Omega-3 and Vitamin D Together: Timing

Quick answer

NIH describes no effect of fish oil on vitamin D or the reverse, and the large VITAL trial tested both. Both are absorbed better with a meal that contains fat, so one meal suits both. Adults need 15 to 20 mcg (600 to 800 IU) of vitamin D a day; no amount is set for EPA or DHA.^1,2,3

Key facts

VITAL gave 25,871 US adults 2,000 IU of vitamin D3 and 1 g of fish oil a day, separately and together, for a median of 5.3 years.^1,2
In a trial of 50 older adults, a breakfast with fat gave a 32% higher peak of vitamin D3 than a fat-free breakfast.⁴
A high-fat meal raised EPA absorption from ordinary fish oil from 69% to 90%.⁵
Adults need 15 to 20 mcg (600 to 800 IU) of vitamin D a day, with an upper limit of 100 mcg (4,000 IU). No recommended amount is set for EPA or DHA.^3,6
Cod liver oil supplies EPA and DHA plus vitamins A and D, in amounts that vary from product to product.^1,7

The trial that tested both

This pair has an unusual advantage: a large trial was built around it. Its full name is VITamin D and OmegA-3 TriaL, and it used a two-by-two design so that each supplement could be judged alone and with the other.^1,2

VITAL, the largest US trial of vitamin D, gave 2,000 IU of vitamin D3 a day or a placebo to 25,871 adults (men 50 and over, women 55 and over) for a median of 5.3 years. Most already had adequate levels: only 12.9% started below 20 ng/mL.^2,8

In the VITAL trial, 25,871 US adults (men 50 and older, women 55 and older) took 1 g of fish oil a day, with 460 mg of EPA and 380 mg of DHA, or a placebo for a median of 5.3 years. The supplement did not significantly lower the rate of the trial's main combined heart outcome.^1,9

The headline result is modest. In generally healthy adults, most of whom already had adequate vitamin D, neither supplement significantly changed the trial's main outcomes, and for heart outcomes the vitamin D results did not vary by whether people also took the fish oil. That is not a finding that the supplements are useless for everyone. It is a finding that, for those outcomes, adding them to an already adequate intake showed no measurable gain.^2,8,9

What each is graded for

Raises EPA and DHA levels in the blood*^1,10

Strong evidence

In a five-month randomized trial in 115 healthy adults, 600 mg a day of EPA plus DHA from standard fish oil raised the omega-3 index (the share of EPA and DHA in red blood cell membranes) by 59%, with no change on placebo. NIH notes that all the common forms of omega-3 supplement raise blood EPA and DHA. Typical US intake from food is only about 90 mg a day.

Amount studied: 300 to 1,800 mg of EPA plus DHA a day; the 59% rise was at 600 mg a day for about five months

Contributes to normal muscle function*^2,11,12,13

Moderate evidence

Low vitamin D can cause muscle weakness, and 'contributes to the maintenance of normal muscle function' is a nutrient-function statement permitted in the EU. Extra vitamin D has not improved strength in trials: a pooled analysis of 54 placebo-controlled trials (8,747 people) found no benefit for muscle strength or physical performance, and a three-year trial of 2,000 IU a day in 2,157 adults aged 70 and over found no gain in physical performance. Read this as a reason not to run low, not as a strength aid.

Amount studied: The recommended daily intake; DO-HEALTH tested 2,000 IU a day for three years

Best time to take fish oil and vitamin D

The answer is the same for both: with a meal that contains some fat. NIH says vitamin D is best absorbed with a meal or snack that includes some fat, and the fish oil studies show the same dependence on the fat in the meal.^3,5

In a randomized study of 50 healthy older adults, one dose of vitamin D3 taken with a breakfast containing fat gave a 32% higher peak blood level of vitamin D3 than the same dose with a fat-free breakfast. The type of fat made no difference.⁴

How quickly each builds up^1,2,14,15
	Vitamin D	Fish oil
Blood level of the measured form	Leveled off at around week 6 at every dose	Serum EPA leveled off after 4 to 8 weeks
Pace	Blood 25-hydroxyvitamin D has a half-life of about 15 days	EPA in red blood cells took about 28 days to make half of its rise
Long-term marker	Changes over weeks	The omega-3 index reflects roughly the previous 120 days
Time of day	NIH names none	NIH names none

Because both build up over weeks to months, no single day's timing matters much. The sources stress taking them regularly with meals.^14,15

Cod liver oil and combined products

Cod liver oil supplies EPA and DHA plus vitamins A and D, in amounts that vary from product to product. Vitamins A and D can be harmful in excessive amounts.^1,7

If you take cod liver oil, count its vitamin D toward the total as well as the vitamin D from any separate supplement. The upper limit for vitamin D is 100 mcg (4,000 IU) a day for adults from all sources, including food and drinks.^3,7

What’s in ours

Omega-3: Fish oil concentrate, 1,000 mg per serving, from the label

What’s in ours

Vitamin D3: Vitamin D-3, 50 mcg (2,000 IU) per serving, from the label
Men's Multi: Vitamin D, 10 mcg per serving, from the label
Ashwagandha Complex: Vitamin D3, 20 mcg per serving, from the label
Immune Support: Vitamin D3, 40 mcg per serving, from the label

Our Omega-3 is a fish oil softgel without vitamin D, and our Vitamin D3 is a separate product, so the two are easy to tell apart on a label.

Too much, medicines and who should ask first

Too much vitamin D raises blood calcium. Signs include nausea, vomiting, muscle weakness, confusion, pain, loss of appetite, dehydration, passing a lot of urine, great thirst and kidney stones. They are linked to blood levels far above normal, usually over 150 ng/mL (375 nmol/L).^2,3

For fish oil, NIH says high doses of omega-3s may cause bleeding problems with warfarin or other anticoagulants and might lengthen bleeding time, and large trials found slightly more irregular heart rhythm with 4 g a day. Vitamin D can also interact with thiazide water pills, which reduce the calcium lost in urine.^1,3,6

Vitamin K, including K2, is often sold combined with vitamin D. Vitamin K is fat-soluble and is absorbed the way dietary fat is, so a meal with fat helps all three. The caution is warfarin: vitamin K works against it, and NIH advises people taking it to keep vitamin K intake the same from day to day. One study in healthy volunteers on a warfarin-like medicine found that 45 mcg a day of MK-7, a form of K2, lowered the INR by about 40%.^16,17,18

Ask first if you take warfarin or another blood thinner. High doses of omega-3s may add to bleeding, and vitamin K, including K2, can weaken warfarin.^6,17
Ask first if you have high blood calcium, kidney disease, kidney stones or an overactive parathyroid gland.³
Ask first if you take a thiazide water pill, a statin, steroid tablets, orlistat or a bile acid sequestrant, which can interact with vitamin D.^2,3
Ask first if you are allergic to fish or shellfish, or have atrial fibrillation or another heart rhythm problem.^1,19
Ask first if you are pregnant or nursing, or giving either supplement to a baby or child.^3,6

Questions people ask

Can you take omega 3 with vitamin D?

The NIH sheets describe no effect of one on the other, and the two were given together in the large VITAL trial. A meal with fat suits both. Check the totals if you also use cod liver oil or a multivitamin.^1,2

What is the best time to take fish oil and vitamin D?

Our sources name no hour for either. Both are absorbed better with a meal that contains fat, so take them with a meal you eat regularly.^3,5

Can you take omega 3 with vitamin D3 and K2?

Our sources describe no interaction between omega-3 and vitamin D or K. Vitamin K is the one to ask about if you take warfarin, because it works against that medicine.^16,17

Is fish oil better than vitamin D?

They do different jobs, so the comparison does not hold. Fish oil supplies EPA and DHA, and vitamin D is needed to absorb calcium and for normal bones, muscles and immune function.^1,2

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Sources

*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.