People in my circle have been talking a lot about the Impossible Burger, which is a plant-based meat substitute designed to imitate the flavor of, and to compete with, ground beef hamburgers. Discussion so far has largely focused on how the taste compares to beef hamburgers. This is my attempt to compare the Impossible Burger to beef on nutrition. I’m not comparing price, since availability is still limited and the current price is unlikely to remain stable over time.
This post was difficult to write, and doesn’t reach any clear conclusions about which is better. This isn’t because I think they’re equivalent, or close to equivalent; rather, I think it’s probably the case that the Impossible Burger is either significantly more or less healthy than beef, but am left with considerable uncertainty about which way the difference goes. This is due to a combination of uncertainty about the Impossible Burger’s actual chemical composition (some important details aren’t disclosed) and uncertainty about how healthy beef is (the quality of research in this area is quite poor). Ultimately I was forced to settle with identifying the relevant differences, flagging many of them as subject to uncertainty and/or controversy, and leave it at that.
The Outside View
Both beef and the Impossible Burger fall in reference classes with possible health concerns. Beef is red meat; the Impossible Burger is a processed food. Red meat is correlated with bad health outcomes in observational studies (here’s a meta-analysis); unfortunately this is a study methodology with an extremely poor track record, and there isn’t really anything better to go on. Intervention studies exist, but none that are long-term enough to measure mortality, only indirect biomarkers, and they find no effect (meta-analysis).
There are a number of differences between the Impossible Burger and beef, so to keep track of them all, here’s a nutrition-facts-panel-style table. More detail on each of the rows where there’s a difference below.
The Impossible Burger FAQ says that “bioavailable protein, iron, and fat content are comparable to conventional 80/20 ground beef”, but the fat content on the label matches more closely to 85/15 ground beef, so I’ll use that as the basis for comparison. (Beef is notated as percent-lean/percent-fat, and typically ranges from 93/7 to 70/30, with 80/20 or 85/15 most commonly used in hamburgers.)
Impossible Burger ingredients: Water, Textured Wheat Protein, Coconut Oil, Potato Protein, Natural Flavors, 2% or less of: Leghemoglobin (soy), Yeast Extract, Salt, Soy Protein Isolate, Konjac Gum, Xanthan Gum, Vitamin C, Thiamin (Vitamin B1), Zinc, Niacin, Vitamin B6, Riboflavin (Vitamin B2), and Vitamin B12.
Other information sources:
* Estimated based on ingredients list, but probably pretty accurate
** Estimated based on ingredients list, with a large error margin
† A difference that’s significant but where it’s unclear or controversial which is better
The fat in the Impossible Burger comes from coconut oil, which is mostly composed of medium-chain triglycerides (MCTs). MCTs are commonly used by people trying to induce ketosis – that is, to make their body use fat for short-term energy needs (as opposed to making cell membranes out of it, storing it in the liver for use over a longer time horizon, or storing it in fat cells for long-term storage). This is probably a good thing, but it’s unusual, and puts the Impossible Burger in a distinctly different nutritional niche than beef burgers, and may interact strangely with unusual metabolisms.
Beef contains both omega-3 and omega-6 fats, while the Impossible Burger contains neither. The standard line is that absolute quantity of omega-3 and omega-6 fats doesn’t matter, but ratio does. Unfortunately, there isn’t a clear answer to what the ratio or amounts are in typical ground beef; they depend on both the breed of cow and on what it ate (grass-fed beef leads to a more favorable omega-3 ratio), and the 3:6 ratios range from 1.8 to 13.6. The former is probably good, the latter is probably bad. Beef also contains vaccenic acid, which is a trans-fat. Trans fats as a category have been found to have detrimental health effects, but this was based on the distribution of trans fats that resulted from partial hydrogenation.
Overall, the Impossible Burger’s fat is probably better than beef fat.
The main dietary purpose of beef, as eaten in practice, is to provide protein. With regards to protein, the nutrition facts panels of ground beef and the Impossible Burger look pretty similar; beef has more, but only slightly (23.6g vs 20g per 85g serving). However, not all protein is created equal; proteins are made up of amino acids in varying proportions, and if something contains more of the amino acids you don’t need but lacks the amino acids that you do, that’s not ideal.
From the ingredients label, the protein in the Impossible Burger mainly comes from textured wheat protein and potato protein, with additional small amounts from leghemoglobin, yeast extract, and soy protein isolate. The proportions aren’t disclosed, nor is the overall amino acid profile. There’s a reasonably good justification for this; providing that information isn’t customary for processed foods, and their upstream ingredient suppliers don’t necessarily provide amino acid profile information either. Still, we can infer some things about the protein in the Impossible Burger based on the order of the ingredients list: at least 13g of textured wheat protein, between 2g and 7g of potato protein, at most 1.7g of leghemoglobin and yeast extract, and at most 430mg of soy protein isolate. The closest I could find to a public statement about the amino acid profile of the Impossible Burger is a tweet saying
The #impossibleburger contains all essential and non-essential amino acids. The amount of bioavailable protein is comparable to beef.
This isn’t entirely reassuring. Suppose they had taken a large amount of bioavailable but incomplete protein, and mixed in a small amount of complete protein. That would make the statement true, but it would be nutritionally poor. As it turns out, potato protein is a complete protein and wheat protein isn’t, so this might in fact be what happened. Depending what part of the plant you use, wheat has a Protein Digestibility Corrected Amino Acid Score somewhere between 0.25 and 0.53, as compared to 0.92 for beef. I checked out some producers of textured wheat protein, but they didn’t disclose their amino acid profile either.
The component that gives beef much of its distinctive flavor is hemoglobin, which is a blood protein that transports oxygen in mammals. The Impossible Burger’s signature ingredient is leghemoglobin, a protein which provides a similar taste and color. Leghemoglobin was originally isolated from the roots of soybeans, and is produced using genetically modified yeast. Leghemoglobin is the Impossible Burger’s most controversial ingredient, largely because of publicity around Impossible Foods’ conversations with the FDA, which were publicized when an environmentalist organization, ETC Group, used a FOIA request to get them. This was then used as a platform to criticize FDA practices in general.
The FDA’s concerns, however, were specifically about allergenicity. With some searching, I was able to find one report of an allergic reaction possibly related to the Impossible Burger. I contacted the author of that post, and they reported that blood tests failed to identify any allergies, and the only time they’ve ever had an allergic reactions was the one time they tried the Impossible Burger. That is the only example of a possible allergic reaction to the Impossible Burger I could find; if there are others, they haven’t been written about publicly. And it’s somewhat speculative; it might’ve been a reaction to something else, since they (understandably) didn’t try it again. Overall, leghemoglobin doesn’t concern me very much; trying it doesn’t seem notably higher risk than trying any other new food processed food, and if there does turn out to be an allergenicity problem, I expect we’ll find out (with prevalence numbers) soon enough.
The Impossible Burger lists “natural flavors” on the ingredients above the 2% mark, meaning at least 2% of it consists of undisclosed ingredients from that category. Those ingredients could potentially be bad.
Beef contains creatine, which was found to have cognitive benefits when given as a supplement to vegetarians (but not to meat eaters).
The Impossible Burger contains 5g of carbohydrates (most likely as impurity in the textured wheat protein). If it’s on a bun, this is pretty small. It does make the Impossible Burger less suitable for low-carb/ketogenic diets, though.
Overall, the Impossible Burger seems good enough from a nutrition perspective to be competitive with beef. However, I have reservations about aspects of its composition that aren’t publicly known, particularly the amino acid profile and what might be lurking under the “natural flavors” heading. Limited availability means I won’t be eating this in the short term, but once it’s sold in grocery stores and reaches a price not too much higher than ground beef, I’ll probably start eating it.