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Depending on your diet, you may need to take certain supplements to cover off nutrients you aren’t getting from food.

The Question

How do I know if I need to take vitamin supplements? Are there some I should take every day to be healthy?

The Answer

There are a few reasons you might need to take a supplement. Depending on your diet, you may need to take certain supplements to cover off nutrients you aren't getting from food.

Or, if a blood test shows you are deficient in a certain nutrient (e.g. iron, vitamin B12, vitamin D), a supplement will be required to replenish your body's stores.

In some cases, nutritional supplements are used to help treat certain health conditions. Vitamin C, for example, is often used to reduce cold symptoms. Fish oil is also taken to lower elevated blood triglycerides (fats).

There are four daily essentials you might need to bridge nutritional gaps in your diet: a multivitamin, vitamin D, calcium and omega-3 fatty acids (fish oil). I routinely recommend a daily multivitamin and mineral supplement to my clients. For menstruating women, who require 18 milligrams of iron each day, a one-a-day supplement helps boost iron intake.

It's recommended that people over age 50 take a multivitamin to ensure they're getting B12 in a well-absorbed form. Older adults are more vulnerable to B12 deficiency because they're more likely to have decreased production of stomach acid, which is needed to release B12 from proteins in food. It's also a good idea to take a daily multivitamin if you're following a low calorie diet.

To keep your bones healthy, adults aged 19 to 70 require 600 international units (IU) of vitamin D each day and older adults require 800 IU. But some people will need more to maintain a sufficient level of vitamin D in their bloodstream. Sun exposure, skin colour, obesity, age and diet all have an impact on the body's vitamin D stores. To account for individual differences, most experts recommend taking 1000 to 2000 IU of vitamin D each day to maintain adequate stores.

When it comes to calcium, I encourage people to meet daily needs through their diet. Calcium plays a role in maintaining healthy bones, keeping blood pressure in check and guarding against colorectal cancer. Adults aged 19 to 50 need 1,000 milligrams each day; older women require 1,200 milligrams. Calcium requirements for men don't increase to 1,200 milligrams until after age 70.

One cup of milk and 3/4 cup of yogurt delivers roughly 300 milligrams of calcium as does 1 1/2 ounces of hard cheese. Calcium-enriched beverages such as soy, rice and almond milk and orange juice also provide about 300 milligrams per cup. Cooked green vegetables, legumes, almonds, tofu and canned salmon with the bones also provide some calcium.

If you need to supplement your diet with calcium, I typically recommend products made from calcium citrate, which provide 300 to 350 milligrams per tablet.

Consider taking an omega-3 fatty acid supplement if you don't eat oily fish (e.g. salmon, trout, sardines). Higher intakes of DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid) – the two omega-3 fatty acids in fish oil – are linked with a lower the risk of heart disease and Type 2 diabetes. Getting too little DHA may also increase the risk of Alzheimer's disease.

Aim for a daily intake of 1,000 milligrams of DHA and EPA (combined), the equivalent of eating 12 ounces of salmon per week. The dose of DHA plus EPA in fish oil capsules is typically 300, 500 or 600 milligrams. Per teaspoon, liquid fish oils contain a higher dose.

My advice: Get your nutrients from foods as much as possible. Along with vitamins and minerals, a healthy diet delivers fibre and hundreds of protective phytochemicals. That's something a supplement can't do.