brain foggy

Brain Foggy? Are Bariatric Surgery and B12 to Blame?

August 15, 2022

Brain Foggy? Are Bariatric Surgery and B12 to Blame? Your brain has a demanding job. To do it well, it needs both calories and nutrients, including vitamins and minerals.

Did you know that your brain uses 20% of your calories?

That’s a good bite out of your daily calories. The brain prefers carbohydrates as its energy source but cannot store glucose like other organs or muscles in your body. What you eat and when you eat make all the difference in a brain that feels energized versus one that feels foggy. One big benefit of eating three meals and snacks, when needed after surgery, is that you are continually providing energy to the brain. At first, your carbohydrate intake will be fairly low, but it will increase as you heal and move toward a diet of regular foods. A smart nutrition strategy is to choose complex carbs which are high in fiber and nutrition, such as black beans, chickpeas, and sweet potatoes, along with fruit such as blueberries and strawberries as well as leafy greens, yellow squash and carrots.

You get the idea…highly nutritious carbohydrates versus empty calorie carbs which are mainly calories that are highly refined and loaded with sugars but contain little to no nutrition.

B-vitamins, folate, zinc and other vitamins and minerals all join in with calories to keep the brain healthy and less foggy. Many vitamins and minerals work together as a team or what’s called “synergistically”. That’s the case with the nutrients that feed your brain. B-vitamins, folate, zinc and other vitamins and minerals, such as thiamin, all work together like a softball team.

Deficiencies may cause issues such as symptoms of depression, poor memory, problems with attention span and learning as well as fatigue, mood and appetite changes or what just feels like brain impairment or brain fog. Routine lab work after your surgery is so important because of these potential brain issues.

Vitamin B12 also known as Cobalamin

Let’s zero in on vitamin B12, also known as cobalamin, which falls in the category of a water soluble vitamin. Has someone told you to take vitamin B12 for brain fog after bariatric surgery? Malabsorptive surgeries (RYGB, SG, BPD/DS) affects B12 absorption. Several factors are at play here. Less B12 is released after surgery where much of the stomach is bypassed or removed. The absorption of B12 can also be affected due to changes in acid production and reduced availability of what’s called the “intrinsic factor”. This intrinsic factor helps the B12 to be absorbed in the small intestine and used by the body.

When it’s not there or insufficient, B12, called the “extrinsic factor”, doesn’t get absorbed and used as it should. You could experience brain fog symptoms and feel like your coordination is off, plus experience numbness and tingling of your arms and legs. As we mentioned, this is a prime reason why routine screenings are so important and typically done every six months or so. These screenings help your health care provider pick up on a possible deficiency, hopefully, before it becomes a problem.

A B12 deficiency after bariatric surgery is common but did you know that B12 deficiency also increases with age? Often, as you get older, you tend to eat less and often eat fewer animal products rich in B12, which decreases the amount of B12 in your diet. This might surprise you, but one third of people 50+ don’t absorb B12 from their food well because they no longer produce enough stomach acid. They may also be lacking in the intrinsic factor which is produced in the stomach and helps to utilize and absorb B12. So in addition to surgery, age could be a factor in your B12 levels too.

A low vitamin B12 blood level often goes hand-in-hand with what feels like brain fog

Have you heard the word “homocysteine”? It’s an amino acid in the blood and high levels have been tied to a deficiency of B12 but also dementia. The good news is that the homocysteine level can be lowered by making sure your diet is adequate in vitamins B6, B12, and folate, which then seem to help retain that brainpower you want every day.

Two other tips to keep in mind:

  1. Are you taking metformin or proton-pump inhibitors (PPIs) like Prilosec, Nexium or Prevacid? These meds reduce stomach acid and remember, stomach acid is necessary to absorb B12. Even meds such as Zantac or Pepcid can increase the risk for B12 deficiency.
  2. Did you know that drinking alcohol reduces the absorption of B vitamins such as B12 and thiamine? Important to know since your levels could already be borderline or low.

Do you recall where you can find B12 in food? Animal protein foods like meat, eggs, cheese, fish, chicken, and milk are all terrific sources as well as fortified foods, such as breakfast cereals. Fortified means that the vitamin was added to the product and did not occur naturally. Include as many of these in your diet as you can, but remember that the amount of B12 needed after surgery is typically higher than what food can provide.

How much vitamin B12 do you need after surgery?

So how much vitamin B12 do you need after surgery? The dose is 250-500 micrograms (mcg) a day with most suggestions in the 350-500 microgram range daily or 1000 mcg every other day.  The dose depends on your surgery, your lab results and how you take it…meaning under the tongue, injection, etc. Sometimes an intramuscular injection of B12 or a nasal spray will be ordered by your health care team. You can take B12 at any time or with any other supplements. It’s likely that your multivitamin will have enough B12, so check the label before you buy additional.

Be sure and discuss your lab screenings with your health care team before you decide to take any extra B12. Routine lab work along with B12 food sources and supplements to meet the higher requirements all work together to help prevent deficiencies and ward off brain fog.

Registered dietitian nutritionist Dr. Susan Mitchell is host of the podcast Bariatric Surgery Success.

Susan Mitchell


Registered dietitian nutritionist Dr. Susan Mitchell is host of the podcast Bariatric Surgery Success. Selected as one of the Best 35 Dietitian Podcasts in 2021, Bariatric Surgery Success was chosen from thousands of podcasts on the web ranked by traffic, social media followers, domain authority & freshness. Dr. Susan helps you conquer cravings, emotional eating and weight regain after bariatric surgery with a focus on your nutrition and health, journey and success.