Tuesday, October 3, 2023

Everything you want to know about B–vitamins

B–vitamins are vital for cell metabolism and blood vessel health. As one ages, one gets vitamin B–6, B–9, B–12 deficiencies. Plus, vegan people are often severely deficient in B–vitamins.

Executive Summary

There are at least eight different B–vitamins. They function in a similar way and are interdependent. They are found in the same food sources. Hence, they are grouped together.

B–vitamins are catalysts and cofactors in many body processes. They are vital for nerve function, cell production, immunity, energy production, and healthy pregnancy.

As one becomes older, one may develop vitamin B6, B9, and B12 deficiencies. Vegetarian and vegan people are often severely deficient in B–vitamins. Read the full article below for many sources of B–vitamins, including vegan sources.

B–vitamins are linked to vascular integrity and can lead to medical conditions that involve blood vessel damage such as dementia, stroke, and heart disease.

It may not be worthwhile to test for deficiencies of various B–vitamins unless there is a specific medical reason or your doctor advises them. It is better to look at blood homocysteine levels, instead. Aim to keep it below 6.3 µmol/L.

B–vitamins are a group of water-soluble vitamins that are important for the metabolic activities of our body cells.

While they are chemically different compounds, they are often found in the same food sources. Also, their functions are similar or interdependent. Hence, they are grouped together as B-vitamins. Individually, they are named or numbered separately, such as folate or vitamin B9.


Cell metabolism needs many enzymes and cofactors, which act as catalysts for the body’s processes and speed them up. In the absence of these catalysts, the processes progress very slowly, often by many orders of magnitude.

Let us say that a process takes 0.6 seconds to complete, with the help of catalysts. Without those catalysts, it may take 1,000 times more time. So, it will need 600 seconds, or 10 minutes, to complete. If a cell uses that process to generate energy, it will take 10 minutes for the cell to get any energy to work.

No wonder such a person will not be able to walk. From the time his brain tells his legs to start walking, it will be 10 minutes before they muster the energy to do so. This is a figurative example of how enzymes and cofactors, such as B–vitamins, work.

Some B–vitamins are not cofactors but are precursors, or raw materials, for such cofactors.

Members of the B–Vitamin Family

In literature, you will find a mention of more than twenty-five of B-vitamins. They were numbered from B1 to B20. Some others were named Bf, Bm, Bp, Bv, etc.

Now, for a chemical compound to be called a vitamin, it has to fulfill two criteria:

  1. It should be required in the functioning of the body; and
  2. The body should not be able to make it on its own.

It was found later that many of these twenty-five B–vitamins could be synthesized by the body. And some others were not required by the body, after all. So vitamins, such as B4 and B8, are no more B–vitamins.

Some B–vitamins are made by our body, but not by the bodies of some animal species. So they are B–vitamins for those animals, but not for us humans. That is, they are not vitamins in the first place for humans.

So, effectively, there are eight B–vitamins relevant for us, viz. from B1 to B12, except B4, B8, B10, and B11.

There are some claims by people that vitamin B17 or amygdalin is able to prevent or cure cancer. But I could not find any good published studies to support those claims. Since this is a controversial matter, I would stay out of the debate and not consider it a B–vitamin for this article.

As an aside, vitamin D is not a vitamin either. It is synthesized by the body in the skin, on exposure to sunlight or ultraviolet rays.

Consumption of B–Vitamins

B–vitamins are water-soluble vitamins. So if you consume them in excess, they are excreted out of your body. As a result, their levels will rarely reach toxic levels in the body.

Your body cannot store B–vitamins, except vitamin B12, for long periods of time. So, you need to regularly consume B–vitamins through foods.

Functions of B-Vitamins

Vitamin B1 (Thiamine)

  • Helps in nerve function
  • Helps in energy production (carbohydrate breakdown to produce energy)
  • Helps in cell growth

Vitamin B2 (Riboflavin)

  • Supports nervous system
  • Helps in red blood cell production
  • Helps in growth and development
  • Helps in the use of other B–vitamins
  • Helps the eyes and skin

Vitamin B3 (Niacin)

  • Produces cholesterol
  • Helps in the use of other B–vitamins
  • Essential in hormone production
  • Helps skin
  • Helps digestive system
  • Helps nervous system

Vitamin B5 (Pantothenic Acid)

  • Helps in hormone production
  • Helps in the use of other B–vitamins
  • Helps in making cholesterol
  • Helps in making red blood cells
  • Helps in energy production (by the breakdown of carbohydrates and fats)

Vitamin B6 (Pyridoxine)

  • Helps in hormone production
  • Helps in the production of red blood cells
  • Helps digesting system
  • Helps nervous system
  • Helps immune system
  • Helps in metabolising carbohydrates, proteins, and fats
  • Helps in retaining proteins and carbohydrates as fuel
  • Helps in enzymatic reactions
  • Helps in making neurotransmitters
  • Helps in making hemoglobin

Vitamin B7 (Biotin)

  • Helps store energy
  • Helps metabolize carbohydrates, proteins, and fats
  • Helps energy production
  • Helps with hair, nail, and skin health
  • Help product fatty acids

Vitamin B9 (Folic Acid)

  • Helps in the production of red blood cells
  • Helps in female fertility and conception
  • Helps in pregnancy, to prevent birth defects, such as spina bifida
  • Helps in DNA creation

Vitamin B12 (Cobalamin)

  • Helps in the production of red blood cells
  • Helps in DNA creation
  • Helps immune system
  • Helps nervous system
  • Helps in protein metabolisation

RDIs of B–Vitamins

Daily Recommended dietary intakes or RDI of various B–vitamins are given in Table 1 below. There are different RDIs for men and women. Note that these are the new numbers for the USA.

In some special conditions, such as pregnancy, the numbers might be different. For example, in pregnancy, vitamin B9 RDI is 600 µg and not 400 µg.

Also, note that the numbers are sometimes different for different countries. That is because a country’s government takes a call on those numbers, based on its ethnic composition. For reference, I have also mentioned RDI numbers for the Indian population as given by an Indian government agency.

The upper limit is the level above which harmful effects can be seen. Since B–vitamins are water-soluble, they are excreted out of the body in the urine. So, their upper limit level is not, or cannot be, established.

Read on this website, a comprehensive article on Recommended dietary intakes of various nutrients.

Table 1. RDIs of various B–vitamins in the USA and India
VitaminUSA RDI (M)US RDI (F)India RDIUpper limit
Vitamin B11.2 mg1.1 mg1.4 mgUnknown
Vitamin B21.3 mg1.1 mg1.6 mgUnknown
Vitamin B316 mg14 mg18 mg35 mg
Vitamin B55 mg5 mgUnknown
Vitamin B61.7 mg1.3 mg2 mg100 mg
Vitamin B730 μg30 μgUnknown
Vitamin B9400 μg400 μg200 μg1000 μg
2.5 μg2.4 μg1 μgUnknown

Signs of B–Vitamins Deficiency

Deficiencies of different B–vitamins show signs specific to their shortfalls:

Vitamin B6 Deficiency

  • Anemia
  • Mouth ulcers
  • Chapped lips, cracks at the corner of the mouth
  • Tingling, or numbness, in hands and feet
  • Red, scaly, greasy, itchy, and inflamed skin, especially near oil-producing glands in the scalp, face, and chest
  • Mood disorders, such as irritability, confusion, and depression

Vitamin B9 (Folate or Folic Acid) Deficiency

  1. Anemia
  2. Mood disorders, such as irritability, confusion, and forgetfulness
  3. Sore mouth
  4. Diarrhea
  5. In pregnancy, an increased risk of birth defects such as spina bifida

Vitamin B12 Deficiency

  1. Anemia
  2. Tingling, or numbness, in hands and feet
  3. Mood disorders, such as irritability, confusion, and forgetfulness
  4. Poor muscle coordination, loss of balance

Sources of B-vitamins

Many foods contain some amount of nutrients. So when is a food item considered a good source of any nutrient? The rules of thumb for any food item to be called:

  1. A good source of a nutrient: one serving of the food item must contain at least 10 to 19% of the recommended daily intake (RDI) of the nutrient.
  2. High in a nutrient: one serving of the food item must contain at least 20% of the RDI of the nutrient.

Serving Size

Here is a simple rule for the size of a single serving:

  • Fruits: 150 gm
  • Vegetables: 75 gm
  • Grains, nuts, seeds, legumes, beans, fish, egg, and meats: a quantity that gives about 120 calories

Read more about this: What is a serving size?

Now, just to make life more miserable, remember that this serving size is given by the Department of Health, Australia. They may be somewhat different in other countries.

Food Sources of B–Vitamins

  • Vitamin B1: Grains, port, tuna, and mussels
  • Vitamin B2: Mushrooms, almonds, dairy products, and chicken
  • Vitamin B3: Organ meats, beef, fish, chicken, eggs, dairy productions, and nuts
  • Vitamin B5: Leafy green vegetables, organ meats, meats, dairy products, legumes, and avocados
  • Vitamin B6: Liver, beef, white meat, fatty fish, potatoes, all non–citrus fruits
  • Vitamin B7: Beef, pork, sardines, egg yolks, whole grains, sweet potatoes, spinach, and broccoli
  • Vitamin B9: Leafy green vegetables, fatty fish, oranges, peanuts, asparagus, broccoli, and Brussels sprouts
  • Vitamin B12: Meats, eggs, and dairy products. There are no vegan sources, except nutritional yeast and Shitake mushroom

B–Vitamin Contents

I tried putting together a table of contents of various foods that are high in B–vitamins. But I gave up after some time when I found numbers all over the place. For example, two equally authentic sources claimed one large egg (50 g) contains 9% and 18% of RDI of vitamin B12, respectively. So, look at the tables below as just rough numbers.

Vegan Sources

Table 2. Percentages of RDIs of various B–vitamins in vegan food sources
Food ItemCategoryServingB1B2B3B5B6B7B9B12
Black beansLegumes100 gm38%
Chick peasLegumes100 gm41%
EdamameLegumes100 gm71%
Green peasLegumes100 gm14%
Kidney beansLegumes100 gm34%
LentilsLegumes100 gm53%
Pinto beansLegumes100 gm44%
Roasted soy nutsLegumes100 gm52%
Collard greensVegetables100 gm24%
Romaine lettuceVegetables100 gm34%
Spinach, cookedVegetables100 gm36%
Spinach, rawVegetables100 gm48%
Turnip greensVegetables100 gm29%

Vegetarian, Non–Vegan Sources

Table 3. Percentages of RDIs of various B–vitamins in vegetarian, non–vegan food sources
Food ItemCategoryServingB1B2B3B5B6B7B9B12
Cheese, cheddarDairy100 gm33%
MilkDairy250 ml7%26%9%18%
Yogurt, frozen, vanillaDairy250 gm30%17%
Yogurt, plainDairy250 gm24%39%
Yogurt, plain, greekDairy250 gm54%82%
Yogurt, vanillaDairy250 gm52%52%

Non-Vegetarian Sources

Table 4. Percentages of RDIs of various B–vitamins in non–vegetarian food sources
Food ItemCategoryServingB1B2B3B5B6B7B9B12
Egg, large (two)Eggs100 gm30%14%66%10%18%
Salmon, cookedFish100 gm18%29%50%19%47%51%
Tuna, cannedFish100 gm92%
BeefMeat100 gm5%8%39%6%31%29%
Beef, grilledMeat100 gm64%
Beef, liverMeat100 gm12201876951138651386%
Beef, liver, grilledMeat100 gm3500%
Chicken, breastMeat100 gm7%69%10%30%6%
Chicken, dark meatMeat100 gm13%33%12%18%5%
HamMeat100 gm16%
PorkMeat100 gm69%24%24%9%27%14%
Turkey, breastMeat100 gm8%37%7%28%7%
Turkey, dark meatMeat100 gm15%17%14%19%7%
Blue musselsShellfish100 gm20%25%15%19%400%
ClamsShellfish100 gm10%25%17%7%1648%
OystersShellfish100 gm8%26%18%4%480%

Testing for Deficiencies

The biggest problem that arises with B–vitamins deficiency is high homocysteine levels. Read a comprehensive article on this website talking about that: Are B–vitamins and dementias related? The article explains the damage caused in the body by high homocysteine levels. It shows that the B–vitamin deficiency is the main cause of those high levels. So, it makes sense to test if you have a deficiency of any B–vitamin.

To check for B–vitamin deficiencies that can raise your heart and brain disorder risks, people do just their blood vitamin B12 tests. There are three limitations in such blood vitamin B12 checking:

  • It does not tell you about vitamins B6 and B9 levels in the blood. Deficiencies of either can cause trouble, as mentioned above, even if vitamin B12 levels are fine.
  • Blood homocysteine levels may go up, even before vitamins B6, B9, or B12 levels dip low enough to be flagged abnormal.
  • Homocysteine levels can go high in kidney disease, underactive thyroid (hypothyroidism), or alcoholism. In such patients, levels of vitamins B6, B9, or B12 may be normal.

Of course, if your doctor has advised you vitamin B12 test, you should go with that advice. For example, your doctor may have advised you blood vitamin B12 test to rule out pernicious anemia. That is a different disease category than what high homocysteine levels lead to.

However, if it is allowed in your country, and so, if you are going to check your vitamin B12 levels for your own satisfaction, do consider a blood homocysteine test, instead. It is a common and relatively inexpensive test.

First published on: 19th June 2019
Image credit: Steve Buissinne from Pixabay
Last updated on: 23rd May 2022


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