What is the nutritional value of crab fat?

January 12, 2026 •

4 min read

While many seafood lovers relish crab meat, the yellow or orange substance known as crab fat, or tomalley, is a delicacy for some but a mystery to others. Often containing a concentrated dose of flavor, its nutritional profile is distinct from the white meat of the crab and comes with important considerations.

Quick Summary

The nutritional value of crab fat, also known as tomalley, differs from the lean meat, containing a higher concentration of omega-3 fatty acids along with certain minerals. However, it also accumulates environmental toxins and should be consumed with caution, especially if the crab's source is unknown.

Key Points

Rich in Omega-3s: Crab fat contains a higher concentration of heart-healthy omega-3 fatty acids compared to the lean meat.
Source of Minerals and Vitamins: It is also a source of essential minerals like selenium, copper, and zinc, as well as B vitamins.
Potential for Contaminants: As the hepatopancreas, crab fat can accumulate environmental toxins and heavy metals, posing a potential health risk.
Higher Calorie and Cholesterol Count: Compared to lean crab meat, the tomalley has a much higher fat and cholesterol content, and is calorically dense.
Source Matters: The safety of consuming crab fat heavily depends on the environmental conditions and source of the crab.
Moderation is Key: For those who choose to eat it, moderation is recommended due to the potential presence of contaminants and high cholesterol.
Lean Meat is Safer: The lean, white meat of the crab is a safer, low-fat alternative that still provides protein and some omega-3s.

Understanding Crab Fat (Tomalley)

Crab fat, or tomalley, is a soft, yellow-orange substance found in the body cavity of crabs. It is technically the hepatopancreas, an organ that functions similarly to a liver and pancreas, and is where the crab processes and stores nutrients. While considered a delicacy in many culinary traditions, it is also the part of the crab where environmental toxins, such as heavy metals and contaminants, can accumulate. This makes its consumption a topic of debate and caution.

Key Nutrients in Crab Fat

Crab fat is known to be a source of various nutrients, though its composition can vary by crab species and diet. Compared to the lean muscle meat, tomalley can contain a higher concentration of certain vitamins, minerals, and fats. Some key nutritional components include:

Omega-3 Fatty Acids: Similar to other seafood, crab fat contains polyunsaturated omega-3 fatty acids, which are beneficial for heart and brain health. These healthy fats can help reduce inflammation and support overall cardiovascular wellness.
Vitamins: Tomalley can be a good source of vitamins, including B vitamins, which are essential for metabolism and energy production.
Minerals: It often contains a higher concentration of minerals than crab meat, such as selenium, copper, and zinc, which play roles in immune function, antioxidant defense, and more.

The Risks and Safety Considerations

Despite its potential nutritional benefits, the primary concern with consuming crab fat is the risk of contamination. The hepatopancreas's function as a filter means it can accumulate pollutants from the crab's environment. The Washington State Department of Health, among other organizations, has issued warnings regarding the consumption of crab butter (tomalley) due to higher levels of contaminants like polychlorinated biphenyls (PCBs). While this is a regional concern and contaminant levels can vary, it is a crucial factor for consumers to consider.

To mitigate risk, it is important to know the source of your crab. Crabs harvested from pristine, monitored waters are generally safer. However, for most home cooks, the origin may be unclear. As such, many health advisories recommend limiting or completely avoiding tomalley consumption, especially for children and pregnant women.

Nutritional Comparison: Crab Fat vs. Crab Meat

To illustrate the difference, here is a simplified comparison of the nutritional profile of crab fat versus lean crab meat. This table highlights how the caloric and fat content are concentrated in the tomalley.


Nutrient (per 100g)	Lean Crab Meat	Crab Fat (Estimated)	Notes
Calories	83 kcal	High, potentially double or more	Calorie density is much higher due to fat content.
Total Fat	0.74g	Much Higher	The defining component of "crab fat."
Saturated Fat	0.2g	Higher	Saturated fat levels are elevated in the tomalley.
Omega-3s	~320 mg (approx.)	Higher	Concentrates beneficial polyunsaturated fats.
Protein	18g	Low to Negligible	The lean meat is the primary source of protein.
Cholesterol	97mg	Higher	The hepatopancreas filters and stores cholesterol.
Vitamins	Various B vitamins	Often higher concentration	Accumulates fat-soluble vitamins.
Minerals	Zinc, Selenium, Copper	Often higher concentration	Accumulates minerals from the crab's diet.

A Culinary Perspective

For those who choose to enjoy crab fat, it is often incorporated into rich sauces, used as a flavor base for soups, or simply scooped out and eaten with the meat. Its creamy texture and intense flavor can enhance a variety of dishes. Many recipes, particularly in Southeast Asian cuisine, highlight the tomalley. For example, a dish like 'Alavar sauce' often utilizes crab paste or fat to create a savory, aromatic coconut-based sauce.

For most, the flavor and texture are the primary appeal, while the nutritional aspect is a secondary concern. If you decide to include it in your cooking, remember to use it sparingly and ensure the crab comes from a clean, reputable source. If you are uncertain about the crab's origin, it is safer to stick to the lean, white meat.

Conclusion

While the nutritional value of crab fat includes a concentration of healthy omega-3s and other minerals, it is essential to consider the potential health risks. As the hepatopancreas, or tomalley, can accumulate environmental toxins, cautious consumption is advised, especially if the crab's harvest location is unknown. For a delicious and safer experience, most individuals can simply enjoy the lean, protein-rich meat, which also provides a good source of omega-3s and other essential nutrients. Those who wish to consume the fat should do so in moderation and only with assurance of a clean, toxin-free source. By understanding both the benefits and risks, you can make an informed decision and enjoy crab responsibly.

For further reading on seafood safety guidelines, the Washington State Department of Health offers specific advice.

Frequently Asked Questions

The yellow or orange substance found in a cooked crab is known as tomalley or crab fat. It is the crab's hepatopancreas, an organ that functions like a liver and pancreas to filter nutrients.

While technically edible and considered a delicacy, crab fat can accumulate environmental toxins and heavy metals. Safety depends on the crab's source; if uncertain, it's best to limit or avoid consuming it.

Yes, crab fat is a source of omega-3 fatty acids, which are beneficial for heart health. The concentration of these polyunsaturated fats can be higher in the tomalley than in the lean meat.

Compared to lean crab meat, crab fat has a higher concentration of cholesterol. The crab's hepatopancreas is where cholesterol and fat are processed and stored.

Crab fat (tomalley) is the hepatopancreas, a yellow-orange digestive organ. Crab roe is the reddish-orange, granular mass of eggs found in female crabs.

Due to the potential for environmental toxins, it is generally recommended that children and pregnant women avoid consuming crab fat. It is safer to stick to the lean, white meat.

No, cooking does not remove or destroy heavy metals and other environmental contaminants that may be present in crab fat. These toxins are not affected by heat and remain in the tomalley after cooking.

Lean crab meat is a healthy, low-fat source of high-quality protein, as well as essential minerals like selenium, zinc, and copper, and vitamins such as B12 and folate.