New Delhi, Nov. 30: America’s science academies today released fresh guidelines for daily intake of calcium and vitamin D, but doctors in India caution that some of the new values may not apply to sunlight-shunning Indians.

A report from the academies has also challenged claims from independent studies over the past decade that vitamin D can protect people from cancer, heart disease, diabetes, and auto-immune diseases.

The report specifying the recommended daily intakes has acknowledged the protective effect of calcium and vitamin D for bone health, but has cautioned that excessive use of either may increase the risk of certain diseases.

An expert committee that reviewed more than 1,000 studies found that a majority of Americans and Canadians are receiving adequate amounts of calcium and vitamin D, and warned of emerging evidence that too much of these nutrients may cause harm. The panel’s report says most Americans and Canadians need no more than 600 or 800 units of vitamin D and 700 to 1,300mg of calcium per day.

“These are conservative values — and may not apply to India where we’ve been seeing widespread vitamin D deficiency,” said Ambrish Mithal, a senior endocrinologist in Delhi and a specialist in bone health, who was not associated with the report.

Mithal and a colleague Nidhi Malhotra had last year compiled the results of several studies from India over the past decade and warned about widespread prevalence of vitamin D deficiency in men, women, as well as children. The studies from different Indian cities suggest that nine out of 10 school girls, seven out of 10 adults, and eight out of 10 pregnant women have vitamin D deficiency.

Calcium is available in many foods — milk, yoghurt, cheese, broccoli, and fish with soft bones. But the body needs vitamin D to absorb calcium for bone health. Low levels of calcium or vitamin D can weaken the bones.

The body makes vitamin D when skin is exposed to sunlight. The vitamin is also available in fatty fish such as tuna or mackerel and, in tiny amounts, from egg yolk.

“We have abundant sunlight, but our fondness to stay away from the sun is probably contributing to vitamin D deficiency,” Mithal said.

Earlier this year, the International Osteoporosis Foundation had recommended that older adults should aim for 800 units to 1000 units of vitamin D per day, while people who are obese, or have limited sun exposure may need up to 2000 units per day.

The daily intake values specified by the US committee are intended for people with minimum exposure to sunlight. The committee has also specified safe boundary limits above which the potential for harm increases.

The committee’s report said studies over the past decade linking vitamin D to cancer, cardiovascular diseases, diabetes, and other diseases have “provided often mixed and inconclusive results and could not be considered reliable”.

Concerns about excessive intake of these nutrients have emerged in North America where some manufacturers have been fortifying cereals, juices and milk with calcium and vitamin D. Such fortified products are now increasingly available in India.

The committee cautioned that excessive calcium has been associated with kidney stones, while excessive vitamin D may damage the kidneys and the heart. “Indeed for some cancers, there appears to be an increase in incidence associated with higher vitamin D intake,” its report warned.

Doctors say Indians appear to need more supplementary vitamin D than Caucasians. “Our dark skin hampers penetration of sunlight to its lower layers, which is essential for vitamin D synthesis,” said Alok Sachan, head of endocrinology at the Sri Venkateswara Institute of Medical Sciences, Tirupati. “And for vegetarians, sunlight is virtually the only source of vitamin D,” Sachan told The Telegraph.

One study on vitamin D replenishment by Mithal and his colleagues last year has shown that 60,000 units each month — equivalent to 2,000 units per day — was able to sustain the required levels of vitamin D in the body.

Until recently, vitamin D formulations in India came in high doses — tens of thousands of units. “We hadn’t paid attention to vitamin D deficiency, and the industry hadn’t been pushed to making low dose formulations,” Sachan said.

But several low dose vitamin D formulations — which will allow people to take between 1000 and 2000 units per day — are about to enter the market.