DHA: Benefits, Side Effects, Best Time to Take It & More

DHA

(Docosahexaenoic Acid)

Evidence: Very High
Possible Benefits: Very High
Safety: Reasonable

What is DHA?

DHA (docosahexaenoic acid) is one of the omega 3 essential fatty acids. It can either be sold in an omega 3 supplement or as an isolated fatty acid. Most people use DHA and omega-3 supplements for improving cognitive, emotional, and cardiovascular health. This article is about the main benefits of DHA and omega 3 supplements, their potential side effects, the best time to take them, and more.

What does DHA do for the body?

Along with EPA and ALA, DHA is one of the 3 main types of omega-3 fatty acids. Each of them has its unique functions in the body.

ALA (alpha-linolenic acid) is a plant-based form of omega 3 that can be converted into EPA and DHA in the body, but the conversion rate is low, typically less than 5%. This means that a person would need to consume large amounts of ALA to get the same benefits as EPA and DHA.

High intake of ALA has been shown to improve cardiovascular health, blood sugar control, inflammation, cholesterol levels, and more. However, whether or not any of these benefits are specific to ALA or achieved through its conversion to EPA and DHA is not yet clear.

DHA (docosahexaenoic acid) is a major component of the brain and is important for brain development and function. Studies have shown that DHA is associated with improved cognitive function, mood, and mental health. The same also applies to EPA, though to a lesser degree.

DHA is important for the development of the fetus during pregnancy and may be beneficial for the mother’s mental and emotional well-being.

It is also a major component of the retina and is important for eye health. Studies have shown that DHA is associated with a reduced risk of age-related macular degeneration.

EPA (eicosapentaenoic acid) is very effective at reducing triglycerides and symptoms of depression and anxiety.

Both EPA and DHA have anti-inflammatory properties and can help to reduce inflammation throughout the body. This can be beneficial for people with conditions such as rheumatoid arthritis, asthma, and other inflammatory conditions.

Both EPA and DHA have also been shown to have beneficial effects on heart health. EPA has been shown to lower blood pressure, reduce triglyceride levels, and improve the health of the blood vessels. DHA has been shown to improve heart rate variability, which is a measure of the flexibility of the heart. Together, they can help to reduce the risk of heart disease.

Possible benefits

The benefits mentioned below are dose-dependent. Generally, the higher the dose, the more pronounced the effects are. However, they do reach a plateau at a certain point. We will discuss the best dosing protocol later in this article.

Major benefits

Reduced triglycerides – Both EPA and DHA are extremely effective at reducing triglyceride levels. The reductions are in the range of 15-30%. Those with higher baseline triglycerides often see the biggest improvement.
Reduced symptoms of depression – Omega 3 supplements are comparable to pharmaceuticals, such as fluoxetine, in majorly depressed people.
Reduced symptoms of lupus – The supplement can reduce the symptoms of systemic lupus erythematosus by as much as 50%. Most studies show an improvement of about 30%. Interestingly, doses of 160mg EPA and 140mg DHA work better in this regard than higher doses.
Improved well-being – This benefit applies mainly to depressed individuals but also to those who do not suffer from depression.

Minor benefits

Reduced anxiety – An improvement was observed in medical students and likely applies to anyone with a stressful lifestyle.
Reduced cognitive decline – 900+ mg of DHA has been shown to slow down cognitive decline but lower doses do not seem to have much effect if any.
Improved reaction time – This benefit is relatively mild but applies to most people with low EPA and DHA intakes.
Reduced symptoms of ADHD – DHA doses of 300+ mg can reduce the negative symptoms of ADHD in children.
Reduced cortisol – This effect is small and likely secondary to the other benefits.
Reduced symptoms of bipolar disorder – The supplement does not directly affect manic phases but it can reduce the symptoms of depression related to BPD.
Improved photoprotection – High doses of omega 3 (1800+ mg of EPA) can reduce the risk of DNA damage, immunosuppression, and erythema in response to sunlight. It can also prolong the time required for
sunlight to induce reddening of the skin and prevent sunburns.
Reduced blood pressure – The supplement can reduce blood pressure in those with abnormally high blood pressure. In otherwise healthy individuals, omega 3 supplements do not affect blood pressure.
Reduced inflammation – The evidence on this is highly mixed and unreliable. With that said, omega 3 does seem to positively influence some inflammatory cytokines.
Reduced aggression – This benefit is secondary to improving mood and general well-being.
Increased HDL-C – This benefit is small and only applies to people with unhealthy cholesterol levels. In these individuals, the supplement may also reduce LDL-C and vLDL-C.
Improved exercise-induced oxygenation – This metric is shown to be improved in elite-level athletes. However, it is not as reliable as some fitness influencers claim.
Reduced liver fat – The reduction is seen in people with NAFLD.
Improved memory – The supplement may improve memory but the evidence is limited.
Improved processing accuracy – This improvement was noted in healthy adults and was assessed by the number of errors in a cognitive test.
Increased infant birth weight – Mothers with higher omega 3 intakes (from either food or supplements) give birth to infants with higher birth weights independent of gestational age.
Reduced insomnia – A notable improvement was noted in women with PMS.
Reduced headaches – Women with PMS tend to experience headaches less often and less severely when they take omega-3 supplements.

Possible side effects

These side effects are dose-dependent. The risk for them increases (often linearly but sometimes exponentially) as you increase the dose. Some of the side effects only apply to very high doses.

Nausea
Stomach cramps
Diarrhea
Fishy aftertaste
Fishy burbs
Blood thinning – Omega-3s can act as blood thinners, so it’s important for people taking blood-thinning medication or about to have surgery to talk to their doctor before taking omega-3 supplements.
Allergic reactions – People who are allergic to fish should avoid omega-3 supplements made from fish oil. Algae oil is usually safe in this regard.
Omega 3:6 imbalance – Omega 3 and 6 have to be kept in balance as too much of one can cause problems if not enough of the other is present. The optimal ratio between the two is somewhere between 1:4 to 4:1. Most people get too much omega 6 and too little omega 3s but if you consume high amounts of fish and take fish oil while getting a low amount of omega 6, too much omega 3 can also lead to an imbalance.
Increased LDL-C – Omega 3 supplements can increase LDL-C by about 5-10% in people with high triglycerides.
Oxidation – Omega 3 is prone to oxidation and can become a pro-oxidant that can easily cause more harm than good in the body. This is why you need to choose the brand you get omega 3 from carefully and store the supplement well.
Toxicity – While acute toxicity is extremely rare, taking high amounts of omega 3 could lead to chronic toxicity and cause some health problems. To prevent chronic toxicity, it is best to stay below 4 grams a day unless you have a great reason to take more.
Heavy metal toxicity – Fish oils tend to have notoriously high levels of methylmercury in them. This is why it is usually the best option to take algae oil instead of fish oils. If you do decide to supplement with fish oil, cod liver oil, and krill oil are usually safer than the other forms as far as mercury levels go.
Contamination – Besides mercury, fish oils are also often contaminated with PCB, dioxin, and organochlorine.

Who should not take DHA?

You should probably avoid taking the supplement if you:

experience a severe adverse reaction after taking the fatty acid
take blood thinners
are on a tight supplement budget (since there are more cost-effective supplements on the market for most people)

Who will benefit the most?

You should consider taking the supplement if you:

are on a vegan or vegetarian diet (algae oil is the best option in this case)
consume very little omega 3
eat high amounts of omega 6
have high triglycerides
suffer from depression, ADHD, or bipolar disorder
suffer from lupus

Omega 3 oils

There are many different types of omega 3 oils. The most popular ones include:

Fish oil – Fish oil is the most common supplemental form of omega-3. It is typically made from cold-water fish such as salmon, mackerel, and anchovies. This is usually the cheapest but also the most contaminated type of omega 3 supplement.
Krill oil – Krill oil supplements are a newer form of omega-3 supplement made from small crustaceans called krill.
Cod liver oil – The main difference between cod liver oil and krill oil is that cod liver oil contains a high amount of vitamins A and D. This can be a great thing for people deficient in those nutrients but it can also be problematic for those who already consume too much vitamin A.
Flaxseed oil – Flaxseed oil is a plant-based source of omega-3s, primarily ALA. ALA has a lower conversion rate to EPA and DHA than the other forms of omega-3s, so to get the same benefits as EPA and DHA, a person would need to consume larger amounts of flaxseed oil.
Algae oil – Algae oil supplements are made from a type of microalgae called Schizochytrium sp. which is rich in DHA. These supplements are suitable for vegetarians and vegans. Even if you are not a vegan or a vegetarian, algae oil is superior to the other form in the vast majority of cases because it tends to contain significantly lower levels of contaminants.

What omega 3 supplement is the best?

In the vast majority of cases, algae oil is much safer than fish oil, cod liver oil, or krill oil. This is mainly because algae oil is far lower in contaminants, such as methylmercury, PCB, dioxin, and organochlorine.

Fish oil is usually the cheapest option but also the worst one for health. It is the most contaminated form and doesn’t have additional benefits other than providing omega 3 fatty acids.

Cod liver oil is worth consideration for people who suffer from a vitamin D or vitamin A deficiency. The oil can provide a high amount of both of these nutrients. However, this can also be a bad thing if you already consume too much vitamin A. In that case, you should stay away from cod liver oil and take a different type.

If you do decide to go for cod liver oil because of its vitamin A and D content or for fish oil because of its cheap price, make sure to find a high-quality brand selling non-oxidized, wild-caught oil low in contaminants.

TL:DR, algae oil is almost always the best option.

How much DHA should you take?

The safe and effective dose range of combined EPA and DHA can be anywhere from 300 mg to 3 grams, depending on your goals.

2 grams of combined EPA and DHA appear to be the best daily dose for most people. This amount should provide most of the benefits without meaningful side effects.

Some people may benefit from doses higher than 2 grams. These include people with high triglyceride levels and rheumatoid arthritis.

Counter-intuitively, some people may benefit more from lower doses than higher doses. For example, people with lupus benefit the most from doses of about 160 mg of EPA and 140 mg of DHA.

Keep in mind that omega 3 should also be kept in balance with omega 6. The optimal ratio between the two is anywhere from 1:4 to 4:1.

The upper safety limit for omega 3 is not well-established. To stay on the safe side, don’t take more than 4 grams daily unless you have a great reason to do so. Higher amounts may cause problems if you take the supplement for a prolonged period.

Food sources of DHA

Fish are by far the richest food sources of omega 3 fatty acids, followed by some nuts and seeds.

Here is a list of foods rich in omega 3s and how much they contain:
Salmon: 2,200 mg
Tuna: 1,000 mg
Sardines: 1,800 mg
Anchovies: 1,200 mg
Mackerel: 1,500 mg
Herring: 1,500 mg
Flaxseeds: 55,000 mg
Chia seeds: 32,000 mg
Walnuts: 12,000 mg
Spinach: 120 mg
Kale: 150 mg

Please keep in mind that the plant sources, such as flaxseeds and chia seeds, mostly contain omega 3s in the form of ALA, which further has to convert into EPA and DHA and the conversion rate is relatively small.

Therefore, if you are a plant-based eater or avoid fish, it may be a good idea to supplement with omega 3s.

While some nuts and plant oils are high in omega 3, they also tend to be very high in omega 6 and therefore typically do not support a good balance between omega 3 and 6.

Best time to take DHA

DHA is fat-soluble so make sure to take the supplement with food to absorb it well.

Whether you take the supplement in the morning or the evening doesn’t matter much.

Unless it feels too impractical, spread the daily dose into 2+ smaller doses throughout the day.

Interactions

Omega 6
Omega 3 and 6 have to be kept in balance as too much of one can cause problems if not enough of the other is present. The optimal ratio between the two is somewhere between 1:4 to 4:1.
Vitamin E
Vitamin E protects omega 3 fatty acids from oxidizing, both inside and outside the body. It is important to note that if omega 3 fatty acids have already oxidized, vitamin E cannot fix them back to normal. Taking vitamin E with rancid fish oil will not make it beneficial or non-harmful. With that said, the more omega 3 fatty acids you take, the more vitamin E you will need.
Green tea
Omega 3 fatty acids increase the bioavailability of EGCG and other catechins in tea.
Turmeric
Turmeric and omega 3 appear synergistic for reducing breast cancer cell proliferation. In theory, this combination may also lead to increasing BDNF (brain-derived neurotrophic factor) but more evidence is needed to support this.
Fucoxanthin
These two supplements may be synergistic for anti-obesity effects.
Statins
Omega 3 works synergistically with statins in terms of improving cardiometabolic parameters.

Where to buy DHA

Which brand you chose will have an enormous effect on how you react to the supplement. Unfortunately, many brands sell oxidized omega 3 oils or capsules which are likely to do more harm than good.

Amazon is the best option for ordering omega 3 supplements in most countries. They offer some very affordable products backed by many positive reviews. Also, you can choose from a wide range of brands without having to search through other markets on the internet.

Beware some brands display the dosage per serving instead of per pill or capsule. Therefore, you may accidentally buy something less potent than you intended. Do not fall for this marketing trick.

FAQ

You can take the fatty acid daily and do not need to cycle it. However, it is certainly not a problem if you don’t take it every day. Not taking the supplement every once in a while could lead to better absorption. That is yet to be proven or disproven.

All of these options are fine. The two most important things to consider are the price and dosing. Powders are almost always the cheapest form. However, you may need a highly accurate scale to dose them correctly (preferably 0.001g). You can get one for as little as $20 from Amazon. Dosing the powders also takes some time that can add up over months or years. The disadvantage of capsules is that they often contain bovine gelatin, which rarely comes from an ethical source.

Yes. Most fatty acids, including DHA absorb and digest well if you take them before falling asleep. The supplement should not impact sleep quality in any significant way.

This fatty acid can oxidize and become harmful if kept in bad conditions. Unfortunately, many omega 3 supplements are already heavily oxidized by the time you buy them, which is why choosing a high-quality brand is important.

Keep the supplement in a cold, dark, and dry place, and it should remain just as potent for many months.

While toxicity is rare, too much DHA in the system can cause some health problems, often related to oxidation or causing an imbalance in fatty acids. It is best to stay below 4 grams a day to prevent these side effects.

You may need more of this fatty acid if you:
– don’t get enough omega 3 from food
– consume too much omega 6
– wish to lower your triglycerides
– suffer from lupus
– suffer from depression, ADHD, or bipolar disorder
– eat high amounts of omega 6
– consume very little omega 3

The half-life of DHA in the body is about 3 days. For EPA, it is about 5 days. ALA only stays in your body for a few hours before it gets utilized.

In the long term, you need to take the supplement for about 2-4 weeks to begin noticing the benefits.

Unfortunately, most omega 3 supplements on the market are not vegan-friendly. However, you can buy algae oil that is vegan-friendly and may also be superior to other sources of omega-3. If you buy omega 3 in a capsulated form, beware that the capsules often contain animal-based gelatin. Instead, find a brand that puts its products into cellulose capsules.

DHA is fat-soluble, so you need to take them with food to absorb them well.

DHA should not break a fast unless you take a very high dose at once. If you practice time-restricted eating, take this fatty acid during your eating window to make sure it absorbs well and doesn’t break your fast.

References

Most of the information provided in this guide is supported by scientific research that can be found and verified in the PubMed medical library. We highly encourage you to use the library to verify anything said in this article. We excluded from consideration studies that are either confounded or have a high conflict of interest.

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