In the early 20th century, it was believed that humans only needed four types of nutrients: proteins, carbohydrates, fats, and minerals. Today, we know otherwise. In recent times, scientists have discovered that a severe deficiency of certain vitamins can lead to “deficiency diseases”. 

Well-known, but rare, deficiency diseases:

However, when these conditions were essentially eliminated in many places around the world with “food fortification” and improved food supplies, it was assumed that vitamin deficiencies no longer existed. We now realize that genetics, diet, chronic diseases, lifestyle, exposure to environmental toxins, and more can affect an individual’s nutrition requirements. According to a 2006 report by the World Health Organization, one in three people around the world are deficient in a variety of vitamins and/or minerals. Often, diet is not sufficient for making up these inadequacies and supplements may be recommended.

 Water-Soluble Vitamins vs. Fat-Soluble Vitamins

Vitamins are classified into two main categories: water-soluble and fat-soluble. Fat-soluble vitamins require fat in the diet in order to be absorbed. These vitamins are stored in the liver and fat tissue of the body and may be available for use when needed. Water-soluble vitamins, by contrast, dissolve in water and are not stored in the body. 

Water-soluble vitamins – These are easily dissolved in water and absorbed in the intestinal tract. Water-soluble vitamins are rarely stored in the body, so if an excess amount is present, the body will excrete it through the kidneys and the urine.

 Vitamin B6 (Pyridoxine)

Vitamin B6 is involved in over 100 biochemical reactions in the human body and plays an important role in nerve and overall brain health. It is also important in the metabolism of sugar molecules, cholesterol, and protein. A 2008 study showed that “substantial proportions of some population subgroups” do not have sufficient vitamin B6 levels. A deficiency is frequently present if one is low in vitamin B12 and folic acid

Risk Factors for Vitamin B6 Deficiency:

  • Regular or excessive alcohol consumption 
  • Obesity or overweight
  • Pregnancy
  • Malabsorption conditions (leaky gut, celiac disease, Crohn’s disease, ulcerative colitis)
  • Being elderly
  • Eating a vegetarian diet
  • Taking certain medications

Medications such as the diabetes drug metformin and the diuretic furosemide can increase the risk of vitamin B6 deficiency. Women on birth control pills or who are former users of birth control pills are also at risk for vitamin B6 deficiency according to studies, so extra caution should be taken by those who take this medication. 

Vitamin B6 is absorbed in the jejunum, the mid-portion of the small intestine. Having good gut health is important for absorption of B6 all vitamins and minerals. 

Symptoms of Vitamin B6 Deficiency

  • Seborrheic dermatitis (Dry scalp)
  • Fatigue
  • Confusion
  • Numbness
  • Carpal tunnel syndrome

Food Sources of Vitamin B6:

  • Pork
  • Beef and beef liver
  • Turkey/chicken breast
  • Salmon/tuna
  • Chickpeas
  • Bananas
  • Potatoes
  • Pistachios

It is recommended that most adults consume 1 to 2 mg per day of vitamin B6, while most children need anywhere from 0.1 to 1.3 mg per day, depending on age. However, some believe the recommended levels should be increased. Do not take more than recommended on any given supplement bottle. Otherwise, consuming more than recommended may cause symptoms of neuropathy in some. 

Vitamin B6 is available in a quality multivitamin or B-complex supplement, and also as an individual supplement. 

Vitamin B12 (Cyanocobalamin)

Vitamin B12 (also referred to as cobalamin or cyanocobalamin) is an important nutrient that your body requires to help optimize brain, nerve, and blood health. The cobalt mineral plays an important role in its structure. Vitamin B12 is a water-soluble vitamin, meaning the body will eliminate what it does not need. One cannot overdose on this vitamin. 

Studies from the United States demonstrate that up to one in six (17 percent) of those aged 60 and older are deficient in vitamin B12, while upwards to one in 15 (6 percent) of those under age 60 are deficient. Many other populations around the world are equally affected. In the northern part of China, for instance, a 2014 study showed that up to 45 percent of Chinese women were deficiency in vitamin B12. Africa, Russia, Europe, and the Middle East populations also have high deficiency rates. Those with a reduced intake of meat are at increased risk for deficiency, as are vegetarians

Medications such as metformin and most acid reducers (omeprazole, pantoprazole, etc.) increase the risk of vitamin B12 deficiency as they inhibit absorption in the gut. Routine alcohol intake is a risk factor for deficiency, and those who suffer with alcoholism are more susceptible.

Signs and Symptoms of Vitamin B12 Deficiency

  • Anemia (megaloblastic)
  • Abnormal platelet count (can be low or elevated)
  • Burning tongue (burning mouth syndrome)
  • Depression
  • Fatigue
  • Hallucinations and confusion
  • Insomnia
  • Elevated homocysteine (increased risk for heart attack, stroke and blood clots)
  • Loss of balance
  • Memory loss (vitamin B12 deficiency is more common in those with dementia)
  • Ringing in the ears (tinnitus)
  • Vitiligo (a skin condition where sections of the skin lack color, i.e. hypopigmentation) 

One can also have numbness and tingling in legs and arms. Doctors refer to this as peripheral neuropathy. Neuropathy is common in those with diabetes but may also affect those with pre-diabetes or sometimes those without diabetes. 

Food Sources of Vitamin B12

  • Beef/ Chicken/Turkey
  • Fish
  • Eggs
  • Dairy products
  • Spirulina (a blue-green algae)

When vitamin B12 levels are not sufficiently reached with diet, it may be taken as a supplement. It can be taken as a capsule, tablet, sublingual, or gummi. Also, vitamin B12 is also found in a B-complex vitamin.

Folate (Vitamin B9)

Folate is an important water-soluble vitamin required for healthy cell division and proper nerve development. It is required for adequate production of DNA, RNA, and amino acids. A common form of the vitamin that is added to vitamins and food is folic acid. The word folate is derived from “foliage”, a reference to green leafy vegetables and plant foods, where folate is found in abundance.

In the United States, up to 20 percent of teenage females do not get adequate amounts of folic acid. A 2017 study in the European Journal of Clinical Nutrition suggested up to 85 percent of women in the United Kingdom aged 16-49 are at risk for deficiency. Men and women from Asia, Europe, Africa, and the Middle East are also at risk.

Maternal intake of folic acid may reduce risk of autism in babies, according to a 2018 study in JAMA Psychiatry. Prenatal vitamins contain folate and, when taken, can help prevent neural tube defects and cleft lips and palates in babies. Women of childbearing age should take folate routinely, according to many health professionals.

Risk Factors of Folate Deficiency

  • Diet low in vegetables
  • Certain medications (triamterene, methotrexate medications)
  • Routine or excessive alcohol intake
  • Malabsorption syndromes (leaky gut, celiac disease, Crohn’s disease, ulcerative colitis)
  • Medications can reduce absorption (acid reducers, methotrexate, seizure medications)

Symptoms of Deficiency

  • Neuropathy and nerve impairment
  • Depression
  • Anemia, megaloblastic
  • Nerve impairment and memory loss
  • Elevated homocysteine (increased risk for heart attack, stroke, and blood clots)
  • Neural tube defects in baby (if mother is deficient during conception and early pregnancy)
  • Increased risk of certain cancers (colon, lung, pancreas, esophagus, bladder)

Food Sources of Folate

When diet does not provide sufficient folate, a folate or folic acid supplement should be considered. This is especially important in women of childbearing age. It can be consumed as an individual supplement, part of a B-complex vitamin, or as part of a quality multivitamin or prenatal vitamin. The minimum dose is 400 mcg, and rarely is a dose of more than 1,000 mcg recommended.

Vitamin C (Ascorbic Acid)

Vitamin C, also known as ascorbic acid or L-ascorbate, has been one of the most researched vitamins over the last five decades. 

A search of the scientific literature reveals that over 63,000 studies have been conducted on vitamin C since 1968, and almost 20,000 studies in the last decade alone. Medical research has shown that vitamin C helps promote immune system, heart, vascular system, and overall brain health among many other benefits. Low blood levels of vitamin C are associated with higher risk of cardiovascular disease and death. 

According to a 2009 study in The American Journal of Clinical Nutrition, over seven percent of people age six and older were vitamin C deficient when their blood levels were measured. More than half of those surveyed consumed low amounts of vitamin C rich foods. 

In my career, I have diagnosed three American patients with scurvy, a disease that was traditionally diagnosed in British sailors and common among malnourished pirates, both whom had limited access to fresh fruit. However, it is believed that scurvy is more common than realized even today and that we should be measuring vitamin C blood levels in those at risk and with poor diet. Tobacco users have lower vitamin C blood levels than non-smokers. 

Symptoms of Vitamin C Deficiency 

  • Bone pain
  • Bruising
  • Depression 
  • Fatigue
  • Joint pain
  • Muscle aches
  • Swelling

Food Sources of Vitamin C

  • Vegetables (peppers, broccoli, kale, Brussels sprouts)
  • Fruits (papaya, oranges, cantaloupe, kiwi, strawberries)

Health benefits of Vitamin C

  • Anemia treatment (increases absorption of iron when taken together)
  • Promotes collagen regeneration and overall skin health
  • Promotes gum and dental health
  • Promotes heart and vascular health
  • Improves endothelial function (inner lining of blood vessels)
  • Provides immune support
  • Provides memory support
  • Helps prevent upper respiratory infections/cold
  • May help in the treatment of sepsis (blood infection)

The minimal amount of vitamin C needed to prevent scurvy is about 60 mg per day, and this can be met by eating foods rich in ascorbic acid. Those who supplement will consume between 250 to 1,000 mg per day. Vitamin C is available as a powder, capsule, tablet, and gummy formulation. 


  2. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes: Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: National Academy Press; 1998.
  3. Morris MS, Picciano MF, Jacques PF, Selhub J. Plasma pyridoxal 5’-phosphate in the US population: the National Health and Nutrition Examination Survey, 2003-2004. Am J Clin Nutr 2008;87:1446-54.
  4. Wilson SM, Bivins BN, Russell KA, Bailey LB (October 2011). "Oral contraceptive use: impact on folate, vitamin B₆, and vitamin B₁₂ status". Nutrition Reviews. 69 (10): 572–83. doi:10.1111/j.1753-4887.2011.00419.x. PMID 21967158.
  5. Students show 17% of those 60 and older are vitamin B12 deficient, page 62, accessed October 29, 2017
  6. Dang S, Yan H, Zeng L, et al. The Status of Vitamin B12 and Folate among Chinese Women: A Population-Based Cross-Sectional Study in Northwest China. Sengupta S, ed. PLoS ONE. 2014;9(11):e112586. doi:10.1371/journal.pone.0112586.
  7. Accessed October 17, 2017
  8. Bailey RL, Dodd KW, Gahche JJ, et al. Total folate and folic acid intake from foods and dietary supplements in the United States: 2003-2006. Am J Clin Nutr 2010;91:231-7
  9. European Journal of Clinical Nutrition. 2017 Feb;71(2):159-163. doi: 10.1038/ejcn.2016.194. Epub 2016 Oct 12.
  10. Levine SZ, Kodesh A, Viktorin A, et al. Association of maternal use of folic acid and multivitamin supplements in the periods before and during pregnancy with the risk of autism spectrum disorder in offspring. JAMA Psychiatry 2018;75:176-84.
  11. He H, Shui B. Folate intake and risk of bladder cancer: a meta-analysis of epidemiological studies. International Journal Food Science Nutrition 2014;65:286-92. 
  12. Moser MA, Chun OK. Vitamin C and Heart Health: A Review Based on Findings from Epidemiologic Studies. Int J Mol Sci. 2016;17(8):1328. Published 2016 Aug 12. doi:10.3390/ijms17081328
  13. American Journal of Clinical Nutrition. 2009 Nov;90(5):1252-63. doi: 10.3945/ajcn.2008.27016. Epub 2009 Aug 12.
  14. Callus CA, Vella S, Ferry P. Scurvy is Back. Nutr Metab Insights. 2018;11:1178638818809097. Published 2018 Nov 21. doi:10.1177/1178638818809097. (Scurvy is more common than realized)
  15. Atherosclerosis. 2014 Jul;235(1):9-20. doi: 10.1016/j.atherosclerosis.2014.04.004. Epub 2014 Apr 18. (Vitamin C improves endothelial dysfunction)
  16. Journal of Critical Care. 2018 Feb;43:230-234. doi: 10.1016/j.jcrc.2017.09.031. Epub 2017 Sep 18. (Vitamin C may help in the treatment of sepsis)