CLINICAL

  NUTRITION

THE BUZZ ABOUT THE Bs

A VISIT WITH THE EIGHT MEMBERS OF THE VITAMIN B FAMILY

THIS COLUMN is the second in a series on individual nutrients often found in multivitamin/mineral supplements and their link with eye health. This month’s focus: The vitamin Bs — some of the biggest unsung heroes in nutritional health, as described below.

Here, I provide an overview of this vitamin family, the ocular and systemic effect of each member and which patients are most likely to benefit from supplementation.

OVERVIEW

The B vitamins are a group of eight water-soluble nutrients found in a wide variety of plant- and animal-based foods, such as asparagus and poultry. Collectively, they are involved in virtually every functional system in the body, including energy production, DNA synthesis, red blood cell formation and nervous and immune system regulation, among scores of others.

Deficiencies in the B vitamins may occur in isolation or as part of a more widespread deficiency of water-soluble nutrients, as is sometimes seen in alcoholics, or in persons who have absorption difficulties due to GI or eating issues, such as food intolerances or anorexia.

For most patients, B vitamins work best when taken or eaten in combination with each other — think a “B complex” vitamin or a high quality complete multivitamin/mineral supplement. Studies reveal that the B vitamins compete with each other for absorption, so excess of one may reduce absorption of another.

As always, a dietary analysis — or better yet, serum or blood cell analysis — of nutrient status is advisable prior to starting supplementation. When recommending supplementation, be sure to alert the patient to take it with food or a beverage, as many people have nausea or GI upset when taking B vitamins on an empty stomach.

B ROLES

Here’s a look at the effect the vitamin Bs have on ocular and systemic health:

• B1 (thiamin). B1 deficiency is associated with scotomas in “nutritional amblyopia,” reveals a study in Current Ophthalmology. Systemically, supplementation with Vitamin B1, and especially its fat-soluble predecessor, benfotiamine, may improve glucose and insulin levels, possibly reducing the damage caused by hyperglycemic states.

• B2 (riboflavin). A decreased incidence of cataracts has been associated with higher dietary intake of riboflavin, and it is the substance used in conjunction with UV light in corneal cross-linking to treat corneal ectasia. In addition, keratitis may result from deficiency, and severe B2 deficiency may present as corneal neovascularization, so bear this in mind as an uncommon culprit. In terms of systemic health, adequate intake may ameliorate the frequency and severity of migraine headaches, says a study in the American Journal of Epidemiology.

• B3 (niacin). Niacin significantly increases HDL, which is essential for transport of the macular carotenoids lutein and zeaxanthin. Further, in pharmacologic doses, niacin has been shown to reduce overall serum cholesterol. It is often prescribed with other lipid-lowering medications, such as statins.

• B5 (pantothenic acid). Pantothenic acid has proposed anti-viral properties and may reduce the incidence and severity of herpes zoster relapses. More research is needed to add clarity to this potential application.

• B6 (pyridoxine). Pyridoxine supplementation in gyrate atrophy patients who have a genetic subtype may reduce serum ornithine levels by as much as 50% and, thus, slow the decline in retinal function, shows a study in Current Ocular Therapy. Patients who have type 2 diabetes are more likely to be deficient in vitamin B6 (as is the case with B1). This is especially true in patients with diabetic nephropathy, endothelial dysfunction and inflammation, reveals a study in Diabetes Research and Clinical Practices.

• B7 (biotin). A deficiency may present as skin rashes around the eyes, nose and mouth, conjunctivitis and/or impaired immune function, reveals Advances in Nutrition. Systemically, this vitamin benefits hair, skin and fingernails by acting as an enzyme and/or coenzyme in hair follicles, nail plates and other structures of the body’s surface.

• B9 (folate, folic acid). Adequate intake of folic acid has been suggested to carry a slightly lower risk of exfoliative or suspected exfoliative glaucoma, shows a study in JAMA Ophthalmology. In conjunction with B6 and B12, B9 may help reduce the frequency, severity and disability of migraine headache, says a study in Headache.

• B12 (cobalamin). Injections of B12 ameliorate the symptoms of herpetic neuralgia. In combination, thiamine and cobalamin locally injected have been shown to have benefit in reducing the itching and pain caused by herpes lesions, says the Clinical Journal of Pain. Further, a deficiency in B12 has been linked with eyelid myokymia. Also, B12 is currently a popular supplement used in conjunction with some weight loss medications and programs, as it has been suggested to augment weight loss when used in conjunction with reduced caloric intake. In addition, B12 injections have been shown to be effective in reducing the duration of symptoms in Bell’s palsy, says a study in JAMA. B12 deficiency is more common in patients who have diabetes and in alcoholics for the reasons explained previously, and certain genetic risk alleles make some people unable to “methylate” cobalamin into a usable form. B12 injections are now widely available for supplementation.

MOST LIKELY TO BENEFIT

When diet is inadequate, patients who have diabetes type 1 or type 2, those who suffer from migraines, people who drink alcohol to excess, those complaining of eyelid myokymia and patients who have elevated cholesterol are the most likely to benefit from supplementation, studies reveal. For additional information on the B vitamins, such as what constitutes adequate amounts, the Linus Pauling Institute at The Oregon State University (lpi.oregonstate.edu) has an excellent, extensive database that is free to the public. OM

KIMBERLY K. REED, O.D., F.A.A.O. is an associate professor at the NOVA Southeastern University College of Optometry in Fort Lauderdale, Fla., a member of the Ocular Nutrition Society and author of numerous articles on ocular nutrition, disease and pharmacology. She is also a frequent continuing education lecturer. To comment on this column, email Dr. Reed at Kimreed@nova.edu, or visit tinyurl.com/OMcomment to comment on this article.