Was thinking about eating tofu instead of eggs as a protein source so I did some research.
Essential amino acids are the main concern here of course, because that?s the primary reason we?re eating the protein in the first place ? to get nutrients that our body needs so that we don?t die. I also look at content of branched-chain amino acids (BCAA) because they are of particular interest to physically active people (like myself). Then I make some observations about other nutritional content and stuff.
I am going to try to make this as unbiased as possible. Just stating facts and comparing things.
Biological Value
First let?s start with bioavailability of protein:
?Biological value (BV) is a measure of the proportion of absorbed protein from a food which becomes incorporated into the proteins of the organism?s body. It captures how readily the digested protein can be used in protein synthesis in the cells of the organism. Proteins are the major source of nitrogen in food. BV assumes protein is the only source of nitrogen and measures the proportion of this nitrogen absorbed by the body which is then excreted. The remainder must have been incorporated into the proteins of the organisms body. A ratio of nitrogen incorporated into the body over nitrogen absorbed gives a measure of protein ?usability? ? the BV.? (https://en.wikipedia.org/wiki/Biological_value)
A short and sweet of BV is that while it is not an exact measurement of how much protein is ?utilized? by the body, it does provide insight as to which sources of protein provide greater protein availability than others. If you?re familiar with Glycemic Index (GI https://en.wikipedia.org/wiki/Glycemic_index) it?s kind of like that. It?s a tool to better gauge the effects of certain foods on the body, but it?s by no means an exact measurement device. Point is, foods with a high BV are better utilized by the body. The theoretical (laboratory setting, perfect environment and setup, etc), would mean that 100 BV means that your body is absorbing 100% of the consumed protein, and 50 BV would mean 50% absorption. But actual absorption relies on many factors ? just as eating a cookie (high GI) could yield a lower sugar spike than an apple (lower GI) in certain circumstances.
So what are the BV of eggs and soy? Let?s take a look at some figures (from the BV Wikipedia page, source links on the page):
Chicken egg: 94Soybean curd (tofu): 64
We see here, that eggs have a BV of 94 while tofu has 64. The takeaway is that soy has a BV which is about 68% that of eggs. Does that you mean get 68% of the protein from tofu as you would from eggs? Again, not exactly. Lots of factors at play, etc. But the point is, that?s not just a few points ? that?s a considerable difference.
Essential Amino Acids
?An essential amino acid, or indispensable amino acid, is an amino acid that cannot be synthesized de novo (from scratch) by the organism, and thus must be supplied in its diet. The nine amino acids humans cannot synthesize are phenylalanine, valine, threonine, tryptophan, methionine, leucine, isoleucine, lysine, and histidine.? (https://en.wikipedia.org/wiki/Essential_amino_acid)
??there are three BCAAs: leucine, isoleucine, and valine? The three proteinogenic BCAAs are among the nine essential amino acids for humans, accounting for 35% of the essential amino acids in muscle proteins and 40% of the preformed amino acids required by mammals.? (https://en.wikipedia.org/wiki/Branched-chain_amino_acid)
Egg: https://nutritiondata.self.com/facts/dairy-and-egg-products/111/2
?Firm tofu?: https://nutritiondata.self.com/facts/legumes-and-legume-products/4467/2
?Regular tofu?: https://nutritiondata.self.com/facts/legumes-and-legume-products/4468/2
Observation 1: At a 100g serving of all three food items, ?firm tofu? has the highest overall content, ?eggs? are in the middle, and ?regular tofu? has the lowest protein content. I imagine this is because the reason ?firm tofu? is ?firm? is because it?s more dense. Smash your beans harder together and you have more total bean and therefore more total nutrient.
Observation 2: Regarding protein quality: So I compared serving sizes that are nearly equated for protein content. I would have been ultra specific but the website I used for nutritional data only has a few options for serving sizes. In any case I chose a 1/4 block of ?firm tofu? (81g) which has 12.8g total protein, to compare to 100g of ?whole raw egg? which has 12.6g total protein. A difference of 0.2g protein, not that big of a deal. So on to the amino acids.
Tofu
Here are the essential amino acids provided by the 12.8g of protein in the serving of 81g of tofu:
histidine: 372mgisoleucine: 633mgleucine: 971mglysine: 842mgmethionine: 164mgphenylalanine: 622mgthreonine: 522mgtryptophan: 199mgvaline: 645mg
Total EAA: 4970mgTotal BCAA: 2249mg
Eggs
Here are the essential amino acids provided by the 12.6g of protein in the serving of 100g of eggs:
histidine: 309mgisoleucine: 672mgleucine: 1088mglysine: 914mgmethionine: 380mgphenylalanine: 681mgthreonine: 556mgtryptophan: 167mgvaline: 859mg
Total EAA: 5626mgTotal BCAA: 2619mg
So, with a serving that has 0.2g (200mg) less total protein, eggs still have both higher total essential amino acid content (by 656mg) as well as higher BCAA content (by 370mg).
Conclusion
Well, unfortunately when considering protein, eggs are the clear winner. Tofu has less essential amino acids, less BCAAs, and 68% the BV of eggs. You have to eat nearly double the amount of tofu in order to get the same protein effect as you do from eggs.
Afterthoughts
The following observations are based on the 81g serving of Tofu vs the 100g serving of eggs in order to keep everything based around the overall theme of matching protein content.
– Tofu is lower in saturated fat, lower in monounsaturated fat, and higher in polyunsaturated fats when compared to eggs.
– Tofu is absent of cholesterol while eggs are very high in it.
– Tofu is higher in carbohydrates (eggs have almost 0).
– Tofu has some fiber, eggs do not have any
– Tofu is void of vitamin B12, a nutrient that must be obtained by eating animals or animal products (can?t get B12 from plants). Eggs have decent amount clocking in at 22%DV. I mention this because primary consumers of tofu are vegans and vegetarians and as such, it?s worth keeping in mind that you still won?t find your B12 here.
– Tofu is void of vitmain D. Eggs only have a measly 9% though. Just mentioning this for the same reason as B12. Luckily vegans and vegetarians can go outside and catch some sun for vitamin D (food isn?t the only option). Well, at least that works for half of the year where I live. Less further north, and more further south. Anyway that?s a completely different topic.
– Tofu is very low in all other vitamins, it?s highest one being thiamin at about 10%DV. However, it does have decent mineral content. Calcium at 55%DV and manganese at 48% are the standouts. Eggs have higher overall vitamin content but lower overall mineral content. If you look at overall vitamin/mineral content of each, they end up being pretty comparable in regard to overall micro nutrient profile
