Predominantly plant-based diets have benefits, but they can also cause underappreciated health problems.
The reason? Those who avoid animal food products often do not get enough B-12, the much-needed vitamin found in animal products that helps build red blood cells, repair DNA, and protect the brain.
That could be dangerous. Whether through more animal foods, including eggs and dairy, or a dietary supplement, Americans must ensure they get enough of this micronutrient.
Most vegans (folks who don't eat animal products) and vegetarians (people who don't eat red meat, seafood, or poultry) are short on B-12. A study published in the American Journal of Clinical Nutrition found nine in 10 vegans had below-normal levels of B-12.
Vegetarians fare a bit better thanks to dairy and eggs, but they also fall short. About 55 percent of children on a vegetarian diet have inadequate B-12 levels, according to a study.
As a physician scientist who has dedicated the past 50 years of my professional career to studying vitamin B-12, I know that B-12 deficiency can have serious health repercussions.
The symptoms start slowly, with indicators like fatigue, mood changes, and pale skin. But these can escalate to issues like vision loss, imbalance, and paralysis.
B-12 deficiency is also known to raise the risk of developing depression, dementia, and even cancer.
The nutrient is also critical for normal intrauterine development. Babies who don't receive enough B-12 in the womb could develop a dangerous defect. Indeed, expectant mothers with B-12 deficiency are up to five times more likely to have a child with a potentially disabling or fatal birth defect.
A new Harvard study reports that the children of women given B-12 supplements during pregnancy and in the weeks immediately after birth score higher on expressive language tests at age two.
Children also need B-12 for their proper development. Kids short on B-12 can face problems with digestion and growth. Such deficiencies have even been linked to neurological and behavioral disorders.
Getting enough B-12 isn't difficult with a proper diet or supplements, if necessary. The recommended daily dose for most adults is 2.4 micrograms per day; pregnant women and nursing moms need a touch more.
To put that in context, there are about 1.3 micrograms of B-12 in a serving of steak, 1 in an eight-ounce glass of milk, and 0.5 in one egg. Thus, getting enough B-12 is relatively easy for people who eat from these food groups.
Those on plant-based diets, especially if pregnant or nursing, need to pay particularly close attention to their B-12 intake.
Fortunately, B-12 supplements are safe and generally inexpensive. So long as the stomach and intestines are functioning normally, a relatively small daily supplement will suffice, with 50, 20, even 10 micrograms being sufficient.
People with absorption problems may require higher doses, typically between 500 -1000 micrograms daily, or regular injections of B-12.
Vegetarians and vegans aren't the only ones at risk of B-12 deficiencies. The elderly, folks who take heartburn medications to reduce stomach acid, patients with celiac or Crohn's disease, and even people who have undergone gastric bypass surgery for obesity are also vulnerable.
Also, increased intake of folic acid, through supplement use as well as from its addition to grains and cereals, poses an added risk to people with low B-12 levels.
B-12 is extremely important. Whether by adding enough scrambled eggs and milk to their diets - or taking a supplement - people must ensure they're getting enough of it.
Dr. Ralph Green is a research scientist at the University of California.