Health claims on food are proliferating, and one that's particularly popular is using omega-3 fatty acids to improve cardiovascular health, among other things. Here's the lowdown on this healthful type of fat.

Q. Are omega-3s absolutely necessary in our diets?

A. It depends. "There's needed, and there's needed," says Debra Palmer Keenan, a nutrition professor at Rutgers University. They're essential fatty acids — meaning our bodies don't manufacture them. "You can probably live without eating any omega-3s, but you may not function as well. Your health outcomes might not be as good."

Additionally, omega-3s are found in breast milk and have been shown to be important in brain and eye development, explains Jay Whelan, a professor of nutrition and an omega-3 researcher at the University of Tennessee. According to Keenan, "It's been documented that healthier children are born to women who get the proper amounts of the omega-3s DHA and EPA."

Omega-3 and omega-6 fatty acids share the same pool of enzymes and go through the same oxidation pathways while being metabolized. Omega-6s are typically found as linoleic acid, which is in many processed foods as well as meat, egg yolks and cooking oils, including sunflower, safflower, corn, cottonseed and soybean oils. According to Whelan, "A typical American diet tends to contain approximately 15 times more omega-6 than omega-3 fatty acids." This is one of the reasons some researchers say we need more omega-3s — to make up for the imbalance. Although we need both, the imbalance can increase risk for long-term health problems such as cardiovascular disease.

Q. Why not just reduce omega-6 consumption?

A. "We don't know to what extent high intake of omega-6 fatty acids compromises any benefits of omega-3 fatty acid consumption," says Whelan.

Q. What are omega-3s, and is there a difference between the omega-3s in fish and those in walnuts?

A. Omega-3 fatty acids are a type of polyunsaturated fat. There are a few types of omega-3s: EPA (eicosapentaenoic acid), DHA (docosahexaenoic acid) and ALA (alpha linolenic acid).

"They are not the same thing. We have to stop talking about omega-3s and talk about DHA and EPA and ALA as separate fatty acids," says Keenan. "All three are long-chain fatty acids, but EPA and DHA are longer. They can be formed from ALA, but it's not a process that the human body performs efficiently," he adds.

EPA and DHA, which come from fish oils, are the most valuable to health and wellness. Both play an important role in normal function of the heart, brain, eyes, nervous system, kidney and liver. These "essential" fats have also been proved to reduce the risk of cardiovascular disease and inflammation.

ALA is found in leafy, green vegetables and some commonly used oils such as canola and soybean. Some novelty oils, such as flaxseed oil, contain relatively high concentrations of ALA, but are not commonly found in the supermarkets.

"If you get ALA from walnuts, flaxseed or canola oil, it can be beneficial because it gets converted to DHA and EPA, but that's only if ALA is already lacking in your diet, which it probably isn't," says Whelan. Eating more ALA just for it to be converted to EPA and DHA is not recommended. "The amounts converted are very small, and in the long run, ALA starts to replace the needed DHA in the tissues — not a good thing," adds Whelan.

According to most research, ALA is not a viable source of EPA and DHA, and cannot replace fish and fish oils in the diet. "ALA is still a good guy with its own benefits, even if it's not converted. ALA helps to temper or reduce cardiovascular risk," says Whelan. However, Whelan believes that ALA, while not as effective as EPA and DHA in reducing risk of cardiovascular disease, might work independently, helping reduce risk in other ways than simply being converted to DHA and EPA.

Q. Why are omega-3s getting so much attention?

A. One of the key health benefits of omega-3 fatty acids is that they significantly reduce the risk for sudden death caused by cardiac arrhythmias and decrease all-cause mortality in patients with coronary heart disease. In addition to helping regulate the heart, omega-3s prevent the formation of clots and act as anti-inflammatories.

In fact, the U.S. Department of Health and Human Services Agency for Healthcare Research and Quality studied omega-3s and concluded that, "Overall, a number of studies offer evidence to support the hypothesis that fish, fish oil or ALA-supplement consumption reduces all-cause mortality and various CVD outcomes, although the evidence is strongest for fish or fish oil." If you look at the studies, many with thousands of participants, the research looks very strong.

Last year, the FDA allowed this claim to be placed on certain foods: "Supportive but not conclusive research shows that consumption of EPA and DHA omega-3 fatty acids may reduce the risk of coronary heart disease. One serving of (name of food) provides (x) grams of EPA and DHA omega-3 fatty acids." The label must state how much omega-3 fatty acids the product contains. However, the FDA didn't require the food to contain a minimum amount of omega-3s to carry the claim.

Q. Are there other health benefits?

A. "This could be one of those nutrients that becomes a 'magic bullet,' but we don't say things are conclusive until there have been many studies. And with heart disease, we say it's conclusive. There are many other things that they're looking at that are looking strong but are not quite there yet," says Keenan, the Rutgers University professor.

Charles Stuart Platkin is a nutrition and public-health advocate. Write to info@thedietdetective.com.