Where to start
These guides answer a narrow question: in which everyday foods has a compound been measured, and how much did the studies find? Each page takes one compound and reports published values for foods, with the unit, the sample and the year. They do not say what a compound does in the body, and they recommend no amount.
The five pages cover spermidine, taurine, betaine, glycine and astaxanthin. For the rules that govern what a pack may say about a food, read how to read a food label.
How food composition values are produced
A value in a food table comes from a laboratory analysis of samples, or from a compilation of earlier analyses. Researchers collect samples of the food, prepare them in a stated way and measure the compound with an analytical method. The result is expressed in a unit such as milligrams per kilogram, milligrams per 100 grams or grams per 100 grams, and it describes those samples, not every example of the food.
Several choices change the number. Whether the food is raw or cooked, how it was cooked, the variety and origin of the sample, the season and the analytical method can all move a value. The guides in this topic show examples: the same food can differ between two studies, and cooking can remove part of a compound that dissolves in water.
Why two tables rarely agree
- Units differ: per kilogram, per 100 grams, per serving or per gram of dry matter.
- Samples differ: a food bought in Spain in one study and a mix of published values in another.
- Methods differ: two laboratories can report different numbers for the same sample.
- States differ: raw, boiled, grilled, baked or processed.
- Compounds differ: one compound, or a total of several related ones.
Each guide converts units where it helps, flags the conversions it made itself and avoids ranking two sources against each other when they used different methods.
All guides in this topic
Spermidine: which foods contain it?
Two studies read in full on October 27, 2026: an analysis of 109 foods sold in Spain (Foods, 2021) and a food database built from published studies (Food & Nutrition Research, 2011).
Taurine: which foods contain it?
Three publications read on October 27, 2026: a 1990 study of common foods, a 2003 study of cooking and a 2020 review.
Betaine: which foods contain it?
Two publications read on October 27, 2026: the measurements by Zeisel and colleagues (Journal of Nutrition, 2003) and the review by Craig (American Journal of Clinical Nutrition, 2004).
Glycine: which foods contain it?
Glycine values from the USDA FoodData Central database, with the PubChem record, a review on collagen structure and the European gelatin manufacturers, read on October 27, 2026.
Astaxanthin: which foods contain it?
Sources and amounts from the review by Ambati and colleagues (Marine Drugs, 2014) and two opinions of the European Food Safety Authority (EFSA), from 2020 and 2026, read on October 27, 2026.
Words you will meet on these pages
- Polyamine
- A small nitrogen-containing molecule found in all living organisms; spermidine is one.
- Amino acid
- A building block of proteins; glycine and taurine-related compounds are discussed in these guides.
- Carotenoid
- A family of red, orange and yellow pigments; astaxanthin belongs to it.
- Dry matter
- What remains of a food once its water is removed; some tables use it as the basis of a value.
- Novel food
- In European Union law, a food that was not consumed to a significant degree in the Union before May 1997 and that needs an authorization.
- Acceptable daily intake
- A safety limit set by a scientific panel; it is not an amount to aim for.
What these pages do not say
- They attribute no property to any compound.
- They recommend no amount, per day or per meal.
- They repeat no regulatory wording that applies to a specific product.
- They rate no product and name no brand.
To adapt your diet to your situation, a doctor or dietitian can advise you. These pages present food composition data and do not replace medical advice.
How these guides are made
Each guide is written for readers in the United States. It names its sources, gives the date on which each was read and says whether the full text or only the abstract was read. Values are quoted as published, and any conversion made by the guide is labelled as such.
Frequently asked questions
Are these guides medical advice?
No. They present food composition data from named studies and databases. They attribute no property to any compound, recommend no amount and do not replace advice from a doctor or a dietitian, who can take your own circumstances into account.
Which guide should I read first?
Start with the compound you have seen mentioned: spermidine, taurine, betaine, glycine or astaxanthin. Each page lists the foods in which published studies found it and explains why the numbers vary. The Where to start section links all five.
Why do the numbers differ between sources?
Because units, samples, methods and the state of the food differ. The same food can give different values in two studies, and cooking can change what remains. The guides flag these differences instead of ranking one source against another.
Do these guides say how much to eat?
No. They report which foods contain a compound and how much researchers measured, and they say explicitly that they recommend no amount. A safety limit quoted from a scientific panel is not an amount to aim for.