Vitamin D is made in the skin as a result of exposure to sunlight. The problem is, if you live at latitude of 42 degrees (a line approximately between the northern border of California and Boston) the sun’s rays are too low between November and February for your skin to get the sunlight needed for cutaneous vitamin D synthesis.^{1, 2}

If you live at latitude below 34 degrees north (a line between Los Angeles and Columbia, South Carolina) your body can make vitamin D from sun exposure year-long. However, it’s important to expose a large portion of bare skin (like your midriff) to mid-day sun for at least 15 minutes every day. Most people are unable to fit this into their schedule, so vitamin D supplementation is highly recommended, especially since so few foods contain it.

Foods containing vitamin D

Fatty fish such as salmon, trout, tuna and sardines, milk, and fortified cereals provide more than 100 IU per serving. And mushroom is the only food in the produce section that has vitamin D.  But you’d have to eat an awful lot of these foods to get the recommended daily dose of vitamin D, which is 2400 IU, according to a study published in the Journal of Nutrition.* For instance, you would have to eat at least five servings of salmon a day or drink 20 cups of fortified milk.

Who should take a vitamin D supplement?

The highest levels of vitamin D are naturally found in farmers who spend a lot of time outdoors and in people who take vacations or live in areas that are sunny and warm in winter.

But most people, and especially the elderly, are vitamin D deficient. Vitamin D deficiency is especially common in the elderly. Researchers have found a correlation between vitamin D deficiency and low mood, depression and worse cognitive performance in older adults. In a recent study, 1618 patients who averaged 73.8 years old were tested for vitamin D deficiency. Those with severe vitamin D deficiency were twice as likely to suffer from depression.3

Another study of a cross-section of 80 older adults, 40 with mild Alzheimer’s disease and 40 healthy adults, found that vitamin D deficiency was associated with low mood and impairment on two of four measures of cognitive performance. 58% of the participants had abnormally low vitamin D levels. After adjusting for age, race, gender, and the season in which vitamin D levels were studied, researchers correlated vitamin D deficiency with an active mood disorder. The deficiency was also related to a worse performance on the cognitive performance test called Short Blessed Test (SBY). There was no difference in performance on the Mini-Mental State Exam (MMSE). 4

Vital to overall health

We now know that every body cell has a receptor for vitamin D, which is why it is so crucial to overall health. Vitamin D is most commonly known for helping the digestive system absorb calcium and phosphorus. In that way it helps the body build and maintain healthy bones. But it does much more.

Adequate vitamin D is believed to play a role in the reduction of falls, as well as supporting cardiovascular health, a strong immune system and cognitive function. ⁵

Higher vitamin D intake is associated with a lower risk of developing Alzheimer’s disease, according to research done at the Angers University Hospital in France. Another recent study at the VA medical center in Minneapolis found that low vitamin D levels among older women are associated with a higher risk of cognitive impairment and a higher risk of cognitive decline. Both studies were published in the Dec. 3, 2012 issue of the Journals of Gerontology Series A: Biological Sciences and Medical Sciences.

Babies born with low levels of vitamin D may be more likely to develop multiple sclerosis (MS) later in life than babies with higher levels of vitamin D, according to a study published in the November 30, 2016, online issue of Neurology®, the medical journal of the American Academy of Neurology.

Vitamin D

• Regulates blood serum calcium and phosphate levels
• Stimulates calcification of the bone
• Increases absorption of calcium from the intestines
• Decreases excretion of calcium from the kidneys
• Supports T-cell production and the immune system
• Has been shown to reduce risk of some forms of cancer, MS, diabetes and cardiovascular disease (6-9)
• Plays a role in regulation of blood pressure
• Supports immunity and helps reduce stress

Vitamin D deficiency may exacerbate osteopenia, osteoporosis, muscle weakness, fractures, autoimmune diseases, infectious diseases, multiple sclerosis and cardiovascular disease, cognitive function.

Recent studies have suggested that women and men who increase their vitamin D intake above 400 IU of vitamin D a day reduce risk of developing multiple sclerosis by approximately 40%. ⁷

Also, scientists theorize that one of the reasons that influenza occurs in the wintertime is that we do not manufacture enough vitamin D, and the resulting vitamin D deficiency might promote our susceptibility to the flu virus. 10

How much is enough?

*According to a study published in the Journal of Nutrition (March 9, 2009) adults need at least four times the current recommended dose of 600 IU of vitamin D. 11

In 2008 The American Academy of Pediatrics (AAP) doubled its recommended minimum intake for infants, children and teens from 200 IU to 400 IU per day. ¹²

Why are co-factors important?        

Other nutrients are needed in order for Vitamin D to work optimally in the body. Make sure your nutritional supplement contains the following:

• VITAMIN D3 (Colecalciferol 1,000 IU/g.) Vitamin D refers to two biologically inactive precursors – D3, also known as cholecalciferol, and D2, also known as ergocalciferol. Vitamin D3 is produced in the skin on exposure to UVB radiation (290 to 320 nm), and is more bioactive than D2.
• BORON is involved in the action of Vitamin D on the cell wall. Most Americans do not consume enough of the foods that contain boron, such as green vegetables, fruit, nuts and whole grains.
• MAGNESIUM–All the enzymes that metabolize Vitamin D require magnesium. It is also required in each of the steps concerned with replication, transcription and translation of genetic information, and thus it is also needed for the genetic mechanism of action of Vitamin D.
• ZINC –A zinc molecule sits at the base of the vitamin D receptors on the cells in your body, which helps them to function properly.
• VITAMIN K-2 helps direct Vitamin D to calcify bones while preventing the calcification of organs and blood vessels.
• VITAMIN A —Vitamin D requires Vitamin A to bind to the Vitamin D receptor.

So unless you are going on a long vacation this winter to a tropical climate, make sure you take enough vitamin D to protect your overall health and reduce your risk of getting the flu.

References

1. Holick MF. Vitamin D: the underappreciated D-lightful hormone that is important for skeletal and cellular health. Curr Opin Endocrinol Diabetes 2002;9:87-98.
2. Holick MF. Vitamin D. In: Shils ME, Shike M, Ross AC, Caballero B, Cousins RJ, eds. Modern Nutrition in Health and Disease, 10th ed. Philadelphia: Lippincott Williams & Wilkins, 2006.
3. Lapid MI, Cha SS, Takahashi PY.Clin Interv Aging. 2013;8:509-14. doi: 10.2147/CIA.S42838. Epub 2013 May 3.
4. Wilkins CH, Sheline YI, Roe CM, Birge SJ, Morris JC. Vitamin D deficiency is associated with low mood and worse cognitive performance in older adults.Am J Geriatr Psychiatry. 2006 Dec;14(12):1032-40.
5. Stechschulte SA, Kirsner RS, Federman DG. Vitamin D: bone and beyond, rationale and recommendations for supplementation. Am J Med. 2009 Sep;122(9):793-802.
6. Garland, CF; Garland, FC; Gorham, ED; Lipkin, M; Newmark, H; Mohr, SB; Holick, MF (2006). “The role of vitamin D in cancer prevention”. American Journal of Public Health 96 (2): 252–61. doi:2105/AJPH.2004.045260. PMID16380576
7. Munger KL, Zhang SM, O’Reilly E, Hernan MA, Olek MJ, Willett WC, Ascherio A.  Vitamin D intake and incidence of multiple sclerosis.  Neurology2004; 62(1):60-5.
8. Penckofer S, Kouba J, Wallis DE, Emanuele MA. Vitamin D and diabetes: let the sunshine in. Diabetes Educ. 2008 Nov-Dec;34(6):939-40, 942, 944 passim.
9. Wang TJ, Pencina MJ, Booth SL, Jacques PF, Ingelsson E, Lanier K, Benjamin EJ, D’Agostino RB, Wolf M, Vasan RS. Vitamin D deficiency and risk of cardiovascular disease. Circulation. 2008 Jan 29;117(4):503-11. Epub 2008 Jan 7.
10. Cannell, J.J., Vieth, R., Umhau J.C., et.al. Epidemic influenza and vitamin D. Epidemiology and Infection (2006), 134:6:1129-1140 Cambridge University Press
11. Nelson, M.L. Blum, J.M, Hollis, B.W., Rosen, C., Sullivan, S.S. Supplements of 20 ug/d Cholecalciferol Optimized Serum 25-Hydroxyvitamin D Concentrations in 80% of Premenopausal Women in Winter. Journal of Nutrition, March 9, 2009, Volume 139, Pages 540-546, doi:10.3945/jn.108.096180
12. Wagner, C.L., Greer, F.R. Prevention of Rickets and Vitamin D Deficiency in Infants, Children, and Adolescents. Pediatrics 122 No. 5 November 2008, pp. 1142-1152 (doi:10.1542/peds.2008-1862)