Vitamin D and Calcium Go Well Together
Vitamin D and
Calcium Combat Cancer
Large amounts of these nutrients reduced the
all-cancer risk in postmenopausal women by 60%
By Hyla Cass, M.D.
ome things go so well together, don’t they? Peaches and cream, fish and chips, wine and cheese, bacon and eggs, chocolate and just about anything, . . . Are you starting to salivate? Good, because I have another great pair for you. It’s . . . oh, the title gave it away, didn’t it? Although the prospect of a vitamin/mineral combo may not set your taste buds tingling, the rest of your body would be grateful for a good daily dose of this dietary dynamic duo.
We have long known that vitamin D and calcium are essential for our health and that proper calcium metabolism depends critically on adequate amounts of vitamin D, a steroid hormone popularly known as the “sunshine vitamin.” Both of these nutrients play important roles in the prevention and treatment of various diseases. A new study published by researchers at Creighton University in Omaha, Nebraska, however, has startled the medical world by providing unusually strong evidence of an anticancer effect for the vitamin D and calcium pair. Dr. Cedric Garland, a prominent vitamin D researcher at UC San Diego (who was not involved in the study), said,
The findings . . . are a breakthrough of great medical and public health importance. No other method to prevent cancer has been identified that has such a powerful impact.
Like Striking Oil
Got your attention? Then let’s see what the researchers were looking for, and what they found. Their initial objective was to examine the efficacy of calcium alone and calcium plus vitamin D in maintaining bone health and preventing bone disease, such as osteoporosis. Their interest in cancer was secondary—until they analyzed their data and saw what they had. Imagine drilling for water and finding oil instead—it must have been something like that. They decided to defer publication of their findings regarding bone health and publish their cancer findings first.
The study was a 4-year, randomized, double-blind, placebo-controlled trial involving 1179 healthy postmenopausal women from a nine-county rural area of eastern Nebraska. The women’s average age was 67; their average body mass index was 29 (i.e., as a group they were considerably overweight but not quite obese); their circulating vitamin D levels were within the normal range; and they had all been cancer-free for at least 10 years before the trial began. All of them were white, although that was not a criterion for inclusion in the study.
The women were divided into three groups who were given the following supplements to take daily (Ca is the chemical symbol for calcium):
- Calcium, as either calcium citrate (1400 mg of Ca per day) or calcium carbonate (1500 mg of Ca per day), plus a vitamin D placebo. This group was called Ca-only.
- Calcium (as above) plus vitamin D in the form of cholecalciferol (vitamin D3), 1000 IU (25 mcg) per day. (The government’s recommended Daily Value for vitamin D is 400 IU.) This group was called Ca+D.
- Calcium and vitamin D placebos (the control group).
Vitamin D (with Calcium) Reduces Cancer by 60%
Over the 4-year period, 50 women developed nonskin cancers of various kinds—13 during the first year and 37 thereafter. Analysis of the data showed that the risk for such an event was reduced by 47% in the Ca-only group (compared with placebo) and by 60% in the Ca+D group. Remarkable! Suspecting that some of the cancers found during the first year may already have been present but undetected at the outset of the study, the researchers reanalyzed the data using only the 37 cases that developed during the final 3 years. The results showed that the risk reduction for the Ca-only group was nearly unchanged at 41%, but for the Ca+D group, it improved substantially to 77%!
Further data analysis showed that the results were unaffected by age or body mass index, but they did correlate significantly with the women’s vitamin D levels at baseline and after 1 year: the higher the vitamin D levels at either of these time points, the lower the risk of developing cancer. There were no serious supplement-related adverse events during the course of the study.
The Sun and Vitamin D Reduce Cancer Risk
The vitamin D-induced risk reduction for all cancers seen in this study jibes with, and provides strong support for, observations made over the past half-century. It was first noticed over 60 years ago that there is a geographic pattern of cancer mortality in North America that follows the sun, in an inverse sense: the greater the average yearly amount of sunlight in a given region, the lower the nonskin cancer incidence and the lower the mortality rate for many kinds of cancer. This protective effect of the sun was attributed to the fact that solar ultraviolet radiation synthesizes vitamin D from 7-dehydrocholesterol in our skin, via photochemical reactions stimulated by the short-wavelength, high-energy UVB rays.*
How Much Vitamin D and Calcium Do We Need?
Except during winter months, especially at latitudes above about 40º, the sun can easily provide all the vitamin D most people need. Indeed, many people do get most, if not all, of their vitamin D from exposure to the sun’s beneficent rays. The trouble is, though, that many others do not get enough exposure, for various reasons. The people most likely to be deficient in vitamin D are those who live in northern latitudes, especially in the northeastern United States, where a common type of air pollution (acid haze, which precedes acid rain) blocks much of the solar ultraviolet radiation.
Paradoxically, in our commendable zeal to avoid skin cancer by covering up or using sunscreen when we’re outdoors, we may be setting ourselves up for a greater risk of most other types of cancer. Sunscreen blocks vitamin D synthesis more effectively than it prevents skin cancer (an SPF value of only 8 reduces vitamin D synthesis by 95%). An easy way to solve this problem is to get about 10–15 minutes of sun exposure on our arms or legs before applying the sunscreen, three times a week.
People who don’t get outdoors much (or at all) are at the greatest risk of vitamin D deficiency. Many of the elderly fit that description, and their risk is further increased by the reduced capacity of their skin to synthesize vitamin D even when it is exposed to the sun. Most foods, unfortunately, are poor sources of this fat-soluble vitamin, the exceptions being fatty fish (such as salmon), fish-liver oils (yuck!), and fortified milk and cereals. Thus, for many people, supplementation is the best way to ensure adequate supplies of this bone-building, cancer-preventing vitamin.
For many years, the government’s recommended daily intake of vitamin D has been 400 IU. In a recent review article published by some of America’s leading authorities on vitamin D, however, the authors pointed to studies demonstrating the beneficial use—with no toxicity—of vitamin D doses of many thousands of IU daily. They concluded,
These studies indicate that ideal daily doses of vitamin D exceed current recommendations by an order of magnitude.
Since “order of magnitude” means “roughly a factor of 10,” the authors are saying that amounts of about 4000 IU (with considerable latitude in either direction) would be ideal.
We also need calcium, of course—plenty of it, as calcium is the body’s number one mineral. About 99% of it is found in our bones and teeth. The rest is in our blood and soft tissues, where it plays physiological roles so crucial to our survival that an inadequate intake will cause the body to demineralize its own bones (which weakens them, of course) to make up for the deficiency. Maintaining serum calcium levels within a narrow range is vital for normal functioning of our nervous system as well as for regulating the secretion of various hormones, such as insulin.
The best food sources of calcium are dairy products and certain vegetables and grains—but do we get enough calcium? No, according to scientists at the Linus Pauling Institute (LPI), who report that “Average dietary intakes of calcium in the U.S. are well below the adequate intake (AI) recommendation for every age and gender group, especially in females.”
While recommending that we get as much of our calcium as possible from food (because foods contain other important nutrients that make the calcium more bioavailable), the LPI scientists state that supplementation may be necessary for those who have difficulty in achieving that goal. They recommend that adults through age 50 consume a total (diet plus supplements) of 1000 mg of calcium daily; for older adults, they recommend 1200 mg/day.
The calcium intakes recommended for the U.S. population are higher than those in most other countries because of our higher intake of protein, which causes the urinary excretion of calcium. It’s also worth noting that, although supplemental calcium alone cannot usually restore lost bone mass in individuals with osteoporosis, it can help prevent further loss.
- Higdon J. Vitamin D. Linus Pauling Institute, Corvallis, OR, 2004.
- Cannell JJ, Vieth R, Umhau JC, Holick MF, Grant WB, Madronich S,
Garland CF, Giovannucci E. Epidemic influenza and vitamin D.
Epidemiol Infect 2006;134(6):1129-40.
- Higdon J, Drake VJ. Calcium. Linus Pauling Institute, Corvallis, OR, 2007.
Indeed, the Creighton University researchers cited a large body of evidence linking low vitamin D levels with an increased risk of cancer. Referring to “25(OH)D” (25-hydroxycholecalciferol), the principal chemical form in which vitamin D circulates in the blood, they concluded their own report by saying,
We found that improving vitamin D nutritional status substantially reduced all-cancer risk in postmenopausal women. Furthermore, baseline and treatment-induced serum 25(OH)D concentrations were themselves strong predictors of cancer risk. These findings highlight the importance of promoting optimum vitamin D status and underscore the value of achieving and maintaining a high serum 25(OH)D concentration.
Hey, What About the Calcium?
By now you’re probably wondering why all the attention is focused on vitamin D, when calcium alone produced such a strong effect. Good question, and in the answer lies a cautionary tale. Raw data can be highly misleading, especially to those who are not experts in the science in question and in the mathematical methods required for data analysis. Which of these methods are used in a given case depends on the nature of the study protocol in question, and invalid conclusions can be drawn if the methods are inappropriate to the case.
In this study, statistical calculations (presumably appropriate ones) indicated that the protective effect observed in the Ca-only group was marginal and might be due merely to chance. Thus the role of calcium was unclear, but the authors opined that if its effect was real, it could plausibly be connected to the patients’ vitamin D status. The protective effect of that nutrient was not in doubt—the analysis showed a real and substantial benefit from vitamin D when used together with calcium.
When Intervention Is Better than Observation
The significance of this study lies partly in the fact that it was the first interventional trial to assess the efficacy of large amounts of supplemental vitamin D in preventing cancer. Here the subjects were given the vitamin in accord with a known regimen so that its effects could be measured over a period of time.
For many years previously, there had been a growing body of evidence of such anticancer effects based on observational studies, in which the incidence of cancer was correlated with the study group’s demographic and nutritional profiles, such as their geographic location and their circulating vitamin D levels (the source of which is hard to account for because most of it comes from sun exposure). Observational studies are extremely valuable, but interventional studies are often better able to discern real effects, owing to the controlled nature of the trial.
Stay Tuned, but Supplement
The Creighton University study raises two obvious questions: What about premenopausal women? What about men? For the answers, we’ll have to stay tuned for future studies, but our knowledge of the biological effects of vitamin D, particularly with regard to its inhibition of cell proliferation, makes it reasonable to suppose that the results will be similar. Science is full of surprises, though, and only hard evidence will tell the tale. Meanwhile, we should all make sure that our bodies are well supplied with vitamin D and calcium—they go so well together.
- Lappe JM, Travers-Gustafson D, Davies KM, Recker RR, Heaney RP.
Vitamin D and calcium supplementation reduces cancer risk: results
of a randomized trial. Am J Clin Nutr 2007;85:1586-91.
- Ross T, Conn J. Associated Press report, June 7, 2007.
Dr. Hyla Cass is a nationally recognized expert in integrative medicine, an assistant clinical professor of psychiatry at the UCLA School of Medicine, and the author or coauthor of several popular books, including Natural Highs: Supplements, Nutrition, and Mind-Body Techniques to Help You Feel Good All the Time and 8 Weeks to Vibrant Health: A Woman’s Take-Charge Program to Correct Imbalances, Reclaim Energy, and Restore Well-Being.