4 supplements a doctor specializing in nutrition and healthy aging takes daily, including herbs and vitamins

• Dr. Michael Greger has dedicated his career to studying how lifestyle choices can help us live longer.
• As well as eating a whole-food plant-based diet, he takes supplements daily.

Dr. Michael Greger has dedicated his career to studying aging and helping his patients and the general public lead healthier lives.

A physician who specializes in nutrition and an author, Greger shares information about how lifestyle choices can impact lifespan and makes recommendations based on research from his books, including "How Not To Die" and "How Not To Age," and via his charity, NutritionFacts.org.

Greger endorses a whole-food, plant-based diet similar to the one eaten in Blue Zones, which are areas including Sardinia, Italy, and Loma Linda, California where people live around a decade longer than the country's average.

However, he also takes some supplements that he believes are beneficial for longevity.

In the US, supplements aren't FDA-regulated in the same way as over-the-counter medications, he told Business Insider. So it's hard to guarantee that a supplement contains what its label says, he said.

"They're just really not concerned about purity because there's really no incentives. They just want to make something dirt cheap so they can sell it. So I'm concerned about contaminants," Greger said of some supplement manufacturers.

So he makes sure he's taking a high-quality product by only using supplements tested and verified by USP, a non-profit focused on drug quality and safety.

He shared four supplements that he takes regularly to help boost his health and prevent disease.

Vitamin D

Greger takes a vitamin D supplement every day. It helps the body absorb calcium and phosphorous and is needed for healthy teeth, bones, and muscles.

There is also some research to suggest that vitamin D might be protective against advanced cancer, but overall, data suggests that there isn't a link between vitamin D and developing cancer, according to the American Cancer Society.

Most people get enough vitamin D from sunlight, but those living in colder climates are unlikely to get enough during winter and fall.

Vitamin D is found in a small number of foods including animal products such as oily fish, red meat, egg yolks, and some fortified products such as breakfast cereals.

Greger eats mainly plant-based foods and said that he doesn't get enough sun, particularly in the winter, so he takes 2,000 International Units of vitamin D3, which is usually found in animal products.

That is higher than the daily 600 IU of vitamin D recommended by the National Institutes of Health, but Greger believes this is the amount required for optimal health.

The maximum suggested daily requirement is 4,000 IU per day for healthy adults, according to The Cleveland Clinic.

Vitamin B12

Vitamin B12 supports the function of nerve cells and is needed for red blood cell formation and DNA synthesis.

Like vitamin D, it's almost exclusively found in animal products and you can't get it from the sun, meaning vegetarians and vegans are at risk for deficiency.

"People eating a plant-based diet must ensure a regular, reliable source of vitamin B12 throughout their lifespan," Greger said.

Greger said he takes 2,000 micrograms of vitamin B12 a week. The recommended daily allowance is 2.4 mcg daily, however, the lowest doses in B12 supplements tend to be many times the recommended dietary allowance, according to Harvard Medical School. This is because the body doesn't absorb most of what's in the supplement.

Vitamin B12 is generally considered safe, even at high doses, and has no established maximum dose, according to Healthline.

Algae-based DHA

Greger takes an algae-based DHA supplement daily for brain health and cognitive function, he said. DHA is an omega-3 fatty acid, and it makes up 25% of the brain's total fat content. The brain is 60% fat in total.

DHA is crucial for brain development in infants, but it might also help prevent cognitive decline and memory problems as we age, according to a 2016 review.

With age, the brain goes through natural changes, such as a reduced ability to absorb nutrients, and DNA damage, which mimics what happens when DHA levels fall, according to Healthline.

There is some evidence that taking a DHA supplement can improve memory and other brain functions in people with mild memory problems.

Turmeric, black cumin, ground ginger, and amla

Every day, Greger makes a supplement himself by wrapping up ground turmeric, black cumin, ground ginger, and dried gooseberry powder, also known as amla, in edible film, which is essentially a transparent sheet of potato.

"These are whole foods. They're not really supplements," he said. "You put the powders that taste horrible, and you wrap it up like a wonton, dip it in water, and then you just swallow this little pouch."

They all contain antioxidants, molecules that fight free radicals in the body. These are compounds that can cause illnesses such as heart disease, cancer, and diabetes.

Turmeric contains polyphenols, which are anti-inflammatory, while research suggests that black cumin could also lower cholesterol levels. Ginger can help with digestion and bloating.

Amla is a great source of vitamin C, which is good for immune function, and has been linked to improved cholesterol levels.