More than 40 years ago, research on Greenland Eskimos revealed they had shockingly low rates of heart disease despite a high-fat diet. This led researchers to look further into the consumption of long-chain fatty acids in fish as protective against heart disease.
These new discoveries brought forth another realization: mammalians’ brains are rich in a certain kind of omega-3 fatty acid: DHA (docosahexaenoic acid). In fact, after analyzing fossils experts believe that the consumption of DHA in seafood was “the” turning point in the evolution of the human brain.
In short, the human brain needs DHA and its partner EPA (eicosapentaenoic acid) for growth, development, and maintenance.
So, let’s discover together why DHA and EPA are important for children, adolescents, and adults and how much is needed to optimize health.
What are Omega-3 fatty acids?
Chemically speaking, omega-3 fatty acids are polyunsaturated fats that the body can’t make. Omega-3s have many double bonds (poly) and are unsaturated (contain at least one double bond). The final double bond is located on the three-carbon atom after the omega, often referred to as the “tail.”
First, there’s essential short-chained alpha-linolenic acid (ALA) rich in flaxseed and green leafy vegetables and linoleic acid (LA) rich in vegetable seed oils.
Today we’re talking about the long-chain omega-3s DHA and EPA. Although they can technically be made from ALA, the conversion rate is low making them essential in the diet.
Although DHA plays a more dominant role, EPA is also important. They work together as fuel for cell membranes, the structures vital for life processes. Both EPA and DHA attach to phospholipid molecules the building block of cell membranes, helping to make them more fluid.
When membranes are fluid, they work more efficiently. It’s like adding water to a slide. Think how much faster you can go.
In short, having adequate levels of DHA and EPA in the membranes optimizes growth, renewal, and the overall function of human cells. Most important, DHA and EPA are found in high levels in membranes of the brain and retina.
DHA early in life
When a house is built, so is its foundation and the right materials are needed to do it right.
This is what happens in utero and during infancy with DHA, a time its importance is undisputed. After all, the brain grows at an incredible rate during pregnancy and the first few years of life.
Starting in the second half of pregnancy, baby’s brain begins to rapidly accumulate DHA. This reaches 4 grams by the time a child is 4 years old. No other fatty acids accumulate in the brain as DHA does.
This is why DHA intake is so important for pregnant women, especially in the last trimester. In fact, DHA plays a protective role in postpartum depression, pregnancy-induced hypertension, and pre-term birth. It’s also important during breastfeeding as getting DHA through diet or supplements increases levels in breastmilk.
Leading health organizations like the American Academy of Pediatrics acknowledge the importance of DHA during the first 1000 days of life. This starts at conception (early neurodevelopment), affecting long-term brain and eye health
DHA maintenance and remodel
Just like the foundation of a house matters, so does maintaining the house.
So if dietary intake of DHA and EPA declines, the membrane profile can suffer. That’s because brains are plastic, continuing to go through synaptic turnover throughout not just childhood but life.
Adolescence signals another “building period” for the brain but it’s more of a remodel than starting from scratch. Puberty is the second-fastest growth spurt after infancy.
In fact, DHA continues to increase in the brain during adolescence to reach about 15% of fatty acids.
The brain remodel starts by pruning synapses in the frontal cortex, increasing white matter, and maturing the brain until the age of 25!
According to one review in the Journal Nutrients:
The brain’s frontal lobes are particularly responsive to the supply of DHA during development. Decades of work have clearly established the responsibilities of the frontal lobes for executive and higher-order cognitive activities including sustained attention, planning and problem solving, and the prefrontal lobe in particular for social, emotional, and behavioral development. Therefore, maintaining optimal lipid composition in these brain regions, and specifically DHA levels, is not only important during the development and maturation of the brain from gestation through childhood and adolescence but such maintenance is also critical for successful aging of the adult brain
Unfortunately, the brain tends to atrophy with age. According to one study, postmenopausal women with higher blood levels of omega-3 fatty (omega-3 index) had a larger brain and hippocampal volume 8 years later.
In short, DHA and EPA are to the brain, what calcium is to the bones.
DHA & EPA health benefits
Benefits of DHA and EPA show up in one of four key areas: mood, behavior/cognition, inflammation, and heart health.
One amazing way DHA and EPA work is changing how genes are expressed. According to one study, EPA and DHA changed the expression of 1040 genes! The end result was fewer expressed genes involved in inflammation and heart disease risk.
They are also precursors for anti-inflammatory compounds, positively affect lipid metabolism, and enhance brain connectivity. The figure below details the key mechanisms for these benefits, plus more.
We also know that individuals with brain-related disorders such as ADHD, autism, and mood disorders like depression, tend to have lower concentrations of omega-3s in their blood. This is also true for disorders like Alzheimer’s and heart disease.
This doesn’t prove cause and effect as these disorders could also cause changes in DHA metabolism. Plus, not everyone with low blood levels of omega-3s experiences problems.
Yet supplying the brain with adequate DHA and EPA levels remains important.
Mixed RCT studies
With strong observational data, researchers set up randomized control trials (RCTs) to determine cause and effect. These results have been less impressive leading some to conclude that omega-3s play less of a role after the early development stage.
Looking at a recent meta-analysis of these trials on children, there are positive results for sleep and kids with ADHD in terms of symptoms and cognitive performance. Yet research on asthma, autism, learning, and cognition are mixed.
When it comes to cognitive function in older adults without impairment, supplementation hasn’t been shown to help. And heart disease DHA/EPA intervention studies are less conclusive, though they do show a benefit in reducing death from cardiac events. Yet one review focusing on supplementation only found higher doses of 1-2g reduced the risk of fatal myocardial infarction (35%), myocardial infarction (13%), CHD events (10%), and mortality (9%)
Various meta-analyses also show improved pregnancy outcomes with DHA supplementation. And one 2019 review in Nature concluded: “Current evidence supports the finding that omega-3 PUFAs with EPA ≥ 60% at a dosage of ≤1 g/d would have beneficial effects on depression.”
One reason study findings vary is researchers often measure intake of omega-3s (such as in fish and/or fish oil supplements) and not blood levels. And the amounts of fish oils given varies as some provide as little as 16.5mg and as high as 3600mg. Some contain only DHA and others both DHA and EPA.
One review found that the most beneficial outcomes for cognition in children occur with an omega-3 index (amount in red blood cells) of >6%. And for adults and heart disease an omega-3 index over 8% fare better.
So just because RCTs are mixed doesn’t mean DHA and EPA are not needed. That’s like saying kids don’t need vitamin C because studies don’t prove it prevents colds.
DHA & EPA Recommendations
Unfortunately, the Institute of Medicine has never set Dietary Reference Intakes (DRI) for DHA and EPA. Instead, they say that 10% of ALA can be for EPA or DHA. This comes out to a meager 100mg per day.
This is significantly lower than what is recommended by international groups.
As a result, omega-3 fatty acids aren’t highlighted as nutrients of public health concern like vitamin D and potassium are.
GOED (the Global Organization for EPA and DHA) provides a summary of recommendations around the world. In the chart below, I provide the highlights.
Most organizations recommend a minimum of 500mg DHA/EPA for adults and 250mg DHA/EPA for children. Dietary Guidelines for Americans recommends adults consume 8oz seafood each week which depending on the source can supply 250mg – 500mg (higher for oily fish) daily. The American Heart Association emphasizes oily fish in their two times-a-week recommendation.
Pregnant and lactating women can have up to 12 ounces of fish of low-mercury sources of fish per week and should bet at least 200-300mg DHA/day.
Yet more will be needed depending on the use. For example, for those with active heart disease, 1g of EPA and DHA is recommended. There are specifics on the amount and ratio of DHA and EPA for treating depression. And people with high triglycerides may take up to 4g under a doctor’s supervision
To gain the benefits during pregnancy women may need to take 600mg DHA according to a recent review so check with your healthcare provider. In fact, one hospital found that they saved $1484 per infant giving women 600mg DHA in the last two months of pregnancy.
According to the aforementioned review on children, intakes of >450mg DHA/EPA may be needed to see benefit with an omega-3 index of >6%. And for adults, research suggests we may need more than is recommended to reach an omega-3 index of 8%.
Seek medical advice if you are adding fish oil to help with a specific condition like ADHD, depression, or heart disease. Be sure your healthcare provider is knowledgeable about the research on omega 3s and the condition.
How much DHA and EPA are we getting?
According to the 2020 Dietary Guidelines, approximately 20 percent of adults and 6 percent of children consume seafood twice per week.
I took the data on fish intake and estimated DHA/EPA per day assuming seafood is a mix of fatty fish and non-fatty fish like shrimp. Here’s what I found:
12- 24 months consume <.5 a week which is about 23mg per day
2-8 consume 1oz a week which is about 47mg/day (24-31% recommendations)
9-13 consume 1-2oz/week which is 47-94mg/day (19-47% recommendations)
14-18 consume 1-3oz/week which is 47-141mg/day (19-47% recommendations)
Adults and pregnant women consume 5oz/week which is 234mg/day (47% recommendations)
Lactating women get the most at 8oz per week which is 375mg/day (75% recommendations)
You can see that most are getting less than half of current recommendations.
Food sources of DHA & EPA
Of course, increasing fatty fish is the way to go. The Fisk trial included 8–9-year old’s who were given 300g (equal 10.5oz) of fish per week for 12 weeks. Another group of kids were given the same amount of poultry.
The children given fish increased their intake of DHA and EPA to 749mg/day (593-891). They also had higher levels of vitamin D and an omega-3-index 2.3% higher than the poultry group. They had improved cognitive performance especially when it came to attention and better HDL and triglyceride levels.
In general, 2 servings of fatty fish (see chart) per week is about 500mg/day DHA and EPA. Although mercury poisoning is a concern it’s rare as most people are far below recommendations.
That being said, stick with low mercury servings of fish including salmon, light tuna, trout, and trout. See this list for smart seafood choices.
Other sources don’t provide much DHA and EPA as you can see from the chart. Milk with added DHA can add up, but it would take a lot to make a difference. And rarely is EPA added to food.
Let kids know the importance of fish for their brain and heart health and don’t stop offering it no matter how many times it’s turned down. Consider dedicating one night a week to fish and find different ways to prepare it.
Fish Oil supplements
If fish intake is inconsistent or simply refused, then fish oil supplements can fill in gaps.
Remember to look at not just to total grams of fish oil, but the mg of DHA and EPA on the label. If it’s not provided move onto the next supplement. The FDA recommends no more than 2 grams (2000mg) total omega-3 fatty acids from supplements — and no more than 3g combined with diet — unless advised by a healthcare professional.
Those who don’t eat animal products such as vegans can look for an algae-based DHA supplement.
Omega-3 fatty acids DHA and EPA are important for growing children and adults. Listed below are the key takeaways.
- The human brain needs DHA and its partner EPA for growth, development, and maintenance
- If pregnant or breastfeeding, aim for 2-3 portions of low-mercury oily fish per week or supplement with at least 200mg and up to 600mg DHA daily.
- As children wean off breast milk or formula, aim to include fish twice weekly, including oily fish. For kids who are inconsistent with their fish intake, consider supplementation.
- Most adults need at least 500mg/day of DHA and EPA through diet and/or supplements but may need more to reach optimal levels of omega-3s in the blood.
- Check the label for the amount of DHA and EPA in supplements to be sure you understand how much it provides
- Adults and pregnant women, if possible, should get their blood levels of omega-3 checked. For more on my experience on that, see this podcast.
For more about nutritional needs at every age and stage, check out Fearless Feeding: How to Raise Healthy Eaters From High Chair to High School