Margaric acid

Margaric acid, also called heptadecanoic acid (17:0, C17H34O2), is a saturated fat with 17 carbons. That is an odd number, while most saturated fats in the body have an even number of carbons. Pure, it is a solid that melts at 61.3 °C.

In 1957 chemists reported it in butterfat and in mutton fat. It is still found mainly in dairy fat and in the fat of ruminant animals such as cattle and sheep. Its 15-carbon neighbor, pentadecanoic acid (C15:0), has its own page: see pentadecanoic acid.

What sets margaric acid apart is its use as a marker. Researchers use its level in blood as a sign of how much dairy fat people eat. In large cohort studies (studies that follow big groups of people for years), people with higher levels had a lower risk of type 2 diabetes. The catch is that the body makes some of its own.

In a 7-day human trial, fiber and propionate raised it. In mice, an enzyme called HACL1 supplies part of it. So a high level does not prove that someone ate more dairy, and nothing shows that eating more of it helps.

The name is also older than the molecule. In the 1800s, “margaric acid” was a pearly fat that turned out to be a mixture of two other fatty acids. The real 17-carbon acid kept the name. The story is in the history section below.

Health benefits of margaric acid

• ★★Dairy servings nudged blood margaric acid upIn 124 healthy adults, 3 dairy servings a day for 4 weeks raised blood 17:0 (margaric acid) slightly, to 0.42% of fatty acids against 0.39%. The test food was dairy as a whole, not margaric acid alone.
• ★Blood 17:0 may not mark dairy intakeIn a trial of 30 young adults, a high-dairy diet raised 15:0 but not 17:0. In 62 adults, 17:0 stopped tracking dairy fat once liver fat was counted.
• ★Inulin fiber raised blood 17:0 in 7 daysIn 16 healthy adults, 30 g a day of inulin, a fiber, raised blood 17:0 by 11% in 7 days. Propionate (6 g a day) raised it by 13%, and cellulose had no effect.
• Population studyLinked to less type 2 diabetesPooling 16 studies of 63,682 people, high blood 17:0 (90th percentile) went with 0.65 times the diabetes risk of low (10th percentile). In a European study, each typical step up in 17:0 (1 SD) went with 0.67 times the risk.
• Population studyLinked to less cardiovascular diseaseAcross 18 studies, the top third of blood 17:0 had 0.86 times the cardiovascular risk of the bottom third. These markers cannot tell dairy foods apart, and most were measured only once.

Foods high in margaric acid

Margaric acid comes mostly from the fat of ruminant animals. In a test of foods, butter held 423 mg of C17:0 per 100 g; nonfat dairy products had none that could be detected. Some fish carry it too: pinfish and mullet had 41 and 67 mg per 100 g, and capelin had none.

Dairy fat and beef carry about twice as much 15:0 as 17:0. Seafood and human tissue are the other way round, with about twice as much 17:0 as 15:0.

In our USDA ranking the amounts are small. Per serving, ground beef leads with 0.25 g in 4 oz (113 g). Then come farmed Atlantic salmon, macadamia nuts, olives and semi-skimmed cow’s milk at 0.03 to 0.04 g. Per 100 g, ground beef has 0.22 g, olives 0.15 g and macadamia nuts 0.12 g.

Nuts and olives rank high in USDA data. But the human studies we found tie blood 17:0 to dairy, fiber, wheat, coarse grains and fish, not to those foods. In one trial, 3 servings a day of dairy lifted plasma 17:0 only from 0.39% to 0.42% of fatty acids.

How margaric acid works

Most of what is known about how the body handles margaric acid comes from one small human trial, mice and cells. Four ideas matter. Some of it comes from food, and some is made from fiber by gut bacteria and the liver. Its blood level is a shaky stand-in for dairy intake, and no one knows if it does anything itself.

We found no study that tracked how well the body absorbs margaric acid on its own.

Food and the body both supply it

The ratio of 15:0 to 17:0 is about 2 to 1 in dairy fat and beef. In human plasma it is about 1 to 2, which is hard to explain by diet alone. A review of odd-chain fatty acids lists alpha-oxidation as one possible way the body makes them.

A mouse study supports it: mice without the HACL1 enzyme had about 26% less 17:0 in plasma. In human cells, the ELOVL6 enzyme lengthened 15:0 to 17:0.

Fiber can raise it

In 16 healthy adults, 7 days of inulin (a type of fiber) or propionate raised plasma 17:0, and cellulose did not. In heart attack survivors, 17:0 tracked fiber intake as well as dairy. In a study of 746 adults, it went with fiber too. The authors of the trial suggest that part of the diabetes link seen for odd-chain fatty acids may relate to fiber.

The body’s routes in one picture

Why it is a shaky dairy marker

A marker is only as good as its link to the food. In a controlled diet trial of 62 adults, 15:0 and 17:0 stopped tracking dairy fat once liver fat was counted. In a young-adult trial, a dairy diet raised 15:0 but not 17:0. In children, dairy fat correlated with 17:0 at the start (r = 0.25) but not after 12 weeks.

In the Food4Me study, repeat blood measures agreed less for 17:0 than for 15:0 (repeatability score 0.32 against 0.62). In rats, more dietary fat lowered 15:0 but not 17:0. So 15:0 is usually the better marker. 17:0 is better treated as a mixed signal of dairy, fiber and the body’s own metabolism.

What has been seen in people

In people, higher blood 17:0 went with lower diabetes risk in pooled cohorts (0.65 times the risk across 16 cohorts). It also went with lower heart disease risk in a meta-analysis (0.86 times the risk). These are observational links.

The trials that raised 17:0 changed dairy, fiber or propionate at the same time. The one mouse study that added 17:0 itself saw no benefit for fatty liver or insulin resistance. So the data fit a marker of a healthy pattern better than a fat that protects on its own.

How much margaric acid do you need?

No official body sets a daily amount of margaric acid. The FDA has set no Daily Value for it and the EU no EU Reference Intake. We found no intake value for it in the 2010 report on fats from the UN food and health agencies (FAO and WHO).

It is not an essential fatty acid, and the body makes some of its own, so there is no daily need to meet. We found no deficiency state tied to a lack of it, and no national survey of how much people eat.

Forms of margaric acid: absorption and effects

We found no trial of margaric acid as a supplement. It reaches people in dairy and ruminant fat, in fish fat, indirectly through fiber, and as a lab chemical used in fatty acid testing. The honest bottom line is that no study compared forms, and no study in people gave it as a capsule.

Form	What it is	What studies show	Source
Dairy fat, beef and mutton fat	17:0 inside triglycerides with other fatty acids	Butter held 423 mg per 100 g and nonfat dairy none detectable. Three servings a day of dairy raised plasma 17:0 from 0.39% to 0.42% of fatty acids. It was reported in butterfat and mutton fat in 1957.	1, 2, 8, 9
Fish	17:0 in fish fat	Pinfish and mullet had 41 and 67 mg per 100 g and capelin none. Fed to dolphins, they raised daily C17:0 intake from 400 to 1,700 mg and serum 17:0 rose. There was no human trial.	1
Fiber and propionate	Not margaric acid: gut-made propionate the liver can turn into odd-chain fats	In 16 adults, 7 days of inulin (30 g a day) or propionate (6 g a day) raised plasma 17:0 by 11% and 13%. Cellulose did not.	3
Pure C17:0 and methyl heptadecanoate	Lab chemicals used as a standard in fatty acid analysis	Historically used as internal standards, because they were thought to be too scarce in humans to matter. Tallow contains methyl heptadecanoate, so the standard did not work well for tallow-based biodiesel tests.	5, 6, 7
Added C17:0 (supplement-type use)	Pure C17:0 mixed into feed	We found no trial in people. In mice on a high-fat diet, 20 weeks of added C17:0 did not prevent fatty liver or insulin resistance.	4

One thing most readers do not expect: before it became a marker, chemists used C17:0 as an internal standard. That is a known amount added to a sample so other fatty acids can be measured against it. A review notes that this rested on the belief that humans had little of it.

A 2017 milk method also used C17:0 as the internal marker. Since milk fat and tallow carry some, a lab has to check that its sample does not.

Is margaric acid safe? Supplements, dose and interactions

At food amounts, margaric acid is not a concern in any source we found. We found no upper limit from any authority and no human trial of a margaric acid supplement. So there are no dose or safety data for one. The points below come from the studies on this page.

• No supplement data. The only added-C17:0 experiments are in mice and cell dishes. Dolphin results come from a small study with no control group. Its findings are part of a patent application, so they are not a guide for people.
• Mixed signals in older adults. In the Cardiovascular Health Study, high 17:0 went with fewer cardiovascular deaths (0.77 times the risk) but more non-cardiovascular deaths (1.27 times). It had no link with total deaths, and the cause of that extra risk was not clear.
• Cell studies are not advice. Margaric acid killed pancreatic and lung cancer cells in dishes. No animal or human cancer data came with those papers, so it is not a cancer treatment.
• It is still saturated fat. The 49-study meta-analysis that found lower risk with 17:0 also found higher risk with even-chain saturated fats. Its authors back current advice to cut saturated fat. If you have diabetes, heart disease or high LDL cholesterol, talk to a doctor or dietitian before changing your diet.

How to get more margaric acid

• Food sources. The fat of dairy, beef and mutton leads, with ground beef at 0.25 g in 4 oz in our ranking. Remember that nonfat dairy had none that could be detected.
• Fiber. In a 7-day trial, 30 g a day of inulin raised plasma 17:0 by 11%. That is a large amount of one fiber, and the trial did not test health outcomes.
• Do not chase it. No trial shows that raising 17:0 improves health. The sensible route is a varied diet with enough fiber, with saturated fat kept moderate.

History of margaric acid

The French chemist Michel Eugène Chevreul showed by 1824 that fats are made of glycerol and fatty acids, and he identified several of them. Among the acids he described from animal fat was one he named margaric acid. The name comes from the Greek word for pearl, for the pearly shine of its crystals. For decades chemists counted it, with oleic and stearic acid, as one of the three fatty acids that make up most animal fat.

It turned out not to be a single substance. In the early 1850s the German chemist Wilhelm Heintz took the supposed margaric acid apart. He found a mixture of stearic acid (18 carbons) and palmitic acid (16 carbons), the second previously unknown. According to a biography from the American Oil Chemists’ Society, the work began with an attempt to find margaric acid in human fat.

Heintz later made a true margaric acid in 1857, with properties very different from the old one. True C17:0 was found afterward in trace amounts in fats and oils. In 1957 three chemists reported n-heptadecanoic acid in butterfat and in mutton fat.

The pearl word lives on in margarine. The spread took its name from the same Greek root. In 1964 a Dutch journal ran a history of the margarine concept “from Chevreul to Mège-Mouriès”.

Today the name margaric acid sits on the real 17-carbon acid. 19th-century textbooks that mention “margaric acid” are usually describing a mixture.

Frequently asked questions about margaric acid

What is margaric acid?

Margaric acid, also called heptadecanoic acid (17:0, C17H34O2), is a saturated fatty acid with 17 carbons. It is found mostly in dairy fat and the fat of ruminant animals such as cattle and sheep. The body also makes some of its own.

Is margaric acid the same as heptadecanoic acid or C17:0?

Yes. Margaric acid, heptadecanoic acid and C17:0 or 17:0 all name the same 17-carbon saturated fatty acid. Do not confuse it with pentadecanoic acid (C15:0), which has 15 carbons and its own page.

Does margaric acid lower diabetes risk?

Not shown. In 16 pooled cohorts (63,682 people), higher blood 17:0 went with less type 2 diabetes (0.65 times the risk), but these are only links. We found no trial of giving margaric acid. The one mouse study that added it saw no benefit for fatty liver or insulin resistance.

Which foods have the most margaric acid?

In our USDA ranking, ground beef leads with 0.25 g in 4 oz. Farmed Atlantic salmon, macadamia nuts, olives and semi-skimmed cow’s milk follow at 0.03 to 0.04 g a serving. In a separate test, butter held 423 mg per 100 g, while nonfat dairy had none that could be detected.

Does the body make margaric acid?

Some of it, yes. In 16 adults, 7 days of inulin or propionate raised plasma 17:0 by 11% and 13%. In mice, deleting the HACL1 enzyme cut plasma 17:0 by about 26%. In human cells, ELOVL6 lengthened 15:0 to 17:0.

Is margaric acid a good marker of dairy intake?

Only a rough one. Dairy trials raised plasma 17:0 slightly: 3 servings a day took it from 0.39% to 0.42% of fatty acids. But other trials found no change, and fiber also raises it. 15:0 is usually the better dairy marker.

Is there a margaric acid supplement?

We found no human trial of one. The only added-C17:0 experiments are in mice and cells, and a dolphin study with a patent behind it. Talk to a doctor before taking any fatty acid supplement for a health condition.

Why is it called margaric acid?

The name comes from the Greek word for pearl. In the 1800s Chevreul gave it to a pearly fat. In the early 1850s Heintz showed that fat to be a mixture of stearic and palmitic acid. The real C17:0 later took the name.