Happy new year! When the holiday festivities have faded and the long winter months seem to stretch into infinity, people want to reinvent themselves, to get back on the bandwagon, eat healthier and get back into the gym.

It takes time

We're going to try something new this year — think of today as day 1 in a lifetime of good health. Habits, whether good or bad, take time to develop. It takes time to build healthy habits like taking your vitamins and also to unwind bad habits like chronic overeating or smoking. Slowly undoing bad habits while committing to good ones is the key.

Nutrition works in the same way. It takes time for nutrients to become replenished or depleted in your body. For example, it can take many months for new vegetarians to see their vitamin B12 levels drop to the point of deficiency and even longer for them to feel the effects. Even if current levels are normal, it's a good idea for people who adopt a plant-based diet to start supplementing B12 as soon as they stop eating animal products.

Replenishment and depletion

Another crucial nutrient that takes time to build up and deplete is vitamin D. Deficiency is associated with a higher risk of many diseases including cancer, autoimmune, cardiovascular, musculoskeletal and neurological diseases. If you're in a high risk group, such as those who avoid the sun or have darker skin pigmentation, you can promote healthy blood serum levels by supplementing 1,000 to 2,000 IU per day.

Women who are pregnant or hoping to become pregnant should take prenatal vitamins before contraception. The neural tube, which eventually becomes the brain and spinal cord, develops in the first month of pregnancy—before many women even know that they're pregnant. For this reason, The Mayo Clinic advises that women of reproductive age take prenatal vitamins regularly.

It takes up to six months for DHA levels in a woman to build up adequate levels in her system, according to the American Pregnancy Association. However, the FDA advises that pregnant women limit their intake of fish to 2 servings a week due to concerns over mercury content, so it can be hard for pregnant women to get enough omega-3 DHA at the time when they need it the most.

Short-term gains versus long-term results

In 2019, forget about short-term resolutions and start thinking more long-term. A lifetime of good health is made up of thousands of small steps — ordering salad instead of the burger, taking the stairs instead of the elevator and taking your vitamins every day.

These individual decisions may not have any overt effect on your health, but taken as a sum, they can make a world of difference in leading a longer, healthier life.