What is omega 3 and how much do women need?

What are omega 3 fatty acids?

Omega 3 fatty acids are unsaturated fats. The two forms named on supplement labels and in most guidance are EPA and DHA, and oily fish such as salmon, sardines and Atlantic mackerel are the main food source. It can help to see omega 3 as one part of a mostly unsaturated way of eating, alongside olive oil, nuts and seeds, instead of a single nutrient to chase.

The words differ a little between countries. US guidance counts servings and sorts fish into Best Choices and Good Choices, and canned light tuna sits in Best Choices without being described as oily. UK guidance counts portions and uses the term oily fish, and the NHS does not count tuna as an oily fish. When a US fish list and a UK one look different, that is usually why.

What does the evidence say about omega 3?

The clearest finding is for triglycerides, a type of fat carried in the blood. Supplement doses of EPA/DHA lower triglycerides in perimenopause, at menopause and in the years after it, and the evidence at those stages is graded moderate.

In the reproductive years the moderate grade rests on something different: a DHA/EPA supplement is described as useful if you eat little oily fish, especially in pregnancy. At this stage a supplement fills a gap in the diet rather than acting as a treatment.

In perimenopause, 2 servings of oily fish a week is tied to heart health and triglycerides, and possibly to mood. The word possibly matters: mood is a hopeful signal that is not settled, so it sits best as a welcome extra, with the heart as the main reason for the fish.

At menopause the cholesterol picture shifts, because LDL cholesterol rises, a change tracked in the SWAN study of midlife women (Matthews et al., 2009). That is the background to the guidance to eat mostly unsaturated fats and limit saturated fat, with oily fish named beside olive oil, nuts and seeds. If you are weighing up your own numbers, you may find it useful to read about high cholesterol symptoms in women.

After menopause, oily fish keeps its place for heart health, and possibly for brain health. The heart finding is the firmer of the two.

For children the grading is lower. The evidence for omega 3 supplements in childhood is weak, and oily fish is the preferred route.

How much omega 3, and how often?

2 servings a week is the figure for adult women: 2 servings of fish in the reproductive years, and 2 servings of oily fish in perimenopause, at menopause and after it. For girls and teenagers the figure is 1–2 servings of oily fish a week.

Pregnancy and breastfeeding have their own figures. US advice from the FDA and EPA is 2–3 servings a week of Best Choices fish, or 1 serving of Good Choices fish, with a serving about 4 oz. In the UK, the NHS suggests at least 1 portion of oily fish (about 140 g cooked) a week and no more than 2 if you are pregnant, trying to conceive or breastfeeding.

Some fish carry more mercury. The US list for pregnancy is king mackerel, marlin, orange roughy, shark, swordfish, Gulf of Mexico tilefish and bigeye tuna; the NHS names shark, swordfish and marlin.

A supplement is an option for women who eat little oily fish: 250–500 mg a day of DHA/EPA in the reproductive years and 1–2 g a day of EPA/DHA in perimenopause, at menopause and after it. The units differ, so it is worth checking how much EPA and DHA a label lists.

What have omega 3 studies shown and not shown?

The findings that hold up are that supplements lower triglycerides, with the evidence graded moderate, and that eating oily fish goes with heart health. The outcomes people often hope for most, learning and behavior in children and protection against dementia later on, have thinner results.

In children, supplements haven't been shown to improve learning or behavior in most cases. That is a statement about capsules and takes nothing away from fish as part of a child's week.

In the years after menopause, there is little evidence that omega 3 supplements prevent dementia. Fish belongs to a heart-healthy pattern that may also help the brain, and keeping these modest qualifiers in view supports a food-first approach that leaves room for your own preferences, budget and diet.

Next steps

A good place to start is one week of your own meals: counting how many included fish, and whether any were oily, tells you more than a label can. If the count is close to 2, there may be nothing to change. If fish is rarely on your plate, or you eat vegan, a supplement or a conversation with a dietitian are both reasonable routes. If you are pregnant, planning a pregnancy or breastfeeding, a midwife, OB-GYN or GP can help you match your country's fish list to what you like to eat. Omega 3 is one small part of eating well, and how you get it depends on your diet, your health and your preferences. It is not one size fits all.