Download Dec 2006: The Role of Food Supplements in Preventing Chronic

Vol. 13, No. 4, December 2006
The Role of Food Supplements in Preventing Chronic Disease
Following Canada’s Food Guide to Healthy Eating is still a good idea.
The problem is that a large part of the general population is not
following the guide. Surveys show that most Canadians eat less
than five servings of fruit and vegetables daily, and only about onethird of Canadians eat fruit and vegetables five to 10 times per day
(Perez, 2002; Statistics Canada, 2001).
Different diets for different diseases are not necessary, but a pattern
of eating that includes whole grains, plant oils, and vegetables and
fruit is important. While it is possible for most people to have
a healthy diet by following food guide recommendations, some
scientists recommend taking a multivitamin/mineral supplement
for “optimum nutrition” (Fletcher and Fairfield, 2002).
Optimum nutrition is the appropriate balance between food
choices and supplements to yield the greatest health benefits.
Several promising relationships between supplements and health
benefits are discussed below.
Information about Specific Supplements
Folic Acid and Vitamin B12
Folic Acid and Heart Disease
Although there have not been any clinical trials to show that folic
acid lowers heart disease rates, we know that folic acid can lower
high homocysteine levels. Higher homocysteine levels are associated
with an increased risk of heart disease (Lee et al., 2003; van Oort et
al., 2003).
Folic Acid and Breast or Colorectal Cancer
Folic acid can also reduce the risk of both breast and colorectal
cancer. The Nurses’ Health Study showed that women who were
long-term users (about 15 years) of multivitamins containing folic
acid had a much lower risk of colorectal cancer (Giovannucci et al.,
1998). Further study has shown that consuming even one alcoholic
drink interferes with folic acid, increasing the risk of certain types
of cancer like breast cancer, particularly in women with low folic
acid intakes (Zhang et al., 1999).
Folic Acid, Vitamin B12, and Cognition
Findings from the “Nun Study” suggest that the severity of
Alzheimer disease-related brain changes may be influenced by folate
status (Snowdon, Tully, Smith, Riley, & Markesbery, 2000).
Vitamin B12 can improve cognitive function in the elderly,
who often have low levels of vitamin B12, but does not reverse
dementia. Some of the changes in cognitive function may also be
related to cardiovascular disease, which reduces oxygen flow to
the brain (Eastley, Wilcock, & Bucks, 2000; Nilsson, Warkentin,
Hultberg, Faldt, & Gustafson, 2000).
Calcium and Vitamin D
Calcium, Vitamin D, and Colorectal Cancer
Calcium and vitamin D are thought to work together to reduce the
risk for colorectal cancer. Recent studies have shown that calcium
reduces the risk of adenomas, which are precursors to cancer, only
when vitamin D levels are higher (Grau et al., 2003).
Vitamin D and Immunity
The latest research on vitamin D suggests that vitamin D is not
only very important in bone health, but may also help to control
immune responses. Low levels of vitamin D may affect autoimmune
diseases such as multiple sclerosis, rheumatoid arthritis, or Type 1
diabetes (Cantorna and Mahon, 2004). New roles for vitamin D
may mean that the Dietary Reference Intake (DRI) will have to be
revised upward.
Alberta Centre for Active Living
11759 Groat Road, Edmonton AB T5M 3K6
Tel.: 780-427-6949/Fax: 780-455-2092
1-800-661-4551 (toll-free in Alberta)
E-mail: [email protected]
Web site: www.centre4activeliving.ca
Selenium and Prostate
Cancer
The Nutritional Prevention
of Cancer Trial suggested
that a 200 µg selenium
supplementation reduced
the risk of prostate
cancer by approximately
50%. This level is almost
four times that of the
Recommended Dietary
Allowance (RDA), but still
within the upper level (a
measurement that ensures
safe levels of intake) (Clark et al., 1996). More research is needed to
confirm these findings before recommending this amount for the
general population.
What Do Canadians Need to Know about Supplements?
Taking large doses of single supplements could be harmful for
people who already have heart disease or cancer, as it could make
their condition worse. This is the case for smokers taking betacarotene supplements and patients with heart disease taking high
levels (>400 IU) of vitamin E. Consult your doctor, pharmacist, or
dietitian before taking high doses of vitamins.
Some Recommendations
• If you take a supplement, take a multivitamin and mineral
supplement and consult a health professional before taking
single high-dose supplements.
• People with multiple risk factors for cardiovascular disease
or who have CVD should not take high-dose vitamin E
supplements (>400 IU).
• Because of the potential interaction among folate status,
alcohol intake, and the risk for breast and colorectal cancer,
people who drink alcohol should increase their dietary folate
intakes or to take a folic acid supplement that allows them to
meet the RDA.
• People over 50 should meet their vitamin B12 RDA by eating
food fortified with vitamin B12 or taking a vitamin supplement
that includes vitamin B12.
• People at high risk for chronic diseases should consult a
registered dietitian for dietary advice about how to improve
micronutrient intakes.
Optimum nutrition is intended to lower the risk for chronic
disease and improve the quality of life. For people at-risk,
supplement intakes may need to exceed nutrient recommendations
for healthy Canadians. You can take in optimal amounts of
vitamins and minerals in three ways: diet, food fortification, or
food supplements.
Eating a diet that is moderate in all things and provides variety and
balance is critical to good health. Foods provide vitamins, minerals,
and other phytochemicals that positively affect health.
Milly Ryan-Harshman (PhD, RD), nutritionist and scientific writer. For
this article’s references, please visit the centre’s website at
.
www.centre4activeliving.ca.
Dietitians of Canada
Alberta and Territories Region
PO Box 74090, Strathcona Postal Outlet
Calgary AB T3H 3B6
Tel.: 403-217-5211/Fax: 403-217-5212
Web site: www.dietitians.ca/index.html
The Alberta Centre for Active Living is the Canadian Health Network Active Living Affiliate.