Food Literacy
Part 5 ended on a line worth carrying into this one. Protein is the only one of the three raw materials that carries nitrogen. Carbohydrate and fat are built from carbon, hydrogen and oxygen. Protein adds a fourth element, and that single difference is why your body cannot improvise its way to an amino acid it did not eat.
It is also, as it turns out, how the number on the front of a protein tub gets calculated.
You are standing in an aisle holding two options. One is a plastic jar with a number on the front, 25 grams, in a font larger than anything else on the label. The other is a bag of hemp seeds with no claim on it at all. The honest question is not which one is healthier. It is a narrower and more useful question: what does that 25 actually mean, and who verified it before it reached the shelf?
The principle. The protein number on a label is not a count of protein. It is a measurement of nitrogen, multiplied by a fixed conversion factor. That works because protein is where the nitrogen is. It also means the number describes an element, not a quality, and not a source.
The Number Comes From a Nitrogen Test
The rule is written down, and it is short. 21 CFR 101.9(c)(7), the paragraph of federal food labeling law that governs protein, says “protein content may be calculated on the basis of the factor 6.25 times the nitrogen content of the food.” The measurement is a standard laboratory nitrogen test, and the result is multiplied by 6.25 because protein averages roughly 16 percent nitrogen by weight, and 100 divided by 16 is about 6.25.
A tub is a supplement, so it carries a Supplement Facts panel written under a different rule, 21 CFR 101.36. That rule does not restate the protein math. It points at the first one: under 101.36(b)(2)(ii)(A) the amounts on a Supplement Facts panel “shall be expressed in the increments specified in § 101.9(c)(1) through (7).” Different panel, same arithmetic.
Nothing about that is a scandal. It is how protein has been measured in food chemistry for over a century, and for a whole food it works well, because in a lentil or a hemp seed essentially all the nitrogen is sitting inside actual protein.
What it means is more interesting once you are looking at a manufactured powder rather than a seed. The test cannot tell where the nitrogen came from. Any nitrogen-bearing compound in the tub counts toward the total, whether or not it is a complete protein and whether or not your body can build anything out of it. Free amino acids sold cheaply by the kilogram carry nitrogen. So do several compounds that are not protein at all. The chemistry does not distinguish, because it was never asked to.
One guardrail does exist, and it is worth stating rather than leaving the gap sounding wider than it is. Under 21 CFR 101.36(b)(2)(i), “protein shall not be declared on labels of products that… contain only individual amino acids.” A tub of free amino acids cannot call them protein. What the rule does not do is govern the mixture: a real protein with other nitrogen-bearing ingredients alongside it is measured as one number.
This is not a claim that your tub has been tampered with. It is the reason the number on the front deserves less weight than its font size suggests, and the reason DD keeps pointing you at ingredient lists instead. Part 7 covered how to read one.
The detail almost nobody notices. The grams line and the Percent Daily Value line are computed two different ways. The Percent Daily Value must use a corrected figure, the grams multiplied by a protein quality score (101.36(b)(2)(iii), routing to 101.9(c)(7)(ii)). The grams line gets no such correction.
And here is the part that turns it around. That same rule reads “the percent Daily Value for protein, when present”, because on a Supplement Facts panel the protein Percent Daily Value is optional. So the quality-adjusted number is the one a company may leave off, and the uncorrected one is the number in the big font.
Who Checked It Before It Reached the Shelf
A protein powder is almost never sold as a food. It is sold as a dietary supplement, which is a different legal category with a different rulebook, set by the Dietary Supplement Health and Education Act of 1994.
Here is how the Food and Drug Administration describes its own role, in its own words: manufacturers and distributors “are responsible for evaluating the safety and labeling of their products before marketing,” and the agency “has the authority to take action against any adulterated or misbranded dietary supplement product after it reaches the market.”
Read those two halves together. The company evaluates its own product. The regulator arrives afterward, if something goes wrong and somebody notices. That is not a loophole somebody found; it is the design, written into the statute in 1994. It is the same shape as the story the Apeel article tells about self-certified safety, and it is worth recognizing in both places.
One more piece of the label is worth knowing. If a tub lists a “proprietary blend,” federal rules at 21 CFR 101.36(c)(3) require the label to print only the total weight of the blend. The ingredients inside get listed in descending order by weight, which tells you the ranking, but the individual amounts are not required. A blend can be honest and still tell you almost nothing about proportions.
The Heavy Metal Question, Answered Honestly
You have probably seen a headline about heavy metals in protein powder. The findings are real and so is the context, and DD is going to give you both, including the part that cuts against the alarming version.
What was found: Consumer Reports tested 15 protein powders and reported that three servings a day of some products exceeded limits proposed by the United States Pharmacopeia, a standards-setting organization. A larger follow-up tested 133 products and reported elevated levels in about 40 percent of them.
What happened next, which got far less attention: Bandara and colleagues (Toxicology Reports, 2020) ran a formal risk assessment on those reported concentrations, comparing arsenic, cadmium, mercury and lead against Environmental Protection Agency reference doses. Their cumulative hazard index came in below 1, and they concluded that the exposures “do not pose an increased health risk” at one or three servings a day. The highest values, approaching but not crossing the threshold, were in mass gain products. The lowest were in whey.
And the disclosure that belongs beside it: all three authors of that risk assessment work for a consulting firm that does this kind of analysis on retainer. That does not make the arithmetic wrong. It does mean the paper should be read as one input rather than as a verdict, exactly as the advocacy testing should be.
Which leaves a smaller, sturdier conclusion than either camp is selling. The measured levels look unlikely to hurt anyone at normal intake. The thing worth reacting to is that consumer groups were the ones doing the measuring. Nobody was required to look first.
So How Good Is Plant Protein, Actually
Here DD has to be careful, because this is the point where a plant-first site is tempted to overclaim, and the evidence does not support it.
Protein quality gets scored two ways. The older one is the Protein Digestibility Corrected Amino Acid Score, which is what federal labeling still uses. The newer one, recommended by the Food and Agriculture Organization of the United Nations in 2013, is the Digestible Indispensable Amino Acid Score. The difference matters: Mathai and colleagues (British Journal of Nutrition, 2017) compared the two in pigs and found the older style of score came out higher than the newer one for pea protein concentrate, wheat, and both soy forms they tested, which they read as the older method overestimating those proteins. It ran high for skimmed milk powder too, so this is not purely a plant story. The generous number is the one the label uses.
Herreman and colleagues (Food Science and Nutrition, 2020) scored 5 animal and 12 plant proteins on the newer scale. One caveat belongs in front of the table rather than under it: these categories use the reference amino acid pattern for children aged six months to three years, which is the pattern the scoring system is built around, and scores shift if a different pattern is used. The result is still not the one either side of this argument wants.
| Digestible Indispensable Amino Acid Score | What scored there |
|---|---|
| Above 100 excellent quality |
Casein, egg, pork, and potato protein |
| 75 and above high quality |
Whey, soy |
| Below 75 no quality claim |
Pea, hemp, oat, rice, corn, fava bean, canola, lupin, rapeseed, gelatin |
Two things there deserve saying out loud. Hemp and pea both land in the bottom band, so anyone telling you a hemp or pea powder out-scores whey on protein quality is not reading the same table. And potato protein scored with egg and casein, which is the genuine surprise in the data and almost never mentioned anywhere.
Two disclosures belong here too. All four authors of that paper work at a potato protein company, and potato finishing at the top of their table is a fact a reader should weigh. And soy appears in the table because removing it would misrepresent the evidence; DD reports it and does not recommend it, consistent with everything else on this site.
For hemp specifically, House and colleagues (Journal of Agricultural and Food Chemistry, 2010) measured it directly. Whole hemp seed scored 49 to 53 percent on the older scale with protein digestibility of 84.1 to 86.2 percent. Dehulled hemp seed scored 63 to 66 percent, with digestibility of 83.5 to 92.1 percent. Lysine, an amino acid your body cannot make, was the first limiting amino acid in every hemp product tested. Taking the hull off improved both the digestibility and the score, which is the paper’s own conclusion.
So hemp is not a protein champion, and DD is not going to pretend otherwise. What hemp is, is a seed. It arrives with its fat, its fiber and its minerals still attached, which is the argument DD makes about food generally and does not need to inflate here.
And the finding that resolves it. The same paper reports that plant proteins complement each other: mixed in the right ratios, they reach a quality score none of them hits alone, and the authors conclude this shows “the potential to achieve an optimal nutritional efficiency with plant proteins alone.” The specific pairings they modeled were potato, soy and pea against the other plant proteins. Separately, and this is general nutrition rather than a finding of that paper, the amino acid running short in hemp and in grains is lysine, and legumes are where lysine is plentiful: lentils, beans and chickpeas. Eating across a week does the work that no single seed does.
The Question Underneath All of It
Before optimizing a supplement, it is worth knowing whether the gap it fills is there. Berryman and colleagues (American Journal of Clinical Nutrition, 2018) analyzed protein intake across nearly 58,000 people aged two and older in the national health and nutrition survey. Usual intake was above the estimated average requirement in every demographic group they measured. Adults aged 19 to 30 averaged 88.2 grams a day. Among adults, relative intake ran from about 1.10 grams per kilogram of ideal body weight in those aged 71 and over up to roughly 1.32 in some groups. Two different reference numbers matter here and they are often mixed up: the estimated average requirement, the bar that study used, is 0.66 grams per kilogram, and the recommended dietary allowance, the more familiar figure, is 0.8.
That is a population average, not a statement about you, and there are real reasons an individual might want more: heavy training, recovery, pregnancy, older age, or simply a day that got away from you. But it reframes the aisle. For most people most of the time, a powder is solving a convenience problem, not a deficiency.
Where Diet Discipline Stands
Separating the evidence from the opinion, the way we do whenever a topic has a marketing budget attached.
The evidence: the label number is a nitrogen measurement times 6.25. Supplements are self-evaluated before sale and policed afterward. Proprietary blends disclose a total and not the parts. Heavy metals have been found in testing, and the one published risk assessment put the exposure below the threshold of concern. Hemp and pea score in the lowest protein quality band; whey scores higher; mixed plant proteins score higher than any of them alone. Most American adults already exceed the requirement.
Not established: that protein powder is harmful at normal intake. We looked for that and did not find it, and we are not going to imply it because it would make a better headline.
Our position: a protein powder is a convenience format, not a food group, and it should be bought the way you would buy any manufactured product whose maker graded its own homework. Read the ingredient list rather than the front. Prefer a short one. Prefer a brand that pays for independent testing, because the law does not make anyone do it. And treat the tub as the backup rather than the plan, because a scoop delivers one isolated fraction while a seed or a bean delivers the fraction plus everything it grew attached to.
Myth vs Reality
Myth: Plant proteins are incomplete, so you have to combine them at every meal.
Reality: Plant foods contain all the essential amino acids, in differing amounts, and one is usually scarcer than the rest. Variety across the day and the week covers it, which is what the complementarity finding above describes.
Myth: A higher number on the tub means a better product.
Reality: The number is nitrogen times a conversion factor, and it says nothing about the amino acid profile, the digestibility, or what else came along.
Myth: Someone at a federal agency approved this before it was sold.
Reality: For a dietary supplement, the manufacturer evaluates its own product before marketing, and the agency acts after it reaches the market.
Myth: Hemp protein beats whey.
Reality: On the current scoring system hemp sits in the lowest band and whey in a higher one. The case for hemp is that it comes as a whole seed, not that it wins the score.
The Protocol
1. Turn the tub around. Two minutes. Ignore the front entirely. Find the ingredient list and count the items before the first thing you do not recognize. A short list is a real signal; a long one is not automatically bad, but it is a reason to keep reading.
2. Look for the words “proprietary blend.” If they are there, you are being told a total and a ranking, not amounts. That is legal and it is also a limit on what you can know. Decide whether you are comfortable with it rather than assuming it means nothing.
3. Look for an independent testing mark. Third party certification is voluntary, which is exactly why its presence tells you something. A company that pays for outside testing chose a check the law did not require.
4. Add the lysine, not another scoop. If seeds and grains are carrying most of your protein, the amino acid running short is lysine. Lentils, beans and chickpeas are where it is. This is a grocery decision, not a supplement decision.
5. Ask what the powder is for. Convenience on a hard day is a legitimate answer. Filling a deficiency is a different answer and worth checking, given that most adults already clear the requirement.
What to Watch Over 2 to 4 Weeks
Track how many of your protein grams arrived attached to something else. A cup of lentils brings protein plus fiber plus iron plus folate. A scoop brings protein. Neither is wrong, and the ratio between them is the thing worth knowing about your own week.
Notice hunger, too. Whole food protein arrives with fiber and water and takes longer to leave your stomach, and many people find a meal holds them longer than a shake of the same size does. That is a subjective signal rather than a measurement, and it is still information.
Your action step, today.
Pick up whatever protein product is in your kitchen right now and find two things on it: the ingredient list, and whether the words “proprietary blend” appear anywhere.
You now know what the big number on the front measured, and what nobody was required to measure. That is the whole skill, and it transfers to every tub on that shelf.
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