Side Effects of Vegan B Vitamins

By November 9, 2013Nutrition

What is Vitamin B?

There are 8 separate vitamins which are referred to as “Vitamin B”:

  • B1 (Thiamin, also Thiamine)
  • B2 (Riboflavin)
  • B3 (Niacin)
  • B5 (Panthothenic acid)
  • B6 (Pyridoxine)
  • B7 (Biotin, also called vitamin H)
  • B9 (Called folate in natural form, folic acid in synthetic form)
  • B12 (Cobalamins)

Each of these B vitamins has its own separate function in the body. However, because many of the functions are similar or related, B vitamins are often grouped together. As a group, B vitamins are crucial for aiding in the process of breaking down food into energy. For this reason, they have often been hyped up as helping with weight loss. Further, B vitamins are essential for nervous system function and some studies show that they may help reduce risk of Alzheimer’s.

There are many other essential functions of B vitamins in the body, such as helping in red blood cell formation, hormone synthesis, and cell production. B vitamins have been attributed to numerous benefits, such as:

  • Lowering cholesterol levels (niacin)
  • Fighting depression and stress
  • Reducing cancer risk
  • Increasing energy levels
  • Protecting against heart disease
  • Improving skin, hair and nail quality
  • Managing premenstrual symptoms
  • Stabilizing blood sugar levels

One B vitamin, folic acid, is so essential for new cell growth that it is recommended for pregnant women in their first trimester. Studies show that taking folic acid during pregnancy can reduce risk of health problems like spina bifida, heart defects, and cleft palate.

Vitamin B Daily Recommendations

B1 (Thiamine) (mg/d) B2 (Riboflavin) (mg/d) B3 (Niacin) (mg/d) B5 (Panth. Acid) (mg/d) B6 (mg/d) B7 (Biotin) (μg/d) B9 (Folic Acid) (μg/d) B12 (μg/d)
0-6m 0.3 0.3 2 1.7 0.1 5 65 0.4
6-12m 0.4 0.4 4 1.8 0.3 6 80 0.5
1-3y 0.5 0.5 6 2 0.5 8 150 0.9
4-8y 0.6 0.6 8 3 0.6 12 200 1.2
9-13y 0.9 0.9 12 4 1.0 20 300 1.8
14-18y 1.3 1.3 16 5 1.3 25 400 2.4
19-30y 1.3 1.3 16 5 1.3 30 400 2.4
31-50y 1.3 1.3 16 5 1.3 30 400 2.4
51-70y 1.3 1.3 16 5 1.7 30 400 2.4
70+y 1.3 1.3 16 5 1.7 30 400 2.4
14-18y 1.0 1.0 12 5 1.2 25 400 2.4
19-30y 1.1 1.1 14 5 1.3 30 400 2.4
31-50y 1.1 1.1 14 5 1.3 30 400 2.4
51-70y 1.1 1.1 14 5 1.5 30 400 2.4
70+y 1.1 1.1 14 5 1.5 30 400 2.4
Pregnancy 1.4 1.4 18 6 1.9 30 600 2.6
Lactation 1.4 1.6 17 7 2.0 35 500 2.8

***Information taken from Dietary Reference Reports found at the Institute of Medicine.


Natural Sources of Vitamin B

Vitamin B is quickly flushed out of animals and plants. However, animals are better able to hold B vitamins than plants, which is why they are a much richer source of the vitamin than plants. Foods with the highest content of B vitamins include clams, sardines, fish, lamb, and beef. In general, foods with high amounts of protein tend to be good sources of vitamin B.

Vegetarian food which are a good source of B vitamins include eggs, yogurt, and cheese.  There are also many vegan foods which are good natural sources of vitamin B though. These include:

  • Avocado
  • Pomegranate
  • Dates
  • Watermelon
  • Berries
  • Green vegetables (particularly types of cabbage and dark leafy greens)
  • Squash
  • Parsnips
  • Beans and legumes

While these vegan foods do contain high amounts of most B vitamins, they are not sources of vitamin B12, which (with the exception of nutritional yeast and some algae) is only found naturally in animal products. For this reason, many vegans choose to take a vitamin B12 supplement.

Vitamin Best Vegetarian Sources
B1 (Thiamin) Whole grains, seeds, nuts, beans, squash, watermelon, corn, peas, nutritional yeast, raisins, leafy green vegetables, mushrooms, asparagus, egg yolk
B2 (Riboflavin) Nutritional yeast, dried herbs, nuts, soybeans, most aged cheeses, wheat bran, tomatoes, sesame seeds, leafy green vegetables, yogurt, milk, mushrooms, eggs, bell peppers
B3 (Niacin) Whole grains, nuts, legumes, mushrooms, soy sauce, asparagus, dates, tomato products, bell peppers, leafy green vegetables, corn, sweet potatoes, avocados, nutritional yeast, eggs
B5 (Pantothenic acid) Bran, sunflower seeds, shiitake mushrooms, cauliflower, most aged cheeses, avocados, lentils, split peas, corn, leafy green vegetables, milk, yogurt, nuts, sweet potato
B6 (Pyridoxine) Whole grains, squash, sunflower seeds, shiitake mushrooms, lentils, chickpeas, beans, nuts, bell peppers, leafy green vegetables, bananas, potatoes, yams
B7 (Biotin) Egg yolk, leafy green vegetables, peas, soybeans, yeast, walnuts, peanuts, oats, bananas, avocados, lentils, wheat germ
B9 (Folic acid) Leafy green   vegetables, brown rice, peas, chickpeas, egg yolk, sunflower seeds, legumes, beans, citrus fruits, melon, banana, beets, corn, avocado
B12 Eggs, milk, yogurt, nutritional yeast, some algae


Vitamin B Deficiency

Because B vitamins are so important for metabolism and the nervous system, a deficiency in these vitamins can result in problems like low energy, stress or trouble concentrating. Deficiencies in vitamin B6, B12 or folic acid can also lead to anemia because the vitamins are critical in the production of new red blood cells.

It is important to remember that, even though we usually refer to B vitamins as a group, each does have its own specific function and a deficiency will produce different consequences. If you suspect a vitamin B deficiency, you should visit your doctor and not try to self-diagnose or medicate!

People at risk of vitamin B deficiency include:

  • Vegans (particularly a vitamin B12 deficiency)
  • Alcoholics
  • Pregnant and lactating women
  • The elderly
  • People with certain medical problems, such as intestinal problems, autoimmune disorders, or pernicious anemia

There is also some evidence that contraceptive pills may interfere with the absorption of vitamin B6. For this reason, women taking hormonal birth control may want to speak to their doctors about also taking B6 supplements.

Overdose of Vitamin B

B vitamins are water soluble (as opposed to fat soluble), which means that they are not stored in the body. They will be quickly flushed out of the body through urine, so a vitamin B overdose is not likely. For most of the eight B vitamins, there is absolutely no risk of overdose. The exceptions to this are vitamin B3 (niacin) and vitamin B6.

The recommended daily intake of niacin for adults is 14-16 mg. However, niacin is tolerable in much higher amounts. For healthy adults, the Institute of Medicine has listed the tolerable upper limit of niacin at 35mg/day. Niacin may be prescribed in high dosages for certain health conditions. For example, 1500mg/day of niacin is commonly prescribed for high cholesterol. At these levels, side effects from niacin could occur, such as:

  • Flushing
  • Skin rashes
  • Upset stomach
  • Diarrhea
  • Headache

If large dosages of niacin are taken for prolonged periods of time, it could possibly result in liver damage.

The recommended daily intake of vitamin B6 for adults is 1.2-1.9 mg. Like niacin, vitamin B6 is also tolerable in much higher amounts. The Institute of Medicine lists the tolerable upper limit of B6 for adults at 60-100mg/day. In dosages over 200mg/day for extended periods of time, B6 could result in neurological damage and coordination problems.


Who Needs Vitamin B Supplements?

Vitamin B supplements are prescribed for treating vitamin B deficiency. Since there is such a low risk of an overdose on vitamin B, many people at risk of deficiency may decide to take the vitamins as a preventative measure – particularly vegetarians. Vegans in particular should take vitamin B12 supplements because the vitamin is so difficult to get on a vegan diet.

Even people who aren’t at risk of vitamin B deficiency may decide to take the supplements because of their purported health benefits, like boosted energy, increased metabolism, and better mood.

Best Way to Take Vitamin B Supplements

Vitamin B should be taken with meals or immediately after eating. This will help the body absorb the vitamins.

Vitamin B supplements (like B complex pills) often come in very high dosage amounts. While there is virtually no risk of an overdose on vitamin B, it is pointless to take extremely high amounts of the vitamin. The body will not be able to make use of the high dosage and will just flush it out in your urine (which is why your urine will be very bright yellow after taking a high-dosage B complex vitamin).

To get the most of your B vitamin, consider taking lower dosages several times throughout the day (such as breaking pills in half and taking them at each meal). Or, you can look for extended-released vitamin B pills.

For severe deficiencies in vitamin B, a doctor may prescribe vitamin B injections.

Side Effects of Vegan B Vitamins

There are no natural vegan sources of B12, so all vegans need to supplement with Vitamin B12 if they want to stay healthy.  Yes, there are theories that we may be able to get B12 from algae, from fermented foods, or even get B12 from the bacteria in our guts.  But, so far, the experts have determined that their are no reliable plant-based sources of B12.  That means you might decide to take  B12 or B Complex supplements and, as with all supplements, you might experience some side effects.


Fluorescent Colored Urine


This is riboflavin, aka B2. Now you understand why your pee looks bright?!

If you take a look into the toilet bowl after taking a B complex vitamin, you might be surprised to see that the water is bright yellow.  Since B vitamins are water-soluble, unabsorbed vitamins from your supplement are going to exit through urine.  The bright color comes from B2 (riboflavin), which tints urine a yellowish-orange.  If your urine is really neon, then you are probably taking too high of a dose.  Or, you may want to switch to a time-released B complex supplement.


Having to Pee Like Crazy

B6 is a natural diuretic and helps the body get rid of excess fluids.  This can be very useful in treating bloat (such as before a woman’s period), but it can also be very annoying if it is making you go to the bathroom every 20 minutes!   Vitamin C and magnesium can also be culprits when it comes to frequent urination.  Overdoses of vitamin D may also cause frequent urination as a side effect.


Weird Colored Stools

B vitamins affect digestion as well as bile production.  As your stools go through the digestive tract, they may not absorb as much bile and could become a yellowish color instead of brown.   If your stools don’t turn back to their normal color, check with your doctor as it could be a sign that you are getting too much B5.  Also, see your doctor if your stools turn black. It may be a sign that you are experiencing liver damage from excess B3.  But note that black-colored stools is a really common side effect of iron supplements!


Vivid Dreams

Studies have shown that taking B6 can affect dreams, such as making dreams more vivid or enhancing dream recall.  The hypothesis as to why this happens is that B6 affects the conversion of tryptophan to serotonin.



If you want a good alternative to coffee for helping you stay awake, consider taking B12.  It has been shown to affect melatonin levels and promote wakefulness.  If you are taking B12 purely for health though, then you might want to take the supplement in the morning so you won’t have trouble falling asleep.



No, you are not going through puberty again.  That outbreak of acne may be a side effect of taking too much vitamin B6.  Scientists aren’t exactly sure how the vitamin causes acne but it may have something to do with B6 causing an increase in glucose production, which can lead to acne.


Tingly Sensation

In high dosages, vitamins B3 and B6 can cause a tingly sensation on the skin.  B3 (niacin) causes a warm, tingly feeling by dilating the capillaries.  B6 causes the tingling because it affects the nerves which carry messages to the brain.  The symptoms will usually go away once you stop taking the vitamins but, in some cases, can continue for several weeks.


So, What Can You Do about These Weird B Vitamin Side Effects?

After your body gets used to taking a B supplement and your diet adjusts, the side effects usually go away.  If they persist, it might be because you are taking too high a dosage of B vitamins, or because you are taking too much at once. 

Do yourself a favor and go get a blood test to see your B levels (at least your B12 levels). Your doctor can then help you figure out which supplement is right for you.  If you are already eating a lot of greens, then you might not need a B Complex supplement and just take the B12.  Or you might be taking an unnecessarily-high dosage of B complex.

By the way, I am not a doctor so don’t take any of this as personal medical advice.  I speak from my own experience and accounts from friends only!

To find out about B12 dosages, timing B12 supplements, and types of B12 supplements, read this post about vegan B12 dosage.  If you need B12 supplements, see a list of the top vegan vitamins here.





About Diane Vukovic

Diane Vukovic is a vegan mom, health nut, and kitchen diva. When she's not deducing veggie nutritional facts, she's probably dancing crazily with her daughter or traveling somewhere in Europe.

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