Vitamin D-deficient? Checking out your magnesium intake might help. Plus: kiwis for canker sores and the surprising uses of frankincense.

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Q: Most of us do not get nearly enough vitamin D, but taking a daily supplement of vitamin D-3 may not be enough. I recently read that magnesium deficiency can prevent absorption of vitamin D supplements. Is this true?

A: Yes, it is, but the story is a bit more complicated. The enzymes that process vitamin D in our bodies require magnesium to function well. A recently published study demonstrated that optimal magnesium status is important for improving circulating vitamin D (American Journal of Clinical Nutrition, Dec. 1, 2018).

The majority of American adults don’t get adequate amounts of magnesium in their diets. A higher intake of this mineral increases vitamin D utilization if levels of vitamin D are low.

You can learn more about what vitamin D does and how you can get optimum levels in our “Guide to Vitamin D Deficiency.” Anyone who would like a copy, please send $3 in check or money order with a long (No. 10), stamped, self-addressed envelope to: Graedons’ People’s Pharmacy, No. D-23, P.O. Box 52027, Durham, NC 27717-2027. It also can be downloaded for $2 from our website:

Q: For as long as I can remember, my family and I have suffered off and on with horrible canker sores. We finally realized eating nuts or peanut butter appeared to trigger this problem.

Often, L-lysine didn’t work. I read in your column that eating kiwi fruits helped prevent canker sores. I love kiwis, so I decided to try it.

Lo and behold, I can now eat peanut butter, pistachios, pecans and peanuts as long as I eat a kiwi within a day of consuming the nuts. I haven’t had a canker sore in four years.

A: You are not the only reader who has reported success eating kiwi fruit to prevent or speed healing of canker sores. Scientists have not specifically studied this activity of the green fruit with the fuzzy brown skin (Actinidia deliciosa). However, they have found that an extract from a related fruit, Actinidia arguta, can alleviate skin inflammation through its impact on immune system compounds and cells (Nutrients, Oct. 2, 2018).

Other research has shown that people eating SunGold variety kiwi fruit increase their levels of vitamin C and experience changes in their gut microbes (Nutrients, July 12, 2018). We don’t know if the balance of microbes in the mouth also is altered, though that might potentially contribute to the healing properties of kiwi fruit for canker sores.

Q: I have been told that therapeutic-grade frankincense has healthful properties. My friend said you can apply it to your skin at night to relax and get to sleep. Are these claims true?

A: Frankincense is the fragrant resin of trees in the Boswellia family. It has long been used in traditional Indian medicine, and scientists have confirmed some health benefits.

Boswellia extracts have anti-inflammatory activity (Frontiers in Pharmacology, Apr. 20, 2018). Italian scientists reported that a mixture of L-methionine with boswellia and hibiscus extracts relieved symptoms of urinary-tract infections (Archivio Italiano di Urologia e Andrologia, June 30, 2018).

We could find no research on topically applied frankincense to improve sleep. One cancer center in the U.K. tested personal inhalers called aromasticks to help people sleep (Complementary Therapies in Clinical Practice, February 2016). Patients liked this approach. Some chose a blend of frankincense, mandarin and lavender essential oils.