Veggie Blog

Everyone needs a steady supply of vitamins and minerals to stay well. A balanced diet usually provides them, but in some people, and in some stages of life, the supply runs short. The signs can be vague and easy to miss, which is why it pays to know who is at risk and what to do about it, before you reach for a bottle.

What causes a deficiency?

The usual causes are a limited or poor diet, illnesses or surgery of the digestive tract that reduce absorption, and some medicines. Vitamin B12 is a good example. The NIH says that causes of B12 deficiency include difficulty absorbing B12 from food, a lack of intrinsic factor, surgery on the digestive tract, long-term use of medicines such as metformin or proton pump inhibitors, and a diet that provides too little.

What are the signs?

They depend on the nutrient, and many are general. According to the NIH, a lack of B12 can cause fatigue, pale skin, palpitations, a sore tongue and neurological changes. Iron deficiency anemia can cause weakness, fatigue and difficulty concentrating. Vitamin D deficiency can lead to rickets in children and to osteomalacia, in which bone is defectively mineralized and weak, in adults. Feeling tired is very common and has many other causes, such as poor sleep and stress, so it should not be assumed to be a vitamin shortage. That is why a blood test is more useful than guesswork.

Who is most at risk?

People who follow vegetarian or vegan diets have a higher risk of vitamin B12 deficiency, because the natural food sources of B12 are limited to animal foods. Reliable plant sources are fortified foods such as breakfast cereals and nutritional yeast, or a supplement. Iron needs are also higher for people on vegetarian diets, since the iron in plant foods is not absorbed as well, and the NIH puts the requirement at 1.8 times that of people who eat meat. For B12, others at risk include older adults, people with pernicious anemia or other digestive disorders, and those who have had stomach or bowel surgery. Read our guides to vitamins and your health and vitamin C for more on individual vitamins.

How is a deficiency found and treated?

Your doctor can order blood tests. For B12, the level in the blood is usually measured, and a second marker, methylmalonic acid, can confirm the diagnosis when the result is borderline. Treatment depends on the cause. Vitamin B12 deficiency is typically treated with injections, because they bypass any barriers to absorption, and doctors may choose other options in milder cases. Do not try to catch up by taking huge doses. The NIH points out that taking more than you need costs more and might raise your risk of side effects.

Can supplements prevent disease?

You may read that a mix of vitamins protects against cancer and heart disease. The research does not support that. For community-dwelling, nonpregnant adults, the U.S. Preventive Services Task Force recommends against beta-carotene or vitamin E supplements to prevent cardiovascular disease or cancer, and it finds the evidence insufficient to judge multivitamins or single and paired nutrient supplements for this purpose. See the Task Force recommendation for details. A supplement can help when you have a proven need, but it is not a substitute for food.

So if you often feel tired, or you follow a restricted diet, make an appointment and ask about testing. The NIH fact sheet on vitamin B12 is a good place to read up on what to ask.