Omega-3 is hailed as a must-have for a healthy diet, but what do we really know about this fatty acid? How much of the supplement should you take? What are the health benefits? If we get this fatty acid from fish, are we also ingesting mercury?

We spoke with omega-3 expert Jacqueline Shan to find out the answers to all of these questions. Shan is the creator of Cold-FX and she has now branched into creating omega-3 supplements with her company Afinix.

The health benefits
According to Shan, omega-3s are beneficial to your overall health, but they're especially helpful to your heart, joints and mind.

Heart health: Mayo Clinic reports that omega-3 fatty acids decrease inflammation throughout the body, including in your blood vessels. Because inflammation in the blood vessels can cause damage that leads to heart disease, taking omega-3s can help keep your heart healthy, says Shan, and is particularly beneficial for people who are managing heart disease.

Rheumatoid arthritis: The Arthritis Society of Canada says that omega-3s are beneficial to people who suffer from arthritis caused by inflammation. The organization recommends adding fatty acids to your diet through fish and seeds. In order to reduce joint pain, Shan advises taking an omega-3 supplement along with undergoing occupational therapy.

Brain health: According to Shan, omega-3s support cognitive function, which includes your memory and your ability to deal with stress. Multiple studies have linked omega-3 consumption with slowing down the effects of Alzheimer's disease. Accordingly, the Alzheimer Society of Canada advises eating plenty of foods rich in omega-3 fatty acids to help reduce the risk of Alzheimer's disease.

How much do you need?
Despite omega-3 being so beneficial to our health, our body doesn't actually produce this fatty acid. You have to consume omega-3 fatty acids either through your diet or through supplements. Fish, such as salmon or trout, are excellent sources of omega-3s, as are nuts and seeds. Canada’s Food Guide recommends that adults eat at least two servings of fish per week.

But what about people who don't like fish or who don't eat enough of it during the week? That's where supplements like fish oil come in. There are many omega-3 products available and it can be overwhelming trying to figure out which one to buy. Shan says you need to be picky, especially when it comes to the potency of the supplement.

To figure out the potency of fish oil, look at the bottle's label to see the total amount of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in the product. (Omega-3s are a group of three fatty acids and these are the two mains ones.) Combine the amount of EPA and DHA and compare it to the amount of fish oil in the bottle. Most products have a potency between 20 and 50 per cent, but you want a supplement with over 50 per cent potency, says Shan. Products with a lower potency tend to be cheaper, but they’re not worth your money. "You won't get your health benefits," she says.

Instead, Shan advises buying a product with a higher potency, even if it is a bit pricier. After all, buying a product that is more potent means you'll have to take fewer pills each day.

Read the label
Reading the product label is a great way to find out if you're buying a quality omega-3 product. There are three main things to consider.

1. What's the shelf life?
You want to buy a fish-oil product that is fresh, says Shan, so check the bottle for an expiry date. Also remember to throw out the product once it expires and keep it in the fridge once you’ve opened it.

2. Does it contain an antioxidant?
According to Shan, omega-3s are very sensitive to oxidization. So check the ingredient list to make sure the product contains an antioxidant. Vitamin E is a common anti-oxidant used in fish oil that also has many health benefits.

3. Is there a Natural Product Number?
Health Canada advises you check the product label for a Natural Product Number (NPN), which indicates that the government has approved the product.

What about mercury?
Despite the many health benefits of fish, there are concerns about the level of mercury they contain. However, there are two ways you can limit the mercury you ingest from an omega-3 product.

1. Check the purity.
Before you buy a product, says Shan, you should call the manufacturer to ask them about how they purify the omega-3 from the other impurities found in fish, such as environmental pollutants, heavy metals and pesticides. "It's very important to look into this aspect because not every fish-oil product in the marketplace is made the same," she says.

We're not all scientists, so asking the manufacturer to explain the complex process of how the omega-3s are purified is likely just going to confuse us. Instead, ask the manufacturer how much testing their product goes through and whether they can give you an assurance of how pure their product is.

2. Look for small fish.
A simple way of limiting your exposure to mercury is by buying an omega-3 product that uses small fish. Because fish eat other fish, you want to eat the fish that are lower on the food chain, as they have "less chance of accumulated pollutants in the fish," says Shan. Sardines and anchovies are a good fish to look for in a fish-oil product.

We also have a responsibility to pick products that are environmentally sustainable. Check that the fish you're eating or the fish oil you buy doesn't come from an endangered species of fish.

What are the side effects?
"Omega-3s are considered a very safe product," says Shan. However, you should check with your doctor before starting any new health regimen.

In particular you should be careful if you’re on blood thinners because they can interact with omega-3 supplements, she warns.

If you're looking for other supplements to help you stay healthy, we have everything you need to know about vitamin D.