Vitamin Information Center

An abundance of vitamin C in the diet may help lower a person’s risk of developing type 2 diabetes, new research suggests.

In a study of middle-aged and older men and women, those with the highest blood levels of vitamin C were significantly less likely to develop diabetes over 12 years than those with the lowest levels, researchers found.

Fruits and vegetables are the main source of vitamin C in Western diets, and blood levels of vitamin C are good markers of fruit and vegetable intake, Dr. Nita G. Forouhi, at the Institute of Metabolic Science at Addenbrooke’s Hospital, Cambridge, England, and colleagues note.

The current findings “re-endorse the public health message of the beneficial effect of increasing total fruit and vegetable intake,” the investigators wrote in Archives of Internal Medicine.

Forouhi’s team followed 21,831 healthy men and women who were 40 to 75 years old for the development of type 2 diabetes. At study entry, all participants provided detailed health and lifestyle information, as well as blood samples, which investigators used to determine vitamin C levels.

Over the course of the study, 423 men and 312 women developed type 2 diabetes, an overall rate of 3.2 percent.

According to the investigators, the likelihood of developing diabetes was 62 percent lower in men and women with the highest circulating vitamin C levels, relative to men and women with the lowest vitamin C levels.

Factoring out other characteristics associated with diabetes risk, such as older age, gender, family history, alcohol intake, physical activity, smoking status and body weight did not significantly alter these associations.

These data offer “persuasive evidence of a beneficial effect of vitamin C and fruit and vegetable intake on diabetes risk,” Forouhi and colleagues conclude.

Epidemiological data show an inverse relationship between vitamin D levels and breast cancer incidence. This study investigates the relationship of modeled and measured serum 25-hydroxyvitamin D [25(OH)D] levels with age-standardized incidence rates of breast cancer in 107 countries.

The hypothesis being tested is that breast cancer incidence is inversely related to geographically-dependent cutaneous [skin] sunlight exposure. A multiple regression approach was used to examine the contributions of ultraviolet B (UVB) irradiance to age-standardized incidence rates of breast cancer in the 107 countries with data on these covariates - total column ozone thickness, per capita intake of alcohol and energy from animal and vegetable sources, cigarettes, proportion of female population overweight, and total fertility.

Age-standardized incidence rates were substantially higher at latitudes distant from the equator (R2 = 0.43, p < 0.0001). The dose–response gradient between modeled serum 25(OH)D levels and incidence rates of breast cancer followed a standard inverse dose–response curve Increasing increments in serum 25(OH)D in the range above 22 ng/mL were associated with incrementally lower incidence rates of breast cancer.

According to multiple regression, UVB irradiance adjusted for cloud cover was inversely associated with incidence rates (p = 0.04) after controlling for covariates.

Intake of energy from animal sources was also positively associated with incidence rates (p < 0.01). The overall coefficient of determination, R2, was 0.81 (p < 0.0001).

There was a protective effect of UVB irradiance on risk of breast cancer that was independent of fertility rate, proportion of the population overweight, alcohol intake, animal energy intake, and other covariates.

Source: The Breast Journal, May/June 2008, 14(3) pp. 255-260. PMID: 18422861 by Mohr SB, Garland CF, Gorham ED, Grant WB, Garland FC. Department of Family and Preventive Medicine, University of California San Diego, La Jolla; and Sunlight, Nutrition, and Health Research Center, San Francisco, California, USA [E-mail: cgarland@ucsd.edu]