that provide you with protein for relatively few calories.
Enter the protein to calorie ratio. You divide the number of calories per 100g with the number of grams of protein. This tells you how much each gram of protein “costs” in terms of calories. Lower ratios are then better if you’re trying to build lean mass, or just trying to up your protein intake without gaining weight.
Pure protein scores a ratio of ~4, so this gives us a baseline. Tuna scores 5 (being mostly lean protein), Brown bread scores a lowly ratio of 26. Broccoli has a respectable 12, because while a piece of broccoli has little protein, it has few calories. This is similar to eggs, whose ratio is 11.9. Sainsburies sausages score 17 which might be surprising until you look at how much actual meat is in there. Work out the ratios of your favourite foods using google. Assuming that high protein is good, but high calories is bad, this ratio allows you to optimise both in a single number.
Using these definitions we can start getting at what a good source of protein is. I’d say anything with a ratio higher than 25 cannot be called a good source of protein, because if you only at foods with a ratio of 25 and you restricted yourself to 2500 kcals a day you’d have to eat your whole day’s calories of these foods to get to 100g of protein. And knowing that pure protein gives a ratio of 4 sets the lower limit, so you know foods around here (e.g. tuna in brine with its ratio of 6.1, seitan with a ratio of 5.2 for the veggie-vegans).
Ratios also reveal that most foods that advertise their protein content aren’t great sources of protein at all. Nakd’s protein bars have a ratio of 20, meaning that to get a good 20g of protein eating these bars you’d need to eat 400 calories, which many would regard as a bit more than a snack. MyProtein’s vegan protein bars fare a bit better with a ratio of 17. But soy milk has a ratio of 18, and while it’s no candy protein bar, it’s a fraction of the price, much more readily available and seemingly just as efficient a way of getting lean protein.
Need to get in 40 grams of protein after a workout but not sure what to eat? you can use the ratios: to get that 40g of protein you’d need to eat 680 calories of sausages, or 184 calories worth of tuna.
Likewise you can invert the ratio and do protein divided by calories (probably need the calculator for this one). This tells you how many grams of protein you get per calorie. So tuna gets a 0.2. This can be useful if you want to know how much protein you’d get if you ate, say a piece of tuna with 250 calories. 250 calories of tuna is 250 x 0.2 = 50g protein. If you portion out your day in calories, this is very useful.
This can be a useful shorthand: if you need ~80g a day, then eating 800 calories of foods with a ratio of 10 or better will get you there. This way you know that you have got your protein needs, without taking in a ridiculous amount of calories.
The advantages of using protein to calorie ratios is that if you aim to mainly eat low ratio foods you’ll reach or exceed your protein goals just by eating your daily calories. Ratios are not dependent on the amount you eat, so once you know the ratio for a food, it doesn’t change. If you memorise a couple of easily available foods and their protein to calorie ratios, it makes on the fly diet choice far easier. If you find yourself standing in Tesco needing a snack, would like some protein but don’t want to go nuts on calories, you might try and find foods with ratios of 10–15. This means that eating 200 calories of a food will give you 20–13 g of protein, which is pretty good.
If you start your day eating foods with ratios in the 15–20 mark, try and balance them out with some 5–10 ratio foods. It’s not exact, but it’s far easier than trying to calculate everything, and a diet must above all be easy to follow.
What do you think about the idea of using protein to calorie ratios to help you pick the right foods? It all makes sense in my head, but I’m no dietician. I’d love to hear your comments.