Introduction

It's been shown in several studies that a high calcium intake is linked to lower blood pressure, a lower risk of type 2 diabetes, and lower body weight. A new study by scientists in Quebec, Canada, has looked at the possible links between calcium intake in the diet and blood lipids (i.e the various cholesterol measurements). Their findings have already been incorporated into advertisements for a well-known brand of calcium supplement.

What was done

Participants in the Quebec Family Study were sent questionnaires about their calcium consumption from 1991 to 1998. People taking nutritional supplements were excluded. The subjects were divided into three groups: the first group, who consumed less than 600 mg calcium daily; the second group, who took in 600-1,000 mg daily; and the third, who took in over 1,000 mg daily.

Body weight, waist size, and the percentage body fat were measured. CT scans were used to determine the abdominal adipose tissue (fat). Three-day dietary records allowed calculation of the average daily energy (calories), macronutrients (protein, fat, carbohydrate, etc), and micronutrients (minerals, vitamins, etc).

Fasting blood lipid exams included determination of the total cholesterol, low-density lipoprotein (LDL, or 'bad') cholesterol, high density lipoprotein (HDL, or 'good') cholesterol, and the ratio of total cholesterol to HDL-cholesterol.

What was found

There were 235 women and 235 men in the study; their ages ranged from 20 to 65 years. After adjusting for different ages, calorie intake, percentage of dietary fat and protein, etc, it was found that the women in the less-than-600 mg calcium group had increased body weight, body fat, waist circumference, and abdominal fat compared with those in the other groups. There were no such differences in men. Both women and men in the lower calcium intake groups were 6 to 7 years older than the other groups.

The average blood lipid levels for the 6 groups (men and women separately) are given in the table:

(mg/dL)	Women			Men
	below 600 mg/day	600-1000 mg/day	over 1000 mg/day	below 600 mg/day	600-1000 mg/day	over 1000 mg/day
Total cholesterol	201	191	186	206	201	189
LDL-cholesterol	126	117	111	133	130	119
HDL-cholesterol	50	53	53	41	42	43
Total:HDL ratio	4.16	3.81	3.69	5.23	5.01	4.64

It can be seen that there was a clear link between higher calcium intake and lower total and LDL-cholesterol levels in both women and men; after adjustments were made for different body fat and waist measurements, this linkage was statistically significant i.e. it wasn't due to chance alone.

The total cholesterol:HDL-cholesterol ratio, which is a risk factor for coronary heart disease, showed a reduction in the right direction in women and men taking more calcium; this was also significant after the necessary adjustments were made.

What does this mean?

It's been known for some time that women who consume more calcium have, in general, a lower body weight and less body fat than those who take in lesser amounts. The scientists claim that this study is the first to show that the lipid profile is improved along with more calcium intake, even after allowing for an effect on body weight.

Why is the effect greater in women? It's been shown that changes in blood estrogen levels affect the absorption of calcium from the intestines, so perhaps women absorb more dietary calcium because they possess circulating estrogen in their blood.

In this study, all the calcium that the participants consumed came from their diet - chiefly dairy products. In fact, many women (and men) take calcium supplements in their later years, to ward off osteoporosis. Maybe such people are getting 'fringe benefits' - not only is their chance of developing osteoporosis improved, but also they may find it easier to maintain a reasonable body weight, and to hold their cholesterol levels in check.