A case study of calcium absorption claims on dairy products

Several years ago Stonyfield Farm, Londonderry, N.H., set out to create a yogurt that would help their consumers absorb more calcium . . . naturally. Along the way, there were many decisions to be made. What calcium absorption booster should be used? What should the wording of the claim be? What are the regulations around making a claim?

The answers, which are the result of years of hard work and research, can be seen in supermarket refrigerated cases today. All Stonyfield Farm yogurt products carry a claim of "helps boost calcium absorption," thanks to the unique form of inulin they contain, which is a form of inulin that has been clinically proven to increase calcium absorption.

In the following case study on the development of this claim, we will discuss the importance of calcium and calcium absorption, review the calcium absorption literature and finally outline the claims process.

Calcium and its absorption

Most people realize that consuming the proper amount of calcium in every life stage can help reduce their risk of osteoporosis. But calcium is also important in reducing the risk of hypertension, colon cancer and kidney stones.

Even though the importance of calcium in the diet is well recognized, most people still do not consume enough calcium. According to USDA data, at least 70% of women need an additional 300-500mg per day to meet the recommended calcium intake.

One key to avoiding osteoporosis is to achieve peak bone mass, because a higher peak bone mass will help decrease the risk of osteoporosis in later life. In fact for every 1% increase in bone mineral density, there is a reduced risk of fracture of 6% to 8%. Most people reach their peak bone mass before the age of 30, so it is important to maximize both calcium intake and bioavailability during this period.

In the case of calcium, absorption indicates bioavailability. Since we typically only absorb 30% of the calcium we consume, calcium researchers have been studying factors that affect calcium absorption and are looking for ways to increase this absorption, and thus the bioavailability of the calcium we consume.

Methods matter

The first step in making a claim of enhanced calcium absorption is to determine what product can substantiate the desired claim. Therefore, a thorough review of the scientific literature is needed. To understand this literature, one must first understand the methods used to assess absorption.

In "balance" methods, calcium excreted in feces, urine and, in more sophisticated studies, sweat, are subtracted from ingested calcium to arrive at absorption. Other studies look at calcium increases in blood after ingestion of a calcium dose. However, blood calcium levels are tightly regulated and therefore are a poor indicator of absorption.

Another method used for a period of time measured urinary calcium excretion after ingestion of a calcium dose. This type of methodology is currently not accepted as an accurate and reliable measure of absorption because urinary calcium excretion is known to be more influenced by salt intake than by calcium as discussed by Jackman in the American Journal of Clinical Nutrition.

Today, the dual stable isotope technique is a method of choice for measuring calcium absorption. Two different isotopes of calcium are used. One is injected into the bloodstream and the second is consumed with food. Since the amount of the isotope injected directly into the blood is a known quantity, the proportion of the calcium absorbed from the food is determined by measuring the ratio of the two isotopes. This method corrects for the deficiencies seen in previous methods and is considered a reliable measurement of true calcium absorption.

The studies

Several human studies have been conducted on fructans and calcium absorption. Fructan is the general term for a class of materials that include inulin, oligofructose and fructooligosaccharide (FOS).

Ohta in the Japanese literature examined the effect of a single 3g dose of FOS on 10 men for one day using a urinary excretion method. He reported a 50% increase in calcium absorption. Coudray fed 40g/day of standard chicory inulin to nine young men for 28 days. Using a balance technique, a 58% increase in calcium absorption was observed and reported in the European Journal of Clinical Nutrition. Van den Heuvel used a dual stable isotope technique to examine calcium absorption when 12 young males consumed 15g/day of chicory oligofructose for nine days. A 26% increase in true calcium absorption was reported in the American Journal of Clinical Nutrition.

In 2002, the first U.S. study was conducted at the USDA Childrens Nutrition Research Center at the Baylor College of Medicine by Abrams. Fifty-nine adolescent girls consumed 8g/day of Raftilose‚ Synergy 1 (an enriched inulin formulated to maximize calcium absorption) or oligofructose for three weeks and evaluated calcium absorption using the dual stable isotope technique. Results showed that absorption increased by 18% in the Synergy group while no increase was seen in the oligofructose group.

Uenishi of Kagawa Nutrition University studied the effect of a one-time dose of 3g of FOS in 8 young women on calcium absorption using a urinary excretion method. An increase in urinary calcium excretion was reported in the Japanese Journal of Nutrition and Dietetics. Tahiri in his publication in the American Journal of Clinical Nutrition looked at the effect of 10g of FOS on 12 post-menopausal women for five weeks using a fecal isotope balance technique. Researchers found no significant increase in calcium absorption.

Griffin reported data in Nutrition Research from 54 girls who were fed 8g/day of Raftilose Synergy 1 for three weeks. He used the dual stable isotope technique and noted a 9% increase in calcium absorption. Individuals with lower calcium absorption during the placebo period showed the greatest benefit.

The attached table provides a summary of the literature concerning the effect of fructans on calcium absorption. This type of table may be used to compare the science available on different products to substantiate claims in this area.

Making substantiated claims

Structure/function claims are permitted on dairy products provided that the claims are truthful, not misleading and derived from the nutritive value of the food (65Fed Reg at 1033). While there is no requirement to submit such claims to FDA, if the product is sold in California, state law requires that the labels of all dairy products gain pre-market approval. FDA has stated that it would be misleading to make a claim if it is not adequately supported by sound scientific data. So, claims should be supported by "competent and reliable scientific evidence," which should consist of tests, analysis, research, studies or other evidence conducted and evaluated in an objective manner by persons qualified to do so, using procedures generally accepted in the profession to yield accurate and reliable results. (Fed Reg 28388-90).

The gold standard for such substantiation is to have double-blind, placebo-controlled human studies published in well-respected peer reviewed scientific journals. FDA should recognize the researchers who conduct these studies as experts in their field. The food ingredient proven effective in the study must be the one used in the product bearing the claim. The amount per serving should be at least 25% of the daily amount shown effective in the study. This follows FDA's guidelines for health claims on foods. A thorough evaluation of the science on specific products needs to be considered before a suitable product is chosen to support the desired claim.

After considering the literature and the claim process, Stonyfield Farm chose Raftilose Synergy 1. Why? Two double-blind, placebo-controlled studies were conducted on Synergy 1. These studies used adequate numbers of subjects and methods accepted to yield accurate and reliable results. And finally, they were conducted at institutions and by researchers recognized for their expertise in the calcium absorption field.

So, although the consumer sees a simple burst on the package that states "helps boost calcium absorption," it is easy to see that there is a great deal of good science and regulatory work behind it.