Vitamin D and B12

“I’m thinking of adding Vitamin D to my daily routine,” Tim tells me. “Remind me, what are the benefits?” 

For questions about health and nutrition topics, I visit Dr. Greger at For COVID updates, I listen to Dr. Osterholm’s podcast. Tim calls them my two boyfriends. When we find people (or organizations) we trust, additional information only serves to confuse us. Like clothes and dessert, less is better. 

Treating supplements as some insurance policy is a bad idea. Remember when Vitamin E was touted as a free radical fighter, good for skin, and so forth? Overnight, food companies started fortifying our food with Vitamin E. Studies later suggested that too much Vitamin E can shorten our life span. Supplement producers who capitalize on our fears don’t update us on new studies that may reduce their sales. More and more, we need to find out for ourselves. Better to be self-informed through honest research than influenced by advertisers.

Sufficient Vitamin D wasn’t an issue when our ancestors ran naked in equatorial Africa. Today, we may go without sun exposure for weeks and months. Breastmilk, the perfect food, must be supplemented with Vitamin D so our babies don’t get rickets. 

When I added Vitamin D to my daily regimen years ago, it was based on studies suggesting a link of low Vitamin D to autoimmune disease, cardiovascular problems, poor bone health, etc. Then I discovered that most Vitamin D research were observational studies comparing “apples to oranges.” Observational Vitamin D studies, like false prophets, made promises they couldn’t keep. But they led to better studies that helped us find out the actual impact of Vitamin D. 

More than 15,000 Vitamin D studies have been published in the last four years. Among them are many gold-standard studies comparing “apples to apples.” Gold-standard research aims to eliminate variables that could influence the outcomes. 

56 randomized clinical trials, involving nearly 100,000 people between the ages of 18 and 107, mostly women, randomized to four years of vitamin D supplements or sugar pills. Put all the studies together, and those given vitamin D supplements lived longer, also specifically lowering the risk of dying from cancer.

My 2018 D blood level was 37. According to the lab, 30 to 100 is an average range. Dr. Greger says the sweet spot is around 75 or 80 (nano moles per liter).

Should we get tested for Vitamin D? “What happens when you send a single sample to a thousand different labs around the world?” Dr. Greger explains that the same blood sample results ranged from 20 to over 100. In other words, testing your D blood level is not reliable. 

For those of us who want all the help we can get, the question is, how much should we take? The “answer” depends on whom you ask. The NIH (National Institute of Health) suggests that adults 19-70 take 600 units (IU). If you are over 70, it is 800 units. Dr. Greger says that taking 1,000 units a day will get 50% of the people up to 75 blood levels (nano moles per liter). Taking too much Vitamin D causes toxicity in the body.

Reliable sources, not opinion providers or self-acclaimed experts, move us in the right direction. But at the end of the day, after doing our reading, we make the decision. After all, we have to live with the decisions we make.  

Aside from Vitamin D, B12 deficiencies in older people and vegans is sometimes overlooked. According to, B12 deficiencies “can cause fatigue, nervousness, dizziness, numbness, and tingling in the fingers and toes. Severe, long-term deficiencies may lead to loss of mobility, problems walking, or memory loss.” 


NIH Vitamin D Fact Sheet