Why I Make an Exception for Collagen, as a Vegetarian

I’m a lacto-vegetarian. I eat dairy and I’ll rarely eat beef, but I don’t eat any other kind of meat, nor eggs. I do this for ethical reasons, which I won’t dwell on in this post.¹ I make one exception: every night, I consume 15 grams of hydrolyzed collagen about an hour before sleeping. Industrially, most collagen is produced from animal skin, which is a byproduct of the meat industry. In this post, I’ll describe my reasoning for making this exception, why it could be a good dietary addition even if you’re an omnivore, and also provide an estimate of how much money I’m giving meat producers every year by purchasing collagen.

First, some facts about collagen:

• It’s the most abundant protein in vertebrates, including humans.

• It’s a structural protein that’s found pretty much anywhere that tissues need to be held together.

• There are 28 types, all of which are present in humans, but more than 90% by mass is type I in skin, tendons, ligaments, bones, and blood vessels.

• All proteins are made of amino acid building blocks, joined in a sequence and then folded. Fully one-third of the blocks in collagen are the amino acid glycine. Collagen is by far the best food source of glycine. The next highest sources (beef/chicken muscle and egg white) have only about 10-20% as much, as a percentage of their protein content.

Your body needs glycine to synthesize its own collagen, i.e. to maintain all of those tissues I mentioned. Glycine is not essential. Your body can make its own. The main mechanism for glycine synthesis depends on how quickly the other product of that synthesis, 5,10-methylene-THF, can be disposed. And it is in lower demand. There are pathways to purge the excess 5,10-methylene-THF, which should free capacity for more glycine synthesis during dietary austerity, but there is some preliminary evidence to suggest that this might not occur. In particular, a biomarker study suggests that both omnivores and vegetarians may be functionally limited by the availability of glycine; i.e. they don’t have any to spare. It is unfortunate that there has not been a more powerful study yet to more clearly demonstrate whether glycine is bottlenecked in this way.

Assuming that the bottleneck is real, a 70 kg adult might only be able to synthesize 3 g/day of glycine. Combined with an average intake of 2-3 g/day across dietary types, this is well below the ~12 g/day due to collagen turnover + ~5 g for the synthesis of glutathione, creatine, heme and other products, all of which are more critical than collagen and will take precedence in the case of competition. The gross collagen turnover of ~12 g/day is likely covered by the glycine recycled from the body’s existing collagen, but there is some waste, and more is needed when the total amount of collagen in the body is increasing day-to-day, such as during anabolism (e.g. exercise-induced) or healing from a major injury.

If I’m really only getting 6 g/day through diet and my body’s own synthesis, and if my body has limited capacity to compensate during austerity, and assuming some overhead due to synthesis of new collagen and waste losses, then I may be several grams of glycine below the optimal dietary intake.

Here’s a major objection: pure glycine supplements are available. So why wouldn’t I just take extra glycine directly and avoid the animal products altogether?²

• It seems to be ideal to take glycine at night, before sleep, as it has sleep inducing³ effects, delayed by about an hour on an empty stomach. In my case,⁴ it does help me to fall asleep, but I lurch awake after 5-6 hours and cannot get back to sleep unless I take more glycine (ideally 1 h before I wake up...), and then I sleep longer than I should. I could try to consume smaller amounts of glycine throughout the day, but 1) this increases friction, and the likelihood that the habit will fail, and 2) some of the positive effects may depend on taking a bolus, i.e. a single larger dose, as from a meal containing a significant amount of collagen.

• Proteins are broken down into smaller pieces and ultimately into single amino acids during digestion. Thinking in the usual terms of “choose your protein sources so you get enough of all the essential amino acids”, we might assume that collagen would be fully digested and absorbed only as its individual amino acids, such as glycine. However, it is well-known that partially digested collagen peptides (in particular, chains of two and three amino acids) are absorbed intact. There is a preliminary study in rats that shows that these peptides end up in skin and connective tissue cells after consumption. It’s uncertain whether they have special signaling properties that might be optimal for collagen synthesis; there are some suggestive but weak studies in vitro (e.g. 1, 2), but these use much higher concentrations of collagen than we should expect to see in human tissues after absorption.

• There are some modest RCTs that support supplementation of hydrolyzed collagen for skin hydration and elasticity, as well as pain in knee osteoarthritis. However, these studies are generally industry-sponsored, which is suspect even though meta-analyses support small-to-moderate effects. It’s unclear whether similar effects should be seen for glycine supplementation alone, however some of the skin RCTs show effects at doses that are low enough that should rule out glycine as the cause (e.g. might be a peptide signaling effect).

• This is more speculative, but suppose that our ancestors tended to eat more parts of an animal. That means higher overall collagen consumption, since muscle tissue is relatively poor in collagen content. At the same time, there were almost certainly populations that didn’t consume so much collagen. Perhaps they suffered for it no more than we do, but that doesn’t mean it’s optimal. Evolved systems tend to fail gracefully as much as they can; bad joints and slow healing are a hindrance rather than an obvious death sentence.

In summary, I consume extra dietary collagen:

1. To ensure I’m not bottlenecked on glycine availability for tissue growth and healing.

2. Because I cannot consume pure glycine without disrupting my sleep, or consuming it on an inconvenient and possibly less-effective schedule.

3. More weakly, because partially digested collagen may serve as a signal for tissue growth or something else that was ancestrally relevant.

Note that this is a conservative measure, and based more in uncertainty than in definitive evidence. If you want to take a similarly conservative measure, then depending on how relevant 2 and 3 are to you, you could supplement pure glycine instead.

Note that the amount of collagen I consume is equivalent to only 3 g/day of glycine, and if glycine really is bottlenecked or I’m in certain high-demand situations (e.g. healing from a major injury) this might not be conservative enough.

Now: how much money am I giving to meat producers by doing this?

• 15 g/day → 5,475 g/year → 12 lbs/year

• $35/lb (CAD) → $420/year

• Assuming 5-10% goes to meat producers → $21 to $42/year

For now, I’m okay with offsetting the $42/year ostensibly going to meat producers.

In the future, we should:

• Market time-release glycine supplements which mimic the plasma kinetics of a high-collagen meal. This is doable today, and might be enough to get me to switch away from collagen supplementation. Of course it remains to be seen whether enough demand can be generated to make it profitable in the current environment.

• Determine whether there is a bottleneck on glycine synthesis, and how this varies between individuals.

• Determine the importance of the different partially-digested collagen peptides, and how this varies between individuals. Likewise, potentially market a time-release and fully synthetic glycine + di-/tri-peptide supplement that avoids the meat industry altogether. This is doable today, but there isn’t strong evidence to support that it is more useful than just a time-release glycine supplement.

---

1. Here’s the short version: I think it’s likely (90%+ confident) that most farmed animals can suffer in a way that is meaningfully similar to how I can suffer, even though their suffering is probably less rich. If that is true, then factory farming is a kind of perpetual holocaust that our civilization is committing. But even if I were merely significantly uncertain (conservatively, say >5% confident) that animals can suffer as such, that would be sufficient to induce my to avoid meat. Torture is that intolerable to me; there is no alternative, if I don’t want to be a stupendous hypocrite. I more or less rely on Brian Tomasik’s estimates about where the most suffering occurs. The reason I am more willing to eat dairy (and rarely beef) is that cows are generally not raised in torturous conditions, and may even have net-positive lives.

2. You can get glycine from other sources. If you want to increase the amount of glycine in your diet by 3 g, you’d need to eat only 15 g of hydrolyzed collagen, or:

• ~300 g of chicken or beef muscle

• 24 large egg whites

• ~75 g of protein from pea/soy protein isolate (3-4 scoops or so)

• ~180 g of whey powder (8-9 scoops or so)

• ~750-900 g of firm tofu

• ~125 g of wheat gluten, say as ~300 g of fresh seitan

That’s a lot of protein to consume just to increase glycine. It also means that if there are effects that depend on the peak blood concentration of glycine, or on the presence of partially-digested collagen peptides, these effects would be reduced or absent for these alternative sources.

3. Note that the sleep induction studies are industry sponsored, which makes them less credible.

4. There is individual variability in response to glycine, which is consistent with the inconclusive results seen by LessWrong users who experimented on themselves with glycine supplements.