An Instagram post recently shared by my favourite musical celebrity caught my professional interest. It contained ‘facts’ about plant-based protein sources. When I looked further, I found that other people had shared similar posts across the internet. Unfortunately, that information is somewhat misleading, at least in the context it has been communicated. The infographic of concern states that spinach contains 49% protein, mushrooms 38%, cauliflower 40%, and parsley 34% protein.
Just taking these examples, the post (in the format it has been shared) suggests that if we eat 100g of each of those products we would get:
- 49g protein from spinach
- 38g protein from mushrooms
- 40g protein from cauliflower
- 34g protein from parsley (100g of parsley is a heck of a lot, by the way!).
These figures sound amazing given the average woman needs just 45g and the average man needs 56g per day for basic health; using the calculation of 0.75g protein per 1kg of bodyweight (British Nutrition Foundation). Individuals with health conditions, such as kidney problems, may be require a lower protein intake – your medical team will advise you on this.
So, what is the post really about?
Rather than overall food protein content, these percentages reflect the approximate proportion of calories obtained from protein within the food. However, this piece of helpful contextual information has been omitted from the post.
The calorie content of a food is based on its macronutrient make up:
- 1g of fat provides approx. 9 kcal
- 1g of protein provides approx. 4 kcal
- 1g of carbohydrate provides approx. 3.75 kcal
- 1g of alcohol provides approx. 7 kcal (one unit is approximately 8g of pure alcohol).
Having an understanding of your calorie intake from protein may be helpful for some fitness activities, or if you are monitoring the proportions of your energy intake to follow a particular diet. However, in these instances, it is perhaps better to review the total intake per meal or day, rather than content of individual foods – after all, balanced meals rarely consist of a single food item. In general terms knowing your protein intake as a share of calories is not helpful to knowing if you are consuming enough protein.
Plant protein content by weight
Referring to the nutrient content of a food based on its proportion of the energy provided ignores the total make-up of the food. And, in the case of fruit and vegetables, there is certainly a significant amount of water that isn’t being counted. Let’s take a look at the example veggies above
| Vegetable | Main Content (per 100g) | % protein by weight |
|---|---|---|
| Spinach | Water – 91.4g Total carbohydrate – 3.6g Protein – 2.9g Total fat – 0.4g Other – 1.7g | 2.9% |
| Mushrooms (white) | Water – 92.4g Total carbohydrate – 3.3g Protein – 3.1g Total fat – 0.3g Other – 0.9g | 3.1% |
| Cauliflower | Water – 91.9g Total carbohydrate – 5.3g Protein – 2g Total fat – 0.1g Other – 0.7g | 2% |
| Parsley | Water – 87.7g Total carbohydrate – 6.3g Protein – 3g Total fat – 0.8g Other – 2.2g | 3% |
*Data from SELFNutritionData
As you can see, the percentage of protein content is vastly different from the % reported in the infographic.
Why is this important? In order to know if we are consuming enough protein to meet our daily needs (for the purpose of general good health), we need to know the amount of protein in total that we are eating in each food. Afterall, we generally eat the whole food not just the bits contributing to its calorie content! This is the same for any nutrient that we consume.
The need to combine plant proteins
Protein is made up of amino acids and we need to consume a good range of these amino acids each day, in particular the nine essential amino acids that we cannot make ourselves. Very few plant-based foods contain all the essential amino acids, or enough of them per portion. This means that it is important to ensure that we eat a variety of plant-based protein sources each day.
A few examples of good plant-based protein sources include (protein content based on 100g of the food!):
- Peanuts (raw) – 25.8g
- Tempeh (raw) – 18.5g
- Oats – 16.9g
- Tofu (firm, raw) – 15.8g
- Lentils (boiled) – 9g
- Green peas (raw) – 5.4g
- Chickpeas (canned) – 4.9g (cooked from raw, chickpeas can contain 8.9g protein per 100g)
(All data from SELFNutritionData)
Of course, you need to consider these figures in relation to your portion size – you may not eat 100g of any of the foods listed in a day. 100g gives a nice base for comparison, however.
Be careful what you read and share
A look around the internet suggests that this particular infographic was posted about vegetables to include in juices, which may be why the protein-rich plant foods stated above are not included on it. It is important to fact-check information that we find online – especially if there is no context, reference or source included. The context of the data can make a big difference to its interpretation and use.
