Vitamin D has become an extremely popular supplement – and with good reason. Many people are deficient in the nutrient. That deficiency has serious implications for health.
Research has also shown a wide range of benefits from vitamin D, for people that are deficient and for those who are not.
But, there are two different forms of vitamin D.
Learning the difference between vitamin D2 vs D3 is critical if you want the best health outcomes.
Vitamin D2 vs D3 – What’s the Difference?
Both forms are considered prohormones. They promote the production of 25-hydroxyvitamin D, which is also called 25(OH)D. This is the active form of vitamin D in the body. 25(OH)D levels are what we measure to see the amount of vitamin D that is produced.
The forms are traditionally considered to be equivalent (3). But, there are still some differences.
- Also called ergocalciferol.
- Is obtained from plant sources, particularly from mushrooms.
- Vitamin D2 supplements are often vegan as a result.
- Many foods are fortified with vitamin D2, like cereals, milk and juice. This includes vegan options such as soy and almond milk.
- Also called cholecalciferol.
- Is found in both humans and animals.
- We produce vitamin D3 from a form of cholesterol, in the presence of sunlight (4).
- Most vitamin D3 products and supplements are non-vegan. However, there are some vegan alternatives, such as this one from the brand Doctor’s Best.
- Vitamin D3 is more biologically active (5).
- It is also more structurally similar to the active form of vitamin D.
Which Form is More Powerful?
Health advice often assumes that vitamin D2 and D3 are roughly the same (6). After all, the two forms are very similar to one another.
They do have a slightly different structure, but the variation between them isn’t dramatic. This is why so many foods are fortified with vitamin D2. But, the research doesn’t agree.
- Vitamin D3 increases 25(OH)D levels more significantly (7,8,9) and sustainably (10) than vitamin D2. One study even saw an increase of 74% to 75% for vitamin D3, compared to just 33% to 34% for vitamin D2 (11).
- Vitamin D2 may be less than one-third as potent as vitamin D3 (12).
- Studies show that vitamin D2 has less binding efficiency (13) and shorter duration of action (14).
- The D3 form is more powerful at lowering mortality risk in elderly women (15). Similar effects may exist for other populations and health outcomes too.
- Vitamin D2 also has a shorter shelf life (16), making it less appealing in supplements.
- The molecular weight of vitamin D2 and D3 also means that one IU of vitamin D2 contains less of the vitamin than with vitamin D3 (17). The differences may be significant for health benefits.
The idea that vitamin D2 and D3 are the same is also based on old research and general assumptions (18). There is little evidence to suggest that this is the case for most situations. However, the research is mixed and some studies have failed to find advantages of D3.
What Does Vitamin D Do Anyway?
Vitamin D is an essential micronutrient and plays a role in various biological functions. Studies have linked vitamin D supplementation to many different health benefits.
- Decreased risk of falls (19,20) and fractures (21) in seniors.
- Lowered heart disease risk (22,23,24,25). Mechanisms include slightly decreasing blood pressure (26,27) and decreased triglyceride levels (28). Some authors even suggest vitamin D deficiency may be a heart disease risk factor (29).
- Decreases in overall risk of death and cardiovascular-related mortality risk (30,31).
- May decrease cancer risk (32,33,34).
- Improved fat loss (35,36), although research outcomes are mixed (37,38).
- Improvements to the immune system, including the potential to decrease influenza risk (39,40,41,42).
- May lower diabetes risk and help improve glucose metabolism (43,44).
- Better dental health (45,46). This may be due to the relationship between calcium and vitamin D.
There are also many other potential benefits. Research into the field is ongoing and there is much that we still need to learn.
Vitamin D Deficiency vs Optimal Levels
Some of the observed benefits were for people considered deficient in vitamin D (below 50 nmol/L) but many were not.
Vitamin D deficiency is also a concerning problem. The deficiency is much more common than people assume – to the extent that it is sometimes called an epidemic (47,48). This may be because the symptoms are difficult to recognize and because people assume that they’re already getting enough of the vitamin.
The deficiency can have many implications for health, as symptoms include depression (49,50,51), chronic pain (52,53), slow wound healing (54,55,56), inflammation (57) and a less efficient immune system (58,59,60). Vitamin D deficiency has even been linked to various chronic diseases (61).
These patterns suggest two general ways that increasing vitamin D can help.
- By preventing vitamin D deficiency and the associated symptoms.
- By providing various extra health benefits.
As a result, vitamin D can still be beneficial, even if you’re not deficient in the micronutrient.
Best Sources of Vitamin D
Vitamin D is clearly important, especially the vitamin D3 form. So, how do you get it?
Vitamin D is technically a hormone, not a vitamin. Our bodies produce vitamin D3 in the presence of sunlight. This suggests that simply getting outside more will give you sufficient vitamin D levels. However, there are some issues to be aware of.
- Sunshine is unreliable, especially in winter. The angle of the sun often means you’re getting little vitamin D, even if you are outside (62).
- Your vitamin D synthesis is also affected by geographic location, altitude, time of day, skin exposure and other factors.
- Some groups of people also produce less vitamin D and need more sun exposure. This includes seniors, people with darker skin and anyone who is obese (63,64). Some medical conditions can impact vitamin D synthesis as well, like inflammatory bowel disease (65).
Many of us probably need to get outside more often anyway – and spend more time in the fresh air. But, this mightn’t be enough to get the vitamin D levels you need.
There are also foods that contain vitamin D. The site Rodale’s Organic Life highlights many of these. Key examples include:
You can also look for any foods that are fortified with vitamin D. But, most options will contain the vitamin D2 form. This means you’re getting fewer benefits.
Most people are already eating these foods regularly. Yet, vitamin D deficiency remains prevalent. This suggests that food alone isn’t enough to ensure that you get the most possible vitamin D benefits.
Supplements are often the best choice for vitamin D. They offer a way to get higher doses of vitamin D3. You also know the amount that you’re getting.
However, you do need to choose the product carefully.
- Companies may use D2, D3 or a combination of both.
- Some brands are more reliable than others.
- If the product just says vitamin D and doesn’t state which form – they’re probably using vitamin D2.
It’s best to take vitamin D supplements daily with a source of fat. Fish oil is one option, or you can simply have the vitamin D during a meal.
How Much Vitamin D Do You Need?
Finding the ideal vitamin D dose is an incredibly controversial topic. There are multiple perspectives with no consensus about how much vitamin D is needed (66).
Official recommendations suggest relatively low levels of vitamin D.
- The National Institutes of Health (NIH) considers 50 nmol/L (or 20 ng/mL) of 25(OH)D to be sufficient for 97.5% of the American population (67). To reach these levels, the NIH recommends an intake of 600 IU of vitamin D per day.
- Doses this low are still enough to prevent rickets in children. But, the low dose offers limited benefits.
- Some research also indicates that higher levels of 25(OH)D are needed. For example, one study found that 25(OH)D concentrations of 75 nmol/L or above were most powerful for decreasing the risk of nursing home admission (68). Other studies have suggested levels of 90 to 100 nmol/L (69).
- Many studies have found benefits at higher doses, such as 700 to 800 IU per day (70)
- Safety research suggests that 4,000 IU per day is safe. Some studies indicate that higher doses (up to 10,000 IU per day) may also be safe (71,72).
Such patterns suggest that 600 IU of vitamin D3 per day is too low. Instead, higher doses are needed to see all the possible benefits. The site Examine.com offers more details about research and the doses that have been examined.
Between 1,000 and 2,000 IU per day is a common place to start.
- This offers the potential for benefits but is still far under the safe upper dose.
- It also means you can get vitamin D from other sources without being concerned.
Some people use higher doses. Very high doses (like 50,000 IU) are sometimes used weekly or monthly instead, for people who are severely deficient. But, you should always consult a doctor before using high doses and have your vitamin D levels monitored.
Vitamin D3 is one of the few nutrients that should be supplemented in most situations.
But, food and sunlight simply aren’t a reliable source of vitamin D3 – not for most situations.
- We do live in a mostly indoor society. We’re often inside working in the sunniest parts of the day. Our sun exposure is also limited when we’re outside too – by things like shade, sunscreen, hats and long sleeves.
- If we could get enough vitamin D from the sun and from food, studies would show fewer benefits from vitamin D supplementation. Instead, research strongly suggests that vitamin D deficiency is significant and puts people at risk.
Vitamin D3 supplements are a good way to get the vitamin D you need and protect your health.
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