Is Margarine Really Bad for You? The Real Issue Is Trans Fats and the “Quality of the Oil”

Bottom line first: what people mean by “margarine is harmful”

The biggest reason margarine has been called “bad for your health” is industrially produced trans fatty acids that used to come largely from partially hydrogenated oils (PHOs). Because trans fats are known to worsen blood lipids and raise cardiovascular disease risk, the WHO has strongly urged countries to reduce and eliminate industrially produced trans fats.

But this is the crucial point: “margarine = always harmful” is not true. Thanks to regulations and product reformulation, many margarine products now contain far less trans fat. In Japan as well, trans fat levels in margarine and related products are described as trending downward, and recent domestic data suggest the situation is not “as high as it used to be.”

On the other hand, when manufacturers reduce trans fats, they may replace them with oils that are higher in saturated fat (for example, some palm-based fats). That creates a different issue: “trans fats decreased, but saturated fat is higher.” In other words, when discussing margarine, you’ll get the most stable conclusion by looking not only at trans fats or only at butter, but at the overall picture: fat quality and how it’s eaten.

This article is especially useful for:

• Households using spreads for young children’s breakfasts and snacks
• People told their LDL (“bad” cholesterol) or triglycerides are high and want to rethink fats
• Anyone trying to calmly sort out the “butter is good / margarine is bad” narrative
• People who look at labels but still don’t know what to choose

1. What margarine is, and how it differs from butter

Margarine is generally a fat-based food made by emulsifying mainly vegetable oils (or vegetable + animal fats) into a solid or semi-solid form. Butter is primarily milk fat. A simple way to think of margarine is “processed oils shaped to be used like butter.”

What matters here is that you can’t sort foods cleanly into “plant-based = healthy” and “animal-based = unhealthy.” The health impact depends more on factors like:

• How much trans fat it contains
• How high it is in saturated fat
• How you’re getting unsaturated fats (omega-3/6, etc.) overall
• Total intake (a thin spread on bread vs. large amounts via fried foods and sweets)

2. Trans fats are the biggest concern behind “margarine is harmful”

2-1. Why trans fats are a problem: bad for the heart and blood vessels

Trans fats tend to raise LDL (“bad” cholesterol) and lower HDL (“good” cholesterol), and are associated with higher risks of heart disease and stroke. Multiple public institutions consistently highlight this, and the American Heart Association also explains that trans fats increase heart disease and stroke risk.

The WHO notes that industrially produced trans fats can contribute to cardiovascular deaths and urges countries to eliminate them.

2-2. Separate “industrial” from “natural” trans fats

There are two broad types of trans fats:

• Industrially produced: created through processing such as partial hydrogenation
• Naturally occurring: present in small amounts in ruminant animal fat (trace amounts in dairy and beef)

Regulation mainly targets the industrial type. EU rules, for example, set limits while excluding naturally occurring animal trans fats.

2-3. Why PHOs (partially hydrogenated oils) were often the core culprit

Historically, margarine and shortening were often made by partially hydrogenating vegetable oils to:

• make them solid at room temperature,
• improve mouthfeel, and
• increase resistance to oxidation.

That process can increase industrially produced trans fats.

In the U.S., PHOs were considered a major source of artificial trans fats. The FDA determined PHOs are not “generally recognized as safe (GRAS)” and moved to remove them from the food supply. For many uses, after 2018 PHOs could no longer be newly added to foods, and through transition measures they have largely disappeared from the market.

3. Regulation worldwide: the EU sets a legal cap, the U.S. removed PHOs, Japan says “overall intake is low—but watch for skewed diets”

3-1. EU: industrial trans fats limited to “2 g per 100 g of fat”

In the EU, industrially produced trans fats (excluding animal-origin trans fats) are legally capped at 2 grams per 100 grams of fat in foods.

A strength of this approach is that consumers don’t need to decode labels to stay safer—marketwide trans fat levels are structurally kept below a threshold.

3-2. U.S.: PHOs effectively removed from foods

The U.S. advanced policy in the direction of “PHOs cannot be used in foods.” The FDA published final determinations and transition measures (including distribution sell-through periods), creating a system that reduces the main market source of artificial trans fats.

3-3. Japan: average intake is low, but “skew” can matter

In Japan, official materials often summarize that “under a typical diet, the impact is small.” The Ministry of Agriculture, Forestry and Fisheries cites domestic surveys and Food Safety Commission evaluations indicating Japanese average trans fat intake is below the WHO recommendation (less than 1% of total energy), and that “under normal diets the impact is small.”

At the same time, the Ministry of Health, Labour and Welfare’s Q&A notes that earlier surveys found certain levels of trans fats in margarine/shortening, and later testing showed a downward trend.

So in Japan it can be understood not as a “zero issue,” but as a “skew issue”: overall low for society, but potentially higher for people with very unbalanced eating patterns.

4. Are today’s margarines “safe”? A realistic way to think about it

4-1. Today’s discussion can’t stop at “trans fats” alone

As trans fat countermeasures progressed, the major risk factor associated with margarine has become less prominent. In Japan too, studies show long-term changes in trans fat content in margarines, fat spreads, and shortenings.

The next issue that often comes up is saturated fat. If manufacturers increase oils that are solid at room temperature (e.g., some palm or coconut-based fats) to reduce trans fats, saturated fat may rise. Saturated fat is known to raise LDL more easily, and the American Heart Association recommends reducing saturated fat and avoiding trans fats.

So when choosing margarine, it’s rational to look not only for “low trans fat,” but also for whether saturated fat is extremely high.

4-2. Is butter “safer”? Only in a conditional sense

Butter is sometimes seen as reassuring because its trans fats are not industrially produced, but butter is rich in saturated fat from milk fat, and overeating can contribute to higher LDL.
In the end, framing it as “butter is safe / margarine is harmful” can distract from improving the overall diet. The key is: for any fat, health impact depends on both amount and how it’s used.

5. How to choose in real life: a shopping checklist that prevents confusion

Here are practical decision rules you can use every day. Rather than memorizing nutrition science, building a “selection habit” tends to stick.

5-1. First check ingredients: whether “partially hydrogenated” is present

• If the ingredients list includes “partially hydrogenated oil” (or similar wording), it is closely linked to industrial trans fat risk, so avoiding it is generally the safest choice—especially useful when checking imported or overseas processed foods.

Even though countermeasures have progressed in Japan, label-checking remains a simple, strong strategy as long as “not absolutely zero” remains possible.

5-2. Next check the nutrition label: use saturated fat to decide “how much”

Some products list saturated fat on the nutrition label. Even if trans fats are low, a high-saturated-fat type is not ideal for heavy spreading. The AHA also supports limiting saturated fat.

5-3. Examples: choosing by purpose

• Daily toast (high frequency)
  → Look for both “low trans fat” and “moderate saturated fat.” Use a thin layer.

• Small amounts for cooking (e.g., adding aroma to a vegetable stir-fry)
  → If total fat use is small, product differences matter less than simply not overusing.

• For children’s bread/snacks
  → The riskiest pattern is “every day, a lot.” Reduce the spread amount, and add satisfaction with foods like peanut butter (low sugar), cheese, eggs, etc.

6. Changes more effective than “quitting margarine” outright

Over-focusing on margarine can make you miss the “main battlefield” of diet: fried foods, sweets, sugary drinks, and ultra-processed food frequency. Major trans fat sources can sometimes hide more in baked goods, snacks, fried foods from eating out, and sweet breads (especially in places with a history of PHO use).

That’s why an effective order of operations often looks like this:

• First, reduce processed foods containing partially hydrogenated oils (identify via labels)
• Next, lower the frequency of fried foods and sweets
• Finally, adjust household spreads (butter/margarine) mainly by amount

This route tends to deliver health benefits with less stress.

7. Summary: margarine’s “harm” depends on manufacturing history and how you eat it

Margarine’s reputation for being “harmful” comes from the historical problem of industrial trans fats—a topic consistently highlighted by the WHO and the American Heart Association.

Meanwhile, countermeasures have advanced globally: the EU set a legal cap (2 g per 100 g of fat), the U.S. removed PHOs, and Japan frames average intake as low while noting trans fats in margarine-type products have been trending downward.

So the practical conclusion today is:

• Rather than making margarine the single villain, first avoid PHOs (partial hydrogenation)
• Next, don’t overuse oils high in saturated fat
• For spreads, what matters even more than “what you spread” is how much you spread

If you ask “what should I do starting today?”, here’s one simple recommendation:
Cut the amount you spread on bread in half, and add satisfying foods like eggs, yogurt, nuts, and fruit. It’s a low-friction way to improve both fat quality and total intake.

References and information sources

• WHO: Trans fat (fact sheet)
• WHO: REPLACE trans fat (framework to eliminate industrial trans fats)
• EU: Commission Regulation (EU) 2019/649 (industrial trans fat cap: 2 g per 100 g of fat) PDF
• FDA: Trans Fat / PHOs (status and policy on partially hydrogenated oils)
• FDA: Final Determination Regarding PHOs (transition measures)
• American Heart Association (AHA): Trans Fats (LDL ↑ / HDL ↓, heart disease risk)
• Japan Ministry of Health, Labour and Welfare: Q&A on trans fats (levels, downward trend, etc.)
• Japan MAFF: Trans fats explained quickly (Japan intake overview)
• Food Safety Commission of Japan: Risk Assessment Report Trans Fatty Acids in Foods (2012, English PDF)
• Iida Y.: Transition of trans fatty acid contents of margarines, fat spreads, and shortenings in Japan (Journal of Oleo Science, 2025)