The Truth About Vitamin B12

Here’s the truth: you need vitamin B12 in your diet to make healthy red blood cells and support your nervous system, and only a few plant foods, like seaweed, mushrooms, and nutritional yeast, naturally contain B12.

Vitamin B12 is made by anaerobic bacteria in the gut, and animals naturally make it in their gastrointestinal tracts and absorb it. If you eat animal protein, then you naturally get some vitamin B12.

So that means people who eat animal protein have sufficient B12 levels, right?

Not so fast. Interestingly, I find deficient and insufficient vitamin B12 levels in lots of my patients, whether or not they eat meat. How can that be? Just like many other processes in the body, vitamin B12 absorption is a complex process that only starts with consuming the vitamin. Absorption of B12 is dependent on age, strength of stomach acid, use of pharmaceutical medications like metformin or acid-blockers, history of prior bowel surgery, damage to the gut lining from autoimmune conditions like Crohn’s, infections like Helicobacter pylori, and bacterial overgrowth, just to name a few.

So you might wonder if you should supplement with vitamin B12 regardless of whether you eat plants. The answer is maybe. How do you know if you need to supplement? You can easily check your level with your doctor.

Another vitamin that plant-forward eaters need to be knowledgeable about is vitamin D because it is naturally found almost exclusively in animal products, like the oily fish herring, mackerel, salmon, and sardines, as well as egg yolks, red meat, and liver, especially from lambs. (Porcini mushrooms are a plant-based source.) It’s also added to a lot of foods, such as milk (this is why your milk carton says “vitamin A D fortified”) and breakfast cereal, to help the public get more of this essential nutrient.

You may ask the same question about whether vitamin D deficiencies are more common in people who don’t eat animal products. Just as with vitamin B12, I see a lot of patients with vitamin D deficiencies and insufficiencies. In fact, except in rare cases, I see lower-than- recommended vitamin D levels in almost every patient who is not taking a vitamin D supplement.

Why are vitamin D levels almost universally a problem? It’s not because people are not eating animal products. It’s because the best way to get vitamin D is to step outside, and most of us live our lives without spending as much time in the sunshine as we need.

Vitamin D is known as the sunshine vitamin because it’s naturally created in our bodies upon exposure to sunlight, and the best way to increase vitamin D levels is to expose a good amount of skin to the sun for at least twenty minutes every day. This presents a problem for many of us, including me. I live in Connecticut, where it’s only comfortable to be outside in a tank top and shorts for about three months of the year. And of course, we are all concerned about skin cancer and wrinkles, so we tend to lather up with sunscreen (which is good for us!), but sunscreen doesn’t allow our bodies the exposure to sunlight they need.

It’s important to get vitamin D because it’s crucial to the absorption of other important nutrients like calcium, iron, magnesium, phosphorus, and zinc through the gut. Poor vitamin D levels are associated with all kinds of health problems, including heart disease, cognitive impairment, asthma, cancer, and the bone-softening condition called rickets. So get your bum in the sun for ten to twenty minutes a day in the summer, take a vitamin D3 supplement in the fall, winter, and spring, and eat some yummy salmon once a week.