If youre 50 or older, Uncle Sam says yes. Heres why and how best to get it.
When the latest federal Dietary Guidelines for Americans were released earlier this year with the recommendation that people age 50 and older should get extra vitamin B12 through fortified foods or supplements, one expert commented, Its not very difficult to anticipate the sudden spate of fortified with vitamin B12 as recommended in the 2010 Dietary Guidelines messaging that will populate the fronts of boxes and bags. Before the hype hits the grocery stores, what should you know about vitamin B12? Do you really need more? And why cant older people simply meet their B12 needs by eating more of the right foods?
There is probably more vitamin B12 deficiency in the population than is appreciated, says Irwin H. Rosenberg, MD, editor of the Tufts University Health & Nutrition Letter. Some studies have shown that 15%-30% of older people are low in B12.
Dr. Rosenberg recently co-chaired a World Health Organization (WHO) consultation about B12 and folic acid that defined this deficiency as a worldwide issue. Part of the problem is a global shortfall of animal proteins that supply B12. Even in the US, vegans and vegetarians who dont consume dairy products and eggs should be aware of the risk of vitamin B12 deficiency, because dietary sources of B12 are limited to animal foods.
What is low when it comes to vitamin B12? You need a blood test to be sure. Blood levels below 150 picograms per milliliter (pg/mL) are clearly low, says Dr. Rosenberg. Levels between 150 and 300 are uncertain.
The recommended daily allowance (RDA) of vitamin B12 for adults is 2.4 micrograms (mcg), with higher RDAs for pregnant and lactating women. Thats about the amount in three ounces of beef or three glasses of milk. Most Americans actually get more than the RDA, with the average daily intake at 3.4 mcg. Note that the Daily Value (DV) for B12 that you see reflected in percentages on Nutrition Facts labels is much higher, 6.0 mcg. That DV is based on older data, Dr. Rosenberg explains, and would be lower if the US Food and Drug Administration, which regulates Nutrition Facts labeling, followed the recommendations of an Institute of Medicine panel on B vitamins he chaired three years ago. Dr. Rosenberg is currently on a National Institutes of Health (NIH) expert panel studying B12 measurements.
The Acid Test
So why all the fuss about B12? As people get older they are more at risk of deficiency, Dr. Rosenberg explains, because they dont absorb B12 as well from food. The stomach acid needed to utilize B12 from food declines with age.
Although B12 is a water-soluble vitamin, when naturally present in foods such as meat, fish, poultry, eggs and dairy products, B12 is bound to proteins. In your stomach, hydrochloric acid and gastric protease (an enzyme that breaks down proteins) release the B12 for your body to use. But people with low levels of stomach acids cant extract as much dietary B12.
|Others at Risk
The vitamin B12 found in fortified foods, such as breakfast cereals, is different. The synthetic B12 added to foods or used in supplements is already in a free form that the body can absorb.
Atrophic gastritis, which decreases the secretion of hydrochloric acid in the stomach, affects between 10% and 30% of older adults. So the Institute of Medicine recommends that people over 50 obtain most of their vitamin B12 from fortified foods and supplements. Without blood tests, theres no way to know for sure if youre getting enough B12 from the food you eat. But one bowl of fortified cereal-check the label to make sure-can provide all the B12 most people over 50 need in a day (see box). Other foods fortified with vitamin B12 include soy milk and meat substitutes.
Even if your stomach produces plenty of acid, you could still be at risk for B12 deficiency. Dr. Rosenberg explains, So many people take proton-pump inhibitors now for indigestion or reflux. These work by shutting off gastric acid. In addition to proton-pump inhibitors, sold under brand names such as Prilosec and Prevacid, medications called H2 receptor agonists can also interfere with B12 absorption. These drugs are sold as Tagamet, Pepcid and Zantac, among other brands.
B12, Your Body and Your Brain
What happens if you dont get enough vitamin B12? Your body needs B12 for proper blood-cell formation, neurological function and DNA synthesis. According to the NIH, signs of vitamin B12 deficiency can include anemia, fatigue, weakness, soreness of the mouth or tongue, constipation, loss of appetite and weight loss. Neurological changes, such as numbness and tingling in the hands and feet, can also occur, along with difficulty maintaining balance. Vitamin B12 deficiency has been associated with depression, and research has suggested that extra B12 can help ward off depression in the elderly. Too little B12 can also manifest in confusion and poor memory.
The symptoms of B12 deficiency overlap with those of Alzheimers disease, says Dr. Rosenberg. That raises the question of whether similar nutritional factors contribute to Alzheimers-or to Alzheimers symptoms.
|Food Sources of Vitamin B12
(mcg/serving, % of RDA)
Beef liver, 1 slice-48.0 (2000%)
Clams, breaded and fried, 3 oz.-34.2 (1425%)
Rainbow trout, wild, 3 oz.-5.4 (225%)
Salmon, 3 oz.-4.9 (204%)
Rainbow trout, farmed, 3 oz.-4.2 (175%)
Beef, top sirloin, broiled, 3 oz.-2.4 (100%)
Yogurt, plain, 1 cup-1.4 (58%)
Haddock, 3 oz.-1.2 (50%)
Tuna, white, 3 oz.-1.0 (42%)
Milk, 1 cup-0.9 (37%)
Swiss cheese, 1 oz.-0.9 (37%)
Egg, 1 whole large-0.6 (25%)
Chicken, roasted, 1/2 breast-0.3 (12%)
But a direct link between vitamin B12 levels and the development of dementia remains elusive. Too little B12 can cause an accumulation of an amino acid, homocysteine, high levels of which have been associated with Alzheimers disease as well as cardiovascular disease. Studies have shown that B12 supplementation can significantly decrease homocysteine levels. But any accompanying benefits in cognitive function have mostly failed to be proven.
A 2010 study published in the journal Neurology did find an association between both homocysteine levels and blood levels of vitamin B12 and risk of developing Alzheimers disease. The study followed 271 older adults, average age 70.7, in Finland for an average 7.4 years. Higher homocysteine levels were associated with increased risk of developing Alzheimers, while higher B12 levels were linked to a reduced risk. The association with B12 was more notable with older age.
Nonetheless, two reviews of the scientific evidence for the Cochrane Library and a systematic review of randomized trials all found theres insufficient evidence to conclude that B12 protects against dementia. The same was true for B12 in combination with folic acid or vitamin B6.
The current state of the evidence is similar regarding heart disease. Much as with dementia, studies have shown that extra B12 reduces homocysteine-but the risk of cardiovascular disease doesnt drop as well. The American Heart Association has stated that the available evidence is inadequate to support a role for B vitamins in reducing cardiovascular risk.
The National Library of Medicine does rate supplemental vitamin B12 as possibly effective for age-related macular degeneration (AMD). Some studies have suggested a link between extra B vitamins and reduced risk of this leading cause of blindness among older Americans. The evidence for other nutritional interventions to reduce AMD risk is stronger, however, and worth considering before making the leap to vitamin B pills. (See page 8 in this issue and our January 2009 report on Tufts HNRCA Laboratory for Nutrition and Vision Research.)
Other claims for vitamin B12 supplements are on much more shaky ground. Because B12 plays a role in energy metabolism, for example, supplements are often promoted as energy enhancers or endurance boosters, and athletes pop them in hopes of improving performance. According to the NIH, however, Vitamin B12 supplementation appears to have no beneficial effect on performance in the absence of a nutritional deficit.
|Vitamin B12 in Popular Cereals
(mcg/serving, % of RDA)
Note that Nutrition Facts labels on cereals base percentages on the much-higher DV. Suggested serving sizes vary; figures here are all based on 1 cup and do not include milk.
Whole-Grain Total-8.0 (333%)
Grape Nuts-7.4 (296%)
Special K-6.0 (250%)
Total Corn Flakes-4.5 (187%)
Post Raisin Bran-3.2 (133%)
Fiber One-3.0 (125%)
Kelloggs Corn Flakes-2.7 (112%)
Rice Krispies-2.5 (104%)
Corn Chex-1.6 (67%)
Kashi GoLean-0 (0%)
Quaker Oatmeal Squares-0 (0%)
Shredded Wheat-0 (0%)
The National Library of Medicine rates vitamin B12 as possibly ineffective against sleep disorders and for stroke prevention. Theres insufficient evidence to rate the effectiveness of B12 in a host of other hoped-for treatments, including for shaky-leg syndrome, eczema and psoriasis, allergies and cancer prevention. (In fact, a 2009 analysis of homocysteine-lowering trials with folic acid and B12 in Norway found an increased cancer risk among those receiving the supplements.)
Although you certainly want to get enough vitamin B12, more is not necessarily better. The Institute of Medicine has not set a Tolerable Upper Intake Level (UL) beyond which too much B12 can be dangerous, and it says that no adverse effects have been associated with excess vitamin B12 intake from food and supplements in healthy individuals. But your bodys ability to absorb B12 from any source is finite. In healthy people, only about 10 mcg of a 500 mcg vitamin B12 supplement actually gets absorbed.
People who should not take B12 include those with Lebers disease, a hereditary eye condition. Patients with pernicious anemia should take the vitamin under a doctors supervision.
Some things besides medications may interfere with your bodys ability to absorb vitamin B12. Potassium supplements and heavy alcohol use may reduce B12 absorption. And vitamin C supplements might destroy dietary vitamin B12, so to be on the safe side, take these at least two hours after meals.
For most people, though, worries about vitamin B12 can be easily addressed and any forthcoming supermarket hype safely ignored. If youre 50 or older, a daily bowl of fortified cereal or a B12 supplement or multivitamin containing at least 2.4 mcg should do the trick. Vitamin B12 may not have the magic powers that some hucksters claim, but your body cant do without it-so be B12 smart.