Frequently Asked Questions About Vitamin D

Why do we need vitamin D?

Every tissue in our bodies needs vitamin D and will not work correctly if we do not get enough. In its most extreme forms, vitamin D deficiency produces rickets in children and osteomalacia (bone softening) in adults. Milder degrees of deficiency are now understood to be one of the causes of a vast array of chronic diseases, including osteoporosis, impaired immune competence, various autoimmune diseases (such as diabetes and multiple sclerosis), several cancers (breast, colon, lung, lymphoma and prostate, among others) high blood pressure, pregnancy complications and cardiovascular disease. All may develop because of, or be exacerbated by, vitamin D deficiency. Asking the body to deal with these disorders without adequate vitamin D is like asking a fighter to enter battle with one hand tied behind his/her back.


What is vitamin D?

Vitamin D is one of the chemicals that the tissues of our body use to unlock the DNA blueprints which each tissue contains and which are needed for our cells to produce the many biochemical products required for their day-to-day functioning.


Where do I get vitamin D?

The principal source of vitamin D is your own skin. A chemical compound naturally present in the superficial layers of skin is converted, on exposure to UVB radiation, to cholecalciferol (vitamin D3). However, we manufacture this vitamin D only if we expose our skin to UVB radiation. If we spend all day indoors or go out only in the early morning or late afternoon, we don’t produce any vitamin D. You can also get vitamin D from food (limited), supplements and other UVB sources.


How long should I be outdoors?

There is no single right answer. A light skinned person, wearing a bathing suit, will make about 15,000 IU of vitamin D in 15-20 minutes in July at midday. Darker-skinned individuals can do the same, but it will take twice as long.


What is the effect of sunscreen?

Sunscreen blocks UVB radiation and prevents the manufacture of vitamin D.


What about skin cancer?

The brief exposure needed to produce adequate vitamin D is not enough to cause skin cancer. However, if you are worried about that risk, apply sunscreen after the first 15 minutes of exposure.


Does the body have to process vitamin D before it becomes active?

The body converts vitamin D, whether by mouth or made in the skin, to a compound called 25-hydroxyvitamin D [25(OH)D]. This compound circulates in the blood and is the measure physicians or scientists use to assess vitamin D status. High levels of serum 25(OH)D show that you are getting enough vitamin D, while low levels indicate deficiency.


How much vitamin D do I need?

The body needs at least 4000 IU/day in order to maintain a healthy concentration of 25(OH)D in the blood. Because most of us don’t get enough sun exposure, the little vitamin D we get that way, plus food and fortified food sources, totals no more than about 2000 IU/day. Thus in order to meet the body’s need for about 4000 IU/day, most adults should take supplements providing 1000-3000 IU daily. Check grassrootshealth.net to download a table showing the relationship between intake and resulting serum levels.


Is vitamin D safe?

Vitamin D is safe, if consumed in reasonable quantities. (See ‘How much vitamin D do I need?’) It is instructive to know that outdoor summer workers by the end of summer will typically have serum levels of 60-80 ng/ml (150-200 nmol/L). However vitamin D is an extremely potent compound, and if taken in abnormally high doses, can produce severe toxicity leading even to death. However, there have been no reported cases of vitamin D toxicity at serum levels of 25(OH)D below 200 ng/ml (500 nmol/L).


What about calcium and vitamin D?

Vitamin D enables the body’s regulation of calcium absorption. With inadequate calcium or vitamin D intake, there is insufficient calcium absorption. However, there is no hyper-absorption with high vitamin D levels. There is also a substantial body of evidence indicating there is an inverse relationship between calcium intake and kidney stone risk.


Is it important to take vitamin D daily?

For the optimal benefits of vitamin D supplementation, enough vitamin D should be provided on a daily basis to ensure that stable circulating concentrations of vitamin D are maintained, and a serum 25(OH)D level in the range of 40-60 ng/ml (100-150 nmol/L) is achieved and sustained.


What about the current IOM (Institute of Medicine) published requirements for vitamin D?

The IOM recently (2010) increased the ‘no observable adverse event level’ to 10,000 IU/day. 4000 IU/day can be considered a safe upper intake level for adults aged 19 and older. This is significant progress. They tripled the intake for all individuals up to age 50. Their focus was limited, however, to skeletal health, not the full array of diseases considered by the D*action Scientists’ Panel.

Frequently Asked Questions about D*action

How long does it take to receive my blood spot test?

After you complete your questionnaire and pay for your test, your order is fulfilled within 2 business days. We ship first class mail from San Diego, CA.


How do I find my participant ID?

You received an email from GrassrootsHealth with a subject “Thanks for joining D*action”, the participant ID is in that email. Alternatively, you may login to D*action (www.grassrootshealth.net/test); scroll down the page until you see a box; click on “Start or review the D*action Participant Questionnaire now”. The next page that appears lists your participant ID right under the header.


I lost my password. How do I get into my account?

Go to www.grassrootshealth.net/test and click on “Need New or Forgot Password?” in the left column. The system will then email you a new password. Use this password to login. You may then change your password by clicking on “account settings” in the left column.


I don’t remember the email I used to login.

Please email customerservice@grassrootshealth.org with your name, address, and phone number. We will let you know which email you used as your login.


I want to change my email for D*action.

Since your email is your login, this must be changed by GrassrootsHealth. Please email customerservice@grassrootshealth.org with your name, old email (login) and new email. We will notify you when it is changed.


I never received a confirmation email; did I pay for a test?

Please contact customerservice@grassrootshealth.org. We can let you know your status and when you will receive the blood spot test. Typically you will receive the blood spot test within 5-7 business days of completing the questionnaire and paying for the test.


Can I participate if I live in _______?

Absolutely! Anyone, anywhere is welcome to participate.


Can NY residents take part in the study?

Yes, residents of NY are now welcome to participate in the study. Due to past laws in the state of New York regarding blood crossing the state line, New York State residents could not join D*action. This law has been changed and now you can complete an at-home blood test with GrassrootsHealth even if you live in New York State.


How long does it take to receive my results?

It is currently taking from 10-15 days from the time you record doing the blood spot test (and mailing to GrassrootsHealth) until we post your results (US addresses.) You will receive an email (to the email address you provided as login to D*action) when we have the results.


Is there an additional cost to mail a kit overseas?

No. You just have to pay postage on the return envelope.


I signed up for the whole study and now it is time for me to take my second test, how do I do that?

The same way you did the first one! Please login to D*action (www.grassrootshealth.net/test) and complete the questionnaire. Your old data has been saved and except for your primary information, the questionnaire is clear. Please carefully review your answers. When you get to the end, if you have already paid (a subscription), do not enter your credit card in PayPal again – we already have your payment. Then, complete the blood spot test, return it, and await your results!

Frequently Asked Questions About the D*action+Omega-3 Project

What is the Omega-3 Index?

The Omega-3 Index is a blood test that measures the amount of omega-3 fatty acids (EPA and DHA) in red blood cell (RBC) membranes. It is expressed as a percent of total RBC fatty acids. It is a long-term and stable marker of omega-3 status, and it reflects tissue levels of EPA+DHA. An Omega-3 Index over 8% is associated with the lowest risk of death from heart disease and below 4% with the highest.


What is the cost of the Omega-3 Index test?

The Omega-3 Index test comes with the vitamin D test; the combined cost is $99 plus $5 shipping for a single kit, or you can choose to subscribe to either a one year or five year subscription. With both subscriptions we will automatically bill your credit card and ship you a test every 6 months.  Choose the one year subscription to receive one kit now and another kit in 6 months at $97 plus $5 shipping each, or the five year subscription for a kit every 6 months at $95 plus $5 shipping.  The cost includes the collection kit, the envelope to send in your blood spot, and a detailed report of your results, which will include your Omega-3 Index and your 25(OH) vitamin D serum level.


If I’m already a D*action participant, can I use the same login and participant ID for D*action+Omega-3?

You will create a new login and password at https://omega3d.grassrootshealth.net/register to join D*action+Omega-3. You may use the same email address as your former D*action account, but write the new ID that is generated for you on this web page when you turn in your blood spot cards. Your D*action login, password and ID are still all valid for D*action  – but if you are choosing to test both nutrients going forward you will use this new login and password.


Where do I go to order the vitamin D and Omega-3 Index test kit?

You can order your test kit from the dashboard within your new account generated at https://omega3d.grassrootshealth.net.


How quickly will the results be available?

It takes 7-10 days from the time we receive your completed blood spot test with questionnaire until we post your results; incomplete questionnaires will cause an additional delay. You will receive an email (to the email address you provided as login to the D*action+Omega-3 project) when we have the results, which will be posted to the Results page within your omega3d.grassrootshealth.net account.  You must log in to your account to view your results.  Log in here.


How do I collect the sample for the Omega-3 Index testing?

The process for collecting the dried blood spot samples for both our vitamin D test and the Omega-3 Index test is the same as that for the vitamin D blood spot test, with just a few exceptions. Be sure to write your new D*action+Omega-3 participant ID on both blood spot cards first. You may use the same finger prick for each blood spot card if there is enough blood. In case a second prick is needed, an extra lancet and band-aid have been included in the kit.


You may refer to our how to video here, and apply it to both the vitamin D and Omega-3 Index blood spot tests.

Frequently Asked Questions about the Omega-3 Index Test

How is the Omega-3 Index different from other fatty acid profile tests?

A single finger prick should provide enough blood to measure your Omega-3 Index. This eliminates the need to have your blood drawn at a clinic and the hassle of sending hazardous materials (blood) through the mail. You can collect your sample and send it through the mail from the comfort of your own home!

The Omega-3 Index test can give you an unbiased view of your dietary intake of omega-3s as well as a relative measure of heart disease risk.

Other fatty acid tests do not use the same analysis methods and cannot be interchanged with the Omega-3 Index.

The unique method used with the Omega-3 Index test has more research behind it than any other commercially-available test, and new studies continue to be published.

How is the Omega-3 Index different from other fatty acid profile tests (from a researcher’s perspective)?

A. It differs in several ways.

First, the sample types the lab typically uses (red blood cells or dried blood spots versus whole plasma or plasma phospholipids). Each of these sample types has a unique fatty acid profile, so you cannot compare the EPA+DHA level in RBCs to the EPA+DHA level in plasma, or in plasma phospholipids – the numbers will be quite different, even from the same lab. So regardless of which lab you choose to work with, you should always order the same type of test if you want to be able to track trends in the same patient over time. The lab we use focuses on RBC and whole blood (dried blood spot) analyses because from either one they can provide the Omega-3 Index. These metrics provide the best reflection of tissue omega-3 fatty acid status. In addition, there is considerably more day-to-day variation in the plasma tests than in the RBC – (or whole blood) – based tests, and an acute load of omega-3 fatty acids (from fish or capsules) will significantly perturb the plasma-based markers but not the RBCs.

B. The uniqueness of the specific method used by the lab

Second, even if you order the RBC-based assay from two different labs, there is no guarantee that you’ll get the same answer. That’s a big problem. The reason is that, unlike serum cholesterol or glucose or calcium, there is no standardized method (i.e., internationally recognized gold standard) to which all labs must peg their assays. There is no standard test material to which all labs are required to conform. So your EPA+DHA, for example, might be 6.7% in Lab A and 5.2% in Lab B. Which one is “right?” We don’t know what “right” is because there is no formal standard. However, obtaining the Omega-3 Index from the lab we use guarantees you a metric that has been accepted in over 100 research publications over the last 9 years, making it the most published of all the commercially-available methods. A significant advantage of the Omega-3 Index test is the ability to correlate it to clinical outcomes from major epidemiological and interventions studies.

C. The provision of dietary recommendations to correct deviations from “normal”

The research supporting a target of 8% is strong, and it is known that you can specifically raise the Index by eating more omega-3. We don’t, however, know exactly how much EPA+DHA any particular person should be told to take to achieve the 8% target. People differ, and so each person’s response to supplemental omega-3s will vary. Just like one cannot predict how much serum cholesterol will go down when a patient is placed on statins, we cannot accurately predict how the Omega-3 Index will respond to an increased intake; it must be individually tested.


If I am taking omega-3 supplements, won't my Omega-3 Index be above 8%?

Not necessarily. There is no way to predict – for any given person – what your Omega-3 Index will be just by knowing how much fish you eat or how many capsules you take. Individual differences in metabolism, absorption, and genetics make it impossible to predict with certainty how a given person will respond to supplements.


How can I know if I am getting enough omega-3?

The only way is to directly measure the Omega-3 Index.


What is the target range for the Omega-3 Index?

The target Omega-3 Index is 8% and above, a level that current research indicates is associated with the lowest risk* for death from coronary heart disease (CHD). This is also a typical level in Japan, a country with one of the lowest rates of sudden cardiac death in the world. On the other hand, an Index of 4% or less (which is common in the US) indicates the highest risk*. At present, there is no reason to suggest that the target should be different for men vs. women, or for different age groups. Whether there is an upper limit of safety for the Index is not clear, but there is likely a value above which there is not likely to be any additional health benefit. Further research will help define this level.

*In this context, “risk” refers only to that associated with differing levels of omega-3 fatty acids. Risks associated with other factors such as cholesterol, blood pressure, diabetes, family history of CHD, smoking, or other cardiac conditions are completely independent of the Omega-3 Index. All risk factors – including the Omega-3 Index—should be addressed as part of any global risk reduction strategy.


What can I do to change my Omega-3 Index?

To increase your Omega-3 Index, you need to increase your intake of EPA+DHA. The amount you would need to take in order to raise your Omega-3 Index into the target range (>8%) depends in part on your starting level, but it cannot be predicted with certainty as described above. Nevertheless, if your Omega-3 Index is between 4% and 8%, it may take an increase of EPA+DHA intake of 0.5 -1 gram (500 – 1000 mg) per day. This can be accomplished in two ways: eating more oily fish and/or taking fish oil supplements. On the other hand, if it is less than 4%, it may take an increased intake of 1-3 g (1000 – 3000 mg) per day. Although this can be accomplished by eating more oily fish, fish oil and other marine omega 3 supplements are usually necessary to achieve this level of EPA+DHA intake.


What is the purpose of the reference ranges for the Omega-3 Index?

Included with each the 5 classes of fatty acids are “reference ranges.” The reference range is provided simply to give an idea of how these values compared to a large number of others taken from a relatively healthy population. In the case of the RBC assay, the reference range was taken from approximately 11,000 individuals whose samples were submitted to the laboratory for analysis. In the case of the dried blood spot assay, the reference range was taken from approximately 27,000 individuals. No information regarding the state of health of any of these individuals is known. In both cases, the reference range encompasses 99% of the individuals in their respective populations. Although “average,” these are not necessarily “optimal” levels, i.e., target levels or levels that one should to attempt to achieve. Providing an actual target or optimal level for the Omega-3 Index has been adequately validated by much research. 


Does your Omega-3 Index test lab follow Good Lab Procedures? Are your assays validated per FDA guidance?

Yes, the lab we use for the Omega-3 Index test (OmegaQuant) follows Good Laboratory Practices. All of their assays are validated. In particular for plasma/serum total and free (i.e., unbound) concentrations of EPA, DHA, DPA and ARA have been validated per the Guidance for Industry: Bioanalytical Method Evaluation (FDA; May, 2001). 

Frequently Asked Questions about Performing the Blood Spot Test

How do I get more blood to flow?

Make sure you wash your hands under very warm water. Try pricking the side of your pinky finger and wipe the first spot of blood off with gauze. Then, milk your finger as you fill the blood spot card.


I am worried my blood spots are not big enough. Can I get another card?

Yes, but first measure your blood spots if you have one spot that is 6 mm (1/4”) in diameter, then the card is valid. Or you can have 2 spots that are (1/8”) 4.5 mm in diameter. If you didn’t get that much blood, email customerservice@grassrootshealth.org and we can mail you another blood spot card and lancets.


Can blood be taken from other parts of the body?

Yes, your earlobe and toes are two other good alternative areas.


Is the Omega-3 Index test a fasting test?

No. It is not necessary to fast before collecting your sample; however, it is best to collect the sample before taking fish oil supplements.


Will my blood spot test expire?

The kit itself does not expire, however the completed Omega-3 Index blood spot sample does expire 28 days after the date of collection. Because of this, it is important to send your blood spot test back to GrassrootsHealth immediately after completion, and to complete your online health questionnaire as quickly as possible to avoid delay in processing.

If you delay too much in filling out the questionnaire after your either your Omega-3 Index or vitamin D blood spot date, then we may ask you to fill out another blood spot card.

Documentation and Materials

Can I purchase one of the videos on your home page to run in my office?

Yes, they were created and are sold by the University of California, San Diego. They cost $20 – $25 for each video and can be purchased at UCSD TV.


I am a doctor and promote vitamin D and D*action frequently, can I link to your web site?

Absolutely! You may advertise our web site as much as you want. Doctors and other health care practitioners are also encouraged to complete our free vitamin D CMEs to become a GrassrootsHealth Certified D*practitioner, after which you can request to be listed on our website. More information can be found on our D*practitioner page.


I would like to handout more vitamin D materials at work/home/play. Can you provide any?

If you notice, many of our pages also have a pdf form. Just check the bottom of the page and click on “Printable Download (PDF)”. On the home page, in the lower right are two very good documents for this – “California Call to D*action” and “Disease Incidence Prevention Chart”. We also distribute a tri-fold “Does Vitamin D Prevent Cancer?” and some cards, “Scientists’ Call to D*action”. We would appreciate a donation for these; email susan@grassrootshealth.org to let us know how many you need.

Vitamin D Health Questions

Why does GrassrootsHealth recommend having 40-60 ng/ml of vitamin D (25 OH D) as opposed to 50 ng/ml or 60 ng/ml being the lower limit on some of the other vitamin D web sites?

GrassrootsHealth has gathered a group of 40 researchers/practitioners who AGREE that at least 40-60 ng/ml is necessary. The key to our public health effort is to have a consistent message, and all 40 members agree that 40 ng/ml is the minimum. There are, as you note, people who think it should be higher. Getting everyone to at least 40 ng/ml is still a major achievement, however! This would solve many of today’s world-wide health problems.


How quickly does supplementation take effect?

Generally, with a constant dose, it takes about 3 months of dosing in order to reach a plateau. However, there are some regimens which use very high doses for a few days or weeks to push up the level more rapidly.


How reliable is your vitamin D test?

GrassrootsHealth uses ZRT Laboratory (www.zrtlab.com). Key considerations are that they are CLIA (Clinical Laboratory Improvement Amendments) certified, which ensures the lab conforms to federal regulations regarding testing, and that they participate in DEQAS, the Vitamin D Quality Assessment Scheme, which provides control samples to ensure assay accuracy. The blood spot assay is performed using liquid chromatography/tandem mass spectrometry (LC-MS/MS), the gold standard in 25(OH)D testing. Download this document from ZRT which gives more information.


What is the D2 level that is reported with my blood spot test? What does it mean?

D2 is frequently very low or ‘0’. The only sources of D2 are from some supplements and maybe a small amount in foods. D3 is what your body makes from the sun and that’s the version of the supplement that our panel recommends.


Can you recommend a doctor that understands D health?

While we cannot personally recommend a specific doctor for your needs, our D*practitioner page has a list doctors and other health care providers who have completed at least one of our vitamin D CME courses. If your doctor does not seem familiar with vitamin D, when you visit your doctor, take a copy of the Disease Incidence Prevention Chart and the Call to D*action and discuss it with him/her. That’s a good way to start!