A Beginner’s Guide to Fish Sauce

Everything you need to know about the flavor-packed Vietnamese condiment.

There were many years when the mention of fish sauce in the United States elicited disgust—that is, if the person I was talking to had heard of it at all. On the occasions when I met Vietnam War veterans, we often discussed the merits of fish sauce. Some appreciated its role in Vietnamese food; others were repulsed by it. The ignorance and negativity toward my motherland’s national condiment miffed me—not least because fish sauce isn’t as strange as people seemed to think. Ancient Rome had a similar seasoning called garum. The Chinese version is named yu hai and the Japanese have shottsuru.

In recent years, however, the tide has begun to turn in fish sauce’s favor. People in the United States have gotten more comfortable with Vietnamese food and warmed up to fish sauce in other applications, like as a dressing for brussels sprouts or a savory base note to Bolognese.

Here are my tips and insights based on years of eating, using, and exploring fish sauce—particularly in Vietnamese food.

What is fish sauce?

Fish sauce is the liquid that results from salting and fermenting seafood. It’s a traditional, practical way of preserving protein and it lends umami depth to many savory Asian dishes. The cuisines of Vietnam, Thailand, and the Philippines rely on fish sauce the most. In Vietnamese, fish sauce is called nuoc mam, and it’s known as nam pla and patis in Thai and Tagalog.

To make fish sauce, fresh fish (usually anchovies, but other types of fish or shellfish may also be used) are packed in layers of salt in large earthenware jugs, wooden casks, or concrete vats. Bamboo racks and rocks are placed on top to keep the fish from floating as their juices are drawn out during fermentation.

Left in a hot, sunny place, microorganisms break down the fish and turn them into liquid. After months or even more than a year, the fluid is removed via a spigot at the bottom of the salting container, or by siphoning.

This first extraction, called nuoc mam cot or nuoc mam nhi in Vietnamese, is the most prized. Slightly oily, richly flavored, and deeply hued, it is often reserved for dipping sauces and special occasions. To get more use from the same fish, salted water is added and after a shorter second fermentation period, a lesser-quality condiment is collected for everyday use.

Like bourbon, fish sauce from different aging containers is often blended before bottling, but I’ve tasted single barrel bottlings in Vietnam and the flavor differences ranged from prosciutto to porcini. Kosher fish sauce that’s produced without shellfish (the seafood haul is arduously hand sorted) is delicately flavored and friendlier to use for cooks who are new to the condiment. I’ve also sampled fish sauce that tasted flat, too briny, and overly salty.

Inspect a label and you’ll notice that along with fish and salt, there may be other ingredients in the mix. For example, sweeteners (sugar or fructose), flavor enhancers (MSG or hydrolyzed wheat protein), or a preservative (sodium benzoate). Pure fish sauce is fish and salt, but the add-ons help producers to create a desired flavor and product that’s shelf stable and competitively priced. From my experience, fish sauce with sodium benzoate tends to have an unpleasant edge. But additives don’t need to be a deal breaker: the Three Crabs brand made by Viet Huong contains hydrolyzed wheat protein and is the go-to for many people.

Buying Fish Sauce

Traditional cooks like my mom go through first-press nuoc mam fast, which is why they keep both high- and lower-grade fish sauces on hand. The nice stuff is reserved for table use and making dipping sauces while the less expensive bottle is for cooking. I exclusively use high-grade fish sauce—at $4 to $8 per bottle, it doesn’t break my budget and it helps me make consistently tasty food.

When buying fish sauce, hold the bottle up to the light and look for an amber-red, clear liquid. At home, open the bottle and take a whiff. It should smell woodsy and earthy, like dried porcini. Take a taste on small spoon or cucumber slice. It should taste pleasantly briny rather than fishy.

Excellent fish sauce typically comes in glass bottles. If the bottle is communicating Vietnamese provenance and quality, the words “nhi” or “thuong hang” may be on the label to indicate it was made using the first and best extraction.

Ca com anchovies or simply just “anchovies” signal a premium product. The slender, silvery ca com variety of anchovy is harvested in the Gulf of Thailand and is considered to make the best fish sauce.

There are other more minor factors that go into making good fish sauce, like the quality of the salt, and how the mixture is managed during fermentation—stirred or not stirred, for example. One producer claims that the climate on Phu Quoc Island creates a fish sauce with extra oomph.

Fish sauce quality can be quantified in “degrees N,” which denotes the concentration of nitrogen and protein—a higher number means a richer and more complex sauce. High-end fish sauce made in Vietnam includes the nitrogen levels on their labels, like two of my favorites, Son and Red Boat. I tried rich, somewhat oily 50°N fish sauce and gave some to my parents because it was unusual (my dad is somewhat of a fish sauce connoisseur). For all-purpose cooking and eating, a nuoc mam with a 40°N or 30°N is fine.

Vietnamese fish sauce producers care about the N indicator, so it’s something that shows up mostly on labels for fish sauce geared for the Vietnamese market. You may see Thai Megachef fish sauce on the shelves. The blue label one is most widely distributed in America and, with a sweet-savory flavor, it’s primarily marketed to Vietnamese cooks. That explains why the label includes 30°N and the nuoc mam nhi designation. There’s also Korean Hangul script for people shopping for a kimchi ingredient, and in smaller type, you’ll see “Premium Anchovy Sauce”, which is awkward untill you consider what they’re trying to communicate. Interestingly, Megachef’s brown label is devoid of the N rating and there’s no Vietnamese or Korean messaging. It’s in Thai and English, and the flavor is more robust and less sweet. You’ll do fabulously well with Megachef blue label, but if you see the brown label, buy a bottle.

Another Thai brand, Squid, is not as complex in flavor. I’ve tried Thai Kitchen’s fish sauce over the years but have continued to be disappointed. These brands are okay in a pinch.

Using Fish Sauce

Not all fish sauce has the exact same effect on your food, so take care when cooking with a new brand for the first time. Look at the sodium count per serving on a fish sauce label and you’ll see that the saltiness varies from brand to brand. Three Crabs, for example, is a lot saltier than Red Boat or Megachef. Then there’s also the sweetness factor. If a fish sauce has a hint of sweetness, it is easier to work with to finesse a savory-sweet finish that’s pleasant on your palate.

Don’t think of fish sauce as the equivalent of salt. Fish sauce is a source of savoriness. Salt is salt. I often use fish sauce with salt, and perhaps with sugar or maple syrup, to create umami depth. The salt and sugar balance things out and help to equalize major differences between fish sauce brands. Without the salt and touch of sugar, it can be hard for your tongue to detect when enough is enough and you can end up using too much fish sauce.

If you rarely use fish sauce, refrigerate the bottle. Otherwise, store it in a cool spot in the cupboard. If lots of crystals form or the stuff smells rank, discard the bottle and buy a new one. If the fish sauce is just darkened and more intense in flavor, use less than usual. You can always add more.

And should you want to eat fish sauce like a Vietnamese person, keep some for table use. Pour it in a recycled small glass bottle—a repurposed bitters bottle is the perfect size and the dispenser insert is perfect for sprinkling nuoc mam onto blah food.

Fish sauce isn’t just for Asian fare. Experiment by adding small amounts to savory dishes when you want a deeper flavor. It works wonders in Caesar-style salad dressings, Bloody Marys, albóndigas soup, chili, and tomato-based pasta sauces. Contrary to its name, fish sauce doesn’t add fishy flavor to food, but rather a magical, subtle layer of umami depth.